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Submitted to: American Journal of Botany
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 8/6/2004 Publication Date: 11/1/2004 Citation: Larson, S.R., Jones, T.A., Jensen, K.B. 2004. Population structure in pseudoroegneria spicata (poaceae: triticeae) modeled by bayesian clustering of aflp genotypes. American Journal of Botany. Interpretive Summary: Pseudoroegneria spicata (Poaceae: Triticeae) is an abundant, allogamous species widely adapted to the temperate, semiarid steppe and open woodland regions of western North America. Amplified fragment length polymorphism, neighbor-joining distance analysis, model-based Bayesian clustering, analysis of molecular variance, and related methods of hypothesis testing were used to investigate genetic diversity and population structure among 565 P. spicata plants from 82 localities representing much of the species distribution. Comparisons with four Asiatic Pseudoroegneria species and two North American Elymus wawawaiensis accessions demonstrate cohesiveness in P. spicata. However, P. spicata genotypes group by locality and geographic region based on genetic distance analysis. Average DNA polymorphism among P. spicata localities was significantly correlated (r = 0.58) with geographical distance. The optimum Bayesian cluster model included 2l P. spicata groups indicating that dispersal among sampling locations was not sufficient to group genotypes into one unstructured population. Approximately 18.3% of the DNA polymorphism was partitioned among the 21 regional groups, 14.9% among localities within groups, and 66.8% within accessions. Average DNA polymorphism among Bayesian groups was also correlated (r = 0.53) with the average geographic distance among Bayesian groups, which partly reflects isolation by distance. However, conspicuous regional boundaries were discernable among several divergent genetic groups. Technical Abstract: Pseudoroegneria spicata (Poaceae: Triticeae) is an abundant, allogamous species widely adapted to the temperate, semiarid steppe and open woodland regions of western North America. Amplified fragment length polymorphism, neighbor-joining distance analysis, model-based Bayesian clustering, analysis of molecular variance, and related methods of hypothesis testing were used to investigate genetic diversity and population structure among 565 P. spicata plants from 82 localities representing much of the species distribution. Comparisons with four Asiatic Pseudoroegneria species and two North American Elymus wawawaiensis accessions demonstrate cohesiveness in P. spicata. However, P. spicata genotypes group by locality and geographic region based on genetic distance analysis. Average DNA polymorphism among P. spicata localities was significantly correlated (r = 0.58) with geographical distance. The optimum Bayesian cluster model included 21 P. spicata groups indicating that dispersal among sampling locations was not sufficient to group genotypes into one unstructured population. Approximately 18.3% of the DNA polymorphism was partitioned among the 21 regional groups, 14.9% among localities within groups, and 66.8% within accessions. Average DNA polymorphism among Bayesian groups was also correlated (r = 0.53) with the average geographic distance among Bayesian groups, which partly reflects isolation by distance. However, conspicuous regional boundaries were discernable among several divergent genetic groups. |
