January 15-19, 2011
Town & Country Convention Center
San Diego, CA
Lindsay V. Clark , Marie Jasieniuk
Reproductive mode plays an important role in the evolution of new invasive species following hybridization events. Asexual reproduction can maintain the high fitness associated with heterosis, whereas sexual reproduction produces a greater number of novel genotypes and allows for local adaptation to occur. In previous work, we identified spontaneous hybrids between the native Rubus ursinus (California blackberry) and invasive R. armeniacus (Himalayan blackberry) and between R. ursinus and the non-native R. pensilvanicus (Pennsylvania blackberry). R. ursinus is a sexual, outcrossing species and is the female parent of these hybrids, whereas R. armeniacus and R. pensilvanicus, the male parents, are pseudogamous apomicts (producing approximately 90% of seed asexually but requiring pollination to do so). In the present study, we determine the reproductive mode of the spontaneous hybrids by analyzing genotypes of seeds and seedlings at six microsatellite loci. Most seeds produced by the hybrids are genetically identical to the mother plants, indicating high rates of apomixis. However, the few seeds that germinated produced seedlings with subsets of parental alleles, indicating that the only viable seed was the small amount that was produced sexually. The R. ursinus x armeniacus and R. ursinus x pensilvanicus hybrids will therefore not pass heterosis on to their progeny by apomixis, but could contribute to the evolution of new invasive types through sexual recombination.