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Title: INVASIVE DYNAMICS AND GENOTYPIC DIVERSITY OF COGONGRASS (IMPERATA CYLINDRICA) AT THE POINT OF INITIAL INTRODUCTION IN THE SOUTHEASTERN UNITED STATES

Author
item CAPO-CHICHI, L.J.A - AUBURN UNIVERSITY
item Faircloth, Wilson
item WILLIAMSON, A - AUBURN UNIVERSITY
item PATTERSON, M - AUBURN UNIVERSITY
item VAN SANTEN, E - AUBURN UNIVERSITY

Submitted to: Invasive Plant Science and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/21/2007
Publication Date: 4/1/2008
Citation: Capo-Chichi, L., Faircloth, W.H., Williamson, A.G., Patterson, M.G., Van Santen, E. 2008. INVASIVE DYNAMICS AND GENOTYPIC DIVERSITY OF COGONGRASS (IMPERATA CYLINDRICA) AT THE POINT OF INITIAL INTRODUCTION IN THE SOUTHEASTERN UNITED STATES. Journal of Invasive Plant Science and Management. v1, Issue 2, p 133-141.

Interpretive Summary: Cogongrass [Imperata cylindrica (L.) Beauv.] is a non-native, invasive grass that is displacing native plant populations and causing much economic loss to forest-based ecosystems in the southeastern United States. Nine populations of cogongrass were included in a study of genetic diversity and spread dynamics at the point of initial introduction and its adjacent areas in the southern United Sates. AFLP and PCR analysis was conducted on single plant clones taken systematically from each population. Principal component analysis as well as cluster analysis separated overall clones into three main clusters. The initial population formed a separate subcluster. Gene flow (Nm), inferred from '-statistics, describing the genetic differentiation between pairs of populations ranged from 0.60 to 5.55. The rates of gene flow could offset population differentiation (Nm > 1), whereas for others random genetic drift could result in population divergence (Nm < 1). The lack of significant relationship between gene flow and geographic distance as well as genetic and geographic distances suggest that the invasion dynamics of I. cylindrica into the southern United States is primarily through human activity.

Technical Abstract: Nine populations of cogongrass [Imperata cylindrica (L.) Beauv.] were included in a study of genotypic diversity and spread dynamics at the point of initial introduction and its adjacent areas in the southern United Sates. Clones evaluated with two primer pairs yielded a total of 137 AFLP loci of which 102 (74.4%) were polymorphic. Within population variance accounted for 56% of the total variation and among population variance 44% (P < 0.05). Total gene diversity (HT) across all populations was estimated to be 0.18 and within population gene diversity ranged from 0.07 to 0.16 with the initial population catching the lowest value. This indicates high multilocus heterozygote deficits. No private alleles were found among the nine populations. Allelic differentiation was not correlated to geographic distance. Principal component analysis as well as cluster analysis separated overall clones into three mains clusters. The initial population formed a separate subcluster. Gene flow (Nm), inferred from '-statistics, describing the genetic differentiation between pairs of populations ranged from 0.60 to 5.55. The rates of gene flow could offset population differentiation (Nm > 1), whereas for others random genetic drift could result in population divergence (Nm < 1). The lack of significant relationship between gene flow and geographic distance as well as genetic and geographic distances suggest that the invasion dynamics of I. cylindrica into the southern United States is primarily through humans.