Crypticity within supratidal rockpools

Abstract

Estimates of global biodiversity are usually limited by the existence of species with reduced or not apparent morphological differences. This handicap is frequently associated with ecologically specialised taxa due to environmental constraints through stabilizing selection. Supratidal rockpools are very dynamic environments with dramatic changes in water level as a result of cycles of rain and desiccation, which affect water availability and their physicochemical characteristics (e.g., salinity or temperature) and lead to a very specialised fauna. Here, we study the genetic diversity and phylogeographic patterns of supratidal rockpool Ochthebius (Coleoptera: Hydraenidae) in the Iberian Peninsula. We used both mitochondrial and nuclear DNA to highlight the presence of morphologically cryptic lineages, suggesting plausible dispersal barriers that help us understand their genetic isolation, fuelled by historical and contemporary marine hydrogeography. Past geological events (i.e., Messinian Salinity Crisis) matched the topological splits between lineages, whilst current wind and coastal oceanic currents determine the phylogeographical structure of Ochthebius lineages. This study shows that oceanic processes are also key to understand the evolutionary dynamics on the supratidal habitats. Moreover, we set the basis for deeper analysis of rockpool Ochthebius but further studies are needed for decision-making on whether these genetic lineages should represent novel species.