The Cacteae Research Website is established for the dissemination of information relating to Cactaceae, Subfam. Cactoideae, Tribe Cacteae.
New Research in Cacteae:
Comparative biology of Cacteae (Cactaceae): the role of heterochrony in the evolution of form.
Charlie Butterworth, Desert Botanical Garden, 1201 N. Galvin Parkway, Phoenix, Arizona, USA 85008-3437
Mark Porter, Graduate Program in Botany, Rancho Santa Ana Botanic Garden, 1500 N College Ave., Claremont California, USA 91711-3157
Terresa Terrazas, Programa de Botanica, Colegio de Postgraduados, Montecillo, Estado de Mexico, Mexico
J. Hugo Cota-Sanchez, Department of Biology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
Cacti represent an astounding radiation of desert plants in the New World. With diverse morphological forms, cacti, especially members of tribe Cacteae, the North and Central American Barrel Cacti, are immediately recognizable to the vast majority of adults and children, and as such are reputed to be “Nature’s tough survivors.” Despite the group’s popularity, our knowledge of the nature of its radiation, and its genealogical relationships in Cactaceae, remains relatively poor, and different taxonomic treatments are often at odds, due in part to convergent and confusing morphologies. Over the last ten years, a number of studies have used DNA sequence data to resolve relationships among cacti and have demonstrated that, although some historic classifications of subfamilies and tribes reflect remarkable insight, phylogenetic relationships among genera and species in some groups, such as tribe Cacteae, remain elusive.
Previous research by the PIs has addressed a number of issues in tribe Cacteae. However, this research has been far from conclusive and highlights the necessity for a broad-scale, concerted, and collaborative research program aimed at the entire tribe. The proposed research will use modern molecular methods in conjunction with morphological to develop an estimate phylogenetic relationships, evaluate the tempo and mode of morphological evolution, examine the long-standing hypothesis that neoteny (a from of heterochronic change) is a common and repeated pattern of evolution, and to develop a classification in the tribe. Phylogenetic relationships of tribe Cacteae will be estimated using four regions of the chloroplast genome, two low-copy nuclear markers, and two regions of the mitochondrial genome. We will generate a comparative database of 183 morphological and anatomical traits that will be made available at the project’s website. The morphological data will be cladistically analyzed and evaluated using the molecular phylogenies to determine if suites of traits associated with heterochrony display excessively high homoplasy. Lastly, we will test 10 hypotheses of heterochronic evolution, to determine if neoteny is a common and important mode of evolution in tribe Cacteae, as suggested by several authors. This research will provide vital data for addressing taxonomic, developmental and conservation issues in this group of remarkably diverse cacti. Furthermore, the developmental (heterochrony) aspect of this study will form a foundation for future research on evolutionary development in cacti.