Evolutionary analysis of seed size variation and its contribution to non-native invasion

ÖZKAN EREN; JOSÉ L. HIERRO

Congreso; 8th International Conference on Biological Invasions; 2014

Differences in phenotypic traits between native and non-native populations may explain how some species succeed in non-native ranges. Based on recent findings suggesting that larger seeds in non-native than native populations of the worldwide distributed Centaurea solstitialis L. favor seedling establishment under non-native conditions, we initiated an evolutionary analysis of seed size variation in the species. In the current work, we addressed three inquiry lines. First, we conducted extensive field samplings in the ancestral range of the species, Turkey, and in one non-native region, Argentina, to estimate the mean and the variation of the trait in populations from both ranges. Second, we related seed size to gradients of elevation in Turkey and those of precipitation in Argentina to explore for clinal variations in the trait. Lastly, we assessed survival in seedling emerged from small and large seeds in a field experiment in the non-native region to assess whether the environment in that region selects for larger seeds. We found that seed mass in non-native populations exhibited a larger mean and a smaller variance than those in native populations. Also, seed size was negatively related to precipitation in the non-native range and positively related to elevation in the native range. Finally, seedlings emerging from larger seeds exhibited higher survival than those emerging from smaller seeds in the non-native region. Although the influence of founder and maternal effects remains to be assessed, these results suggest that selection on pre-adapted genotypes could contribute to seed size increase in non-native populations. Larger seeds may, in turn, be central for the demographic success of these populations.