Systematics Section / ASPT
Straub, Shannon C.K. , Doyle, Jeff J. .
Phylogenetic Analyses in Legumes Using Multiple Low-Copy Nuclear Genes: Examples from Amorpha L.
LOW-COPY nuclear genes are an ever more important source of data for phylogenetic analyses as they become easier to identify and use in non-model taxa due to the wealth of genomic data from model organisms. Multiple low-copy, intron-containing genes identified using the extensive Medicago truncatula EST collections have been screened for phylogenetically informative variation in several papilionoid legume genera, including Amorpha, a taxonomically difficult North American genus of about 15 diploid and one tetraploid species. The prospective loci (sterol 24-C-methyltransferase, MinD, ARG1, PP1, MMK4, SBPase, CNGC5, Bcop, RPA2, subtilisin, and a gene for a putative chaperonin) were screened by performing test amplifications in a subset of species to survey the size and number of bands produced followed by sequencing if one band greater than 500bp was observed. Sampling was expanded if good sequence with intron variation among taxa was obtained. Among the regions examined up to this final step, low levels of sequence divergence were detected (0.7% to 1.1%), suggesting a recent origin of Amorpha. Although phylogenetic analyses have not provided much resolution of relationships among species, Amorpha appears to be paraphyletic due to the nested position of closely related taxa, Errazurizia rotundata and Parryella filifolia. Network analyses of haplotype data have been employed for assessment of relationships among Amorpha species. Using statistical parsimony at these low levels of divergence is sufficient to show relationships even when there is not enough phylogenetic signal to provide bootstrap support. Analyses of haplotype data from several loci also permit identification of population structure and admixture that can be used to assess if groups defined by patterns of genetic variation correspond to groups delimited based on morphology. These data also provide an opportunity to test whether genetic variation may be structured geographically, rather than by morphologically-based species delimitations, as suggested by chloroplast data.
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1 - Cornell University, L.H. Bailey Hortorium and Department of Plant Biology, 228 Plant Science Building, Ithaca, New York, 14853, USA
Presentation Type: Oral Paper:Papers for Sections
Date: Monday, July 31st, 2006
Time: 3:30 PM