Systematics/Phytogeography / Taxonomie/ Section
Bruneau, Anne , Lewis, Gwilym P. , Herendeen, Patrick S. , Schrire, Brian , Mercure, Marjorie .
Biogeographic patterns in early diverging clades of the Leguminosae.
Subfamily Caesalpinioideae is a paraphyletic grade of 171 genera that comprises the first lineages of the Leguminosae and from which are derived the monophyletic subfamilies Mimosoideae and Papilionoideae. Recent phylogenetic analyses for nearly all caesalpinioid genera resolve several major groups within the caesalpinioid legumes as monophyletic: Cercideae, Detarieae, Dialiinae, and a Caesalpinieae s.l.-Mimosoideae clade (including several monophyletic formerly recognized generic groups). Relationships among the first branching lineages of the legumes are not well supported, with Cercideae, Detarieae and the genus Duparquetia alternatively resolved as sister group to all of the legumes; other inter-lineage relationships are strongly supported. Using 18 well documented fossil calibration points and the Penalized Likelihood method, we estimate the crown age of each of the major caesalpinioid lineages at 34 to 56 Ma. Two distinctive biogeographical patterns are prevalent among the caesalpinioids. In the Cercideae, Dialiinae, Detarieae, and Caesalpinieae s.l.-Mimosoideae clades a repeated pattern occurs where earliest divergent lineages comprise genera with restricted and highly predictable distributions. For example, the Umtiza clade, sister to the Caesalpinieae s.l.-Mimosoideae clade, has a present day distribution which may be the consequence of the fragmentation of once widespread ancestral taxa that were present around the northern rim of the seasonally dry to arid Tethys Seaway, with subsequent dispersal into the Southern Hemisphere via dry succulent biome corridors. Wet forest clades, which predominate in the Detarieae and Dialiinae, show widespread circumtropical relationships at the suprageneric level, although these become largely restricted to major continental regions at the generic level. This biogeographical pattern is, likewise, directly traceable to an early to mid-Eocene, Tethyan Seaway, dry environment diversification of the legume family. Overall, our analyses suggest that the present day distribution of caesalpinioid legumes is the combined result of historical plant migration combined with biome fragmentation, followed by more recent long distance dispersal events.
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1 - Université de Montréal, Institut de recherche en biologie végétale, 4101 rue Sherbrooke est, Montréal, Québec, H1X 2B2, Canada
2 - Royal Botanic Gardens, Kew, Herbarium, Richmond, Surrey, TW9 3AB, England
3 - George Washington University, Biological Sciences, 2023 G St.NW, Washington, DC, 20052, USA
4 - Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3AB, U.K.
divergence time estimates.
Presentation Type: Oral Paper:Papers for Sections
Date: Tuesday, July 29th, 2008
Time: 8:00 AM