A taxonomic revision of amphitrichae, A new section of crotalaria (Fabaceae)

Crotalaria sect. Amphitrichae is described as new to give formal recognition to a strongly supported clade revealed by a recent molecular systematic study. The five known species are restricted to the arid western parts of southern Africa (C. colorata, C. excisa, C. humilis, C. meyeriana, and C. pearsonii). Species of the section are morphologically distinct in having (1) hairs distributed all around the distal part of the style; (2) ridge callosities on the standard petal blade and claw; (3) a rounded keel; (4) a twisted keel beak; and (5) a rounded style. A cladistic analysis of 18 morphological characters resulted in a well-resolved cladogram that recovers relationships within the section. The study revealed that two new species should be recognised, described here as C. giessii and C. kolbergii. A taxonomic revision of the section is presented, with descriptions, diagnostic characters, distribution maps, and illustrations of all seven recognised species.