Molecular investigations in western Palearctic water frogs
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In the green frog hybrids there exists an exclusive cytogenetic reproductive mechanism, referred to as hybridogenesis, whose evolutionary value is still under debate. As a contribution to the knowledge of the possible link between reproductive strategies and phylogenetic relationships, the analysis of repetitive DNA elements in the genomes of the Balkan green frogs, Rana epeirotica and R. shqiperica was carried out to compare their molecular DNA organization with those already known for R. ridibunda and R. lessonae. The Balkan species were chosen, because they give rise to spontaneous, although infrequent and not hybridogenetic hybrids with R. ridibunda. The elements of the RrSl family, a centromeric satellite DNA previously isolated in R. ridibunda, are clustered at centromeric regions also in both Balkan species, although the molecular organization of the RrSl sequences proved to be most similar in R. ridibunda and R. epeirotica. Furthermore, a repetitive DNA family (R1BamHI) is interspersed throughout the genome and is highly conserved in all species examined. Notably, the RIBamHI sequences, correlated to members of the hAT family, represent the first transposable elements found in the genus Rana. In the light of the results obtained so far, further studies are in progress with the aim of isolating and characterizing new families of repeated DNA, as additional results are required to compare the genomes of the different frog species and infer phylogenetic deductions on the genome evolution accompanying the speciation process and occurring inside the Palearctic green frog system. 2004 Taylor & Francis Group, LLC.
