Chloroplast DNA Intraspecific Phylogeography of Prairie Cordgrass (Spartina pectinata Bosc ex Link)

Chloroplast DNA (cpDNA) sequences are appropriate for studying intraspecific phylogeography. Comparing cpDNA phylogeny with different cytotypes provides insights into the origin and establishment of polyploid species. We have previously defined the geographic distribution of cytotypes in prairie cordgrass throughout the different regions of the United States. In this study, chloroplast haplotype variation is explored in 54 populations of prairie cordgrass, using nine noncoding chloroplast regions. These chloroplast analyses were combined with the cytotype surveys of prairie cordgrass to infer the phylogeography and to elucidate the origin of the different cytotypes. In this study, we identified three haplotypes, Prairie Cordgrass Group 1 (PCG1), Prairie Cordgrass Group 2 (PCG2), and Prairie Cordgrass Group 3 (PCG3). In general, related haplotypes were strongly associated with geographic distribution. Useful insertions-deletions (indels) were also found among prairie cordgrass populations. The PCG1 haplotypes collected inthe East North Central to the New England regions of the US, were polyploid (tetraploid, hexaploid, and octoploids), while the PCG2 haplotypes, found in southern South Dakota, Iowa, and Missouri, were primarily octoploids, but also included a small number of tetraploids. The PCG3 haplotypes were octoploids and were collected in North Dakota, South Dakota, and Minnesota.