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Biogeographic patterns of color and size polymorphisms in the European tree frog (Hyla arborea)
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Edité par CCSD ; Société Vaudoise des Sciences Naturelles -
International audience. Despite generally conserved phenotypes across radiations, Hylid frogs exhibit substantial intraspecific variation in size and coloration, especially the background color and the lateral black and white stripe patterns (linea marginalis). We examined these traits in a phylogeographic context across 14 populations (276 adults) representative of the three genetic lineages reported in the widespread European tree frog Hyla arborea. Body size was measured and field photographs were examined to identify discrete color morphs and evaluate stripe intensity. Most of the polymorphism depended on populations, with no effect of genetic diversity and lineage, suggesting that size and color patterns in H. arborea likely result from phenotypic plasticity or micro-evolution at the local scale, potentially mediated by local selective pressures and drift. Frogs belonging to the southern Balkan lineage, however, did feature generally whiter stripes compared to the other lineages. Interestingly, our analyses suggested that the linea marginalis differ between sexes throughout the range: it was overall whiter in males and may thus provide a visual contrast to facilitate nocturnal detection by females, which were experimentally shown to prefer conspicuous mates. Finally, the body size of the frogs, which significantly differed between sexes and populations, did not follow any particular biogeographic pattern, running against Bergmann’s rule. Our analyses provide a framework for future studies on the origin and maintenance of phenotypic variation in amphibians, especially to test the role of eco-geographical factors.
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