THE EVOLUTION OF CAYAPONIA (CUCURBITACEAE): REPEATED SHIFTS FROM BAT TO BEE POLLINATION AND LONG-DISTANCE DISPERSAL TO AFRICA 2-5 MILLION YEARS AGO

Premise of the study: The Cucurbitaceae genus Cayaponia comprises similar to 60 species that occur from Uruguay to the southern United States and the Caribbean; C. africana occurs in West Africa and on Madagascar. Pollination is by bees or bats, raising the question of the evolutionary direction and frequency of pollinator shifts. Studies that investigated such shifts in other clades have suggested that bat pollination might be an evolutionary end point. Methods: Plastid and nuclear DNA sequences were obtained for 50 accessions representing 30 species of Cayaponia and close relatives, and analyses were carried out to test monophyly, infer divergence times, and reconstruct ancestral states for habitat preferences and pollination modes. Key results: The phylogeny shows that Cayaponia is monophyletic as long as Selysia (a genus with four species from Central and South America) is included. The required nomenclatural transfers are made in this paper. African and Madagascan accessions of C. africana form a clade that is part of a polytomy with Caribbean and South American species, and the inferred divergence time of 2-5 Ma implies a transoceanic dispersal event from the New World to Africa. The ancestral state reconstructions suggest that Cayaponia originated in tropical forests from where open savannas were reached several times and that bee pollination arose from bat pollination, roughly concomitant with the shifts from forests to savanna habitats. Conclusions: Cayaponia provides the first example of evolutionary transitions from bat to bee pollination as well as another instance of transoceanic dispersal from the New World to Africa.