Hybridization and speciation in angiosperms: a role for pollinator shifts?

Abstract

The majority of convincingly documented cases of hybridization in angiosperms has involved genetic introgression between the parental species or formation of a hybrid species with increased ploidy; however, homoploid (diploid) hybridization may be just as common. Recent studies, including one in BMC Evolutionary Biology, show that pollinator shifts can play a role in both mechanisms of hybrid speciation.

Figure 1

Allopolyploid species of Nicotiana (Solanaceae) and their parental diploid species. Note that the floral morphology of three of the polyploids, N. repanda, N. nesophila and N. stocktonii (allotetraploids, 2n = 48), is like that of N. sylvestris (a diploid, 2n = 24), adapted for nocturnal hawk-moth pollination, and the fourth, N. nudicaulis, is like that of the other parent, N. obtusifolia (2n = 24), adapted for bee pollination during the day. Photographs taken by Kar Yoong Lim.