Systematics Section / ASPT
Douglas, Norman .
Understanding species limits and phylogeny of the vexing genus Boerhavia (Nyctaginaceae): AFLP and nuclear ITS data.
BOERHAVIA L. (Nyctaginaceae) is a widespread genus of herbaceous annuals and perennials, with a large fraction of species found in the deserts of North America. The plants are typically weedy, and often several species will be found at a given locality. The taxonomy of Boerhavia has long been troublesome (>200 published names for perhaps 40 spp.). Significant progress has recently been made in clarifying the taxonomy of the genus in North America. AFLP fragment and ITS sequence data are used to evaluate taxonomic morphospecies and reconstruct the phylogeny of Boerhavia. Ordination, AMOVA, and distance methods are applied to DNA fingerprint data from individual plants. While a few species are not supported, most taxonomic species appear to represent genetically cohesive groups. A similar pattern is found in ITS sequence data. These data clarify species limits and improve understanding of both where reticulation may be occurring, and for which morphospecies further taxonomic attention is warranted. The phylogeny of Boerhavia was reconstructed using AFLP fingerprints (pooled at the population level) combined with ITS data. This dataset was subjected to a simultaneous phylogenetic analysis in MrBayes, which permitted the use of a model of restriction site evolution for the AFLP data, and separate models for ITS1, 5.8s, and ITS2 stem & loop regions as determined by a secondary structure folding. Four main phylogenetic groups are identified, of which three are perennial. The fourth lineage comprises only annual taxa, which appear to have undergone a radiation in the Sonoran Desert. Though there is little ecological differentiation among the majority of species in the annual clade, many species are well marked by flower characters related to size (perianth length, stamen number). The phylogeny reveals these characters to be evolutionarily labile, hinting that pollination biology may partly explain diversification in Boerhavia.
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1 - Duke University, Department of Biology, 139 Biological Sciences Building, PO Box 90338, Durham, North Carolina, 27708, USA
Presentation Type: Oral Paper:Papers for Sections
Date: Monday, July 31st, 2006
Time: 9:30 AM