A historical biogeographical protocol for studying biotic diversification by taxon pulses

Aim To present a historical biogeographical protocol for distinguishing biotic diversification by taxon pulse radiations from biotic diversification by vicariance. Location Mexico and northern Central America. Methods Brooks Parsimony Analysis (BPA), phylogenetic inference, linear correlation analysis. Results The taxon pulse radiation of 33 clades in nine areas of endemism in Mesoamerica is based on nine episodes of biotic expansion from three areas, and six episodes of vicariance, involving four geographical splits. Nineteen per cent of speciation events are due to vicariance, 25% to peripheral isolates speciation and 56% are within-area events. The species-area curve has a correlation coefficient (r(2)) of 0.47. Extinction events and species richness are highly correlated (r(2) = 0.75), but colonization events and species richness are poorly correlated (r(2) = 0.36), suggesting that colonization is not the main determinant of the species-area relationship. Colonization events are more poorly correlated with size of area (r(2) = 0.05) than are in situ speciation events (r(2) = 0.60). Colonization events and in situ events are poorly correlated (r(2) = 0.02). All areas of endemism have reticulated histories, and have acted as both sources and islands at various times. Main conclusions Taxon pulses can be distinguished from maximum vicariance using this protocol; refining it requires a method for generating area cladograms from complex data and incorporation of direct dating of evolutionary events.