Molecular phylogeny, taxonomy and evolution of the land snail genus Iberus (Pulmonata: Helicidae)

Partial DNA sequences of two mitochondrial genes [cytochrome oxidase subunit I (COI) and 16S rRNA] from 59 specimens of Iberus were used to test the validity of the described morphospecies of this genus, and examine genetic divergences within and between main phylogenetic groups. Both gene fragments showed phylogenetic concordance. The COI gene was found to be faster evolving than the 16S gene and was fully protein-coding with no insertions or deletions. 16S rRNA was more informative than COI for resolving basal nodes. Both individual and combined analyses of the two gene fragments revealed five main phylogroups. These five groups are genetically unique lineages that are allopatrically distributed and considered to have full species status. Further subdivisions were also considered. Shell morphology was suitable for delimiting species boundaries, but several incongruences between morphology and mtDNA phylogeny were observed. These incongruences were considered consequence of hybridization between Iberus cobosi and Iberus marmoratus, and the result of shell shape polymorphism in Iberus rositai. According to spatial patterns of sequence divergence, life habits and shell morphology may be concluded that the keeled-flat shelled snails independently originated several times within Iberus and they could represent cases of similar shell adaptation to a karstic arid environment.