Clay, Danielle , Tank, David , Egger, Mark , Smith, James F. .
Exploring interspecific hybridization in a rare endemic species of paintbrush (Castilleja christii , Orobanchaceae) using molecular and morphological techniques.
Interspecific hybridization is an important evolutionary force in angiosperms, driving extinction and speciation. Additionally, hybridization can have a major impact on species with narrow distributions; when rare species interbreed with more common congeneric species, the genome of the rare plants can become diluted. The genus Castilleja, (paintbrush, Orobanchaceae) has a high potential for hybridization. Castilleja christii is a rare, endemic paintbrush occurring on 200 acres at the summit of Mt. Harrison, Idaho. Observations of intermediate forms between C.christii and other congeneric species led us to explore putative hybridization events occurring on Mt. Harrison. We employed a combination of morphological and molecular data to assess the occurrence and extent of interspecific hybridization in this species. Morphological comparisons between parental types and field-identified hybrids were measured and analyzed using principle components analysis and a hybrid index. We employed the bi-parentally inherited nuclear waxy intron regions to characterize parental genotypes that were compared with the sequences from the putative hybrids to verify gene flow between putative parents and hybrids. Additionally, we employed maternally inherited chloroplast DNA microsatellites to determine the direction of hybridization. This research has implications toward conservations strategies that may contribute to the protection of Castilleja christii .
Castilleja has received recent in-depth attention phylogenetically (Tank and Olmstead, 2008; Tank et al, 2009), however Tank and Olmstead (2008) note that it is still important to study hybridization and life history in Castilleja , specifically organismal traits and rates of diversification. Studies are needed regarding the genetic integrity of Castilleja christii to ensure that introgression and hybridization are not threatening this species with extinction. Further, these results are the first of their kind in dealing with the rare endemic Castilleja christii , and will add to the overall knowledge of the Castilleja genus. These results will also assist managers in decisions regarding future species protections for Castilleja christii , and correlations between phenotypic and genotypic traits will enhance detectability and effective monitoring efforts of Castilleja christii . Additionally, results from this study are far reaching, in that they may be used as a model with which to assess the effects of hybridization on subsequent rare and/or endemic populations.
Tank , D. C. , and R. G. Olmstead . 2008 . From annuals to perennials: Phylogeny of subtribe Castillejinae (Orobanchaceae). Am. J. Bot. 95 : 608 – 625 .
Tank, D.C., et al., 2009. Phylogenetic Classification of Subtribe Castillejinae (Orobanchaceae). Systematic Botany 34(1): 182-197
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1 - Boise State University, Department of Biological Sciences, 1910 University Drive, Boise, ID, 83725, USA
2 - University of Idaho, Department of Forest Resources, Moscow, Idaho, 83844, USA
3 - University of Washington, Herbarium, Burke Museum of Natural History, Box 355325, Seattle, WA, 98195, USA
waxy intron regions.
Presentation Type: Oral Paper:Papers for Sections
Location: 555A/Convention Center
Date: Wednesday, August 4th, 2010
Time: 11:45 AM