Ecology

This thesis presents a case of the aquatic plant species Fanwort (Cabomba caroliniana) significantly naturalizing in Kasshabog Lake in bays where it had been invasive. This significant naturalization presents major implications for invasive species management and invasion biology because the naturalization of invasive species is a phenomenon that has been largely omitted from study within ecology. There are several reasons for this: 1) the most used definition of the term naturalization within invasion biology categorically excluded the sense in which naturalization refers to community integration; 2) the most cited frameworks that have been created and used to describe and study biological invasions have no conception of invasive species naturalization; 3) boundary work has been conducted to exclude consideration of the naturalization of invasive species. Incorporation of an understanding of naturalization into science and management of biological invasions will make our understanding of them more complete.

Author Keywords: Ecological Restoration, Invasion Biology, Invasive Species, Naturalization

Long-term avian population declines, particularly for the avian insectivore guild, are a conservation concern. With widespread and continuing population trends, climate change and its negative effects on avian food resources is a plausible cross-species driver. My goal was to evaluate whether bottom-up trophic effects of climate change could be influencing avian populations. I used a space-for-time approach to assess the influence of snowpack and soil moisture variability on arthropods and subsequent effects on nest survival. In the 2010 and 2011 growing seasons, I sampled arthropods, soil moisture (soil volumetric water content; VWC), snowpack (snow water equivalent; SWE), forest floor depth (L, F, H layers) and soil texture in conifer plantations and mixed deciduous forest in Southern Ontario's Ganaraska Forest (~4, 400 ha). I used additive linear mixed effects models to assess the responses of arthropod groups' (e.g., order or class) relative biomass (g/day) and abundance (count/day) to those variables. Influences for each arthropod group's biomass and abundance were typically in the same direction. Maximum annual SWE significantly positively influenced most arthropod groups and annual relative difference in VWC positively influenced one quarter. In mixed directions, forest type influenced half of the groups and soil texture and forest floor depth each affected less than one quarter. I then used structural equation models to evaluate relationships between SWE, VWC, the biomass of three arthropod functional guilds, and logistic-exposure model calculated daily nest survival rates for American Robin (Turdus migratorius), Eastern Wood-Pewee (Contopus virens), Least Flycatcher (Empidonax minimus), Ovenbird (Seiurus aurocapilla), and Red-eyed Vireo (Vireo olivaceus). Arthropod guilds included diet-based food, predaceous arthropods and soil-dwelling bioindicators. SWE significantly positively influenced food biomass in all five models and negatively influenced predaceous arthropods in three models. Soil moisture had a mix of positive, negative, and null effects. Eastern Wood-Pewee and Red-eyed Vireo nest survival positively related to food and negatively related to predaceous arthropod biomass. American Robin, Least Flycatcher and Ovenbird nest survival did not appear to be related to arthropod biomasses. Through bottom-up relationships, predicted climate change-induced reductions in snowpack may cause food resource declines and negatively affect some forest breeding bird populations.

Author Keywords: Arthropod biomass, Bottom-up, Forest birds, Nest survival, Path analysis, Precipitation

Lake Huron's food web has experienced drastic changes in response to multiple stressors including declines in offshore productivity, decreased trophic transfer efficiency and a transformation of the benthic food web. However, how these changes have affected the diets and isotopic niches of predatory fish is largely unexplored. My diet study analysed stomach contents from five predatory fish species (lake trout, lake whitefish, chinook salmon, rainbow trout, and walleye) from the Ontario waters of Lake Huron. My isotopic study focused on lake trout and lake whitefish, based on community concerns that recovering lake trout are competing with or consuming lake whitefish. By contrast, I found that lake whitefish were a minimal component of lake trout diets, and the diet and isotopic overlap between these two species was low overall, but varied regionally. Both the dietary and isotope analyses reflect the high regional diversity of energy sources used by predatory fish.

Author Keywords: Food web, Isotopic Niche, Lake Huron, Predator-prey, Regime shift, Regional Energy Sources

This thesis is focused on studying the population dynamics of a predator-prey system in a patchy environment, taking anti-predation responses into consideration. Firstly, we conduct mathematical analysis on the equilibrium solutions of the system. Using techniques from calculus we show that particular steady state solutions exist when the parameters of the system meet certain criteria. We then show that a further set of conditions leads to the local stability of these solutions. The second step is to extend the existing mathematical analysis by way of numerical simulations. We use octave to confirm the previous results, as well as to show that more complicated dynamics can exist, such as stable oscillations. We consider more complex and meaningful functions for nonlinear dispersal between patches and nonlinear predation, and show that the proposed model exhibits behaviours we expect to see in a population model.

Author Keywords: Anti-predation response, Asymptotic stability, Dispersal, Patch model, Population dynamics, Predator-prey

This thesis aimed to address potential sources of bias in electronic fish tagging studies in order to advance the methods used by future studies. I first provided a review and meta-analysis of intracoelomic tagging effects in fishes, summarizing the existing literature and assessing the extent to which previously identified research gaps have been filled. I also included the first large-scale meta-analysis on tagging effects, examining the 2% rule using empirical evidence from a broad representation of all published studies. I then assessed the performance of a newly miniaturized predation-sensing acoustic transmitter (Innovasea V3D), demonstrating that V3D transmitters can mitigate predation biases by correctly identifying most predation events without false positives. I finally examined if immobilization via MS-222 or TENS alters the behaviours of fishes in the wild following tagging, and identified the time required for fish to re-establish normal behaviour following transmitter implantation.

Author Keywords: Acoustic telemetry, Electronic tagging, Fish ecology, Predation, Systematic review, Tagging effects