Jean-Claude Monney

Influence of climate on the presence of colour polymorphism in two montane reptile species.

The coloration of ectotherms plays an important role in thermoregulation processes. Dark individuals should heat up faster and be able to reach a higher body temperature than light individuals and should therefore have benefits in cool areas. In central Europe, montane local populations of adder (Vipera berus) and asp viper (Vipera aspis) exhibit a varying proportion of melanistic individuals. We tested whether the presence of melanistic V. aspis and V. berus could be explained by climatic conditions. We measured the climatic niche position and breadth of monomorphic (including strictly patterned individuals) and polymorphic local populations, calculated their niche overlap and tested for niche equivalency and similarity. In accordance with expectations, niche overlap between polymorphic local populations of both species is high, and even higher than that of polymorphic versus monomorphic montane local populations of V. aspis, suggesting a predominant role of melanism in determining the niche of ectothermic vertebrates. However, unexpectedly, the niche of polymorphic local populations of both species is narrower than that of monomorphic ones, indicating that colour polymorphism does not always enable the exploitation of a greater variability of resources, at least at the intraspecific level. Overall, our results suggest that melanism might be present only when the thermoregulatory benefit is higher than the cost of predation.

Systematics of the Swiss asp vipers : some implications for the European Vipera aspis (Linnaeus, 1758) complex (Serpentes Viperidae) : a tribute to Eugen Kramer

Following the opinion expressed by Kramerin 1971, it is commonly accepted that the V aspis complex is composed of 5 subspecies: V a. aspis (Linnaeus, 1758), V a. atra Meisner, 1820, V a. francisciredi Laurenti, 1768, V a. hugyi Schinz, 1834 and V a. zinnikeri Kramer, 1958. However, this point of view was recently challenged and a number of subspecies were elevated to species rank. We had the unique opportunity to study the sample employed by Kramer to revalidate the subspecies V a. atra and V a. francisciredi. Using Kramer`s determinations, but another set of characters, we reanalysed his sample, by applying the same statistical methods (discriminant and canonical analyses), in order to determine whether observed differences among taxa were sufficiently distinctive to warrant recognition as subspecies. The preliminary results of our morphological study allow us to admit the validity of V a. francisciredi Laurenti, 1768, but also to question the subspecific rank of V a. atra Meisner, 1820. These conclusions agree perfectly with the results of our previous genetic study.

Diversifying selection and color-biased dispersal in the asp viper.

BackgroundThe presence of intraspecific color polymorphism can have multiple impacts on the ecology of a species; as a consequence, particular color morphs may be strongly selected for in a given habitat type. For example, the asp viper (Vipera aspis) shows a high level of color polymorphism. A blotched morph (cryptic) is common throughout its range (central and western Europe), while a melanistic morph is frequently found in montane populations, presumably for thermoregulatory reasons. Besides, rare atypical uniformly colored individuals are known here and there. Nevertheless, we found in a restricted treeless area of the French Alps, a population containing a high proportion (>50%) of such specimens.The aim of the study is to bring insight into the presence and function of this color morph by (i) studying the genetic structure of these populations using nine microsatellite markers, and testing for (ii) a potential local diversifying selection and (iii) differences in dispersal capacity between blotched and non-blotched vipers.ResultsOur genetic analyses support the occurrence of local diversifying selection for the non-blotched phenotype. In addition, we found significant color-biased dispersal, blotched individuals dispersing more than atypical individuals.ConclusionWe hypothesize that, in this population, the non-blotched phenotype possess an advantage over the typical one, a phenomenon possibly due to a better background matching ability in a more open habitat. In addition, color-biased dispersal might be partly associated with the observed local diversifying selection, as it can affect the genetic structure of populations, and hence the distribution of color morphs.