Murray, Dennis

Stressors are often an inescapable part of an organism's life. While the effects of many stressors have been well studied individually, potential interactions between stressors exist that may result in greater than additive negative effects. Stressors may be linked by conflicting demands on energy budgets, interfering with important physiological pathways, or necessitating incompatible adaptive responses. Using Ranavirus (FV3) and larval dragonfly predators (Anax spp.) in a 2x2 factorial experiment on green frog (Lithobates clamitans) tadpoles, I investigate the interactions in behaviour, morphology, and metabolism when both stressors were applied in concert. I demonstrate that activity and feeding are reduced additively by both stressors, and tadpoles increase distance between conspecifics in FV3-exposed tanks, but only in the absence of predators. I also note decreases in mass, and a non-significant marginal increase in metabolic rate of tadpoles exposed to FV3. Interestingly, I provide evidence that FV3 can compromise morphometric responses through antagonistic interactions with perceived predation risk exposure, which may result in significantly elevated mortality even when either stressor is present in sub-lethal quantities. Thus, I conclude that sub-lethal exposure to stressors can nonetheless have substantial impacts on organisms and a more integrative approach to examining the impacts of stressors on individual physiology and fitness is necessary.

Author Keywords: Behaviour, Interaction, Morphology, Predation Risk, Ranavirus, Tadpoles

Forestalling biodiversity loss through the establishment of protected areas is a universally accepted conservation strategy, yet despite established guidelines for protected area coverage and placement, much of the world is currently failing to meet its commitments to conservation planning and landscape protection. Calls for the United States to protect more land usually focus on the need for strategic selection of land parcels to bolster protected area coverage and network functionality, but to date there lacks focused research on either the role of private protected areas in conservation planning or the factors affecting individual protected area selection and importance. We determined gaps in conservation planning in the contiguous United States by analyzing the connectivity of protected area networks by state, and assessing the importance of private protected areas in improving linkages in protected area connectivity. We found that all states had low coverage from protected areas (average <8.4% of total land mass), and especially private protected areas (average <1.1% of total land mass), and that the overall contribution of such areas to protected area network connectivity also was low. Terrain ruggedness was identified as the main factor affecting the current location of protected areas, and that protected area spatial layout is a primary influence on landscape connectivity. We conclude that establishment of private protected areas could offer a viable conservation tool for increasing protected area coverage and connectivity, but that current efforts are inadequate to either adequately link existing protected areas or to meet established land protection guidelines.

Author Keywords: Aichi Target 11, conservation planning, graph theory, network theory, private conservation, protected areas

Range contractions and expansions are important ecological concepts for species management decisions. These decisions relate not only to rare and endangered species but to common and invasive species as well. The development of the broad spatiotemporal extent models that are helpful in examining range fluctuations can be challenging given the lack of data expansive enough to cover the time periods and geographic extents needed to fit the models. Archival records such as museum databases and harvest data can provide the spatiotemporal extent needed but present statistical challenges given they represent presence-only location information. In this thesis, I used maximum entropy and Bayesian hierarchical occupancy algorithms fitted with archival presence-only records to develop spatiotemporal models covering broad spatial and temporal extents for snowshoe hare and Canada lynx. These two algorithm types are well suited for presence-only data records and can be adapted to include biological and physical processes, thus improving the ecological realism of the models. Using these modelling methods, I found the extent of occurrence (EOO) and area of occupancy (AOO) varied greatly over time and space for both snowshoe hare and Canada lynx, suggesting that management decisions for these species should include consideration of these variations. While the presence-only data were appropriate for model development and understanding changing values in EOO and AOO, it sometimes lacked the locational accuracy and precision needed to create fine scale ecological analyses, thus resulting in somewhat coarse but potentially relevant conclusions.

Author Keywords: Area of occupancy, Bayesian hierarchical models, Canada lynx, Extent of occurrence, Presence-only data, Snowshoe hare

I assessed how organisms having multiple biotic attributes may have conflicting niche determinants, and whether the realized niche reflects single or multiple attributes. All-female salamanders engage in two biotic states: hybridism and reproductive parasitism. Hybrids should occupy areas transitional to those used by parental species, whereas parasites that engage in competition with hosts should occupy habitats moderately suitable for hosts. Using niche models, I predicted realized niches for unisexual Ambystoma via a hybrid model (environmental predictors) and a parasite model (host suitability predictors). The hybrid model predicted that the unisexual niche would indeed be transitional between parental Ambystoma spp. The parasite model demonstrated unisexual salamanders occupied habitats moderately suitable for hosts, though model validation did not fully corroborate its predictive power. The hybrid model was more descriptive of unisexual occurrence than the parasite model. When species have competing ecological roles a primary biotic attribute may largely derive the realized niche.

Author Keywords: Ambystoma, hybrid, niche, parasite, range, unisexual

Environmental variation can affect consumer trait expression and alter ecological and evolutionary dynamics in natural populations. However, although dietary nutrient content can vary by an order of magnitude in natural ecosystems, intra-specific differences in consumer responses to food quality have not been thoroughly investigated. Therefore, the purpose of my dissertation was to examine the influence of dietary nutrition and other environmental factors on consumer phenotypic variation using the freshwater cladoceran Daphnia. I conducted a series of complementary laboratory and field studies where I examined the effects of dietary phosphorus (P) content and additional biological/environmental variables (multi-elemental limitation, genetic variation, and temperature) on daphnid life-history, biochemistry, body elemental composition, and population growth. In general, phenotypic expression within a species varied significantly in response to all experimental variables, but the relative influence of each was highly context dependent. In my first chapter, I found that dietary P content and environmental calcium (Ca) concentrations both altered Daphnia body Ca:P ratios and growth rates of individuals and affected intrinsic rates of increase at the population level. However, food quality appeared to have a much larger effect on trait expression, and body Ca:P ratios were highly sensitive to other forms of dietary nutrient limitation. Next, I documented significant quantitative genetic variation and phenotypic plasticity in daphnid P content, growth, and P use efficiency of field collected animals grown across dietary P gradients. Trait expression was also influenced by genotype X diet interactions suggesting that consumer responses to dietary nutrient limitation can be heritable and may be adaptive in different nutrient environments. Finally, I found that temperature appeared to override food quality effects and decouple P metabolism in natural Daphnia populations, but total biomass production was affected by both dietary P content and temperature, depending on the nutrient content of the lake. Overall, my dissertation shows that consumer responses to nutrient limitation can vary significantly within a species and that changes in trait expression may be modified by other environmental variables. These results should be incorporated into existing stoichiometric models and used to investigate the eco-evolutionary consequences of consumer phenotypic variation in response to nutritional stress.

Author Keywords: ecological stoichiometry, evolution, life-history, nutrient limitation, nutrient metabolism, zooplankton

Moose are an iconic species, known for their large size and impressive antlers. Eight subspecies are classified in circumpolar regions of the planet - four in North America. Two subspecies are similar in shape and size, the north-western moose (Alces alces andersoni) and the eastern moose (Alces alces americana). It was previously believed that these two subspecies meet in northern Ontario. Earlier genetic population studies used a small number of samples from Ontario, primarily in broad studies covering all of North America.

A comprehensive genetic study of moose populations in Ontario has not previously been conducted. We examined the genetic diversity and population structure at 10 polymorphic loci using 776 samples from Ontario, as well as outgroups from representative populations – Manitoba/Cape Breton, representing A. a. andersoni, and New Brunswick/Nova Scotia, representing A. a. americana. Results indicated three genetic populations in the province, in north-western Ontario, north-eastern Ontario and south-central Ontario. RST values, compared against both FST and Jost's D values for phylogenetic analyses, indicated no phylogenetic pattern which suggests no subspeciation present in the province.

Population movement patterns in Ontario were studied. Gene flow was estimated using genetic and spatial data. Isolation by distance was only seen within the first distance class of 100 kilometres and then not seen again at further distances, indicating that moose display philopatry. There were very few migrants travelling across the province, with a greater number moving gradually north and west, towards better habitat and food sources.

A forensic database in the form of an allele frequency table was created. Three loci showed very low levels of heterozygosity across all three populations. Probability of identity was calculated for the three populations and quantified. Samples with known geographic origins were run against the database to test for sensitivity, with identification of origin occurring at an accuracy level between 87 and 100%.

Within Ontario, there are not two different subspecies, as previously believed, but two different populations of the same subspecies meeting in northern Ontario. The genetic data does not support previous research performed in Ontario. The sample sizes in our research also provide a more comprehensive view of the entire province not seen in any previous studies. The comprehensive research enabled the building of a reliable forensic database that can be used for both management and forensic purposes for the entire province.

Author Keywords: Alces alces, Genetic Diversity, Moose, Ontario, Phylogeography, Subspecies

While hybridization between distinct taxa can have undesirable implications, it can also result in increased genetic variability and potentially, the exchange of adaptive genes or traits. Adaptive variation acquired through introgressive hybridization may be particularly advantageous for species facing rapid environmental change. I investigated a novel, climate change-induced hybrid zone between two flying squirrel species: the southern (Glaucomys volans) and northern (G. sabrinus) flying squirrel. I was interested in the occurrence of hybridization and introgression, the type of selective pressures maintaining the hybrid zone and the potential for adaptive introgression. I found relatively low hybridization and introgression frequencies (1.7% and 2.9% of the population, respectively) and no evidence of selection on hybrids or backcrosses in particular environments. I conclude that the data are more consistent with a hybrid zone maintained by endogenous (environment-independent) selection. I tested for adaptive introgression using two functional genes: IGF-1 and CLOCK. I documented intermediate functional allele frequencies in backcrosses compared to parental populations, suggesting the alleles do not confer fitness advantages in backcrosses. Despite lack of evidence for current adaptive introgression, genetic admixture between G. volans and G. sabrinus may provide adaptive potential should these species face more rapid or drastic environmental change in the future.

Author Keywords: adaptive introgression, flying squirrel, Glaucomys sabrinus, Glaucomys volans, hybridization, introgression