Physiology of a plant invasion : Biomass production, growth and tissue chemistry of invasive and native Phragmites australis populations

Differentiation within Phragmites australis, one of the world's most cosmopolitan and globally important wild plants, and invasions by individual lineages outside of their native ranges is attracting the interest of scientists worldwide. We compared the physiological performance of 89 populations representing distinct genotypes from six phylogeographic groups from Australia, Europe, North America (two groups including native and invasive populations introduced from Europe), South Africa and Far East in a common garden experiment. We show that the populations cluster into two distinct groups: one that includes populations from Europe and Far East together with the North American invasive, and the second the North American native populations with those from Australia and South Africa. Populations within the former group exhibited superior performance in the following traits: they were more vigorous in terms of higher shoot number per pot, greater belowground biomass, longer rhizomes, had greater specific leaf area (SLA), higher N and P concentrations in tissues, and greater investment into generative reproduction. Pooled across phylogeographic groups, P. australis has higher values of maximal photosynthesis (A max ), higher N and P concentrations in tissues, and greater SLA than most vascular plants, represented by the GLOPNET dataset. Whether due to a weak environmental match or genetic differences, the results indicate that invasion by Australian and African populations in the Northern Hemisphere seems unlikely at present. However, it is not possible to exclude the invasion of genotypes of European origin into Southern Hemisphere or other temperate regions.