Impact of colour polymorphism in free ranging asp vipers Sylvain Dubey, Daniele Muri, Johan Schuerch, Naïke Trim, Joaquim Golay, Sylvain Ursenbacher, Philippe Golay, Konrad Mebert
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Background Melanism in ectotherms Thermoregula8on advantage BeFer heat exchanges due to lower reflectance of black skin colour Fitness increase Fitness reducmon Loss in crypsis: increased preda8on risk in some species
Background What do we know today about repmles thermoregulamon? Higher thermal parameters within melanis8c morphs under experimental condimons: Hea8ng rates Equilibrium body T In natural environment? A bit more complicated: Thermoregulatory advantage I II III Thermal parameters Exposure (basking) dura8on and frequency Different (micro- ) habitat choice
Background Differences between color morphs in ectotherms Table 1 Summary of the evidence for color-mediated thermoregulation in living vertebrate ectotherms. Taxon Comparison Quanti fied reflectance Difference in Cooling rate Heating rate Equilibrium temperature Difference consistent in free ranging animals Source Amphibia Rana temporaria Black vs. light brown No Yes No Vences et al. (2002) Reptilia Cordylus spp. Black C. niger vs. brown C cordylus Yes No No No Clusella-Trullas et al. (2009) Ctenophorus nuchalis MSH treated vs. hypophysectomised Yes Yes Yes Rice and Bradshaw (1980) Elaphe quadrivirgata Black vs. brown No Yes Yes No Tanaka (2005, 2007) Liolaemus Silver vs. black Yes Yes Yes Pearson (1977) multiformis painted lizards Podarcis dugesii Black/brown vs. No Yes Yes No Crisp et al. (1979) green Tiliqua scincoides Melanistic vs. wildtype Yes Yes Yes No No This study vs. albino Thamnophis sirtalis Black vs. patterned No Yes Yes Gibson and Falls (1979a, 1979b) Thamnophis sirtalis Black vs. patterned No No Yes Bittner et al. (2002) Vipera berus Black vs. zig-zag morphs No Yes Yes No Forsman (1995) Geen, M.R.S.,Johnston,G.R.,2014. J.Therm. Biol. 43,54 60.
Aims of the study The asp viper (Vipera aspis) MelanisMc morph Polymorphic popula8on in western Swiss Alps & Switzerland Blotched morph 1 Does (micro)- habitat choice differ between the two morphs? 2 3 Do melanismc vipers have higher body temperature? Do melanismc vipers have higher fitness (Body condimon)?
Materials and methods 1 2 3 Sampling: Château d Oex (VD Switzerland) About 65% of melanism Captures: 608 captures (392 individuals) between 2012 and 2014 318 during 2014 Different types of microhabitats: Measures collected: Time of capture Coordinates of capture Air temperature Internal temperature (2014) Body size (Snout- vent length) Colour (melanismc or blotched) ReproducMve status for females Sex
1 Does (micro)- habitat choice differ between the two morphs? 2 3 Do melanismc vipers have higher body temperature? Do melanismc vipers have higher fitness (Body condimon)? 08.10.15 8
Materials and methods 1 Does (micro)- habitat choice differ between the two morphs? Environmental variables (Château d Oex): Al8tude Solar radia8on* (Res. 2x2m) Normalized difference vegeta8on index* (NDVI) (Res. 2x2m) Slope (Res. 2x2m)* Principal component analysis (PCA) (Micro)- habitat Summarize environmental variables in two dimensions (PC1 & PC2) * Computed predictors: NDVI and solar radia8on have been calculated as the average value for days included between April and September (independently of the year)
Materials and methods 1 Does (micro)- habitat choice differ between the two morphs? Vipers captured between 2012 and 2014 Model: GLMM 1 analysis: Response variable: First PCA axis (PC1) 2 analysis: Response variable: Second PCA axis (PC2) Explanatory variables: colour, sex, body size (SVL) + pairwise interac8ons Random: individual s idenmty and year * PCA axes retained from the PCA analysis carried out on environmental predictors
Materials and methods 1 Does habitat choice differ between the two morphs? SWITZERLAND Collec8on of data on the presence of colour paherns and melanism in 2033 individuals of V. berus (900-1970m; 53 pops) and V. aspis (94 pops) Popula8ons characterized by environmental variables relevant for the ecology of Vipera. We included the following variables: popula8on water balance (swb), annual number of degree- days above 3 C (ddeg3), annual number of days with frost (sfroyy), annual sum of precipita8on (precy), average temperature during the summer (tave59), annual mean cloudiness (clou) and annual sum of solar radia8on (srad). Principal component analysis (PCA) Summarize environmental variables (PC1 & PC2)
1 Does (micro)- habitat choice differ between the two morphs? 4 2 0 2 2 1 0 1 2 3 4 PC1 PC2 Melanistic Mean melanistic Mean non-melanistic 4 2 0 2 2 1 0 1 2 3 4 PC1 PC2 PC1 Non-melanistic A C Males Mean males Mean females Females altitude slope solrad NDVI Muri D., Schuerch J., Trim N., Golay J., Baillifard A., El Taher A., Dubey S., 2015. Journal of Thermal Biology 53, 107-112. 2012-2014 1400 1500 1600 1700 1800 1900 1200 1300 1400 1500 1600 Patterned Melanistic Patterned Melanistic Elevation (m) Canton of Vaud Bernese Oberland Castella B., Golay J., Monney J.C., Golay P., Mebert K., Dubey S., 2013. Journal of Zoology 290(4) pp. 273-280. N = 128 (2012) N = 153 (1988-1993) Château d Oex F 2,103 = 6.73, P = 0.018 Bernese Oberland F 1,149 = 7.57, P = 0.0067 High solar radia8on High al8tude Strong vegeta8on cover Steep slope High solar radia8on, Steep slope Strong vegeta8on cover High al8tude Results
Results 1 Does (micro)- habitat choice differ between the two morphs? Results and discussion High solar radia8on, high al8tude High solar radia8on, steep slope 1 PCA axis PC1 0.4 0.2 0.0 0.2 0.4 melanistic blotched 2 PCA axis PC2 0.4 0.2 0.0 0.2 0.4 males females Colour: P = 0.0024 Sex: P = 0.0006 Strong vegeta8on cover, steep slope Strong vegeta8on cover, high al8tude Muri D., Schuerch J., Trim N., Golay J., Baillifard A., El Taher A., Dubey S., 2015. Journal of Thermal Biology 53, 107-112.
Results 1 Does habitat choice differ between the two morphs? Polymorphic popula8ons (i.e. including melanis8c and paherned individuals) are restricted to cooler and weher habitats Switzerland Melanism is associated with thermoregula8on V. aspis: Polymorphic mean on PCA axis 1 = 0.13 Monomorphic on PCA axis 1 = - 1.88 V. berus: Polymorphic mean on PCA axis 1 = 0.26 Monomorphic on PCA axis 1 = 0.49 Broennimann O., Ursenbacher S., Meyer A., Golay P., Monney J.C., Schmocker H., Guisan A., Dubey S., 2014. Biology Le8ers 10, 20140638
Results 1 Does habitat choice differ between the two morphs? Switzerland
1 Does (micro)- habitat choice differ between the two morphs? 2 3 Do melanismc vipers have higher body temperature? Do melanismc vipers have higher fitness (Body condimon)? 08.10.15 16
Materials and methods 2 Do melanismc vipers have higher body temperature? 1 analysis: All vipers captured during 2014 2 analysis: Gravid females captured during 2014 Model: GLMM Response variable: internal temperature Explanatory variables: colour, (sex), body size (SVL), capture hour, month, PC1*, PC2* + pairwise interac8ons Random: individual s idenmty * PCA axes retained from the PCA analysis carried out on environmental predictors
Results 2 Do melanismc vipers have higher body temperature? ThermoregulaMon: Internal temperature in gravid females Internal T dendf Value Std.error F - value P - value Internal temperature ( C) 23 24 25 26 27 28 26.6 C melanistic blotched 24.6 C Intercept 53 24.66 0.71 1206.11 <.0001 Colour [melanis8c] 41 2.00 0.87 5.35 0.0258 MelanisMc gravid females have higher body temperature compared to blotched ones For all vipers captured during 2014 Colour had no significant influence on the internal temperature (P > 0.05) Muri D., Schuerch J., Trim N., Golay J., Baillifard A., El Taher A., Dubey S., 2015. Journal of Thermal Biology 53, 107-112.
1 Does (micro)- habitat choice differ between the two morphs? 2 3 Do melanismc vipers have higher body temperature? Do melanismc vipers have higher fitness (Body condimon)? 08.10.15 19
Materials and methods 3 Do melanismc vipers have higher fitness (Body condimon)? 5.5 5.0 Log (mass) 4.5 4.0 3.5 6.0 6.1 6.2 6.3 6.4 Log (SVL) Residual values of linear regressions with body mass (log- transformed) and body length (log- transformed SVL) as response and explanatory variables, respec8vely
Results 3 Do melanismc vipers have higher fitness (Body condimon)? Body condition 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0-0.01-0.02-0.03-0.04-0.05-0.06-0.07 N = 128 A 2012 Significant interac8on between coloura8on and sex (F 1,77.91 = 3.77, P = 0.0557), Higher body condi8on in melanis8c than in paherned females and no apparent differences in males 0.1 0.075 Female Male B Significant effects of the colour morph (F 1,56 = 4.74, P = 0.034) and of the reproduc8ve state Body condition 0.05 0.025 0-0.025-0.05-0.075-0.1 Non-gravid Gravid Gravid > non- gravid Melanis8c > paherned females BUT! In 2013 & 2014 NS Castella B., Golay J., Monney J.C., Golay P., Mebert K., Dubey S., 2013. Journal of Zoology 290(4) pp. 273-280.
Conclusions and perspec8ves I) Higher body temperature in melanis8c gravid females, but No difference within all vipers captured during 2014 WHY? Different microhabitat choice between morphs Different behaviour in terms of exposure (basking) dura8on and frequency Possible To verify II) Differences in body condi8on between melanis8c and non- melanis8c non gravid females only in 2012 and not in 2013 and 2014 WHY? Context dependant advantage Possible
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