A PHYLOGENY OF THE CHLOROPLAST GENE RBCL IN THE LEGUMINOSAE - TAXONOMIC CORRELATIONS AND INSIGHTS INTO THE EVOLUTION OF MODULATION

Phylogenetic analyses of the chloroplast-encoded rbcL gene in Legumino sae are consistent with previous hypotheses in suggesting that the fam ily as a whole is monophyletic, but that only two of its three subfami lies are natural. The earliest dichotomies in the family appear to hav e involved tribes Cercideae or Cassieae (subtribe Dialiinae), followed by Detarieae/Macrolobieae, ail of which are members of subfamily Caes alpinioideae. The remainder of the family is divided into two clades: (1) Mimosoideae and the caesalpinioid tribes Caeasalpinieae and Cassie ae (subtribes Ceratoniinae and Cassiinae); (2) Papilionoideae. Basal g roups within Papilionoideae are, as expected, elements of the grade tr ibes Sophoreae and Swartzieae. Major clades within Papilionoideae incl ude: (1) a Genistoid Alliance comprising Genisteae, Crotalarieae, Poda lyrieae, Thermopsideae, Euchresteae, and also some Sophoreae; (2) a cl ade marked by the absence of one copy of the chloroprast inverted repe at, with which are associated Robinieae, Loteae, and some Sophoreae; ( 3) Phaseoleae, Desmodieae, Psoraleeae, and most Millettieae, a group a lso marked by presence of pseudoracemose inflorescences; and (4) a wel l-supported clade comprising Aeschynomeneae, Adesmieae, and some Dalbe rgieae. Nodulation is most parsimoniously optimized on the rbcL strict consensus tree as three parallel gains, occurring in Papilionoideae, the caesalpinioid ancestors of Mimosoideae, and in the genus Chamaecri sta (Caesarpinieae: Cassieae).