A case of reproductive character displacement in female palmate newts (Lissotriton helveticus).

Reproductive character displacement is commonly described as larger phenotypic differences between species living in sympatry rather than in allopatry. We investigated this phenomenon on two amphibians found in their contact zone where syntopic and allotopic sites alternate. To test the effect of syntopy with Lissotriton vulgaris on the Lissotriton helveticus phenotype, we studied the morphology of adult males and females while controlling for environmental factors (i.e. land use and flood risk). Using linear mixed-effects models, we found that females of L. helveticus expressed a deeper tail when in the presence of the other species, a pattern consistent with reproductive character displacement. This pattern has been rarely observed in Amphibians. It suggests that male newts incur large mating costs when selecting heterospecific partners. Our study also emphasizes that the evolution of mate recognition systems could occur at a microgeographical scale within a sympatric area.