Cryptic diversity and population structure at small scales: the freshwater snail Ancylus (Planorbidae, Pulmonata) in the Montseny mountain range.

Anthropogenic impacts like intensified land use and climate change are severe threats to freshwater biodiversity and effective biodiversity monitoring is therefore one of the most urgent tasks. This is, however, often hampered by the lack of knowledge regarding the number and ecology of species. Molecular tools have shown many freshwater taxa to comprise morphologically cryptic species, which often occur in sympatry on a small geographic scale. Here, we studied the freshwater snail Ancylus fluviatilis (Mü ller, 1774) species complex in the Iberian Montseny Mountains. We hypothesized that (1) several species of A. fluviatilis sensu lato occur in the Montseny and (2) the different species seldom co-occur in syntopy due to different ecological demands or interspecific competition. We barcoded 180 specimens from 36 sites in the Montseny for the cytochrome c oxidase subunit I (COI) barcoding gene and molecularly identified two Ancylus species. These species seldom occurred in syntopy and a species distribution modelling approach showed differing bioclimatic preferences of the species. One species occurs mainly in cooler, higher altitude streams while the second species occurs in lower-altitude areas with higher temperatures. Tests of population structure showed that both species possibly do not disperse well in the study area and that populations within species might be adapted to certain bioclimatic conditions in different regions of the Montseny. Our results highlight the need to incorporate molecular techniques into routine monitoring programmes. [ABSTRACT FROM AUTHOR]