Microgeographic differentiation among closely related species of B iomphalaria ( G astropoda: Planorbidae) from the A ndean A ltiplano

Direct development and water dependence entail limited vagility in freshwater fauna. In these organisms, the population structure is probably linked to restrictions imposed by the habitat. In this study we investigate the relative contribution of processes stimulating the divergence of populations of B iomphalaria costata ( B iese, 1951) and B iomphalaria crequii ( C ourty, 1907), two freshwater snails occurring in two contiguous and fragmented closed basins from the A ndean A ltiplano using mitochondrial DNA (cytochrome  c oxidase subunit I) sequences, shell morphometric and radular morphology. In order to clarify the species boundaries, a third allopatric species was included: B iomphalaria aymara   V aldovinos & S tuardo, 1991. Molecular analyses recovered two distinct clades: one composed of B . aymara from the Isluga swamps and B . costata from S pring 1 in S alar de C arcote, the single spring occupied by this species, and another integrated by snails from 12 springs spread across the S alar de C arcote and the S alar de A scotán assigned to B . crequii , originally described from the S alar de A scotán. Unlike shell morphometrics, radular morphology was informative for distinguishing these species. The division of the lineages occurred in the L ate P leistocene. A subclade that includes snails from the southernmost springs in S alar de A scotán suggests fragmentation of the distribution of B .  crequii associated with landscape discontinuities. In addition to microvicariance signals, the private haplotypes scattered around both salt spans show that close‐range dispersal is a common biogeographic process in this species. As evolutionary units, the single isolated and restricted population of B . costata has a high priority for conservation. © 2013 The Linnean Society of London