Rhabdiasesculentarum n. sp (Nematoda: Rhabdiasidae) from green frogs of the Rana esculenta species complex in Italy: molecular evidence, morphological description and genetic differentiation from its congeners in frogs and toads

A new taxon, n. sp., is described based on DNA sequence analysis at multiple loci (i.e. mtDNA , 12S rRNA, ITS-1 and partial ITS-2 regions of the nuclear rDNA) and morphometric analysis carried out on specimens collected from the green frogs of the species complex in Italy (i.e. Camerano and Linnaeus, identified genetically by diagnostic allozyme loci). n. sp. was differentiated genetically, at both mitochondrial and nuclear levels, from (Schrank, 1788) ( Hartwich, 1972) and Goodey, 1924 recovered from the toad Linnaeus collected sympatrically with the specimens of and examined in the present study. Moreover, the new taxon proved to be different from the other species of from anurans, which had previously been sequenced using the same genes and deposited in GeneBank. Phylogenetic analyses (MP and ML) inferred from mitochondrial (mtDNA and 12S ribosomal RNA) and nuclear (ITS-1 and ITS-2 of the rDNA regions) sequences datasets were congruent in depicting n. sp. as forming a highly supported clade distinct from the sympatric species , as well as from , characterised on the basis of the same loci. Morphometric analysis and the differential diagnosis of genetically characterised specimens of the new species have revealed differences in several features in comparison with the type-species, Material of the latter species included voucher specimens from Germany deposited by Hartwich (1972) and other specimens collected from in Italy. Among the diagnostic characters, the particular cup-shaped buccal capsule characterising is clearly different from the tear-shaped buccal capsule observed in material of obtained from Berlin Museum and collected in the same geographical area as the green frogs under study. was also found to differ in some measurements and allometric characters from ( Moravec et al., 1997). The data so far collected appear to indicate a host-preference of for and , which belong to the hybridogenetic species complex in Italy.