Hybridization has been directly implicated in the evolution of invasiveness in some plant taxa, and hypothesized to contribute to invasions of many other plant taxa. The genus Rubus (blackberries and raspberries, Rosaceae) is ideal for studying this phenomenon, given that it includes a number of noxious weeds (11 in the United States as listed by the USDA PLANTS Database) and has a history of evolution through hybridization. Using nuclear microsatellite and chloroplast markers, I have identified natural hybrids of the native Pacific blackberry (R. ursinus) with both invasive Himalayan blackberry (R. armeniacus) and introduced Pennsylvania blackberry (R. pensilvanicus) in California. I hypothesize that hybridization of native and introduced Rubus in California has the potential to create new invasive weeds and also alter the genetic composition of native populations. In addition to identifying potential new invasives, my experimental aims focus on understanding the mechanisms by which hybridization can cause invasiveness. These aims are
- assess the reproductive mechanisms and competitive potential of known natural hybrids in California,
- identify any introgression of non-native genetic material into R. ursinus populations, and its positive or negative impact on the fitness of populations and individuals,
- determine whether invasive R. armeniacus is itself a hybrid of other European species, and
- compare gene expression profiles of hybrids to those of known invasives.
Awards
- Plant Sciences Departmental Research Assistantship
- Jastro-Shields Research Grant