Reduced dispersal at non-expanding range margins: a matter of dispersers' identity

The evolution of dispersal at range margins received much attention recently; especially in the context of dynamic range shifts, such as those following climate change. However, much less attention has been devoted to study variation in and selection on dispersal at non-expanding range margins, where populations are often small and isolated, and empirical test is dearly missing. To fill this gap, we tested whether dispersal of an ant-dispersed perennial plant (Sternbergia clusiana), is quantitatively and/or qualitatively reduced toward a non-expanding range margin. We evaluated plant investment in dispersal structures (elaiosome), seed removal rates, and the relative abundance, activity and behavior of low- and high-quality seed dispersing ants in six sites ranging from mesic Mediterranean site (>600 mm of annual rainfall) to arid site (<100 mm of annual rainfall), which marks the southern range margin of the species. In a set of cafeteria and baiting experiments, we found that ov...