TheMacroptilium gracilespecies complex (Fabaceae, Papilionoideae): an integrative taxonomic study based on morphological, molecular and ecological data

Abstract

AbstractMacroptilium gracile (Phaseolinae, Fabaceae) sensu lato is an extremely diverse species distributed from Mexico to Argentina. The taxonomic and nomenclatural history of the species is confusing, due to existing contrasting treatments. All 15 names corresponding to 12 taxa that have often been considered akin to M. gracile were selected here to clarify the identity of this taxonomic aggregate, using morphological, molecular and biogeographical analyses. Univariate and multivariate statistical analyses (nMDS and cluster) of 67 morphological traits were performed on a sample of 109 herbarium sheets. Maximum parsimony and Bayesian inference analyses were conducted using plastid (rpl32-trnL(UAG), trnK-matK-trnK) and nuclear (ITS/5.8S) DNA sequence data on a sample of 31 accessions belonging to taxa of the M. gracile complex and other Macroptilium spp., using three members of related genera (Phaseolus and Vigna) as outgroups. A database with plant locations per taxa was used to elaborate a distribution map, and the potential habitats were estimated through nMDS analysis. Our morphological, molecular and biogeographic results suggest that members of the M. gracile complex belong to three taxonomic entities, for which a new arrangement is proposed accepting Macroptilium gracile (with two varieties) and M. campestre, including two new nomenclatural combinations (M. gracile var. subcoriaceum and M. campestre). Types for all cited names are indicated where available (with a new lectotype designation). Morphological, ecological and distributional data are reported for each accepted taxon.