Seeds contribute strongly to the spread of the invasive genotype of the common reed (Phragmites australis)

Abstract

The introduced subspecies of the common reed (Phragmites australis (Cav.) Trin. ex Steud. subsp. australis; Poaceae) is considered one of the most invasive plants in North American wetlands. Given its relatively low seed set and its tremendous capacity to spread via stolons or rhizomes, it has generally been thought that the spread of vegetative diaspores was responsible for the establishment of new populations. To test this hypothesis, we sampled a single plant from each of 345 visually-distinct common reed stands located along the shores of Lake St. François (southern Quebec, Canada). With a set of six nuclear microsatellite markers, we distinguished 134 different genotypes. The number of individuals sharing the same genotype ranged from one to 16, and averaged 2.1. Most genotypes were encountered only once. We examined the spatial distribution of the most frequent genotypes and found little evidence of clusters along the lakeshore. These data contradict the hypothesis that a common reed invasion is initiated by the introduction of vegetative diaspores from a few clones. Rather, they clearly support the alternative hypothesis that seeds were the primary diaspores responsible for the establishment of common reed populations.

The reproductive biology of Saccharum spontaneum L.: implications for management of this invasive weed in Panama

“…Although the average viability of these other species is typically much lower than the rates we have observed (e.g. less than 20 % for Phragmites australis (Kettenring and Whigham 2009)), they are aggressive invaders in North American wetlands and seeds play an important role in their dispersal (Belzile et al 2010;Daehler and Strong 1994;McCormick et al 2010).…”

Long-term effects of a Phragmites australis invasion on birds in a Lake Erie coastal marsh

“…Sexual reproduction in P. australis is not considered its primary reproductive strategy, but there is mounting evidence that reproduction via seeds is essential for colonizing new areas (Belzile et al, 2010;Kettenring et al, 2016;Kettenring and Mock, 2012). Seed dispersal and sexual reproduction appears to be more common in the introduced lineage than the native and potentially offer more opportunities for seedling establishment (Kettenring and Mock, 2012).…”

“…Seed dispersal and sexual reproduction appears to be more common in the introduced lineage than the native and potentially offer more opportunities for seedling establishment (Kettenring and Mock, 2012). In populations of P. australis that have been examined for genetic relatedness, there is usually a great deal of genetic diversity that is indicative of seeds as a primary reproductive propagule (Belzile et al, 2010;Stabile et al, 2016). The seeds of P. australis mature at the end of its growing season, from September to October, and it can take years after sprouting for flowering shoots to emerge (Ishii and Kadono, 2002;Saltonstall et al, 2010).…”

Life on the edge: reproductive mode and rate of invasive Phragmites australis patch expansion

“…Sexual reproduction and spread likely plays an important role in Phragmites colonization into disturbed habitats across its North American invasion (Belzile et al 2010;McCormick et al 2010a, b;Kirk et al 2011;Kettenring and Mock 2012;Albert et al 2015). Colonization of new areas by seed is likely episodic, coinciding with disturbance to matrix vegetation and hydrologic drawdowns resulting in exposed mudflats (ter Heerdt and Drost 1994;Clevering and Lissner 1999;Alvarez et al 2005;Wilcox 2012) because flooding greatly reduces seedling emergence and growth (Weisner et al 1993;Armstrong et al 1999;Mauchamp et al 2001;Chambers et al 2003;Baldwin et al 2010).…”