Non-native conditions favor non-native populations of invasive plant: demographic consequences of seed size variation?

HIERRO, JOSÉ L.

Coimbra

Workshop; The consequences of neo-allopatry Local adaptation, reproductive isolation and beyond; 2013

Centro de Ecología Funcional, Universidad de Coimbra

Interpopulation variations have been advanced as a mechanism to explain the greater abundance and impact of some organisms in their non-native ranges than in their native ranges. Here, we conducted reciprocal common gardens in southwestern Turkey (home) and central Argentina (away) to explore the hypothesis that greater success of the invasive ruderal Centaurea solstitialis L. in Argentina than Turkey is partially explained by differences between home and away populations. Unusual among common gardens, our experimental design included seed additions to explicitly evaluate population level responses, as well as disturbance and no-disturbance treatments. We documented seed mass in native and non-native populations, and during the experiment, we periodically measured density, plant size, and herbivory. After six months, we determined the establishment of plants from populations from both origins in both home and away common gardens. Seed mass was two times larger for Argentinean than Turkish populations. Density, plant size, herbivory, and final establishment were also greater for plants from Argentinean than from Turkish populations, but only in the common garden in Argentina. In Turkey, no differences between population origins were detected for any variable. As expected, disturbance generally increased plant performance in both regions. Our results suggest that the combined effects of local populations, mediated by demographic consequences of increased seed size, and the physical and the biotic conditions of central Argentina may contribute to the invasive success of C. solstitialis. This is the first study that experimentally supports the idea that seed size variation contribute to demographic differences for an invasive species between native and non-native distributions, but our findings further suggest that seed size effects on demography depend on the ecological context in which population processes occur.