WALLACE, ROBERT S. Department of Botany, Iowa State University, Ames, IA 50011-1020. - Taxonomic placement of morphologically anomalous genera of Cactaceae subfamily Cactoideae.
Several genera within the subfamily Cactoideae of the Cactaceae have
historically been taxonomically problematic, due to the difficulty of
confidently classifying them within the tribal groups of Buxbaum and
the subsequent recent variations on his classification for the
subfamily. Parallelisms, character loss, and nebulously-defined
tribal boundaries have contributed to this confusion, thereby
rendering modern intergeneric classification schemes less robust.
Forthcoming taxonomic revisions of the cactus family require the
assignment of these unusual genera within a defined tribal
classification. Specifically, these studies have been conducted to
evaluate the evolutionary affinities of the genera Deamia
Britton and Rose, Eulychnia Philippi, Harrisia Britton,
Stetsonia Britton and Rose, and Uebelmannia Buining
among others. To provide additional data to assist with tribal
placement of these problematic genera, variation in several molecular
markers from the plastid genome were used. Maximum parsimony
estimates of phylogenetic relationships for representatives of all
major tribal lineages within the subfamily Cactoideae were determined
and used to elucidate the position of the problematic genera.
Phylogenies inferred from these new data are used in concert with
morphological characters to determine the closest evolutionary
relationships for these genera. These studies will ultimately suggest
whether new morphological definitions of evolutionarily-related
generic groups need to be established to reflect a revised tribal
classification.
Key words: Cactaceae, Cactoideae, classification, molecular systematics, phylogeny