Factors affecting relative mite density differ for male and female Greater Horseshoe bats (Rhinolophus ferrumequinum) from Southwest England.

A report of data analysed using R Software for Environmental Statistics, with a specification requiring publication writing style and a 2500 word limit. 

 

Abstract

There is much aggregation of parasites in nature but the factors influencing ectoparasite variation in mammals and how this affects populations are unclear due to costly compensatory behaviours performed, such as grooming. Bat research is lacking due to their sensitivity and protection. This study uses body mass, forearm length and ectoparasite count data collected over decades at low-frequency during the hibernation period of the Greater Horseshoe Bat, to elucidate the different factors affecting average relative mite density (RMD) in males and females of high and low reproductive condition. On average, females were larger than males, carrying more mites, with females of high reproductive condition carrying significantly more than males and non-reproductive females, suggesting lowered immunocompetence or a grooming/reproduction trade-off. Using the Akaike’s Information Criterion and significance of Confidence Intervals, Ordinal Logistic Regression models, show that differing factors are likely to determine RMD for male and female Greater Horseshoe bats with possible implications for their conservation.

Key words: Ectoparasite, variation, reproductive, condition, trade-off

Introduction

Parasites are known to be heterogenetic in mammals (Wilson et al. 2001) but information about the variation in magnitude and probability of infestation within bat populations is lacking (Lucan 2006; Frank et al. 2015; Orlova et al. 2015).Ectoparasite infestation is likely to depend on exposure level and immunocompetence (Hart 1992; Luguterah and Lawer 2015) and females are often more heavily infected than males (Zahn and Rupp 2004; Patterson, Dick and Dittma 2008; Presley and Willig 2008) due to fundamental life-history differences such as sexual size-dimorphism or age differences (Stebbings 1966), and behaviour such as aggregation by reproductive females not exhibited by males (Williams and Findley 1979; Ransome 1991). Reproductive condition and related hormones can also have an effect on overall bat parasite load (Christe, Arlettaz and Vogel 2000).

Bat are rare and highly protected in the UK, (Joint Nature Conservation Committee 2014; The Bat Conservation Trust 2016) carrying a variety of ectoparasites including mites (Sachanowicz, Kristofik and Ciechanowski 2014; Frank et al. 2015) which need contact between bats for transmission (Reckhart and Kerth 2009) The understanding of bats is of ecological importance as they contribute to essential ecosystem services such as insect control and pollination (Kunz  et al. 2011; Ghanem and Voigt 2012; Wanger 2014), and this study aims to investigate variation in average parasitic mite load per individual (relative mite density) in the Greater Horseshoe bat, (Rhinolophus ferrumequinum) using data collected over 34 years from 39 locations, via low-disturbance methods, during autumn and winter months.

In the UK, populations of R. ferrumequinum are confined to southwest England (The Bat Conservation Trust 2016). This species is particularly sensitive to site disturbance (Hutson, Mickleburgh and Racey 2001) but can be handled during torpor (e.g. Park, Jones and Ransome 2000)  in hibernacula over  autumn and winter Similarly to other bat species females are larger and likely have higher relative mite density (RMD) than males.

The Body Condition Index (BCI), a ratio calculated by dividing body mass by forearm length, has been used to investigate ectoparasite load (Speakman and Racey 1986; Lucan 2006; Sharifi et al. 2013; Postawa and Szubert-Kruszyriska 2014) and  preliminary analyses, using scatterplots with linear regression lines and the Spearman’s rank correlation coefficients for the data of  this study, demonstrated that there is no significant correlation between RMD and body condition for R. ferrumequinum  males or females (Appendix 1: Table 1, Fig. 1), supporting similar findings in other bat species (Zahn and Rupp 2004; Lucan 2006; Sharifi et al. 2013, Postawa and Furman 2014;Postawa and Szubert-Kruszyriska 2014)

Body mass, forearm length, and RMD were compared for high and low reproductive condition males and females (indicated by visibility of false nipples in females and testes in males) and regression models were created to explain and predict RMD variation for the sample population as a whole, as well as for male and female data separately, to reveal potential differences in factors determining RMD between males and females.

First, greater body mass, forearm length and RMD was predicted for high reproductive condition (RC) females than for both females of low RC and all males (Sharifi et al. 2013). This is hypothesised to be due to the dynamics between parasite and host that take place within summer colonial roosts of adult females and some juveniles, but which adult males attend rarely and only until females give birth (Piksa et al. 2014). The higher density individuals within a roosting colony can have increases probabilities of horizontal and vertical ectoparasite transmission (Patterson, Dick and Dittmar 2008; Presley and Willig 2008).

RC in males and females is associated with age and body mass (Ward et al., 2014) and parasitic mites may have adapted their reproductive cycle to that of their host (Christe, Arlettaz and Vogel 2000; Lourenco and Palmeirim 2008). High RC (possibly pregnant) females may have a greater RMD than low RC, possibly juvenile, females during the autumn and winter, until the time of birth (summer) when parasites are thought to move onto male and female juveniles in the roost (Christe, Arlettaz and Vogel 2000). Therefore the second prediction of this study is that males of lower RC would have a higher RMD, but lower body mass and forearm length than both higher RC males and low RC females.

Finally, due to the possibility of different underlying causal mechanisms (Ward et al. 2014) influencing their parasite load (Lucan 2006), female RMD variation is predicted to be more dependent on RC than body mass or forearm length, while male RMD variation is predicted to be more dependent on body mass than on RC or forearm length.

Materials and Methods

a. Data Collection

R. ferrumequinum were captured while in torpor, weighed (g), sexed, aged by rating the ossification of joints (Kunz 1988) from 0-4, forearm length measured (mm) and number of wing mites and tail mites counted. The visibility of false nipples was recorded for females, the absence of which indicating non-reproductive condition (Dietz and Dietz 2007). For males, degree of testicular visibility was recorded, and larger or smaller testicle size can be an indicator of higher or lower spermatogenesis, respectively, during autumn and winter (Haarsma 2008).  Bats were released by placement back on the cave wall in a suitable position. Hibernacula temperature, outside temperature and humidity were recorded at least once for most of the sites, except four which contributed very little data in total.

Data was collected between 1976 and 2010 from approximately 39 locations in Southwest England at varying frequencies (Wiltshire Bat Group 2015). Hibernacula at each site were usually visited, between November and April but in total, the majority of data was collected from 7 main locations with most data being collected between 2002 and 2010. Thus, spatial and population dependence is expected of the data. This low-frequency sampling by volunteering members of the Wiltshire bat group, and handling of bats during torpor  (e.g. Park, Jones and Ransome 2000) under the supervision of a licenced bat handler, likely limited disruption.

b. Data Selection and Manipulation

Due to the large number of data entries for which two or more variables were unrecorded, gaps in the data were filled in using the mean of the recorded values (assuming no trend in the data in order to prevent bias), resulting in 1293 males and 1236 female data points for each recorded variable. This enabled statistical analyses without eliminating large parts of useful data.

New variables were systematically created from the raw recorded data. Male testes visibility, originally ranked from 0-4, was categorised into males with more regressed testes (visibility 0, 1 and half of 2) and males with more pronounced testes (visibility 3, 4 and the other half of 2). These categories, along with visibility of false nipples in females, were then given a rank of either 0, representing low RC (males with more regressed testes and females without visible false nipples), or 1, representing high RC (males with more pronounced testes and females with visible false nipples).

RMD was calculated, as the number of tail mites added to wing mites per bat, and since these data contained a high frequency of zero values, they were ranked into 8 ordinal groups (rank 1 = 0-2 mites/bat, rank 2 = 3-5 mites/bat, rank 3 = 6-8 mites/bat, rank 4 = 9-11 mites/bat, rank 5 = 12-14 mites/bat, rank 6 = 15-17 mites/bat, rank 7 = 18-20 mites/bat and rank 8 = 21 or more mites/bat) in order to avoid problems caused by high frequencies of zero values during statistical analyses.

c. Data Analysis

Effects of body mass, forearm length and RC on RMD were investigated using the statistical analysis software R (R Core Team, 2015), with all tests carried out at a 95% confidence interval. Before doing analyses, the data was explored, assessing outliers, distribution normality and homoscedasticity. Six extreme high and low outliers for body mass and forearm length data were removed as these were possibly caused by measurement error. Extreme outliers for RMD were all larger than the average and were not removed as individuals in natural animal populations can experience extreme infestation (e.g. Boulinier, Ives and Danchin 1996; Pierce et al. 2014; Frank et al. 2015).

Since the data for RMD was greatly right skewed, Kruskall-Wallis and Mann-Whitney U tests were done to investigate the differences in ranked RMD between males and females, and between RC groups (Kowalski, 1972). Body mass and forearm length data were found to be nearly normally distributed with similar homogeneity of variances, leading to the use of a one-way ANOVA and two-sample unpaired Student’s t-Tests to examine differences in the two variables between males and females, and between the RC groups.

Ordinal Logistic Regression (OLR) models were fitted using the Proportional Odds Regression function and MASS package in R (Venables and Ripley 2002), to explore the causal relationship between the ordinal dependent variable, RMD and the covariates (predictor variables) body mass, forearm length and RC on variation in RMD. Nine OLR models using the combined male and female data, male-only and female-only data were run and the Aike Information Criteria (AIC), Confidence Intervals (CI) and Odds Ratios were used to select an appropriate model that could explain the variation in RMD for each set of data.

To validate the models, evaluation of the Proportional Odds Assumption was carried out by running a series of binary logistic regressions and assessing the equality of the difference in coefficients of the logits for every outcome of the predictor variable, at each level of the dependent variable.  Finally, the predicted probabilities for the new models, of a given dependent variable level being the case, at every given predictor variable level was plotted using the packages reshape2 (Wickham 2007) and ggplot2 (Wickham 2009) and compared to graphs of actual data in order to assess the models’ effectiveness.

ALL R CODE SCRIPTS

Results

(For all statistical tests except OLR, results were significant unless otherwise stated)

a. Abiotic Factors and Bat Age

Outside temperature ranged from 0-18°C (8.5°C average). Hibernacula temperature ranges 0-18°C (9.1°C average), and humidity ranges 9.6-100% (86.1% average). Bat joint ossification ratings ranged 0-4 but the average was 3.

b. RMD Variation

Females had 1.14 times (Fig. 2) greater average RMD than males (Appendix 2, Table Set 2.a). Females of high RC had 1.063 times significantly greater RMD than females of low RC. Males of lower RC had 1.071 times greater average RMD than males of higher RC but this difference was not significant. High RC females had greater average RMD than all males while there was no significant difference between low RC females and males of either RC (Appendix 3,Table 3.b) , supporting the trend in Fig. 2.

c. Body Mass Variation

Female bats had 1.050 times (Fig.3) greater average body mass than males (Appendix 2, Table 2.b). High RC females had 1.063 times greater average body mass than low RC females, and males of both higher and lower RC. Higher RC males had 1.062 times significantly greater average body mass than lower RC males. There was no significant difference in body mass between low RC females and higher RC males but low RC females had significantly greater average body mass than lower RC males (Appendix 3, Table 4.b). These results support the trend in Fig. 3.

 

 

d. Forearm Length Variation

On average, female bats had 1.017 times (Fig. 4) longer forearms than males (Appendix2, Table 2.b). High RC females had 1.003 times greater average forearm length than low RC females and males of both higher and lower RC (as did females of lower RC). Higher RC males had 1.006 times greater forearm length than lower RC males (Appendix 3, Table 4.c). These results support the trend in Fig.4.

e. Ordinal Logistic Regression modelling

Nine OLR models were created with each predictor variable in turn, using combined, as well as male-only and female-only data (Appendix 4, Table 5). The CI was significant for models using 1. body mass and RC for combined data, 2. body mass for male-only data, and 3) RC and forearm length for female-only data.  The AIC and Residual Deviance for the models that did not have significant CI was also relatively high. In the female-only data, forearm length Odds Ratio showed an inverse relationship with RMD compared to the Odds Ratios for the other significant variables. The predictor variables of these significant models were used to fit three OLR models, M1 (combined data), M2 (male) and M3 (female), that may predict the variation in RMD of R. ferrumequinum (Appendix 5, Table 6) for the sample population.

 

For model validation, the Proportional Odds Assumption was found to be violated for RC in M1 but not for Body Mass (Appendix 6, Table 7). It was not violated in M2 (Appendix 6, Table 8), and was violated for Forearm Length in M3 but not for RC (Appendix 6, Table 9). The predicted probabilities of a given level of the dependent variable being the case, at any given level of each predictor variable, were then plotted for each model and compared to graphs of actual data (Fig.5, 6, and 7). The models were found to effectively predict the change in RMD in relation to 1. Body Mass and RC for the combined data, 2. mass in the male data and 3.forearm length and reproductive condition in the female data .

Model 1 used Body Mass (g) and RC (0=lower, 1=higher) to explain ranked RMD (levels 1-8). This model had the highest AIC, with the effect of RC being found not significant. The Body Mass variable had an odds ratio of 1.06: the odds for a higher outcome in RMD is 1.06 times greater at any higher value of Body Mass compared to the next value down, given that all other variables stay constant (Appendix 5, Table 6). Model 2 used only Body Mass to explain ranked RMD in male bats. This was the model with the lowest AIC, with the same general outcome as for Model 1(Fig. 5.), but with a greater Odds Ratio of 1.09 (Appendix 5, Table 6). Model 3 used RC and Forearm Length (mm) to explain ranked RMD in female bats and also had a relatively low AIC, with the highest Odds Ratio for RC of 1.57 and the lowest odds ratio for forearm length at 0.84, meaning the odds for a higher outcome in RMD is 1.57 times greater at higher RC than at low RC, and approximately 1.2 times greater at a lower forearm length compared to the next value up, given that all other variables stay constant (Appendix 5, Table 6).

Discussion

Ectoparasite load can carry implications for reproduction and survivorship (Giorgi et al. 2001; Simon et al. 2004; Hawlena, Abramsky and Krasnow 2006). Direct impact may occur through resource consumption (Hawlena, Abramsky, Krasnov 2006) and imposing immunocompetence costs (Navarro-Gonzalez et al. 2011), as well as indirectly through pathogen transmission, and changes in habitat selection (Reckardt and Kerth 2007).

Grooming behaviour functions as defence against ectoparasite infestation but carries an energetic and time cost (Giorgi et al. 2001; Godinho et al. 2013) that may also impact the ability of an animal to rest, forage, defend its territory or mate, reproduce and care for young (Giorgi et al. 2001). This energetic cost may also vary according to differences in the cost that different parasite species draw from hosts (Godinho et al. 2013).

For this study of R. ferrumequinum during autumn and winter in southwest England, average RMD was greater in high RC females than any other group, while there was no significant RMD difference between low RC females and any males, supported by other studies (Christe et al. 2007; Encarnacao, Baulechner and Bekcer 2012; Sundari et al. 2012).

Grooming behaviour may be energetically and time restricted in reproductive females and inefficient in low RC individuals that are likely to be juveniles (McLean and Speakman 1997; Viljoen et al. 2011; Encarnacao, Baulechner and Bekcer 2012). Reproductive females may also have reduced immunocompetence due to hormonal changes (Christe et al. 2000) or to a resource allocation trade-off for reproduction (Dzal and Bringham 2013). In addition, reproductive females tend to live in close colonies in maternity roosts for part of the year, often with some juveniles, while non-reproductive females and males roost solitarily (Ransome 1991) leading to a greater probability of parasite transmission within the reproductive female population (Christe, Arlettaz & Vogel 2000; Patterson, Dick and Dittmar 2008).

Modelling found that high RC females are more  likely to have a higher level of mite infestation than low RC females (and all males) but longer female forearms mean lower probability of high-level mite infestation and vice versa (Fig. 7). Greater body mass may mean lower probability of low-level mite infestation and higher probability of higher-level infestation for all bats (Fig. 5) as is the case for males separately  (Fig. 6) but not for females separately. Possible reasons include higher mass providing more surface area and more resources for mites to inhabit (Viljoen et al. 2011) and less energy spent on costly grooming when larger individuals are able to carry the cost of infestation better than small individuals (Giorgi et al. 2001).

Differences in body mass, forearm length and RMD between the study groups were extremely small, as were the predicted increases or decreases in RMD, and there is a general need for future study of factors affecting on  mite infection intensity (average mites per infected bat) and prevalence (percentage of infested bats).

In general, ectoparasite load does not affect overall bat health ( this study’s Appendix 1: Table 1, Fig. 1; Zahn and Rupp 2004; Lucan 2006; Sharifi et al. 2008; Postawa and Szubert-Kruszyriska 2014) but at times of more intense demand on resources, even a moderate parasite load may affect survival. Fluctuations in climate, lack of suitable roosts and decreased food availability such as those faced by bats in the UK (Ransome 1968; Hutson, Mickleburgh, Racey 2001; The Bat Conservation Trust, 2014) can affect ectoparasite prevalence due to temperature (Chen and Mullins 2008; Lourenco and Palmeirim 2008) and humidity changes (Moyer et al. 2002; Zhang et al. 2010), as well as body mass and immunocompetence (Navarro-Gonzalez et al. 2011; Dlugosz et al. 2014). Heterogeneity of infestation impact due to varying energetic and time demands may carry implications for bat population dynamics and conservation that need further investigation over the course of all seasons (Lourenco and Palmeirim 2008; Sharifi et al. 2008).

 

References

Boulinier T, Ivers AR and Danchin E (1996) Measuring aggregation of parasites at different host population levels. Parasitology 112:581-587

Chen BL and Mullens BA (2008) Temperature and humidity effects on off-host survival of the Northern fowl mite (Acari:Macronyssidae) and the chicken body louse (Phthiraptera:Menoponidae). J Econ Entomol 101:637-346

Christe P, Arlettaz R and Vogel P (2000) Variation in intensity of a parasitic mite (Spinturnix myoti) in relation to the reproductive cycle and immunocompetence of its bat host (Myotis myotis). Ecol Lett 3:207-212. DOI: 10.1046/j.1461-0248.2000.00142.x

Christe P, Glaizot O, Evanno G, Bruyndoncks N, Devevey G, Yannic  G, Patthey P, Maeder A, Vogel P and Arlettaz R (2007) Host sex and ectoparasites choice: preferences for, and higher survival on female hosts. J Anim Ecol 76:703-710

Dietz C and Dietz I (2007) Age classification and assessment of reproductive condition in female Greater Horseshoe bats (Rhinolophus ferrumequinum, Chiroptera:Rhinolophidae). In: Dietz C (2007), Aspects of ecomorphology in the five European Horseshoe Bats (Chiroptera:Rhinolophidae), Dissertation, University of Tübingen

Dlugosz EM, de Bellocq JG, Khokhlova IS, Degen AA, Pinshow B and Krasnov BR (2014) Age at weaning, immunocompetence and ectoparasite performance in precocial desert rodent. J Exp Biol  217:3078-3038. doi: 10.1242/jeb.106005

Dzal YA and Bringham RM (2013) The tradeoff between torpor use and reproduction in little brown bats (Myotis licifugus). J Comp Physiol B 183:279-288

Frank R, Kuhn T, Werblow A, Liston A, Kochmann J, and Klimpel S (2015) Parasite diversity of European Myotis species with special emphasis on Myotis myotis (Micropchiroptera, Vespertilionidae) from a typical nursery roost. Parasite Vector 8:1-13. doi: 10.1186/s13071-015-0707-7

Giorgi MS, Arlettaz R, Christe P and Vogel P (2001) The energetic grooming costs imposed by a parasitic mite (Spinturnix myoti) upon its bat host (Myotis myotis). Proc. R. Soc. Lond. B 268:2071-2075. dio: 10.1098/rspb.2001.1686

Ghanem SJ, and Voigt CC (2012). Increasing Awareness of Ecosystem Services Provided by Bats.  In:Brockman HJ, Roper TJ, Naguib M, Mitani JC and Simmons LW (eds) Advances in the Study of Behavior, vol. 44. Elsevier, USA, pp 279-302

Godhino LN, Cripps JK, Coulson G and Lumsden LF (2013) The effect of ectoparasites on the grooming behaviour of Gould’s Wattled bat (Chalinolobus Gouldii): An experimental study. Acta Chiropterol 15:463-472. doi:10.3163/150811013×679080

Haarsma AJ (2008) Manual for assessment of reproductive status, age and helwth in European Vespertilionid bats. Haarsma AJ, Holland http://vleermuizenvangen.nl/index.php/achtergrond-info/voorbeeld-examen Accessed 18 January 2016

Hart BL (1992) Behavioural adaptations to parasites: an ethological approach. J Parasitol 78:256-265

Hawlena H, Abramsky Z, Krasnov BR (2006) Ectoparasites and age-dependent survival in a desert rodent. Oecologia 148:30-39

Hutson AM, Mickleburgh SP and Racey PA (2001) Microchiropteran bats: global status survey and conservation action plan. IUCN / SSC Chiroptera Specialist Group. IUCN, Gland, Switzerland and Cambridge, U.K.

Joint Nature Conservation Committee (2014) EC Habitats Directive. JNCC. http://jncc.defra.gov.uk/page-1374. Accessed 10 January 2016

Kowalski CJ (1972) On the effects of non-normality on the distribution of the Sample Product-moment Correlation Coefficient. J R Stat  Soc 21:1-12. doi:10.2307/2346598

Kunz TH (1988) Ecological and behavioural methods for the study of bats. Smithsonian Institution Press, Washington D.C.

Kunz TH, de Torrez EB, Bauer D, Lobova T and Fleming TH (2011) Ecosystem services provided by bats. Ann. N.Y. Acad. Sci. 1223:1-38 . doi: 10.1111/j.1749-6632.2011.06004.x

Lucan RK (2006) Relationships between the parasitic mite Spinturnix andegavinus (Acari: Spinturnicidae) and its bat host, Myotis daubentonii (Chiroptera: Vespertilionidae): seasonal, sex- and age-related variation in infestation and possible impact of the parasite on the host condition and roosting behaviour. Folia Parasitol 53:147-153

Lourenco S and Palmeirim JM (2008) Which factors regulate the reproduction of ectoparasites of temperate-zone cave-dwelling bats? Parasitol Res 104:127-134

Luguterah A and Lawer EA (2015) Effect of dietary guild (frugivory and insectivory) and other host characteristics on ectoparasite abundance (mite and nycteribiid) of chiropterans. Folia Parasit 62:1-7. doi: 10.14411/fp.2015.021

McLean JA and Speakman JR (1997) Non-nutritional maternal support in the brown long-eared bat. Anim Behav 54:1193-1204

Moyer BR; Drown DM and Clayton DH (2002) Low humidity reduced ectoparasite pressure: implications for host life history evolution. Oikos 97:223-228. doi: 10.1034/j.1600-0706.2002.970208.x

Navarro-Gonzalez N, Verheyden H, Hoste H, Cargnelutti B, Lourtet B, Merlet J, Daufresne T, Lavin S and Hewison AJM (2011) Diet quality and immunocompetence influence parasite load of roe dee in a fragmented landscape. Eur J Wildlife Res 57:639-645

Orlova MV, Zhigalina AV, Orlov OL, Kruskop SV and Bogdanove II (2015) Contribution to the ectoparasite fauna of rare and poor studied bat species of Southern Siberia. Biology Bull 42:254-259

Park KJ, Jones G and Ransome RD (2000) Torpor, arousal and activity of hibernating Greater Horseshoe Bats (Rhinolophus ferrumequinum) Funct Ecol 4:580-588

Patterson BD,  Dick CW and Dittmar K (2008) Sex biases in parasitism of neotropical bats by bat flies (diptera:Streblidae). J Tropic Ecol 24:387-396. doi:10.1017/S0266467408005117

Pierce AA, de Roode JC, Altizer S and Bartel RA (2014) Extreme Heterogeneity in parasitism despite low population genetic structure among Monarch butterflies inhabiting the Hawaiian Islands. PLOS. doi: 10.1371/journal.pone.0100061

Piksa K, Gorz A, Nowak-Chmura M and Siuda K (2014) The patterns of seasonal activity of Ixodes vespertilionis (Acari:Ixodidae) on Rhinolophus hipposideros ins nursery colonies. Ticks and Tick-borne Diseases 5:69-74

Postawa T and Furman A (2014) Abundance patterns of ectoparasites infesting different populations of Miniopterus species in their contact zone in Asia Minor. Acta Chiropterl 16:387-39

Postawa T and Szubert-Kruszyriska A (2014) Is parasite load dependent on host aggregation size? The case of the greater mouse-eared bat Myotis Myotis (Mammalia: Chiroptera) and its parasitic mite Spinturnix myoti (Acari:Gamasida). Parisitol Res 113:1803-1811. doi:10.1007/s00436-014-3826-8

Presley SJ and Willig MR (2008) Intraspecific patterns of ectoparasite abundances on Paraguayan bats: effects of host sex and body size. J Tropic Ecol 24:75-83

R Core Team (2015). R: A language and environment for statistical computing. R Foundation for statistical computing, Vienna, Austria. https://www.R-project.org/

Ransome R D (1968) The distribution of the Greater horse-shoe bat, Rhinolophus ferrum-equinum, during hibernation, in relation to environmental factors. J  Zool 154:77–112. doi:10.1111/j.1469-7998.1968.tb05040.x

Reckardt K and Kerth G (2007) Roost selection and roost switching of female Bechstein’s bat (Myotis bechsteinii) as a strategy of parasite avoidance. Oecologia 154:581-588 doi: 10.1007/s00442-007-0843-7

Ransome RD (1991) Greater horseshoe bat. In: Corbet GB and Harris S (eds), The handbook of British mammals, pp. 88-94, Blackwell, Oxford, UK.

Reckardt K and Kerth G (2009) Does the mode of transmission between hosts affect the host choice strategies of parasites? Implications from a field study on bat fly and wing mite infestation of Bechstein’s bats. Oikos 118: 183–190

Sachanowicz K, Kristofik J and Ciechanowski M (2014) Spinturnicid mites of bats in Albania – host spectrum and morphometrics as a tool of species separation. J Nat Hist 48:2661-2674. doi: 10.1080/00222933.2014.939729

Sharifi M, Fatema M, Najmeh T and Hossain J (2008) Variation in the ectoparasite load reflects life history traits in the lesser mouse-eared bat Myotis Blythii (Chiroptra: Vespertilionidae) in Western Iran. J Parasitol 94:622-625

Sharifi M, Taghinezhad N, Mozafari F and Vaissi S (2013) Variation in ectoparasite load in the Mehely’s horseshoe bat, Rhinolophus mehelui (Chiroptera:Rhinolophidae) in a nursery colony in western Iran. Acta Parasitol 58:180-184. doi: 10.2478/s11686-013-0122-1

Simon A, Thomas D, Blondel J, Perret P and Lambrechts MM (2004) Physiological ecology of mediterranean Blue Tits (Parus caeruleus L.): effects of ectoparasites (Protocalliphora spp.) and food abundance on metabolic capacity of nestlings. Physiol Biochem Zool 77:492-501

Speakman JR and Racey PA (1986) The influence of body condition on sexual development of male brown long-eared bats (Plectus auritus) in the wild. J Zool (Lond) 210:515-525

Stebbings RE (1966) A population study of bats of the genus Plecotus. J Zool 150: 53–75. doi:10.1111/j.1469-7998.1966.tb02998.x

Sundari AA, Bogdanowicz W, Varman DR, Marimuthu G and Rajan KE (2012 Ectoparasite Raymondia lobulata infestation in relation to the reproductive cycle of its host – the Greater False Vampire Bat Megaderma lyra. J Parasitol 98:60-62. doi:10.1645/GE-2833.1

The Bat Conservation Trust (2016) Greater Horseshoe Bat. BCT. http://www.bats.org.uk/pages/-greater_horseshoe_bat-800.html#legal status.  Accessed 10 January 2016

The Bat Conservation Trust (2014) Conservation Research: BCT Science Strategy. http://www.bats.org.uk/pages/research.html Accessed 23 November 2015

Thompson  RCA, Lymbery AJ, Smith  A (2010) Parasites, emerging disease and wildlife conservation. Int J Parasitol 40:1163-1170

Venables WN and Ripley BD (2002) Modern Applied Statistics with S. 4th Edition. Springer, New York

Viljoen H, Bennett NC, Ueckermann EA, Lutermann H (2011) The Role of Host Traits, Season and Group Size on Parasite Burdens in a Cooperative Mammal. PLoS ONE 6: e27003. doi:10.1371/journal.pone.0027003

Wanger TC, Darras K, Bumrungsri S, Tscharntke T and Klein AM (2014) Bat pest control contributes to food security in Thailand. Biol Conserv 171:220-223

Ward HL, Ransome RD, Jones G, Rossiter SJ (2014) Determinants and Patterns of Reproductive Success in the Greater Horseshoe Bat during a Population Recovery. PLoS ONE 9: e87199. doi:10.1371/journal.pone.0087199

Wickham H (2007) Reshaping data with the reshape package. J Stat Softw, 21:1-20 http://www.jstatsoft.org/v21/i12/

Wickham H (2009) ggplot2: elegant graphics for data analysis. Spring, New York

Williams DF and Findley JS (1979) Sexual size dimorphisms in Vespertilionid bats. The American Midland Naturalist 102:113-126. doi:10.2307/2425072

Wilson K, Bjornstad ON, Dobson AP, Merler S, Poglaen G, et al. (2001) Heterogeneities in macroparasite infections: patterns and processes. In: Hudson PJ, Rizzoli A, Grenfell BT, Heesterbeek H, Dobson AP, eds. The ecology of wildlife diseases, pp6-44. Oxford: Oxford University Press

Wiltshire Bat Group (2015). Wiltshire Bat Group Web Page. Wiltshire and Swindon Biological Records Centre. http://www.wsbrc.org.uk/Links/LocalGroups/WBG/wideTemplate.aspx. Accessed 23 November 2015

Zahn A and Rupp D (2004) Ectoparasite load in European vespertilionid bats. J Zool 262:383-391

Zhang L, Parsons S, Daszak P, Wei L, Zhu G and Zhang S (2010) Variation in the abundance of ectoparasitic mites of flat-headed bats. J Mammal 91:136-143

 

Appendix 1.

Preliminary finding for the effects of an immunity indicator on R. ferrumequinum Relative Mite Density:

 

 

Appendix 2.

Results of statistical tests for differences between male and female R. ferrumequinum.

Appendix 3.

Results of statistical tests for differences within male and female R. ferrumequinum: between individuals with false nipples, without false nipples, and between individuals with larger testes and without larger testes.

 

Appendix 4.

Results of Ordinal Logistic Regression modelling used to select the models which best describe variation in RMD.

 

Appendix 5.

Results of Ordinal Logistic Regression modelling for the three selected models which best describe variation in RMD.

 

Appendix 6.

Predicted linear logits.

 

Classification of the Sengis (Afrotheria, Macroscelididae): challenges in taxonomy affecting conservation prioritisation.

Article on issues in conservation 

 

Adjustments in the classification of many species are driven by, not only new technological and ecological discoveries, but also growing awareness of conservation implications involved with erroneous species classification that may lead to losses in genetically, ecologically, and economically valuable biodiversity (Williams et al., 2012; Richards, Miller and Wallace, 2013; Eldridge, Meek and Johnson, 2013).

Species Concepts

Though classification techniques have developed considerably from the first hierarchical classification of all living things by Aristotle (Hamilton and Wheeler, 2008; Lewis, R., 2015), conflicting ideas about the distinction of organisms are still plentiful, more than 20 species concepts are theorised (Mallet, 1995; Mayden, 1997; Wheeler and Meier, 2000) and there is failure to agree on a common definition of a species (Mitchell, 1993; Bachmann, 2001; Frankham et al., 2012). Of the concepts favoured by scientists, most are either pattern-based, defined via morphology or phylogeny (Mallet, 2009; Filatov et al., 2013) or process-based, defined via reproductive isolation or cohesion (Wirtz, Printzen and Lumbsch, 2008; Lagache et al, 2013; Dirlink et al., 2014), but none are without problems (Hausdof, 2011).

The Morphological Species Concept relies on the distinctiveness of measurable physical characters between groups and similarities within them, but the subjectivity of morphological analyses and potential cryptomorphism of species, poses a problem when groups are morphologically identical but genetically distinct (Funk, Caminer and Ron, 2012) or vice versa (Agrawal, 2001). Many evolutionary geneticists think of species in terms of the Biological Species Concept (BSC), defining a species as an actually or potentially interbreeding natural population, that is reproductively isolated from other similar populations with limited gene flow between them (Wheeler and Meier, 2000; Noor, 2002; Coyne and Orr, 2004). This concept has problems dealing with asexual species, hybridization (Papadopulos et al., 2011) and lack of evidence for reproductive isolation of subject organisms (Wu, 2001).

For the Phylogenetic Species Concept (PSC) molecular sequences are analysed as well as morphology, in order to infer shared derived characters that indicate the smallest monophyletic groups with a single common ancestor (Wheeler and Meier, 2000) and these groups are then classed as species. Taxonomists tend to favour this concept as it gives a clear statistical outcome. However, it is dependent on the extent of molecular and morphological data, the outputs of a phylogenetic analysis are hypothesis based rather than a certainty, and there is particular ambiguity around the degree of differentiation necessary to indicate a separate species using the PSC due to its high degree of precision (Agapow et al., 2004).

Benefits and Risks of  Conservation Prioritisation using Phylogenetic Analysis

It is widely acknowledged that global human-induced species extinction risks are not decreasing (State of Nature Partnership, 2013; Secretariat of the Convention on Biological Diversity, 2014, Regnier et al., 2015), and biodiversity loss is greater than the resources available to restore and protect it (Leader-Williams, Adams and Smith, 2010; Mooney, 2010). In addition, the wide-spread assumption that the majority of species are well known to science has been demonstrated to be a misconception (Smit et al., 2008) and it is suggest that global animal and plant species diversity is underestimated (Vieties et al., 2009; Appeltans et al., 2012). Since large numbers of undiscovered species persist in rapidly declining habitats, many may become extinct before they are discovered, contributing to a decline in biodiversity with implications for ecosystem services (Ceballose and Ehrlich, 2009).

Conservation efforts acknowledge the importance of not only protecting animal populations individually, but also the functional and genetic diversity within and between species (Ceballosa and Ehrlich, 2009; Steele and Pires, 2011; Bennett et al., 2014, Leslie, 2015) in aid of preserving genetic representation of past evolution (Grandcolas, Nattier and Trewick, 2014) and evolutionary potential (Taberlet et al., 2012), as well as present ecological traits. Phylogenetics is often used for species delineation, potentially revealing the true biodiversity of taxa or environments, previously unrecognised (Merces et al., 2015). This can influence the assignment of conservation status because revised species taxonomy due to advances in molecular and morphological techniques such as DNA barcoding (Herbert and Gregory, 2005; DeSalle, 2006) or geometric morphometric methods (Zúniga-Reinoso and Benítez, 2015), can lead to altered species population numbers and range sizes (Funk, Caminer and Ron, 2012).

The elevation of a sub-species to species level (Olivieri, 2007; Pinzo and La Jeunesse, 2011 ) or the description of cryptic species previously undiscovered (Lohman et al., 2010; Feinberg et al., 2014) is often the result of molecular phylogenetic analyses. However, the risk for species classifications that are too narrow when using very precise modern techniques is a concern when such classification is used to assess extinction risk and conservation management that is tailored to the separated taxa. For example, there may be an increased risk of extinction through the unintended loss of genetic variation if threatened species are incorrectly split into several separate units and if their breeding is managed as such (Zachos, 2013).

Prioritising conservation via ranking organisms and ecosystems according to evolutionary distinctiveness and phylogenetic diversity is increasingly found effective (Tucker et al., 2012; Volkamn et al., 2014). As it is based on species ancestry and decent, it often captures similarities among species on multiple levels, revealing phenotypical and ecological differences as well as ancestral ones. This may facilitate more efficient management choices, maximising future conservation returns when ecosystems with great evolutionary diversity, as well as genetic and ecological uniqueness are highlighted (Faith and Richards, 2012; Leslie, 2015).

It is expected that regionally restricted phylogenetic lineages, contribute substantially to the total genetic variation of environments (Rosauer et al., 2009). Such species are often rare, occupying small, fragmented ranges and because this means they may also be most at risk of extinction (Cadotte and Davies, 2010), awareness of their genetic importance is vital (Tucker et al., 2012). Unfortunately, lack of data and incomplete or contentious species records may hinder this type of progress (Collins and Halliday, 2005; Steele and Pires, 2011, Funk, Caminer and Ron, 2012).

 

From Elephant-shrew to Sengi: Species Discoveries and Reclassifications

Changes in classification of taxonomic groups occur frequently (Collins and Halliday, 2005; Williams et al., 2012; Buckley et al., 2014) often due to the discovery of new species as scientific efforts and understanding of taxonomy increase.  The elephant-shrews (order Macroscelididae) are an example of a rare, unique and often isolated, phylogenetic lineage that contributes to the distinctiveness of a range of habitats, and awareness of their genetic importance may contribute to the conservation of the valuable environments they are found in (Rosauer et al., 2009; Cadotte and Davies, 2010; Tucker et al., 2012).

Elephant-shrews are very active, wary and well adapted for sprinting away from natural predators. They are insectivores and omnivores (Kerley, 1995) and species range from less than 50g to 700g in weight (Rathbun, 2009), with the smallest species most recently described (Dumbatcher et al., 2014). Some species are very morphologically distinct and easily identified, while others have similar morphologies and distribution overlap, often leading to misidentification (Tolliver et al. 1989). The majority of elephant-shrew species were described in the 19th century based on morphological and behavioural characteristics. The traditional common name was chosen due their elongated snouts and their assumed relationship with the true shrews (Soricidae). Thus, in a publication by Ernst Heackel in 1866, elephant-shrews were placed in the now abandoned, order Insectivora (Tabuce et al., 2001; Stanhope et al., 1998).

The discovery of new fossil evidence means that elephant-shrews are currently accepted as order Macroscelidea (Butler, 1956; Patterson, 1965) and they possess a combination of traits that are unique (Rathbun, 2009): an elongated proboscis-like snout used to forage, saltatorial running, no or limited use of nests, social monogamy, small litters of precocial young and absence of maternal care of neonates (Rathbun, 2009). These are traits that have individually also been associated with small antelopes or anteaters but it was soon realised that elephant-shrews lack close relation to any other living mammals. There have been attempts at linking them to various groups (Rathbun, 1979; Butler, 1995) such as the order Lagomorpha (rabbits, hares and pikas) due to hind leg physiology (Evans, 1942), ungulates due to morphological phylogenetic evidence (Zack et al., 2005), and tree shrews (order Scandentia), a relative of the primates (Simons, Holroyd and Brown, 1991).

Extant and fossil Macroscelidea are all endemic to Africa and analyses of evolutionary relationships using morphological (Oduor-Okeloa, Katemaa and Carterb, 2004; Woodall, 1995), and molecular (Robinson et al., 2004; Svartman et al., 2004) techniques have now strongly, but not without objection (Zack et al., 2005), confirmed the place of Macroscelidea within Afrotheria, along with the elephants (order Proboscidea), sea cows (Sirenia), hyraxes (Hyracoidea), aardvark (Tubulidentata), and golden-moles and tenrecs (Afrosoricida), all of which were previously grouped either with the ungulates or insectivores (Hedges, 2001). Afrotheria is thought to be a distinct ancient monophyletic African radiation, evolved when the continent was isolated from others through plate tectonics (Springer et al., 1997) and its extant clades are not closely related to any other group of mammals (Stanhope, 1998; Staythorpe et al., 1998; van Dijk et al., 2001; Carter et al., 2004; Seiffert, 2007;  Tabuce et al., 2007; Asher and Lehmann, 2008).

The acceptance of the long-suspected super-cohort Afrotheria , and the placement of elephant shrews within it, has drawn both scientific interest (for example, Poulakakis and Stamatakis, 2010) and valuable publicity (‘Insect Hunters’, 2002; ‘Under Open Skies’, 2014) to this unique taxon. In addition, with the progression of molecular identification techniques, new species of elephant shrew are being described, adding to the existing record of species diversity for the habitats in which they are found.

In 1968, Cobert and Hanks investigated the phenotypic relationships among the genera of Macroscelidea based on morphological differences. They identified 2 subfamilies consisting of 4 genera with 14 species in total: the giant, forest-dwelling Rhynchocyoninae (Rhynchoncyon, 3 species) and the soft-furred Macroscelidinae (Elephantulus, 9 species; Petrodromus, 1 species; Macroscelides, 1 species).  Cobert (1971) then described Elephantulus fuscus, raising it to species level from being a subspecies of E. brachyrhynchus. There have been only 22 documented locations for E. fuscus, with a restricted distribution to Malawi, Mozambique and Zimbabwe, and the lack of current habitat and behavioural records for this species means its conservation status is unclear (Rathbun, 2015).

In order to distance Macroscelidea from their mistaken relations, the true shrews, Jonathan Kingdom (1997) suggested the common name “sengi” (a term derived from central African languages) that is increasing in popularity. Five more species have been described since then, often using molecular phylogenetic techniques to resolve minor and sometimes cryptic, differences among the many described forms.

In 2005, Rhynchocyon udzungwesis was observed in the forested Udzungwa Mountains, Tanzania, and declared a new species based on 49 camera trap images, 40 sightings and 5 specimens. It is the largest of all the sengis and is distinguished by unique phenotypic features and allopatric distribution (Rovero et al., 2008). Rovero et al. acknowledge the fact that craniometrics data for this genus is lacking, making a full comparison between new and long-known species very difficult.

Elephantulus pilicaudus was newly distinguished from the phenotypically similar and sympatric E. rupestris and E. edwardii. by Smit et al. (2008) on the basis of strong, morphological, mitochondrial and nuclear DNA, and comparative cytogenetic evidence, from 17 specimens of the new species compared to 25 specimens of E. rupestris and E. edwardii. Smit et al. (2008) also provides a scheme of identification of the distinctive phenotypic characters of E. pilicaudus.

What was thought to be two subspecies of Macroscelides, were both elevated to species level, M. proboscideus (the “Karoo round-eared sengi”)and M. flavicaudatus (the “Namib round-eared sengi”), by Dumbatcher et al. (2012) based on genetic and morphological data, near sympatry with no genetic evidence of gene flow, and differences in habitat use.

Finally Macroscelides micus (Etendeka round-eared sengi) was discovered by Dumbatcher et al. (2014) when an unusual specimen was retrieved from remote Namibia while studying Macroscelides systematics and taxonomy, using phenotypical and DNA evidence. With notable divergence from other Macroscelides at every locus examined and very easily distinguishable morphological features, M. micus is the smallest of the sengis at less than 30g, and appears reproductively isolated. Subsequently, 19 living species are currently described (Rathbun, 2015) in two subfamilies with 4 genera: the giant sengis, Rynchocyoninae (Rhynchocyon, 4 species) and the soft-furred sengis, Macroscelidinae (Petrodromus, monspecific; Macroscelides, 3 species; Elephantulus, 11 species).

Relevance of Species Delimitation to Sengi Conservation

Having been placed in the super-cohort Afrotheria, strong molecular phylogenetic evidence has suggested an unusual ancestry and this information could make sengis a priority for conservation (Kuntner, May-Collado and Agnarsson, 2011). All sengi species are rare so their vulnerability to habitat loss and fragmentation due to anthropogenic effects is concerning , and those found at relatively low densities in forest ecosystems, namely all four species of giant sengis, sub-family Rynchocyoninae, are considered at risk (Nicoll and Rathbun, 1990). The 2013 IUCN Red List of mammals shows R. chrysopygus (the golden-rumped sengi) as “endangered”, R. petersi (the black-and-rufous sengi) and R. udzungwensis (the gray-faced sengi) as “vulnerable”, and R. cirnei (the checkered sengi) as “threatened”. Three species of Elephantulus are listed as “data deficient” and the rest are considered “least concern” (Rathbun, 2015). Knowing and communicating the accurate distribution and population dynamics of individual species is necessary for conservation and only possible under the correct delimitation of taxa (Agapow et al., 2004).

Sengis are habitat specialists, found over a wide variety of extreme African landscapes from dense forests to barren deserts (Rathbun, 2009) and sengi conservation programs have the potential to promote the protection of a variety of African ecosystems. For example, regions in South Africa may be good candidates for sengi conservation as they support a particular diversity of sengis: 2 species being endemic and seven other species are present, from three genera, (Smit et al., 2008). Since the conservation of the sengis in South Africa would need to include the preservation of their habitat, they could be part of an umbrella species scheme to aid the conservation of other rare and endemic species in their ecosystem (Branton, M. and Richardson, J.S., 2011; Hanser and Knick, 2011). However, widely distributed savanna species like those found in South Africa, seem to adapt readily to cultivation, forestry plantations and human development and probably do not require specific conservation programs, unlike forest dwelling sengis, such as Rhynchocyon udzungwesis (Nicoll and Rathbun, 1990). This emphasises the importance of accurate species delineation for the success of conservation action plans.

 

 

Conclusions

No species concept is without uncertainty and the importance of organism classification based on adequate sample sizes and combined genetic, morphological and behavioural information cannot be underestimated (Mace, 2004; Zachos, 2013). The variety of species concepts and related cladistics techniques used, can yield variable species numbers and relationships (Agapow et al., 2004; Wheeler and Meier, 2000). Such ambiguity surrounding the composition and relationships within and between populations and communities can make communicating the need for conservation prioritisation arduous (Mace, 2004), potentially leading to a spread of resources that overlook species of great importance to future ecology and evolution than might currently be realised (Frankham et al., 2012).

Even though the increased use of phylogenetics to confirm taxonomy, analyse diversity and inform management, is generally views as a positive development for conservation (Volkman et al., 2014), a case study by Bennett et al. (2014) showed that placing too much emphasis on evolutionary distinctiveness of species during conservation prioritisation elevated costs and increased risk of project failure, resulting in both lower species number and lower total phylogenetic diversity conserved. It is suggested that varying the emphasis on evolutionary distinctiveness in the prioritisation process can result in the opposite effect, an idea also suggested by Tucker et al., 2012.

Despite uncertainties and controversy surrounding species concepts, phylogeny and conservation, without an attempt at systematically acknowledging the unique traits that sets one group of organisms apart from another in ecosystems, there is the potential for the essential ecosystem functions associated with their exclusive ecologies to be overlooked all together (Ceballose and Ehrlich, 2009; Mooney, 2010).

 

References 

Appeltans, W.; Ahyong, S.T.; Anderson, G.; Angel, M.V.; Artois, T.; Bailly, N.; Bamber, R.; Barber, A.; Bartsch, I.; Berta, A. et al., 2012. The Magnitude of Global Marine Species Diversity. Current Biology, 22(23), 2189-2202.

Agapow, P.M.; Bininda-Emonds, O.R.P.; Crandall, K.A.; Gittleman, J.L.; Mace, G.M.; Mashall, J.C. and Purvis, A., 2004. The impact of species concept on biodiversity studies. The Quarterly Review of Biology, 79(2), 161-179.

Agrawal, A.A., 2001. Phenotypic Plasticity in the Interactions and Evolution of Species. Science, 294, 321-326.

Asher, R.J. and Lehmann, T., 2008. Dental eruption in Afrotherian mammals. [online] BMC Biology, 6(14). Available at: http://www.biomedcentral.com/1741-7007/6/14 [Date Accessed: 17/10/2015]

Bachmann, K., 2001. Species concepts – the continuing debate. New Phytologist, 149(3), 367-369.

Bennett, J.R.; Elliot, G.; Mellish, B.; Joseph, L.N.; Tulloch, A.I.T.; Probert, W.J.M., Di Fonzo, M.M.I.; Monks, J.M.; Possingham, H.P. and Maloney, R., 2014. Balancing phylogenetic diversity and species numbers in conservation prioritization, using a case study of threatened species in New Zealand. Biological Conservation, 174, 47-54.

Branton, M. and Richardson, J.S., 2011. Assessing the Value of the Umbrella-Species Concept for Conservation Planning with Meta-Analysis. Conservation Biology, 25, 9-20.

Buckley, T.R.; White, D.J.; Howitt, R.; Winstanley, T.; Ramo’n-Laca, A. and Gleeson, D., 2014. Nuclear and mitochondrial DNA variation within threatened species and subspecies of the giant New Zealand land snail genus Powelliphanta: implications for classification and conservation. Journal of Molluscan Studies, 80, 291-302.

Butler, P.M., 1995. Fossil Macroscelidea. Mammal Review, 25 (1-2), 3-14.

Butler, P.M., 1956. The skull of Ictops and the classification of the Insectivora. Proceedings of the Zoological Society of London. 126, 452-481.

Cadotte, M.W. and Davies, T.J., 2010. Rarest of the rare: advances in combining evolutionary distinctiveness and scarcity to inform conservation at biogeographical scales. Diversity and Distributions, 16, 376-385.

Carter, A.M.; Enders, A.C.; Kunzle H.; Oduor-Okelo D. and Vogel, P., 2004. Placentation in species of phylogenetic importance: the Afrotheria. Animal Reproduction Science, 82, 35-48.

Ceballos, G. and Ehrlich, P.R., 2009. Discoveries of new mammal species and their implications for conservation and ecosystem services. PNAS, 106(10), 3841-3846.

Cobert, G.B. 1971. Family Macroscelididae. In:  Meester, J. and Setzer, H.W., eds., The Mammals of Africa: An Identification Manual. Washington, DC: Smithsonian Institution Press, Washington, DC. 1-6.

Cobert, G. B. and Hanks, J., 1968. A revision of the elephant-shrews, Family Macroscelididae. Bulletin of the British Museum (Natural History), Zoology [online]. 16, 47-111. Available via: http://biodiversitylibrary.org/page/26204467 [Date Accessed: 15/10/2015].

Collins, J.P. and Halliday, T., 2005. Forecasting changes in amphibian biodiversity: aiming at a moving target. Philosophical Transactions of the Royal Society B. 360, 309-314.

Coyne, J.A and Orr, H.A., 2004. Speciation. Massachusetts: Sinauer Associates, Inc.

Dirlink, M.; Pavlov, P.; Stewart, A.J.A. and Virant-Doberlet, M., 2014. Mate recognition in duetting species: the role of male and female vibrational signals. Animal Behaviour, 90, 181-193.

DeSalle, R., 2006. Species Discovery versus Species Identification in DNA Barcoding Efforts: Response to Rubinoff. Conservation Biology, 20(5), 1545-1547.

Dumbacher, J.P.; Rathburn, G.B.; Smith, H.A. and Eiseb, S.J., 2012. Phylogeny and taxonomy of the Round-Eared Sengis or Elephant-Shrews, Genus Macroscelides (Mammalia, Afrotheria, Macroscelidea). PLoS ONE [online]. 7(3). Available at: e32410. doi:10.1371/journal.pone.0032410 [Date accessed: 12/11/2015].

Dumbatcher J.P.; Rathburn, G.B.; Osborne, T.O.; Friffin, M. and Eiseb, S.J., 2014. A new species of round-eared sengi (genus Macroscelides) from Namibia. Journal of Mammalogy, 95, 443-454.

Eldridge, M.D.B., Meek, P. and Johnson, R.N., 2013. Taxonomic Uncertainty and the Loss of Biodiversity of Christmas Island, Indian Ocean. Conservation Biology, 28(2), 572-579.

Evans, F.G., 1942. The osteology and relationships of the elephant-shrews (Macrosclididae). [online] Bulletin of the American Museum of Natural History, 80, 85-125. Available at: http://digitallibrary.amnh.org/handle/2246/1038 [Date accessed: 12/11/2015

Faith, D.P. and Richards, Z.T., 2012. Climate Change Impacts on the Tree of Life: Changes in Phylogenetic Diversity Illustrated for Acropora Corals. [online] Biology, 906-932. Available at: http://www.mdpi.com/2079-7737/1/3/906/htm [Date Accessed: 12/11/2015].

Feinberg JA, Newman CE, Watkins-Colwell GJ, Schlesinger MD, Zarate B., et al. (2014) Cryptic Diversity in Metropolis: Confirmation of a New Leopard Frog Species (Anura: Ranidae) from New York City and Surrounding Atlantic Coast Regions. [online] PLoS ONE, 9(10). Available at: doi:10.1371/journal.pone.0108213 [Date Accessed: 12/11/2015].

Filatov, M.V.; Frade, P.R.; Bak, R.P.M.; Vermeij, M.J.A. and Kaandorp, J.A., 2013. Comparison between Colony Morphology and Molecular Phylogeny in the Caribbean Scleractinian Coral Genus Madracis. [online] PLoSOne, 8(8). Available at: doi:10.1371/journal.pone.0071287 [Date Accessed: 19/11/2015].

Frankham, R.; Ballou, J.D.; Dudash, M.R.; Eldridge, M.D.B.; Fenster, C.B.; Lacy, R.C.; Mendelson, J.R.; Porton, I.J.; Ralls, K. and Ryder, O.A., 2012. Implications of different species concepts for conserving biodiversity. Biological Conservation, 153, 25-31.

Funk, W.C.; Caminer, M. and Ron, S.R., 2012. High levels of cryptic species diversity uncovered in Amazonian frogs. Proceedings of the Royal Society of B. 279, 1806-1814.

Grandcolas, P.; Nattier, R.; Trewick, S., 2014. Relict Species: a relict concept? Trends in Ecology and Evolution, 29(12), 655-663.

Hamilton, A. and Wheeler, Q.D., 2008. Taxonomy and why history of science matters for science. Isis, 99(2), 331-340.

Hanser, S.E. and Knick, S.T., 2011. Greater sage-grouse as an umbrella species for scrubland passerine birds: a multiscale assessment. In: Knick, S.T., and Connelly, J.W., eds., Greater Sage-Grouse. USA: Forest and Rangeland Ecosystem Science Center, 475-488.

Hausdorf, B., 2011. Progress towards a general species concept. Evolution, 65(4), 923-931.

Hedges, S. B. 2001. Afrotheria: Plate tectonics meets genomics. [online] Proceedings of the National Academy of Sciences USA, 98 (1-2). Available at: http://www.pnas.org/content/98/1/1 [Date accessed: 19/11/2015].

Herbert, P.D.N. and Gregory, T.R., 2005. The Promise of DNA Barcoding for Taxonomy. Systems Biology, 54(5), 852-859.

‘Insect Hunters’, 2002. The Life of Mammals, series 1, episode 2 [Television], BBC One, 27/11/2002.

Kerley, G.I.H., 1995. The round-eared elephant-shrew (Macroscelides proboscideus) as an omnivore. Mammal Review, 25, 39-44.

Kingdom, J., 1997. The Kingdon Field Guide to African Mammals. London: Academic Press.

Kuntner, M.; May-Collado, L.J., and Agnarsson, I., 2011. Phylogeny and conservation priorities of Afrotherian mammals (Afrotheria, Mammalia). Zoologica Scripta, The Norwegian Academy of Science and Letters, 40, 1–15.

Lagache L.,;Leger J.; Daudin J.; Petit R.J. and Vacher C., 2013. Putting the Biological Species Concept to the Test: Using Mating Networks to Delimit Species. [online] PLoS ONE, 8(6). Available at: doi:10.1371/journal.pone.0068267. [Date Accessed: 19/11/2015].

Leader-Williams, N.; Adams, W.M. and Smith, R.J., eds., 2010. Trade-offs in Conservation: Deciding what to save. Blackwell Publishing Ltd.

Leslie, M.S., 2015. Impacts of phylogenetic nomenclature on the efficacy of the U.S. Endangered Species Act. Conservation Biology, 29, 69-77.

​Lewis, R., 2015. Taxonomy, History of – Biology Encyclopedia. [online] Advameg, Inc. Available at: http://www.biologyreference.com/Ta-Va/Taxonomy-History-of.html [Date Accessed: 12/11/2015].

​Lohman, D.J.; Ingram, K.K.; Prawiradilaga, D.M.; Winker, K.; Sheldon, D.H.; Moyle, R.G.; Ng, P.K.L.; Ong, P.S.; Wang, L.K.; Braile, T.M.; Astuti, D. and Meier, R., 2010. Cryptic genetic diversity in ‘‘widespread” Southeast Asian bird species suggests that Philippine avian endemism is gravely underestimated. Biological Conservation, 143, 1885 – 1890.

Mace, G.M., 2004. The role of taxonomy in species conservation. Philosophical Transactions of the Royal Society of London B., 359, 711-719.

Mallet, J., 2009. Alfred Russel Wallace and the Darwinian Species Concept: His Paper on the Swallowtail Butterflies (Papilionidae) of 1865. Gayana 73(2).

Mallet, J., 1995. A species definition for the modern synthesis. Trends in Ecology and Evolution, 10(7), 294-299.

Mayden, R.L., 1997. A hierarchy of species concepts: the denouement in the saga of the species problem. In: Claridge, M.F. et al., eds., Species: the Units of Biodiversity, Chapman and Hall. pp. 381-424.

Mitchell, R.; Bleakly, D.; Cabin, R.; Chan, R.; Enquist, B.; Evans, A.; Lowrey, T.; Marshall, D.; Reed, S. and Stevens, G., 1993. Species Concepts. Nature, 364(6432), 20.

Merces, M.P.; Alfaro, J.W.L.; Ferreira, W.A.S; Harada, M.L. and Silva Jr., J.S., 2015. Morphology and mitochondrial phylogenetics reveal that the Amazon River separates two eastern squirrel monkey species: Saimiri sciureus and S. collinsi. Molecular Phylogenetics and Evolution, 82, 426–435.

Mooney, H.A., 2010. The ecosystem-service chain and the biological diversity crisis. Philosophical Transactions of the Royal Society B., 365, 31-39.

Noor, M.A.F., 2002. Is the biological species concept showing its age? Trends in Ecology and Evolution, 17(4), 153-154.

Nicoll, M.E. and Rathbun, G.B., 1990. African Insectivora and Elephant-shrews: an Action Plan for their Conservation. Switzerland: IUCN.

Olivieri, G.; Zimmermann, E.; Rasoloharijaona, S.; Rakotondravony, D.; Guschanski, K. and Radespiel, U., 2007. The ever-increasing diversity in mouse lemurs: Three new species in north and northwest Madagascar. Molecular Phylogenetics and Evolution, 43, 309-327.

Oduor-Okeloa, D.; Katemaa, R.M.; Cartern, A.M., 2004. Placenta and Fetal Membranes of the Four-toed Elephant Shrew, Petrodromus Tetradactylus. Placenta, 25, 803-809.

Papadopulos, A.S.T.; Baker, W.J.; Crayn, D.; Butlin, R.K.; Kynast, R.G.; Hutton, I. and Savolainen, V. 2011. Speciation with gene flow on Lord Howe Island. PNAS, 108(32), 13188-13193.

Patterson, B., 1965. The fossil elephant-shrews (Family macroscelididae). Bulletin of the Museum of Comparative Zoology, Harvard, 133, 295-335.

Pinzo, J.H. and La Jeunesse, T.C., 2011. Species delimitation of common reef corals in the genus Pocillopora using nucleotide sequence phylogenies, population genetics and symbiosis ecology. Molecular Ecology, 20, 311-325.

Poulakakis, N., and Stamatakis, A., 2010. Recapitulating the evolution of Afrotheria: 57 genes and rare genomic changes (RGCs) consolidate their history. Systematics and Biodiversity, 8(3), 395–408.

Rathbun, G.B. 2015. Elephantulus fuscus. [online] The IUCN Red List of Threatened Species 2015. Available at: http://dx.doi.org/10.2305/IUCN.UK.2015-2.RLTS.T42660A21288491.en. [Date Accessed: 19/11/2015].

Rathbun, G.B., 2009. Why is there discordant diversity in sengi (Mammalia: Afrotheria: Macroscelidea) taxonomy and ecology? African Journal of Ecology, 47, 1-13.

Rathbun, G. B., 1979. The social structure and ecology of elephant-shrews. Zeitschrift fur Tierpsychologie Suppl. 20, 1-77.

Regnier, C.; Achaz, G.; Lambert, A.; Cowei, R.H.; Bouchet, P. and Fontaine, B., 2015. Mass extinction in poorly known taxa. PNAS, 112(25), 7761-7766.

Richards, Z.T.; Miller, D.J. and Wallace, C.C., 2013. Molecular phylogenetics of geographically restricted Acropora species: Implications for threatened species conservation. Molecular phylogenetics and Evolution, 69, 837-851.

Robinson, T.J.; Fu, B.; Ferguson-Smith, M.A. and Yang, F., 2004. Cross-species Chromosome Painting in the Golden Mole and Elephant-Shrew: Support for the Mammalian Clades Afrotheria and Afroinsectiphilla but not Afroinsectivora. Proceedings: Biological Sciences, 271(1547), 1477-1484.

Rosauer, D.; Laffan, S.W.; Crisp, M.D.; Donnellan, S.C. and Cook, L.G., 2009. Phylogenetic endemism: a new approach for identifying geographical concentrations of evolutionary history. Molecular Ecology, 18, 4061–4072.

Rovero, F.; Rathburn, G.B.; Perkin, A.; Jones, T.; Ribble, D.O.; Leonard, C.; Mwakisoma, R.R. and Doggart, N., 2008. A New species of giant sengi or elephant-shrew (genus Rhunchocyon) highlights the exceptional biodiversity of the udzungwa Mountains of Tanzania. Journal of Zoology, 247, 126-133

Secretariat of the Convention on Biological Diversity, 2014. Global Biodiversity Outlook 4 [online]. Montreal, 155 pages. Available at: : http://www.cbd.int/GBO4. [Accessed on: 12/11/2015].

Seiffert, E. R. 2007. A new estimate of Afrotherian phylogeny based on simultaneous analysis of genomic, morphological, and fossil evidence. BMC Evolutionary Biology, 7(224), 13pp.

Simons, E.L.; Holroyd, P.A. and Brown, T.M., 1991. Early tertiary elephant-shrews from Egypt and the origin of the Macroscelidea. Proceedings of the National Academy of Sciences USA, 88, 9734-8737.

Smit, H.A.; Robinson, T.J.; Watson, J. and Jansen van Vuuren, B., 2008. A New species of elephant shrew (Afrotheria:Macroscelidea: Elephantulus) from South Africa. Journal of Mammology, 89, 1257-1269.

Springer, M.S.; Clevem, G.C.; Madsen, O.; de Jong, W.W.; Waddell, V.G.; Amrine, H.M. and Stanhope, M.J., 1997. Endemic African mammals shake the phylogenetic tree. Nature, 288, 61-64.

Staythorpe, M.J.; Madsen, O.; Waddell, W.G.; Cleven, G.C.; de Jong, W.W. and Springer, M.S., 1998a. Highly congruent molecular support for a diverse superordinal clade of endemic African mammals. Molecular Phylogenetics and Evolution, 9(3), 501-508.

Stanhope, M.J.; Waddell, V.G.; Madsen, O.; de Jong, W.; Hedges, B.; Cleven, G.C.; Kao, D. and Springer, M.S., 1998. Molecular evidence for multiple origins of Insectivora and for new order of endemic African insectivore mammals. Proceedings of the Natural Academy of Sciences USA, 95, 9967-9972.

State of Nature Partnership, 2013.  The state of Nature in the UK and its Overseas Territories. [online] The RSPB. Available at: http://www.rspb.org.uk/forprofessionals/science/research/details.aspx?id=363867 [Date Accessed: 12/11/2015].

Steele, P.R. and Pires, J.C., 2011. Biodiversity assessment: State-of-the-Art Techniques in Phylogenomics and species identification. American Journal of Botany, 98(3), 415-425.

Svartman, M.; Stone, G.; Page, J.E., and Stanyon, R., 2004. A chromosomal painting test of the basal Eutherian karyotype. Chromosome Research, 12, 45-53.

Taberlet, P.; Zimmermann, N.E.; English, T.; Tribsch, A.; Holderegger, R.; Alvarez, N.; Niklfeld, H.; Coldea. G.; Mirek, Z., et al., 2012. Genetic diversity in widespread species in not congruent with species richness in alpine plant communities. Ecology Letters, 15, 1439–1448.

Tabuce, R.; Marivaux, L.; Adaci, M.; Bensalah, M.; Hartenberger, J-L.; Mahboubi, M.; Mebrouk, F.; Tafforeau, P. and Jaeger, J-J., 2007. Early tertiary mammals from North Africa reinforce the molecular Afrotheria clade. Proceedings of the Royal Society B., 274, 1159-1166.

Tabuce, R.; Coiffait, B.; Coiffait, P-E.; Mahboubi, M.; Jaeger, J-J., 2001. A New Genus of Macroscelidae (Mammalia) from the Eocene of Algeria: A Possible Origin for Elephant-Shrews. Journal of Vertebrate Paleontology, 21(3), 535-546.

Tolliver, D.K., Robbins, L.w., Rautenback, I.L., Schlitter, D.A. and Coetzee, D.G., 1989. Biochemical systematics of elephant shrews from southern Africa. Biochemical Systematics and Ecology, 17, 345-355..

Tucker, C.M.; Cadotte, M.W.; Davies, T.J. and Rebelos, T.G., 2012. Incorporating Geographical and Evolutionary Rarity into Conservation Prioritization. Conservation Biology, 26(4), 593-601.

‘Under Open Skies’, 2014. Hidden Kingdoms, series 1, episode 1 [Television], BBC One, 16/01/2014.

van Dijk, M.A.M.; Madsen, O.; Catzeflis, F.; Stanhope, M.J.; de Jong, W. and Pagel M., 2001. Protein sequence signatures support the African clade of mammals. PNAS, 98(1), 188-193.

Vieites, D.R.; Wollenberg, K.C.; Andreone, F; Kohler, J.; Glaw, F. and Vences, M., 2009. Vast underestimation of Madagascar’s biodiversity evidenced by an integrative amphibian inventory. PNAS, 106(20), 8267–8272.

Volkmann, L.; Martyn, I.; Moulton, V.; Spillner, A. and Mooers, A.O., 2014. Prioritizing Populations for Conservation Using Phylogenetic Networks.[online]  PLoS ONE, 9(2). Accessible at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3938429/pdf/pone.0088945.pdf [Date Accessed: 12/10/2015].

Wirtz, N; Printzen, C. and Lumbsch, H.T., 2008. The delimitation of Antarctic and bipolar species of neuropogonoid Usnea (Ascomycota, Lecanorales): a cohesion approach of species recognition for the Usnea perpusilla complex. Mycological Research, 112, 472-484.

Wheeler, Q.D and Meier, R., eds., 2000. Species Concepts and the Phylogenetic Theory: A Debate. New York: Columbia University Press.

Williams, P.H.; An, J.; Brown, M.J.F.; Carolan, J.C.; Goulson, D.; Huang, J. and Ito, M., 2012. Cryptic Bumblebee Species: Consequences for Conservation and the Trade in Greenhouse Pollinators. [online] PLoS ONE, 7 (3). Available at: doi:10.1371/journal.pone.0032992. [Date accessed: 12/11/2015].

Woodall, P.F., 1995. The male reproductive system and the phylogeny of elephant-shrews (Macroscelidea). Mammal Review, 25, 87-93.

Wu, C-I., 2001. The genic view of the process of speciation. Journal of Evolutionary Biology, 14, 851–865.

Zachos, F.E., 2013. Species splitting puts conservation at risk. Nature, 494, 35.

Zack, S. P.; Penkrot, T. A.; Bloch, J. I.; Rose, K. D., 2005. Affinities of ‘Hyopsodontids’ to elephant shrews and a Holarctic origin of Afrotheria. Nature, 434, 497–501.

Zúniga-Reinoso, A. and Benítez, H.A., 2015. The overrated use of the morphological cryptic species concept: An example with Nyctelia darkbeetles (Coleoptera: Tenebrionidae) using geometric morphometrics. Zoologischer Anzeiger, 255, 47–53.

 

Pterotermes occidentis: colony structure, eusociality and research project study system.

Part of  a novel research project serving as BSc Zoology dissertation, produced only with the observational aid and expertise of Dr. David Crosse, Dr. Nicole Goodey, Prof. Michael Cant, Daniel Blumgart, and Ignatius W. van Rooyen. 

 

P. occidentis Phylogeny

P. occidentis is a primitive (lower) termite species (Oder: Dictyoptera; Family: Kalotermitidae). Termites share a common ancestor from the cockroach family (Cryptocercidae) and can be thought of as a specialised form of cockroach (Eggleton 2011). After decades of unclear hypotheses and poor taxon sampling, 7 majour termite clades (Families) have been decided upon as illustrated in the diagram on the right.

 

P. occidentis Natural Habitat

The ecological niche that P. occidentis fills in the North American Sonoran Desert to which they are endemic, is that of decomposers. They can commonly be found nesting in dead Arizonon Cercidium trees.

What little water they obtain comes from moisture found in their food source, rare rain storms and dew fall. They depend on the protection from extreme desert weather conditions that their nest, usually enclosed in a dead tree stem and branches, provides.

In September 2011, Prof. Michael Cant and Nicole Goodey extracted P. occidentis colonies from their natural habitat, near Tucson, Arizona for use in research. The colonies were re-established under controlled lab conditions at the Center for Ecology and Conservation, Cornwall.

I was introduced to this highly cooperative primitive termite species in January 2012, when I started working as a lab intern. Joined later by Dr. David Crosse, we began to refine laboratory techniques, starting work on angles of study based on previous work involving primitive eusocial insect species, and theories of cooperative animal behaviour and evolution.

 

 

 

P. occidentis Physiology

P. occidentis is soft-bodied. Workers lack pigmentation while Reproductives and Soldiers are usually an auburn brown colour. These are hemimetabolistic insects meaning they undergo stages of development (metamorphosis) without a pupal stage, but molting  between developmental stages to grow to maturity.

 

 

 

Cuticular Hydrocarbons (CHCs) found on the cuticle of insects are often cited as being particularly important for recognition cues in social insects however this is still a controversial theory.

Correlation studies have shown a wide variation in the CHC profiles between individuals from different colonies, and over time.  These variations in CHC’s between individuals may affect costly social behaviour of insects in a way which can be recorded and used to shed light on the mechanisms of social evolution.

 

 

P. occidentis Colony Structure 

P. occidentis colony life is a complex social system. The colony consists of different termites each of which specialises in a different role.

Pseudergates (sometimes called ‘workers’) lack pigmentation, are soft bodied and have no weaponry, although some may have wing buds at certain stages. Pseudergates grow in size, molting into different stages. They are mainly observed feeding and cleaning the colony, responsible for caring for eggs, the reproductives and soldiers, as well as building the nest.

Pseudergates also care for each other via interactions called trophalaxis and allogrooming. It is thought that they may also molt into soldiers and have been observed in the process of molting into neotenic reproductives in the event of the death of the original reproductuves. Little is known about the mechanisms of determing whether an individual remains a pseudergate, or develops into a solider or reproductive, at a certain point in time. However, it is thought that there may be a connection between environmental conditions, the current number of soldiers or reproductives present, the needs of the colony and whether or not new soldiers or neotenic reproductives are observed to appear.

The majority of the colony is made up of pseudergates at various stages of molt. Some grow wings when food is scarece in preparation for flying away to find a new food source and to start a new colony elsewhere. However, this transformation is reversible and if the food souce is replenished somehow, they lose their wing buds. Little is understood about how these termites determine the size of the food source and the amount of nutrition available at any point in time, or how they know the size of the colony itself.

Soldiers are dark brown in colour,  armoured, have very large heads equiped with pincers and exhibit agressive behaviour more often than other members of the colony. There are relatively few soldiers in the colony and they are responsible for nest defence.

P. occidentis nests are sometimes at risk of invasion by a rival colony in search of a new source of food, or interested in  merging colonies which involves destroying a colony’s current reporductives. Neither situation would be beneficial for the invaded colony as sharing their rare food source with a rival colony threatens their survival. They may also be genetically unrelated to the invading reproductives which means there would be a break down in the altruistic functions of the colony.

In the event of such colony invasion, soldiers may use their large heads to block the tunnels of the nest and their pincers to attack invaders. In this species, the pincers are nore particularly effective and P. occidentis seem to exhibit much lower levels of aggression than many other termite species.

Reproductives are larger than pseudergats but less bulky than soldiers. The older the reproductive, the darker its brown pigmentation and they also posess harder bodies than psuedergates but that are less armoured than soldiers. Each colony has a king and queen whose sole purpose it is to reproduce. Reproductives are less active than other colony members and are usually found together, surrounded by a dense gathering of pseudergates, constantly grooming and feeding their king and queen.

P. occidentis are hemimetabolistic insects, hatching from eggs as nymphs. They appear to be able to molt through nymphal stages, some eventually ending up as fully reproductive and others soldiers. The majority of individuals in the colony, though molting and growing in size, or even growing wing buds, reach neither the reproductive or soldier stage.

It is very important for the survival and efficient function of the colony that individuals of a colony at different stages can recognise each other as being both different, with different functions within the colony, as well as relatives from the same colony, and therefore entitled to the same colony resources and services.

I have observed that when a P. occidentis individual from one colony is introduced to members of a different colony, it is ignored. In other termite species, aggression between the colony members and the unrelated individual may be observed, but even though a non-aggressive approach to a stranger might seem counter productive for the security of the colony, it may work to prevent the occurrence of free riders from other colonies taking advantage of the social and resource benefits of a colony as previous studies suggest that social interaction is essential for the survival of individuals from primitive termite colonies.

Little is known about the mechanisms through which P. occidentis individuals distinguish between relative and non-relative individuals. Inhabiting tree stumps and branches means that termites live in total darkness most of the time and so do not have well developed eyesight, but rather seem to be able to detect changes in lighting. CHC detection or the use of gut symbionts as ways of sharing common markers and recognising each other have been suggested and researched.

In a very dry environment, where temperature extremes are not uncommon and essential resoures are hard to come by, the colony works together to grow and produce many members that all share 50% of their genes with each other as well as with their kign and queen. During this process, they pay a service to the ecosystem by re-working dead plant matter and in doing so, replenish the environment with essential nutrients for it’s continues existence and development.

 

Newly molted pseudergate lacking wing buds.

Older pseudergate with wing buds.

Neotenic reproductive.

 

 

P. occidentis Behaviour 

Common characteristics are found in species that have developed sociality and eusociality:

 1. Mating Systems: inbreeding with periodic out-crossing (for reduction of inbreeding costs) leads to high relatedness within a colony.

 2. Parental Care: (at least to some extent) allows for overlapping generations within a related social group.

 3. Helper evolution: due to high adult mortality, long periods of offspring dependence or delayed age of reproduction.

 4. ‘Fortress Defenders’: primitive (lower) termites often live inside their food source.

 5. Other factors: Mutualistic interactions and restricted dispersal can also foster the evolution of sociality.

 

P. occidentis are ‘fortress defenders’:

Three conditions are needed to explain the occurrence of eusociality in Fortress Defenders:

 – Food and shelter are enclosed in the same resource: the combination of being a long-lasting habitat making and food source makes for highly valuable.

– Due to high value, there is strong competition for the resouce .

– Due to competion, selection should promote evolution of effective defence among rival organisms.

Nestmate Recognition: 

The dry wood that P. occidentis live in and feed off is their most valuable resouce. The evolution of social behaviour is closely linked to the need to defend a valuable resource.

Recognition of nestmates, kinship, caste and reproductive status is crucial for individuals and for the colony as a whole: it is important for knowing who to share limited resources with.

The ability to effectively discriminate works to prevent intra- and interspecific parasitism and theft of limited colony resources.

Allogrooming:

Recognition cues in social insects are thought to be chemical, with hydrocarbons found on the cuticle of insects often cited as being particularly important. According to previous work, CHC composition may change over time and between colonies and individuals.

Because termite colony members may have naturally individual profiles, a constant hydrocarbon transfer may be needed to maintain a similar overall colony profile [Boulay et al. 2000, Campoutus fellah colony integration: worker individuality necessitates frequent hydrocarbon exchanges. Animal Behaviour 59, 1127-113.] and thus grooming between members of the same colony (nest-mates) is frequent.

Allogrooming is found in many social insect species and is a behaviour thought to facilitate the exchange of cuticular hydrocarbons involved in recognition cues.

For many social insects that are haplodiploid (producing some offspring with higher relatedness than others), well known theory of inclusive fitness is accepted to explain social behaviour. However, since termites are homoploid (producing only diploid offspring), inclusive fitness does not always explain termite social behaviour, necessitating further study. 

 

Read the full research study of Pterotermes occidentis completed for the Dissertation in BSc Zoology in 2013… 

 

Read the peer reviewed article published in the Royal Society Open Science online journal in 2016, as a results of the above mentioned work…

 

 

P. occidentis Study System

In September 2011, 4 colonies of varying instar composition and size (34, 112, 139 and 170 individuals) were extracted from dead Cercidium microphyllum trees at four different nesting sites near Tucson, Arizona.

​Each colony was contained inside a transparent Perspex box (206mm x 306mm x 31mm). Inside, slices of 8mm thick Cercidium microphyllum wood was packed next to each other to form an observable termitatium for each colony.

​The colonies were maintained in an incubator set at 28±2°C from 09:00 to 17:00 and 18±2°C from 17:00 to 09:00, on a corresponding Light-Dark cycle, and at a constant low humidity. Water was provided in the form of droplets generously sprinkled over the wood every two weeks.

​Each colony was allocated separate equipment and wood stock to control for cross-contamination of colony specific cuticular hydrocarbon compounds.

 

Light and temperature controlled incubator – left to right: observation arena and three custom designed termitaria on stands.

Light and temperature controlled incubator – paint-mark drying tray, initial design wooden termitarium containing MS1, two new design perspex termitaria.

RW1: Largest colony off its stand; majority of termites accumulated on underside of wood, away from light.

Wood slices: Cercidum wood imported from Arizona, sliced to 8mm in thickness and tied in place with wire through tiny air holes in the side of termitarium walls.

Pseudergate size demonstration.

Termites trying to hide from the light in a small crevice.

Handling Brush: due to soft, delicate bodies, picking individuals up with forceps was impossible. Using a brush to transfer them from one surface to another was harmless and quick.

Neotenic size demonstration: the neotenic from RW1.

Pseudergates size demonstration.

Pseudergates

KR3: Second-largest colony, closed up and on its stand.

Elevation: Wood slices lay on special serrated edges designed to stop termites getting trapped under the wood (causing damage and fatality), while still allowing full termite access to the wood, when termitaria are horizontal. These serrated edges also held wood in place when termitaria were vertical.

 

 

An introduction to Epigenetics

Summary

Epigenetics: the study of heritable changes in gene expression that cannot be explained by changes in DNA sequence.

Leads to an improved understanding of:

  1. Mechanisms underlying natural phenotypic variation

  2. Responses of organisms to environmental change

Further, more extensive research is needed as this is a relatively new, but fast growing branch of science that little is known about thus far.

The image below links to a dynamic presentation entitled “Epigenetics Explored” that I was heavily involved in creating and presenting. It served as a short introduction of main epigenetics concepts to a peer audience.

 

A Divided Developmental Strategy: The Evolution of Insect Metamorphosis.

A magazine article themed “beginnings”. 

 

Insects account for 80-90% of all animal species and the majority of these metamorphose; abruptly transforming in physical structure after hatching or birth. Biologists agree that for metamorphic development to have become so widespread it must hold advantages for survival and reproduction, but exactly how it evolved is a question that even now, lacks a definitive answer.

Insects follow different developmental paths and can be divided into three groups. Ametabolous insects such as the primitive silverfish, show little or no metamorphosis. Hemimetabolous insects including grass hoppers and dragonflies undergo incomplete metamorphosis; hatching as immature nymphal form until they develop wings and genitalia by their final adult moult.

Complete metamorphosis is seen in higher orders of insects such as moths, beetles, bees and flies, all known as holometabolous insects. These hatch as larvae, experiencing little structural change before moulting into a dormant pupa. After time, they emerge as fully formed, sexually mature, winged adults.

One of the best recognised examples of this latter process is the change from caterpillar to butterfly; the forms of which are so different that some early scientists believed they were different animals altogether. In 1669, Dutch naturalist and microscopist, Jan Swammerdam was the first to conclude that larval, pupal and adult insects are not distinct animals but different phases in the development of an individual, where juveniles mature into adults through the growth of pre-existing structures. Now known as imaginal discs, each pre-existing structure is set to eventually differentiate into legs, eyes, antennae or wings.

Caterpillars of the domesticated silk moth can often be found with rudimentary wing structures just under the skin. When such a caterpillar becomes a pupa, it encases itself in a protective coating

forming a chrysalis. Inside, the caterpillar’s tissues are dissolved by enzymes, forming a protein rich pupal soup which fuels the expansion of the imaginal discs and the consequential development of the moth form.

For incomplete metamorphosis there are three stages: 1) pro-nymph, 2) nymph and 3) adult, and can be seen as equivalent to the three stages of complete metamorphosis: 1) larva, 2) pupa and 3) adult. Thus, it is theorised by James Truman and Lynn Riddiford that complete metamorphosis most likely evolved from incomplete metamorphosis. Their suggestion that the holometabolic larval stage evolved 280 million years ago from the hemimetabolic pro-nymphal stage is supported by anatomical, genetic and hormonal evidence.

One group of hormones have proven to be an incredibly important component in metamorphosis evolution: juvenile hormone maintains the morphology of a life stage, suppressing moutling into a new form. They are found both in the pro-nymph and equivalent larval stages at high levels, however it is proposed that there has been a ‘time shift’, resulting in the juvenile hormone appearing earlier and being maintained for longer, leading to an extended pro-nymphal stage.

​
Hemimetabolous pro-nymphs can become nymphal inside the egg or a long as days after hatching. It is theorised that in evolutionary history, some hemimetabolous embryos experienced a genetic mutation causing incomplete absorption of the egg yolk before transforming into pro-nymphs.

Samia ricini (Eri silk moth) caterpillars and cocoon, photos courtesy of D. Blumgart.

 

The resulting extra resource may have created a selective pressure which was great enough for the evolution of pro-nymphs adapted to actively feed on extra yolk. Emergence from the egg before reaching nymphal stage could have led to actively-feeding pro-nymphs retaining this ability to feed on outside food sources.

The combination of an extended pro-nymphal stage as well as a pro-nymph that is capable of actively feeding is advantageous, allowing exploitation of a new environment that is distinct form the adult, therefore separating the resources needed for growth and reproduction.

Over generations the pro-nymphal stage would have become increasingly extended, enabling the eventual evolution of actively feeding pro-nymphs in to ever more caterpillar-like larvae. The pupal stage likely evolved later as a shortened, ‘sessile nymph’ stage so that the caterpillar could mature quickly into its reproductive, winged form.

In comparison to non-metamorphic species where young and adults compete for space and resources, the ecological niches which adults and larvae of metamorphic organisms occupy are very different. Caterpillars focused on leaf consumption and growth, have no interest in the activities of a butterfly found drinking nectar from flowers, searching of a mate. Eliminating the element of competition between the life stages for resources, and sharply dividing the efforts of growth and reproduction allows more individuals to succeed and therefore survive.
​
The sheer number of species on earth that have evolved to metamorphose leaves biologists without doubt that it is a successful strategy. We get continually closer to comprehensively understanding how a process as complex as metamorphosis has evolved, as new information is found theories are bound to be revised, corrected and built upon.

 

Samia ricini (Eri silk moth) adult, photos courtesy of D. Blumgart.