Environmental gradients drive Asteroidea species turnover in the Magellan province

Magellan province rank among the most complex marine landscapes on Earth, where steep environmental gradients shape benthic biodiversity. We examined spatial patterns of sea star (Asteroidea) assemblages across 93 sampling stations spanning the Magellan province (41° – 56°S), encompassing the Chiloense, Kaweskar and Magallanes ecoregions and two depth zones (0–150 m; >150 m). A total of 2,850 individuals representing 32 morphospecies were identified, revealing pronounced latitudinal and bathymetric gradients in richness, abundance and diversity. Generalized linear and additive models identified latitude and depth as primary predictors of diversity, with temperature exerting a secondary influence and salinity showing limited explanatory power. Richness and diversity peaked in shallow Chiloense and deep Magallanes sites, underscoring the interaction between regional and vertical gradients. Multivariate analyses confirmed significant compositional differences across ecoregions and depths, with Ctenodiscus procurator emerging as the dominant species in most assemblages. High β-diversity values (0.4 – 0.8) indicated substantial species turnover rather than nestedness, reflecting strong spatial heterogeneity and limited faunal homogenization. These findings highlight the combined roles of geographic, bathymetric and environmental gradients in structuring sub-Antarcticsouthern Chilean benthic communities and provide a critical baseline for tracking biodiversity responses to ongoing climatic and oceanographic shifts in southern Chile.