Multiple locus phylogeography to evaluate the diversity of the Cold Water Soft Coral Alcyonium spp. (Anthozoa, Octocorallia: Alcyonacea) between South America and West Antarctic Peninsula

The Antarctic marine environment has a unique geologic and climatic
history that has contributed to the evolution of a diverse range of
species. With the environment undergoing warming trends, it is critical to
understand the history of Antarctic species to anticipate the effect of
environmental changes on ecosystem functioning. Soft corals are a crucial
component of the benthic marine assemblage of the Southern Ocean, which is
recognized as a biodiversity hotspot. Nevertheless, our comprehension of
the biogeographical patterns and distribution of this group in the
Southern Ocean is insufficient. In this study, we used molecular
phylogenetic reconstructions, divergence estimations, and species
delimitations to examine the spatial patterns of genetic diversity in
shallow-sea octocorals of the Alcyonium spp. in the Southern Ocean and
adjacent regions, utilizing DNA sequences (mtMutS-COI and 28S) and Genomic
Single Nucleotide Polymorphisms (SNPs) markers. The study revealed
significant genetic differences between different populations, with a
clear genetic break observed between SA and WAP populations. We also
identified four putative species or evolutionary independent units (EIUs),
with one putative species found in the West Antarctic Peninsula, one in
the Patagonian region, and two found in Burdwood Bank and Falkland Island,
respectively. The divergence time estimation indicated that the
diversification process of Alcyonium began about 7.2 million years ago,
with the initial separation occurring between WAP and SA populations.
Furthermore, the study emphasized the critical role played by the Scotia
Sea islands, especially Burdwood Bank, in the evolution of Southern Ocean
biota. Overall, the findings provide evidence for the existence of
multiple species within the genus Alcyonium and information on
the evolutionary history of this group for the first time in the Southern
Ocean.