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Systematics Section / ASPT

Bruneau, Anne [2], Faubert, Elyse-Ann [2], Fougère-Danezan, Marie [2], Nattier, Romain [2], Lewis, Gwilym P. [3], Herendeen, Patrick S. [1].

Patterns and rates of diversification in subfamily Caesalpinioideae (Leguminosae).

A phylogenetic analysis of 154 chloroplast matK gene sequences, representing 99 of the 156 recognised genera in subfamily Caesalpinioideae, and including exemplars from subfamilies Papilionoideae and Mimosoideae, was conducted to test the monophyly of groups supported in previous analyses and to examine patterns and rates of diversification in these early offshoots of the Leguminosae. The topologies obtained are consistent with those derived from chloroplast trnL-F sequences, with resolution at approximately the same taxonomic level, but matK analyses often yield higher clade support. Preliminary analyses, treating indels as separate presence/absence characters, yielded 777 equally parsimonious trees (CI=0.53, RI=0.85). As with previous analyses, tribes Cercideae and Detarieae s.l. are supported as monophyletic (100% bootstrap), while tribes Cassieae and Caesalpinieae are polyphyletic. Papilionoideae are sister to a clade that includes the Mimosoideae, and most Cassieae (except Dialiinae) and Caesalpinieae, while the Mimosoideae are sister to certain genera of the Dimorphandra group. Macro-fossil evidence from both the New and Old World is used to set minimum ages of crown and stem lineages in an analysis of divergence times. Among these we include several Detarieae fossils (assigned to Hymenaea (Dominican Amber, 17-24 Ma), resin-producing Detarieae (Paris Basin, 53 Ma), Aphanocalyx (Tanzania, 46 Ma)), and fossils attributed to the Caesalpinia (Midwest USA, 45 Ma), Umtiza (Colorado, 35 Ma) and Cercideae (Oregon, 36 Ma) clades. Preliminary analyses using the Non-Parametric Rate Smoothing method of Sanderson calibrated with these fossil constraints, suggests early branches in the legume phylogeny diverged between 40 and 55 Ma (Cercideae, Detarieae s.l., Dialiinae). Among these, the morphologically, ecologically and geographically diverse Detarieae represent some of the oldest caesalpinioid legume lineages (55 Ma).

1 - George Washington University, Biological Sciences, 2023 G St.NW, Washington, DC, 20052, USA
2 - Université de Montréal, Institut de recherche en biologie végétale, 4101 rue Sherbrooke est, Montréal, Québec, H1X 2B2, Canada
3 - Royal Botanic Gardens, Kew, Herbarium, Richmond, Surrey, TW9 3AB, U.K.

divergence times

Presentation Type: Paper
Session: 13-2
Location: Cottonwood C (Snowbird Center)
Date: Monday, August 2nd, 2004
Time: 11:15 AM
Abstract ID:293

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