Marine biogeographic realms and species endemicity

TLDR

Marine biogeographic realms have been inferred from small groups of species in particular environments, but no global map based on statistical analysis of all higher taxa exists. This study analyzes 65,000 marine species to delineate 30 distinct realms, mirroring land‑area proportions. Statistical analysis of 65,000 species, including pelagic taxa, identified 30 realms and five nested pelagic realms. The resulting map shows that 42 % of species are realm‑endemic, identifies 18 continental‑shelf and 12 offshore deep‑sea realms, highlights pelagic microscopic plankton and megafauna as the most widespread species, and demonstrates how land barriers, salinity, depth, and environmental heterogeneity shape biota evolution, providing tools for marine reserves, biodiversity assessments, and climate change studies.

Abstract

Marine biogeographic realms have been inferred from small groups of species in particular environments (e.g., coastal, pelagic), without a global map of realms based on statistical analysis of species across all higher taxa. Here we analyze the distribution of 65,000 species of marine animals and plants, and distinguish 30 distinct marine realms, a similar proportion per area as found for land. On average, 42% of species are unique to the realms. We reveal 18 continental-shelf and 12 offshore deep-sea realms, reflecting the wider ranges of species in the pelagic and deep-sea compared to coastal areas. The most widespread species are pelagic microscopic plankton and megafauna. Analysis of pelagic species recognizes five realms within which other realms are nested. These maps integrate the biogeography of coastal and deep-sea, pelagic and benthic environments, and show how land-barriers, salinity, depth, and environmental heterogeneity relate to the evolution of biota. The realms have applications for marine reserves, biodiversity assessments, and as an evolution relevant context for climate change studies.