Evolutionary analysis of seed size variation in native and non-native populations of Centaurea solstitialis L.

ÖZKAN EREN; LEANDRO RAMÍREZ; RABIA ÖZCAN; JOSÉ L. HIERRO

Congreso; Bes and SFÉ Joint Annual Meeting; 2014

Studying intraspecific differences in phenotypic traits between native and non-native populations has received considerable attention because trait differentiation may explain successful invasion in non-native ranges. Yet, the source of the variation is often unknown. Recent studies have found that seeds of the worldwide distributed Centaurea solstitialis are larger in non-native populations from Argentina than native populations from Turkey. Turkey is considered as part of the center of origin of the species, and populations in the region exhibit extensive genetic diversity. Populations in Argentina have presumably been partially founded by Turkish migrants assisted by humans, and also possess high genetic diversity. Thus, founder effects and random genetic drift are unlikely candidates explaining the observed differentiation. As an initial step in exploring additional mechanisms driving seed size variation in C. solstitialis, we conducted extensive field samplings, collecting seeds from 39 populations in each range, and following in Turkey a gradient of elevation. In addition, using data from a previous reciprocal common garden, which in Turkey was located at a low elevation site, we assessed how seed size affected seedling survival in both ranges. We confirmed that seeds from non-native populations are on average larger than those from native populations, and additionally found that, in contrast, the variance of the trait is smaller in non-native populations. Also, seed size was 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, whereas seed size was not related to survival in the native range. These results suggest that selection of individuals with large seeds could have contributed to seed size increase in non-native populations. Larger seeds may, in turn, be central for the demographic success of these populations. Assessments of heritability, selection agents, and maternal effects are underway.