The role of evolutionary history has taken a back seat during the recent explosion of research on invasions. However, one of the best predictors of invasiveness is the size of a species’ geographic range in its native area. Indeed, in the case of Silene vulgaris, native range history appears to capture much of the “heavy lifting” during the evolutionary emergence of invasiveness.

Silene maritima along the southern coast of England (left and center) and in the rocky limestone landscape of the Burren in western Ireland (right).

Speciation and range divergence in the Silene vulgaris complex

While Silene vulgaris is a widespread and common weed throughout its native European range, its immediate congeners are non-weedy and much more restricted. The stark contrast between S. vulgaris and its coastal endemic sister taxa, S. uniflora (= S. maritima), suggests understanding the differences between these recently speciated taxa may shed considerable light on how range expansion evolves. Might these differences also have pre-adapted S. vulgaris towards contemporary invasiveness? This project is developing on several fronts. First, an ecological genomic approach will apply QTL mapping of traits that segregate between S. vulgaris and S. uniflora that are also under selection for invasiveness in S. vulgaris. Second, the historical polarity of major transitions in geographic range and demographic size will be determined for S. uniflora, S. vulgaris, and two of its endemic subspecies, S. vulgaris prostrata and S. vulgaris glareosa.

Segregation of flower number per inflorescence in artificial hybrids between Silene maritima and S. vulgaris (Data adapted from Marsden-Jones and Turrill, 1957). Inflorescence architecture typical of S. maritima (left) and S. vulgaris (right) are also shown. The same traits that differentiate these two taxa are also under strong selection during contemporary invasion of North America by S. vulgaris.

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Silene vulgaris shows a dramatic expansion if geographic range size relative to its sister species and other close congeners (range maps adapted from Atlas Florae Europeae; neighbor-joining phylogeny of ITS1 and 2). Across the genus Silene, geographic range size in Europe strongly correlates with the frequency of citation in the Global Compendium of Weeds.

From left to right: Silene vulgaris growing in a common garden in Ontario (2 pictures), infesting a hay field near Whitehall, VA, and alongside a rail yard in South River, Ontario.