ITS2 variability of Biomphalaria (Mollusca, Planorbidae) species from the Paranapanema Valley (Sao Paulo State, Brazil):: Diversity patterns, population structure, and phylogenetic relationships

The ribosomal DNA internal transcribed spacer 2 (ITS2) has been shown to be a useful genetic marker for species identification and phylogenetic reconstruction in the genus of freshwater snails Biomphalaria (Preston 1910). Additionally, ITS2 studies in Biomphalaria have uncovered significant intra-specific genetic variability suggesting the presence of cryptic species complexes. We obtained ITS2 sequences for the Biomphalaria species B. glabrata, B. tenagophila, B. occidentalis and B. peregrina from the Paranapanema Valley (Sao Paulo State, Brazil) and compared them with a comprehensive set of published Biomphalaria ITS2 sequences using Bayesian inference of phylogeny. Analysis of the resulting trees showed that the newly obtained B. glabrata sequences did not cluster with those from other Brazilian localities and that sub-structuring occurred among Brazilian B. tenagophila populations. Moreover, although ITS2 sequences seem to indicate clear genetic differentiation within both B. glabrata and B. tenagophila, evidence in support of the occurrence of cryptic species is more compelling for the latter. We discuss the significance and implications of the detected patterns of ITS2 variability for taxonomic studies in Biomphalaria.