The diversity and evolution of pollination systems in Annonaceae

Abstract

The pollination biology of Annonaceae has received considerable attention, with data now available for >45% of the genera (or genus-equivalent clades) included in recent molecular phylogenetic analyses. This provides a basis for understanding evolutionary shifts in the pollination system within the family. The present study focuses on subfamilies Anaxagoreoideae, Ambavioideae and Annonoideae, for which robust, well-resolved phylogenetic trees are available. Information is summarized on the pollination biology of individual clades and the evolutionary adaptations favouring different pollinator guilds evaluated. Although the majority of species of Annonaceae are pollinated by small beetles, five other pollinator groups are known: large beetles, thrips, flies, bees and cockroaches. Small-beetle pollination is inferred as the ancestral pollination system, with all other systems being derived. Evolutionary shifts to pollination by large beetles, thrips and flies are unlikely to have been significantly constrained by previous adaptations favouring pollination by small beetles, as many of the adaptations to these different pollinator guilds are similar (including protogyny, partially enclosed floral chambers and olfactory cues). In contrast, however, the evolutionary shift to bee pollination has presumably been constrained by both protogyny (as pollen-collecting bees are unlikely to visit pistillate-phase flowers) and the presence of floral chambers. © 2012 The Linnean Society of London.