Dispersal rather than climate and local environment constrains non-marine snail fauna in west Greenland

Abstract

The biota of North Atlantic islands evokes intriguing questions on its evolution, colonisation routes, and an equilibrium between dispersal limitation and climatic/habitat constraints. While good data on non-marine snails exist for most of the islands, the data for Greenland were observed mainly between 1850 and 1900. The recorded species have been described as Greenland endemics, but this conclusion has never been fully questioned based on evidence. It can be assumed that these passively dispersing invertebrates are in fact of North American origin, due to the shortest distance to the mainland across the Davis Strait. To answer these questions, we collected the snail fauna at 72 sites of five locations across west Greenland. Our sampling revealed a very species-poor fauna, consisting of two aquatic and four terrestrial snail species. Based on mitochondrial and nuclear DNA sequences, the phylogenetic reconstruction and haplotype analysis showed that these taxa are either North American (all aquatic) or European (all terrestrial) in origin. None of them appeared to be endemic to Greenland and they were not even genetically distinct from the mainland populations. At both the macro and habitat scale, the Greenland snail fauna was found to be only a small fraction of the mainland species pool based on climate mapping and analysis of habitat requirements. While it appears to be limited mainly by dispersal, a detailed analysis of bird migration routes and intensity could not explain a puzzling difference in the biogeographical origin of the aquatic and terrestrial components. Terrestrial snails mimic the pattern seen in non-flying beetles, while the aquatic that of some flying insects. The results are a strong reminder that simple linear distance does not make a barrier, and that the barrier permeability can differ even within a group sharing the same dispersal mode and potential.