Mcdade, Lucinda , Tripp, Erin .
A calibrated phylogeny for Acanthaceae supports multiple post-Oligocene dispersal events from Africa to the New World.
We have now documented more than a dozen examples among Acanthaceae of New World clades optimized as having African ancestors. In most of these cases, the New World clade has many more species than its African sister group. These patterns beg for further exploration including consideration of vicariance vs. dispersalist models to explain modern distributions, mode and path of dispersal (when appropriate), relative rates of diversification, and correlates (possible causes) of diversification. In this study, we build capacity to explore these clade level questions by calibrating the phylogeny for the family as a whole. We carefully assessed nearly 50 reports of fossil acanths for correct identification and quality of estimated age, ultimately accepting 16 as reliably identified and dated, and using eight as age constraints. With these and a phylogeny built from nearly 10 kb of DNA sequence data, we tested three competing biogeographical hypotheses to explain the distribution of the species-rich tropical family Acanthaceae: (1) vicariance related to the break-up of the southern, Gondwanan continents (65+ MYA); (2) Boreotropical dispersal (35-54 MYA); and (3) more recent trans-Atlantic dispersal. Our results point to rejection of the first two hypotheses, instead suggesting multiple post-Oligocene long-distance dispersal events followed by repeated episodes of extensive speciation in the New World tropics. We explore these results in the context of dispersal mechanisms, patterns of clade size asymmetry, and correlates of diversification.
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1 - Rancho Santa Ana Botanic Garden, Department Of Botany, 1500 N. College Avenue, Claremont, CA, 91711, USA
2 - Rancho Santa Ana Botanic Garden, 1500 N College Ave, Claremont, CA, 91711, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Delaware C/Hyatt
Date: Wednesday, July 11th, 2012
Time: 11:00 AM