Systematics and Biogeography of Amicia
Tiina E. Särkinen and Colin E. Hughes
Abstract: The genus Amicia comprises seven species distributed disjunctly at mid-elevations across the neotropics with one species in Mexico and six endemic to restricted ranges in the Central Andes of South America. Phylogenetic analyses of nuclear ribosomal and plastid DNA
sequences show Amicia to be monophyletic and confirm its placement in the predominantly South American Adesmia clade of the dalbergioid legumes. Amicia is shown to be closely related to the genera Zornia and Poiretia. These three genera share the same fruit type, articulated loments ornamented with crests, and mostly paripinnate leaves with 2–4 leaflets; Amicia and Zornia further share large, conspicuous floral bracts not present in other genera of the Adesmia clade. Molecular age estimates derived from a plastid phylogeny with multiple accessions of all species suggest that the majority of species diverged 4–10 million years ago, and reveal long species stem lineages as well as robustly supported geographically restricted clades within some species. The geographically structured phylogeny suggests that isolation and dispersal limitation caused by uplift of the Andes has been an important driver of species diversification. A taxonomic account including an identification key, distribution maps, and illustrations for all species, is presented. A new subspecies of Amicia micrantha Harms, Amicia micrantha subsp. tarijensis Särkinen, is described from southern Bolivia.