CROZIER, BONNIE S.* and ROBERT K. JANSEN. Section of Integrative Biology and Plant Resources Center, University of Texas, Austin, TX 78712. - Historical relationships in the American desert plant family Cactaceae.
The study of evolution in deserts has been hindered by the lack of
reliable phylogenies for major desert plant groups. Cacti are
conspicuous members of the American deserts but notorious for
convergent evolution of morphological characters that has thwarted
phylogenetic analysis. We constructed a phylogeny of the Cactaceae
based on DNA sequence comparisons from 6,000 chloroplast nucleotides
and the nuclear Internal Transcribed Spacer. Sampling included more
than 120 species from all currently recognized subfamilies and tribes
of the family and outgroups from the Portulacaceae. Parsimony analysis
resulted in a well-resolved strict consensus tree with strong to
moderate bootstrap support for most branches. Some previously
hypothesized relationships are supported by these results, however
many others are not and provide new insights for improved taxonomy and
classification in the Cactaceae. Cacti inhabit warm deserts and cold,
temperate deserts and tropical, as well as other habitat types, making
them uniquely useful for comparative studies, and for understanding
historical connections between arid regions.
Key words: Cactaceae, deserts, molecular systematics