BUTTERWORTH, CHARLES A. AND ROBERT S. WALLACE.* Department of Botany, 353 Bessey Hall, Ames, IA 50011-1020. - Phylogenetic studies of the Cactus genus Mammillaria Haw. using chloroplast DNA sequence data.
The genus Mammillaria (Cactaceae subfamily Cactoideae)
comprises around 170 species of low growing cacti possessing
tuberculate stem morphologies, distributed throughout Mexico, the
Caribbean, northern South America and the southern USA. Generic
delimitation is difficult, morphologically due to close relationships
with Neolloydia, Coryphantha, Ortegocactus and
Escobaria. A number of infra-generic classifications of
Mammillaria have been proposed, and although based primarily on
morphological data, they are largely incongruent. Preliminary
chloroplast DNA sequence data suggest that Mammillaria, as
currently circumscribed is not monophyletic, and that previously
proposed infra-generic classifications need to be re-evaluated. This
paper presents results from chloroplast DNA sequence data aimed at
assessing the generic boundaries of Mammillaria and its
infra-generic classification.
Key words: Cactaceae, Mammillaria, phylogenetics