Introducing water frogs - Is there a risk for indigenous species in France?
The ecological success of introduced species in their new environments is difficult to predict. Recently, the water frog species Rana ridibunda has raised interest, as different genetic lineages were introduced to various European countries. The aim of the present study was to analyze the potential invasiveness of R. ridibunda and assess the risk of replacement for indigenous water frog species. The investigation of over 700 water frogs from 22 locations in southern France and four locations in Spain shows that the competition with indigenous species is mainly limited to a particular habitat type, characterized by high-oxygen and low-salinity freshwater. The competitive strength of R. ridib…
Is triploidy indisputably determinable in hybridogenetic hybrids by planimetric analyses of erythrocytes?
The size of amphibian erythrocytes is positively correlated to their DNA content. Therefore, planimetry of erythrocytes has long been used to determine ploidy levels in amphibians. In Rana esculenta. a hybrid originating from Rana ridibunda x Rana lessonae natural crosses, planimetric determination of erythrocyte size is used to distinguish diploid and triploid specimen. In the present study we performed planimetric analyses on the hybrid Rana grafi, comprising a second hybridogenetic system with its parental species Rana ridibunda and Rana perezi in southern parts of France. We found size differences of diploid and triploid erythrocytes to range between 26 and 33% in studies on adult R. es…
Inheritance in the water frog Rana ridibunda Pallas, 1771 - Is it Mendelian or hemiclonal?
The genome of Rana ridibunda has been detected in all known hybridogenetic water frog systems. This raises the question whether R. ridibunda is pre-adapted to reproduce hemiclonally by hybridogenesis. We allozymatically compared genotypes of primary oocytes and somatic cells of R. ridibunda females from several sites in southern France. In case of hemiclonal reproduction only one allele per locus is expected to be detectable in oocytes. However, patterns detected from oocytes of analysed females were not different from those of sexually reproducing water frogs. We therefore conclude that R. ridibunda in southern France reproduces sexually and is not pre-adapted to hemiclonal reproduction.