The invasion history in the partially clonal invader, Kudzu (Pueraria montana var. lobata)
Bentley, Kerin Elizabeth
MetadataShow full item record
Due to the future effects of climate change and anthropogenic activities that change habitat, it is of high priority from a conservation perspective to identify how species can adapt quickly to shifts in biotic and abiotic conditions. Invasive species serve as excellent model species for identifying the genetic, evolutionary, demographic and ecological variables that can lead to high fitness in new environments. These species are introduced to a new area and within relatively short time frames exhibit rapid population expansion and geographic spread. They are the success stories for thriving in a new environment, but the mechanisms responsible for adaptation are still unclear. Studies of invasion have highlighted the importance of high genetic diversity present in the invasive range, which is now generally attributed to multiple introductions or high diversity in founders. However, with high diversity there are several evolutionary mechanisms that could produce adaptation to the environment. This has sparked the debate as to how frequently and to what degree natural selection versus demographic process or stochastic events like genetic drift affect the evolutionary trajectory of an introduced species. With the application of next generation technologies to these non-model species, more cases of selection are becoming available to answer these questions, but these studies are still rare. There is also increasing evidence that the mode of reproduction can greatly affect the distribution of genetic diversity in an invasion, influencing the ability of species to invade, but this issue is highly understudied. Cumulative knowledge of invasion histories, including both introduction and evolutionary histories, across species can imply what and how genetic, biological or evolutionary factors may influence invasion. I reconstructed the invasion history of a highly successful invader, kudzu or Pueraria montana var. lobata, by comparing neutral genetic diversity patterns within and among the native and invasive ranges to make inferences about genetic bottlenecking, the effect of a mixed breeding system on genetic diversity, population structure and gene flow as well as test for evidence of natural selection. I found contrasting evidence of the amount of genetic diversity in the invasive range. However, there was consistent evidence across multiple marker types that kudzu was introduced into the United States multiple times from disparate sources across East Asia. These populations exhibited evidence of more sexual reproduction compared to the native range, but upon introduction into the United States, kudzu increased its rate of clonal reproduction, even higher than the rest of the native range. We detected possible evidence of selection on standing genetic variation in the putative source populations prior to the introduction of kudzu into the United States.