Polychaete distribution patterns revisited: an historical explanation

Abstract

AbstractBrooks Parsimony Analysis (BPA) was used to determine the patterns of relationships among areas (and their polychaete species), and whether or not they were caused by vicariance events. Ten clades representing 195 species and 24 global marine areas of endemism were analysed. Phylogenetic and distributional data were sourced from the literature. BPA yielded two minimal‐length area cladograms differing only in the placement of the South‐west Atlantic. Both area cladograms indicated three large‐scale area groups (=realms) related as follows: (Austral, (Boreal, Pantropical)), which correspond to the same three realms, albeit differently related, for terrestrial taxa. Within the Pantropical realm areas were grouped into east and west Tethyan subrealms and within the Boreal realm Atlantic and Pacific subrealms were found. This result is largely concordant with earth history under Plate Tectonics theory and indicates that vicariance has been influential in shaping the present‐day distribution of polychaetes. A model describing the hypothesised sequence of major vicariance events since the Late Jurassic (150 Ma) is illustrated. The existence of three marine biogeographic realms suggests that, for shallow water polychaetes at least, systematic studies would be more effectively conducted at the realm scale rather than global or regional scales.