DNA sequence data, multispecies coalescent and morphometrics shed new light on the systematics of Iberian islamiinae springsnails (Caenogastropoda: Hydrobiidae)

Abstract

Multilocus phylogenies have shown that soft-part anatomy alone is insufficient for the systematics of valvatiform- and trochiform-shelled springsnails of the subfamily Islamiinae (family Hydrobiidae) due to morphological similarities between taxa that are not closely related. However, a solid knowledge of their systematics and species boundaries is crucial to conserve this highly imperilled group. Here, we inferred molecular phylogenies based on two mitochondrial and two nuclear gene fragments from representatives of three morphological species of the Iberian genus Iberhoratia and performed multispecies coalescent and shell variation analyses (geometric morphometrics) to reevaluate their taxonomic status. The resulting phylogenetic analyses, which included homologous sequences of 15 other valvatiform-shelled hydrobiid species endemic to the Iberian Peninsula, depicted the topotypical specimens of I. aurorae and I. gatoa elisai distantly related to one another and the type species I. morenoi. Considering their high genetic divergence and morphological differences from other hydrobiid taxa, we have placed the former two species in the new genera Beatrix n. gen. and Actenidia n. gen. The multispecies coalescent delimitation method DELINEATE, a novel approach to the taxonomy of the Hydrobiidae, and shell morphometric data suggested two species within the ‘I. gatoa elisai’ clade. Based on morphological and molecular evidence, we recognized this clade as Actenidia, a new genus comprising the species A. elisai n. gen., n. comb. and A. baetica n. gen., n. sp. Our results underscore the importance of using multiple lines of evidence to delimitate species of Islamiinae and interpret their systematics. We also discuss the implications of our findings for conserving I. gatoa.