Biodiversity and biogeography of hydroids across marine ecoregions and provinces of southern South America and Antarctica

Abstract

To better understand the biodiversity-biogeographic polar connections between southern South America and Antarctica (SSA & A), we used benthic communities of hydroids as a model to investigate marine assemblages by evaluating classic spatial divisions at different geographical resolutions. Using a georeferenced dataset of 249 species and multivariate analyses, we investigated species' distribution, composition and biogeographic connectivity, and defined assemblages of ecoregions and provinces for the area. Hotspots of rich biodiversity at risk of depletion were defined. Analyses of ecoregions have a more stratified biogeographic structure, and reveal critical regions susceptible to loss of diversity. Analyses of provinces show a clear division between Atlantic-Pacific and Antarctic-Subantartic assemblages, with high biogeographic isolation of the Subantarctic islands. Depending on spatial resolution, the biogeographic position of the Magellan area is spatially contradictory, clustering on the one hand with SSA ecoregions and on the other with Antarctic provinces. Our patterns appear to be driven by different combinations of processes and barriers, reflected in the stratified distribution of hydroids. The high level of endemism and concentration of species at the edge of distribution in the Magellan area and Scotia Arc suggest their transitional nature and particular importance for understanding the historical and ecological connections between SSA & A.

Trait–environment relationships of hydroids (Cnidaria: Hydrozoa) across large spatial and environmental gradients in the Atlantic Ocean

“…Taller and more branched species were observed mainly in Staurotheca , Antarctoscyphus and Symplectoscyphus (Figures 2 and 4b). Staurotheca species of this study are endemic to the Southern Ocean region, whereas Antarctoscyphus and Symplectoscyphus are endemic to the SW Atlantic and Southern Ocean (Miranda et al, 2021). This suggests that the species traits of these genera, although correlated with the environment, are also evolutionarily conserved.…”

Community structure along the Western Antarctic continental shelf and a latitudinal change in epibenthic faunal abundance assessed by photographic surveys

“…High levels of endemism (Hempel, 1985;Griffiths, 2010;Gutt et al, 2013;Miranda et al, 2021) in the western shelf suggest research is needed to understand how diversity, community composition, and faunal richness will change with climate. Given the higher richness, abundance, and diversity of Peninsula region communities compared to the rest of Western Antarctica, further studies should be employed to better understand changes along the continental shelf and assess regions where benthic community diversity may be of interest (e.g., highly stable or highly variable regions).…”