Phylogenetics of the genus Scaevola (Goodeniaceae): implication for dispersal patterns across the Pacific Basin and colonization of the Hawaiian Islands

Abstract

Scaevola, the only genus of Goodeniaceae that has extensively radiated outside of Australia, has dispersed throughout the Pacific Basin, with a few species reaching the tropical coastal areas of the Atlantic and Indian Oceans. Five Australian and most of the non-Australian species are placed in Scaevola section Scaevola based on their fleshy fruits, indeterminate inflorescences, and more arborescent habits. Analyses of ITS sequence data demonstrate that Scaevola is a monophyletic group if S. collaris is excluded and Diaspasis filifolia is included. The genus is Australian in origin, but there have been at least six separate dispersal events from Australia. Four of these dispersals each resulted in single extra-Australian species. The remaining two were followed by radiations that gave rise to large groups, each including one of the widespread strand species, S. taccada and S. plumieri. Remarkably, three of the six dispersals established species on the remote Hawaiian Archipelago, representing at present the largest number of colonizations by any flowering plant genus to these islands.