Differentiation in reproductive strategy between sexual and asexual populations of Antennaria parlinii (Asteraceae)

Plants exhibit wide variation in reproductive traits, and these traits ofte n covary to form distinct strategies. Uniparental reproduction via self-fer tilization is often associated with high reproductive effort and enhanced s eed dispersal, the combination of which is viewed as an adaptive strategy i n ephemeral or disturbed habitats. We investigated the hypothesis that unip arental reproduction via asexual apomixis is associated with a similar suit e of traits and more frequent occurrence in disturbed habitats among popula tions of Antennaria parlinii, a dioecious species that exhibits wide variat ion in sexuality at the population level. By comparing 18 sexual and 21 ase xual populations in Ohio, USA, we found that, as predicted, sexual populati ons were more likely to occur in wooded habitats than asexual populations, which were found more frequently in disturbed roadside ditches and fallow f ields. As expected, plants in asexual populations produced, on average, twi ce as many seeds per inflorescence as plants in sexual populations. Asexual plants also exhibited much higher reproductive effort than sexual plants w hen compared in a common greenhouse environment, indicating a genetic basis for the difference in reproductive output observed in natural populations. Seeds of A. parlinii are equipped with plume-like pappus that enhances win d dispersal. Settling velocity in still air was lowest for diaspores with l ong, highly barbed pappus bristles and small seeds. Compared to sexual popu lations, asexual populations produced diapsores with longer, more highly ba rbed pappus and smaller seeds. Taken together, our results suggest that div ergent selective pressures in different habitats have produced two distinct reproductive strategies in A. parlinii.