Connecting the distribution and diversification of marine plants

Integration of the evolutionary history with distribution of extant species is necessary to explain present‐day diversity, particularly for ‘foundation' species, such as seagrasses, which create habitats of socioecological relevance. Here, we resolved if varying evolutionary history of seagrass families has imprinted the distribution ranges of extant species. Then, we resolved whether the persistence of seagrass families is linked to the extension of their ranges, particularly between those of predominant tropical or temperate distribution. We found strong phylogenetic signal for both the latitudinal midpoint and extent in the distribution of seagrasses, reflecting the legacy of the ancestral niche, with the latitudinal midpoint directly connecting with the thermal niches of extant seagrasses. Still, no phylogenetic signal was observed for the longitudinal extent and area covered by seagrasses. Tropical regions have accumulated seagrasses over longer periods, i.e. the tropics act as ‘museums' for seagrass' diversity, linked to longer phylogenetic lineages depth (a proxy to older species), wider ranges and lower extinction. Temperate families, with comparatively reduced ranges, have otherwise displayed an evolutionary history with considerable extinction. Still, Posidoniaceae show more recent speciation, so temperate regions are current ‘cradles' for seagrasses diversity. In conclusion, the persistence and diversification of seagrass families has imprinted their current ranges.