Aim We investigated the roles of lithology and climate in constraining the ranges of four co-distributed species of Iberian saline-habitat specialist water beetles (Ochthebius glaber, Ochthebius notabilis, Enochrus falcarius and Nebrioporus baeticus) across the late Quaternary and in shaping their geographical genetic structure. The aim was to improve our understanding of the effects of past climate changes on the biota of arid Mediterranean environments and of the relative importance of history and landscape on phylogeographical patterns.
Location Iberian Peninsula, Mediterranean.
Methods We combined species distribution modelling (SDM) and comparative phylogeography. We used a multi-model inference and model-averaging approach both for assessment of range determinants (climate and lithology) and for provision of spatially explicit estimates of the species current and Last Glacial Maximum (LGM) potential ranges. Potential LGM distributions were then contrasted with the phylogeographical and population expansion patterns as assessed using mitochondrial DNA sequence data. We also evaluated the relative importance of geographical distance, habitat resistance and historical isolation for genetic structure in a causal modelling framework.
Results Lithology poses a strong constraint on the distribution of Iberian saline-habitat specialist water beetles, with a variable, but generally moderate, additional influence by climate. The degree to which potential LGM distributions were reduced and fragmented decreased with increasing importance of lithology. These SDM-based suitability predictions were mostly congruent with phylogeographical and population genetic patterns across the study species, with stronger geographical structure in the genetic diversity of the more temperature-sensitive species (O. glaber and E. falcarius). Furthermore, while historical isolation was the only factor explaining genetic structure in the more temperature-sensitive species, lithology-controlled landscape configuration also played an important role for those species with more lithology-determined ranges (O. notabilis and N. baeticus).
Main conclusions Our data show that lithology is an important constraint on the distribution and range dynamics of endemic Iberian saline-habitat water beetles, in interaction with climate and long-term climate change, and overrides the latter in importance for some species. Hence, geological landscape structure and long-term history may codetermine the overall range and the distribution of genetic lineages in endemic species with specialized edaphic requirements.