Recent Long-Distance Dispersal Overshadows Ancient Biogeographical Patterns in a Pantropical Angiosperm Family (Simaroubaceae, Sapindales)

Detailed biogeographic studies of pantropical clades are still relatively few, and those conducted to date typically use parsimony or event-based methods to reconstruct ancestral areas. In this study, a recently developed likelihood method for reconstructing ancestral areas (the dispersal–extinction cladogenesis [DEC] model) is applied to the angiosperm family Simaroubaceae, a geographically widespread and ecologically diverse clade of pantropical and temperate trees and shrubs. To estimate divergence dates in the family, Bayesian uncorrelated rates analyses and robust fossil calibrations are applied to the well-sampled and strongly supported phylogeny. For biogeographic analyses, the effects of parameter configurations in the DEC model are assessed for different possible ancestral ranges, and the likelihood method is compared with dispersal–vicariance analysis (DIVA). Regardless of the parameters used, likelihood analyses show a common pattern of multiple recent range shifts that overshadow reconstruction of events deeper in the family's history. DIVA produced results similar to the DEC model when ancestral ranges were restricted to two areas, but some improbable ancestral ranges were also observed. Simaroubaceae exhibit an early history of range expansion between major continental areas in the Northern Hemisphere, but reconstruction of ancestral areas for lineages diverging in the early Tertiary are sensitive to the parameters of the model used. A North American origin is suggested for the family, with migration via Beringia by ancestral taxa. In contrast to traditional views, long-distance dispersal events are common, particularly in the Late Oligocene and later. Notable dispersals are inferred to have occurred across the Atlantic Ocean in both directions, as well as between Africa and Asia, and around the Indian Ocean basin and Pacific islands.