Buddenhagen, Christopher , Mast, Austin , Thomas, W. Wayt .
Insights into the formation of savanna habitat in the New World tropics and subtropics from the chronogram of the tribe Rhynchosporeae (the beaksedges; Cyperaceae).
The shift from a predominantly forested, warm and wet world to one in which grasslands and savannas form vast biomes after the Oligocene is a poorly understood process. We seek to elucidate the processes and timing of grassland and savanna formation in the New World by looking at the evolution of the tribe Rhynchosporeae (the beaksedges; Cyperaceae), a diverse group of species found in forests and grasslands in tropical and warm-temperate America. We sampled chloroplast DNA sequences (the trnL/F region) from over 70 of the ca. 400 species in the tribe. We inferred the mean age of the crown group for Rhynchosporeae as 36 million years (95% credible interval= 17-58). Fitch parsimony reconstruction suggests that the crown group arose on the Brazilian Shield or in the Caribbean in savanna/grassland habitat, with considerable vagility in the lineage following that origin and at least 4 independent shifts into forest understory or edge. The Caribbean-origin result may be an artifact of sparse sampling of South American species from the early diverging clades in the phylogeny, and we expect a clearly South American origin with further sampling. Many of the SE N American Coastal Plain species share a close relationship, suggesting a migration of a common ancestor from the Brazilian Shield to that area ca. 25 million years ago. Subsequent diversification in the coastal plain has led to over 24 spp. found there. In developing the phylogeny for this analysis, we sampled 18 of the 28 hypothesized sections of Rhynchospora and found that 14 are not monophyletic.
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1 - Florida State University, Department Of Biological Science, 319 Stadium Drive, 319 Stadium Drive, Tallahassee, FL, 32306, USA
2 - New York Botanical Garden, Bronx, New York, NY, 10458-5126, USA
Presentation Type: Poster:Posters for Sections
Location: Battelle South/Convention Center
Date: Monday, July 9th, 2012
Time: 5:30 PM