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Pagano, Alain, and Pierre Joly (1998) Limits of the morphometric method for taxonomic field identification of water frogs. Alytes 16:3-4.

Abstract: Taxonomic identification of the water frogs has evolved since hybridogenesis has been revealed within the Rana esculenta complex. Although the study of protein polymorphism has proved robust in taxonomic information, morphometric measurements are currently used despite of some limits. By comparing results obtained with these two techniques, this study shows that morphometry is does not always provide a decisive taxonomic information for field identification. In the three populations studied, in the mid-Rhone floodplain, the morphs of Rana ridibunda and the hybrid R. kl. esculenta greatly overlap in morphometrical characters.

Plenet, S. and P. Joly, and A. Pagano (1998) Is habitat requirement by an oxygen-dependent frog (Rana ridibunda) governed by its larval stage? Arch. Hydrobiol. (1998) 143/1: 107-119.

Abstract: According to the literature and to our own experience, R. ridibunda is absent from ponds with occasionally low oxygen concentrations. We tested the effects of stochastically fluctuating oxygen concentration on tadpole survival and growth under laboratory conditions. Two experimental treatments (constant and fluctuating oxygen regimes) were arranged in a factorial design with three populations of R. ridibunda.
Stochastic oxygen fluctuation with drops from normoxia to hypoxia did not clearly influence long-term survival (which remained high in all blocks) or growth and development. Only in one population did survival differ between oxygen treatments, and survival was greater under the fluctuating than under the stable oxygen conditions. One population differed from the others in exhibiting slight variations in morphology between treatments. But in no case did these laboratory experiments provide evidence that oxygen regime can affect development of R. ridibunda tadpoles and explain oxygen-dependent habitat use by this species.

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