Breeding habitat partitioning in the Rana esculenta complex: The intermediate niche hypothesis supported
2001
Pagano, Alain | Joly, Pierre | PléNet, Sandrine | Lehman, Anthony | Grolet, Odile
The hypothesis of hybrids occupying intermediate niche was tested in the water frog hybridogenetic complex by investigating the variation of assemblage compositions in different habitats along a gradient of river influence in a large floodplain (upper Rhône, France). The parental species strongly differed in their habitat use. Whereas Rana ridibunda Pallas occupied dead arms close to the active channels, Rana lessonae Camerano occupied marsh ponds. The hybrid Rana kl. esculenta Linnaeus was found in the same ponds as Rana lessonae, as expected in L-E systems where Rana kl. esculenta females act as sexual parasites of Rana lessonae males. However, the proportions of each of these two taxa in mixed assemblages varied according to the degree of river influence, with Rana kl. esculenta predominating in ponds experiencing an intermediate level of flooding (alluvial marsh) and Rana lessonae predominating in less frequently flooded ponds (peat marsh). These results converge with other studies in demonstrating that the success of hybrid frogs depends on niche partitioning along an ecological gradient, which is probably a relevant templet for water frog evolution. In this evolutionary context, hybrid frogs have to deal with a trade-off between habitat selection and mate choice.
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