Population genetic structure and ecological differentiation in the bryozoan genus Reteporella across the Azores Archipelago (central North Atlantic)

Abstract

The processes shaping population dynamics of benthic marine invertebrates with non-planktotrophic larvae are still poorly understood but have seen a renewed interest in applying integrative taxonomic approaches. We used mitochondrial and microsatellite (SSR-GBAS) data to estimate connectivity across islands and seamounts in the central North Atlantic Azores Archipelago in five species of the bryozoan genus Reteporella Busk, 1884. Discordant patterns were inferred between datasets, which might be due to methodological constraints related to the application of multilocus approaches based on amplification to multiple species or due to interspecific introgression in deep waters. A divergent cryptic ecotype of Reteporella atlantica (Busk, 1884) was found in shallow waters, likely resulting from ecologically-driven incipient speciation, posing new questions regarding the role of bathymetrical zonation as a promoter of differentiation. The occurrence of ecologically-driven differentiation and potential interspecific introgression in other bryozoans should be considered, both with potentially important evolutionary and biogeographical consequences. The discovery of incipient species, prompted by ecological factors, calls for the need to consider marine invertebrates when developing conservation strategies in oceanic insular ecosystems.

Keywords

• Cryptic species
• Incipient speciation
• Bathymetry
• SSR-GBAS
• Azores Archipelago