Predicting the impacts of non-native species remains one of the greatest challenges to invasion ecologists. Because of their insularity, freshwater systems are particularly vulnerable to invasions, especially from non-native predators. The research in this thesis explores the role of abiotic and biotic factors in mediating the distribution and impact of Bythotrephes longimanus, a predatory cladoceran that has been introduced to freshwater systems in North America. Although the general impacts of this invasion have been documented, little is known about the factors that modulate them. Using a combination of field surveys and experiments, I tested several hypotheses concerning the influence of interactions with native species, as well as the role of heterogeneity in the light environment, in mediating the impact of Bythotrephes. Results demonstrated that biotic resistance by native macroinvertebrate predators does not play a limiting role in the establishment success of Bythotrephes. However, the within-lake distribution of Bythotrephes was influenced by these macroinvertebrates, suggesting that the native predator context matters when trying to understand the impacts of non-native predators. This was demonstrated with a mesocosm experiment in which the impact of Bythotrephes was constrained by the native Chaoborus larvae. In terms of the abiotic environment, in situ feeding experiments demonstrated that refuges from impact could exist for some prey taxa, as the outcome of predation by Bythotrephes was dependent on light availability and some prey taxa were more successful at evading predation under low light conditions. Finally, results show that adaptive behaviour by prey is also an important determinant of impact, as migrating Daphnia can escape predation effects by Bythotrephes. The combination of light-limited predation and a shallow distribution by Bythotrephes selects for prey that occupy relatively deeper positions during the day. As a whole, this research highlights the importance of complex interactions in mediating the impact of Bythotrephes and may help to explain some of the variation that has been documented among invaded lakes. A better understanding of these complex interactions can improve our ability to anticipate impacts as Bythotrephes continues to spread, as well as provide insight on some of the long-term effects following invasion. / Thesis (Ph.D, Biology) -- Queen's University, 2013-06-17 09:26:35.221

ABSTRACT One cause of declines and extinctions of island species is carnivore introduction. Four carnivores, including the small Indian mongoose (Herpestes auropunctatus), are on the IUCN’s list of 100 of the World's Worst Invasive Alien Species. My thesis summarizes global patterns of carnivore introductions and examines ecological, evolutionary, and management impacts of this mongoose. I study abundances of reptiles and amphibians on mongoose-infested and mongoose-free islands in the Adriatic Sea to determine if factors other than mongoose presence can account for abundance differences. For several reptiles and amphibians, the mongoose is implicated as causing differences. Additionally, I assess species abundance in the small mammal community and activity times of introduced ship rats (Rattus rattus) on the same islands. The mongoose is implicated in a shift in rat activity times, but it is difficult to separate mongoose impacts on small mammal abundance from rat impacts. To manage introduced carnivores, we can exclude, control, or eradicate them. I review literature data on mongoose eradication and control campaigns. I compiled a list of all islands with known mongoose populations and focused on assessing successes, failures, and challenges. The mongoose has been eradicated only on six very small islands. Management at low levels by various techniques has been attempted on many islands, with variable success. On almost all islands of introduction, the mongoose has no potential competitors of similar size. However, on three Adriatic islands where the mongoose was introduced, a similar-sized native carnivore, the stone marten (Martes foina), is present, while on one Adriatic island the small Indian mongoose is the sole carnivore. To see if character displacement occurs in the mongoose when the marten is present, and vice-versa, I examined size variation in the diameter of the upper canine tooth (the prey-killing organ) and skull length in these two species on these islands. Character displacement in both traits was evident for the mongoose but not the marten. Lastly, I developed a simulation model to examine genetic consequences of serial introductions of the small Indian mongoose and found that the potential for population genetic data to determine introduction pathways and sequences is limited.