Systematics/Phytogeography / Taxonomie/ Section
Guilliams, C. Matt , Simpson, Michael .
Phylogenetic relationships in the genus Calyptridium, Portulacaceae.
Calyptridium Nutt. is a small genus of 11 taxa of flowering plants in the Portulacaceae, or Purslane Family. Phylogenetic relationships have been difficult to resolve in the genus due to relatively low-levels of sequence divergence. For example, a recent phylogenetic analysis of the Western American Portulacaceae using two rapidly evolving DNA regions was able to resolve only two nodes within the genus with parsimony bootstrap values above 70. To extend this previous hypothesis of evolutionary relationships in the genus, I have sampled ITS of the nuclear genome and three regions of the chloroplast genome, rps16, trnQ-rps16, and ycf3-trnS. The genus is recovered as monophyletic and sister to Cistanthe ambigua. Two main lineages within the genus are recovered. One lineage, comprising the members of the "C. umbellatum complex", is well supported. Within this group, C. pulchellum is recovered as sister to a lineage consisting of C. umbellatum and C. monospermum. The other major lineage within Calyptridium, consisting largely of annual plants of California, is also well-supported. The earliest diverging taxon of this group, C. quadripetalum, is recovered as sister to a weakly-supported lineage comprising C. pygmaeum, C. roseum, C. monandrum, and C. parryi. Within this group, a lineage containing C. pygmaeum and C. roseum is sister to a polytomous assemblage consisting of C. monandrum and the varieties of C. parryi. Future analyses will include the External Transcribed Spacer (ETS) of the nuclear genome and at least one additional region from the chloroplast genome. It is possible, however, that relationships within the lineage comprising C. monandrum and the varieties of C. parryi are too shallow to be resolved with the rapidly-evolving DNA regions typically used to explore relationships at the species level (e.g., ITS).
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1 - San Diego State University, Department of Biology, 5500 Campanile Dr., San Diego, CA, 92182, United States of America
Presentation Type: Oral Paper:Papers for Sections
Location: Room 1/Woodward
Date: Monday, July 28th, 2008
Time: 10:00 AM