A fundamental question in invasion ecology seeks to understand why certain colonization events are successful and why others fail. For my Master's research, I am exploring the factors that drive the short-term success of introduced populations in multiple model systems.
Does genetic diversity within introduced populations influence short-term invasion success?
It is well supported in ecological literature that genetic diversity is important to the long-term success of colonizing populations. Invading populations with higher genetic diversity experience less inbreeding depression and are better able to adapt to a novel habitat over time. However, there is recent support that genetic diversity may even determine the short-term survival of founding populations. Genetic diversity within founding populations could potentially allow for a higher proportion of individuals to endure the founding event and reproduce, fostering the invader's persistence and spread. Additionally, genetic diversity could be more important for populations that are less-adapted to the environment they are introduced into (i.e. populations introduced via long dispersal events).
Using cheatgrass as a model system, I will address the importance of genetic diversity for invasion success. In common garden experiment in Colorado, I will create experimental founding populations of 32 cheatgrass seeds, with 6 possible treatments--seeds representing 1, 2, 4, 8, 16, and 32 maternal parents (i.e. from low to high genetic diversity). Seeds will be randomly drawn from pools of collected seeds from the Front Range in Colorado and the Great Basin Desert in Nevada and each population will be seeded in late autumn and its annual germination, survival and fecundity will be recorded.
Parsing propagule pressure: what components of propagule pressure most influence invasion success?
Collaborative project with Dr. Katriona Shea and Ciara Hovis (The Pennsylvania State University)
The only consistent predictor of invasion success is propagule pressure: the composite measure of the number of introduction events of a certain species at a specific location (propagule number) and the number of individuals introduced at each event (propagule size). Previous research suggests that increased propagule size and number influence invasion success, however the impacts of other aspects of propagule pressure such as the timing of introduction events, the duration of events, and the genetic diversity within colonizing populations remain largely unexplored. Using two model systems, Carduus nutans (musk thistle) and Tribolium castaneum (red flour beetle), we addressed how timing, duration and genetic variation, as components of propagule pressure, influence short-term invasion success. For each model system, we used a factorial design of three propagule sizes (15, 30 and 60 seeds/eggs), two genetic treatments (low and high diversity), and six different timing schemes. After one generation, we measured the success of establishment, survival, and resulting fecundity of survivors for each treatment. By comparing the impact of propagule pressure on invasion success in two different model systems with similar experimental approaches, we can better understand how consistently propagule pressure predicts invasion success and which specific components within propagule pressure drive that success.