Testing hypotheses on disjunctions present in the primarily woody Boraginales: Ehretiaceae, Cordiaceae, and Heliotropiaceae, inferred from ITS1 sequence data

Hypotheses on the origin of the current distribution patterns and bicontinental disjunctions of Cordiaceae, Ehretiaceae, and Heliotropiaceae (Primarily Woody Boraginales) are tested by pairwise comparison of Kimura two-parameter distances. Estimated absolute dates of fossils and geological events (plate tectonics, climate changes) were used to calibrate a molecular clock. A mid-Cretaceous origin of the Primarily Woody Boraginales is proposed with an initial diversification in South America. Plate tectonics appear to play a minor role in their phylogeography. Most disjunctions are best explained by the rare events of long-distance dispersal because of the widespread occurrence of drupaceous fruits and their potential for endozoochoria. Furthermore, migrations and extinctions might have played a considerable role in the formation of the current distribution patterns.