A Cladistic Analysis of Parkia (Leguminosae: Mimosoideae)

Abstract

A cladistic analysis of the tropical mimosoid genus Parkia was undertaken to examine relationships among the 31 species and to test the monophyly of the three recognized sections. The implications of the cladogram to the evolution of bat-pollination and biogeography were also explored. The analysis, based on 52 morphological characters, resulted in 408 most parsimonious trees. A consensus tree supports the monophyly of sections Parkia and Platyparkia, but section Sphaeroparkia is paraphyletic. The latter section is distinguished by a capitulum of all fertile flowers, a plesiomorphic attribute in this analysis. Characters supporting the monophyly of section Platyparkia include an inflorescence with distal nectar flowers having exserted styles, and fruits with seeds in two rows. Section Parkia is characterized by having sterile basal flowers with nectar flowers just above them, and calyx lobes included in bud. Bat-pollination was mapped onto one of the most parsimonious cladograms to examine the evolution of pollination syndromes within the genus. Our phylogeny is consistent with a single origin of bat-pollination and indicates that entomophilous species of Parkia are basal rather than secondarily derived. Sections Platyparkia and Parkia are separate lineages within the bat-pollinated clade and have independently developed capitulum types adapted to chiropterophily. Characters that are associated with chiropterophily include specialized nectar-producing flowers and basifixed anthers. Several characters, including presence of a staminodial fringe, a nectar ring, and pollen with verrucate sculpturing on the exine, probably represent increasing specialization for bat-pollination. The cladogram supports a South American origin for Parkia but is not consistent with a Gondwanan vicariance event as is usually hypothesized to explain its amphi-Atlantic distribution.