Wilson, Paul , Wolfe, Andrea D. , Armbruster, W. Scott , Thomson, James D. .
Constrained lability in penstemon flowers: how many convergent origins of hummingbird pollination?
OF the 284 species in the clade comprising Penstemon, Keckiella, Nothochelone, Chelone, and Chionophila, most display combinations of floral characters that facilitate pollination by Hymenoptera, which is the ancestral mode of pollination for this clade. Forty-one species present characters that serve to attract and make use of hummingbird pollinators, although some of these ornithophilous taxa are also visited by insects. The partially to wholly ornithophilous species are scattered throughout the traditional taxonomy and across phylogenies estimated from nuclear (ITS) and chloroplast DNA (trnCD and trnTL) sequence data. We estimate the number of separate origins of ornithophily, using bootstrap phylogenies and constrained parsimony searches. These analyses suggest 21 separate origins (or possibly a mixture of origins with some reversals). Because species sampling was incomplete, this could easily be an underestimate. Phylogenetic evidence for 10 origins of hummingbird pollination is overwhelming. This pattern of repeated evolutionary lability suggests that hummingbird pollination is an evolutionary attractor to which species with large sympetalous nectar-rich flowers can readily be drawn in certain ecological circumstances. That penstemons converge in such a complex array of functional traits makes evolution along one path seem facile in contrast to how conservative penstemons seem to be in not evolving to be pollinated by other types of animals such as long-tongued flies or Lepidoptera.
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1 - California State University, Biology Department, 18111 Nordhoff St, Northridge, California, 91330-0001, USA
2 - Ohio State University, Department of Evolution, Ecology and Organismal Biology, 300 Aronoff Laboratory, 318 W. 12th Ave., Columbus, Ohio, 43210-1293, USA
3 - King Henry I. St. University of Portsmouth, School of Biological Sciences, King Henry Bldg, Portsmouth, PO1 2DY, United Kingdom
4 - University of Toronto, Zoology, Toronto, Ontario, M5S 3G5, Canada
Presentation Type: Oral Paper:Papers for Topics
Date: Monday, July 31st, 2006
Time: 1:30 PM