Cryptic diversity within the rotifer Polyarthra dolichoptera along an altitudinal gradient

2. We sequenced 575 specimens of Polyarthra from 42 waterbodies from Germany, Hungary and Italy sampled in summer. Thirty-five lakes were distributed along an altitudinal gradient (250-2564 m a.s.l.) in a geographically restricted area, the Trentino-South Tyrol region, Italy, and one lake (Lake Tovel) was sampled in two basins and at different depths year-round to investigate temporal and spatial patterns of cryptic species. We used the Generalised Mixed Yule Coalescent model to delimit cryptic species (GMYC entities) based on a phylogenetic tree and related their presence/absence to space and the environment by applying Mantel tests and variance partitioning.

1. Cryptic species (species that are difficult or impossible to distinguish morphologically) are found worldwide and neglecting them may hamper our understanding of species-environment relationships. The rotifer Polyarthra dolichoptera occurs across wide environmental gradients, indicating the potential for a cryptic species complex. We used P. dolichoptera as a model to investigate spatial patterns and relationships of cryptic species with environmental variables along a broad altitudinal gradient.