Ancestral Biogeography Reveals Diverse Origins of Costa Rica Margin Seep Invertebrates

Aim This work addressed the hypotheses that invertebrate species from hydrocarbon seeps at the Pacific Costa Rica Margin (CRM) would descend from adjacent biogeographic provinces, and that common ancestral histories would be identified across invertebrate groups. This research asked: (1) What are the ancestral biogeographic origins of seep species at the CRM and (2) do different invertebrate groups at the CRM show common ancestral origins? The aim of this study was to examine the evolutionary history of this novel and biodiverse region in the deep ocean. Location Costa Rica Margin, Pacific Ocean. Taxa Hydrocarbon Seep Invertebrates (Decapoda, Gastropoda, Bivalvia, Polychaeta). Methods Investigations utilised open‐source sequence data from NCBI GenBank to investigate the ancestral origins of 21 seep species across ten genera and three phyla. Phylogenetic frameworks were used as the foundation for reconstructing ancestral biogeographic ranges of species across time. Results A diversity of ancestral origins for CRM species was found, including the Caribbean Sea, the East Pacific Rise and the Northeast Pacific. Species under investigation originated throughout the Cenozoic, with a peak in diversification in the Pliocene. Almost a quarter of the species (mainly foundational, chemosynthetic taxa) showed evidence of vicariance with the Central American Isthmus, while those remaining (mainly consumers) showed Pacific origins. Connections to the Western Pacific implicate either long‐distance dispersal or unsampled stepping‐stone populations. No obvious patterning between ancestral ranges and mode of larval development was found. Main Conclusions The hypothesis that adjacent biogeographic provinces would give rise to CRM species was partially supported by shared ancestry with the East Pacific Rise and Central Northwest Atlantic, but was not supported by shared ancestries with the Northeast and Western Pacific. The hypothesis that common ancestral histories would be found among invertebrate groups was rejected, as nearly all taxa took a different evolutionary route to colonise the CRM. These results highlight the stochastic nature of speciation in the deep ocean, emphasising the interconnectedness of deep‐sea chemosynthetic ecosystems.