Systematics/Phytogeography / Taxonomie/ Section
Brokaw, Joshua , Hufford, Larry .
Polyploid Evolutionary Ecology in Mentzelia section Trachyphytum.
Ecological niche shifts have been suggested as a major factor favoring the establishment of polyploid lineages. To test this assumption, we explore patterns of niche lability and conservatism among polyploid complexes within Mentzelia section Trachyphytum. Section Trachyphytum contains 9 diploid species and approximately 15 polyploid species in several complexes. We estimated realized niche space for extant taxa using ecological data from over 200 populations across the distributional and ecological ranges of the species. The niche parameters for each population locality were composed of 1) climatological data, 2) soil chemistry, 3) substrate physical properties, and 4) estimated community biomass. We chose environmental variables from the full data set that significantly discriminated among taxa using Linear Discriminant Analysis and compared estimated niches using Principal Components Analysis. Both climatic and edaphic variables explained significant levels of variation in habitat niches among species. Ancestral state reconstructions based on current phylogenetic hypotheses generally suggest evolutionary lability and divergence of habitat niches during diploid speciation. In contrast, polyploid taxa exhibited a wide variety of ecological patterns. Niche size was generally correlated with size of geographic distribution. A minority of polyploid speciation events appear to be associated with shifts to extreme or novel regions of niche space. However, the majority of polyploid taxa exhibit intermediate niches consistent with putative hybrid origins. Many exhibit substantial overlap of geographical range and realized niche with putative parents and/or other polyploids, suggesting that open niche space may not be a prerequisite for establishment. Several polyploid taxa with high overlap of niche space appear to exhibit a strategy of colonization of disturbed sites.
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1 - Washington State University, School of Biological Sciences, Po Box 644236, Pullman, Washington, 99164-4236, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Room 3/Woodward
Date: Monday, July 28th, 2008
Time: 1:15 PM