Patterns of endemism in marine researches have been traditionally inferred from approaches ignoring the spatial component of endemism of such patterns. In this contribution, we used a method based on an optimality criterion that evaluates the spatial congruence among the distribution of different taxa and provides a value of endemicity to a given area regardless of how that it was hypothesized. This method has been widely applied to land environments, whereas in the sea it has not been well explored yet. We analyzed the geographic distribution of three crustacean groups (Amphipoda, Copepoda, and Euphausiacea) to search for areas of endemism (AEs) in the Magellan region by applying an optimality algorithm. To summarize among numerous resulting AEs, we employed a meta-consensus criterion based on a clustering analysis. We identified three main AEs and, into most of them, we recognized smaller areas for the first time: Chiloé, Atlantic coast (with a smaller area in San Jorge Gulf and Cape Blanco), and Fueguia (Channels and Fjords, Malvinas/Falklands, Burdwood Bank, and South-West Atlantic transition area). Both Atlantic coast and Fueguia do not strictly match the provinces previously defined in the literature. Our study lays the foundation for a biogeographic scheme into the Magellan region and provides new insights on zones currently placed in marine protected areas for the southern tip of South America, such as Burdwood Bank, Yaganes, and Diego Ramírez-Drake Passage. Integrating distribution patterns of many other organisms for the Magellan region will certainly help reinforce the conservation measures currently implemented.
