Remnant native Phragmites australis maintains genetic diversity despite multiple threats

Abstract

Over the past century, an increasing number of species have been negatively impacted by anthropogenic factors such as habitat disturbance and introduced species. One such plant, Phragmites australis subsp. americanus is a perennial emergent grass found in tidal and inland marshes of the Atlantic coast of the United States. While rarely dominant, it grows in mixed communities and across much of this area its distribution has been reduced dramatically, likely due to eutrophication and the invasion of conspecific P. australis introduced from Europe. In this study, two noncoding cpDNA markers and six microsatellite loci were used to characterize genetic diversity among 58 remnant native P. australis stands from North Carolina to Maine. Five chloroplast DNA haplotypes were identified along with 42 multilocus genotypes. Bayesian exploration detected no population structure (e.g., optimal K = 1), indicating that these individuals form a single population. The analysis also detected no presence of hybrids of native and introduced P. australis in the samples, despite the close proximity of individuals to each other in many cases. These results suggest that the genetic composition of native P. australis across the region remains homogeneous and pure, providing managers with justification for its conservation and a potentially large source of germplasm for use in restoration activities.

Genetic and epigenetic changes during the invasion of a cosmopolitan species (Phragmites australis)

“…In the Great Lakes region, our result predicted a constant threat to the native P. Australis in which the native group exhibited a very low level of epigenetic variation, as well as genetic variation, possibly because of very rare hybridization between the native and introduced groups (Saltonstall, 2011). While the introduced group in the Great Lakes regions also had low genetic diversity relative to those in the Gulf Coast regions, this finding suggested that fewer introductions limited interbreeding there.…”

Physiological ecology and functional traits of North American native and Eurasian introduced Phragmites australis lineages

“…2010 a ; Saltonstall 2011), the underlying question is what caused the introduced lineage to become so invasive in North America? Our review clearly identifies gaps in our knowledge.…”

“…We only included studies that focused on native and non-native lineages along the Atlantic Coast, where clear genetic differences between the lineages had been demonstrated (Saltonstall 2011). We excluded work prior to 2002 in our review because the native and introduced lineages were typically not differentiated prior to that date.…”

The naming of Phragmites haplotypes

“…Subsequent work by myself and others have verified the utility of these minisatellites in defining haplotypes (e.g. Saltonstall 2003Saltonstall , 2011Meadows and Saltonstall 2007;Lambertini et al 2012a, b), although the suggestion of Vachon and Freeland (2011) to both include and exclude repetitive regions from data analysis in phylogeographic studies of Phragmites is an excellent way to test whether relationships suggested by including repetitive mutations are supported by a more conserved dataset that is largely distinguished by base substitutions. In cases where homoplasy is suspected, evaluation of other loci may be needed to resolve relationships.…”