Tripp, Erin A. , Manos, Paul S. .
Is floral specialization an evolutionary dead-end? Pollination system transitions in Ruellia (Acanthaceae).
The very definition of a “pollination syndrome” suggests at least some degree of floral specialization. We studied the evolution of different pollination systems across 115 (of ca. 300 species) of Ruellia (Acanthaceae). Phylogenetic analyses, morphological ordination, ancestral state reconstructions, and a character mapping simulation were conducted to reveal key patterns in the direction and lability of floral characters associated with pollination. We found significant floral morphological differences among species that were generally associated with different groups of floral visitors. Floral evolution has been highly labile and also directional. Some specialized systems such as hawkmoth or bat pollination are likely evolutionary dead-ends. In contrast, specialized pollination by hummingbirds is clearly not a dead-end. We found evidence for multiple reverse transitions from presumed ancestral hummingbird pollination to more derived bee or insect pollination. These repeated origins of insect pollination from hummingbird-pollinated ancestors have not evolved without historical baggage. Flowers of insect-pollinated species derived from hummingbird-pollinated ancestors are morphologically more similar to hummingbird flowers than they are to other more distantly related insect-pollinated flowers. Finally, some pollinator switches were concomitant with changes in floral morphology that are associated with those pollinators. These observations are consistent with the hypothesis that some transitions have been adaptive in the evolution of Ruellia.
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1 - Duke University, Department of Biology, 137 Biological Sciences, Durham, NC, 27708, USA
Presentation Type: Oral Paper:Papers for Topics
Date: Wednesday, July 30th, 2008
Time: 2:00 PM