Phylogeographic analyses and genetic structure illustrate the complex evolutionary history of Phragmites australis in Mexico.

Abstract

Genetic data suggest that three lineages of Phragmites australis are found in North America: the Native North American lineage, the Gulf Coast lineage, and the Invasive lineage. In Mexico, P. australis is a common species, but nothing is known about the distribution or ecology of these lineages. We examined the phylogeography of P. australis to analyze the current geographic distribution of genetic variation, demographic history, and dispersal patterns to better understand its evolutionary history in Mexico. We sampled 427 individuals from 28 populations. We used two noncoding regions of chloroplast DNA to estimate the levels of genetic variation and identified the genetic groups across the species' geographical range in Mexico. We compared the genealogical relationships among haplotypes with those previously reported. A hypothesis of demographic expansion was also tested for the Mexican P. australis lineages. We found 13 new haplotypes native to Mexico that might be undergoing an active process of expansion and diversification. Genealogical analyses provided evidence that two independent lineages of P. australis are present in Mexico. The invasive lineage was not detected with our sampling. Our estimates of population expansions in Mexico ranged from 0.202 to 0.726 mya. Phragmites australis is a native species that has been in Mexico for thousands of years. Genetic data suggest that climatic changes during the Pleistocene played an important role in the demographic expansion of the populations that constitute the different genetic groups of P. australis in Mexico.