Hybridization and cryptic speciation in the genus Pacifigorgia

The shallow waters of the Tropical Eastern Pacific (TEP) harbor a species-rich octocoral fauna, with 7 genera and 124 octocoral species described to date for the region. Of these lineages, Pacifigorgia, with 35 species, is by far the most speciose and abundant shallow-water octocoral occurring in the region. The speciation mechanisms resulting in this remarkable diversity remain speculative, despite the extensive taxonomic and molecular systematic research conducted so far in this region. Using genome-wide SNP markers, we provide evidence for hybridization and extensive cryptic speciation in Pacifigorgia, suggesting that the genus' diversity has been underestimated by traditional systematic research. Our study highlights the difficulties faced by both traditional taxonomy and single-marker based molecular approaches to characterize octocoral diversity and evolution and the role of integrative molecular-morphological research to advance our understanding of this animal group.