Population genetic structure is widespread in many organisms and can be found at small spatial scales. Fine-scale differentiation is the result of ecological and evolutionary processes working together to produce an overall pattern, but the relative importance of these factors in population differentiation is poorly understood. The goals of my research were to describe patterns of population genetic differentiation and to identify ecological and evolutionary factors important for population divergence. To this end, I investigated several aspects of genetic differentiation for three vertebrates in northern California. The focal species were the terrestrial garter snake (Thamnophis elegans) and the common garter snake (Thamnophis sirtalis) that occupy a series of ponds, lakes and flooded meadows in northern California. I found significant genetic differentiation and isolation by distance, as well as correlated patterns of pairwise divergence in both species. Independent estimates of effective population size and bi-directional migration rates also uncovered source-sink dynamics in both species that suggest frequent extinction-recolonization events within a metapopulation context. The generality of source-sink dynamics for an ecologically similar species within the same ecosystem was explored using a third species, B. boreas. I also identified ecological correlates of several population genetic parameters for all three species. Although F[subscript ST] were similar, B. boreas had larger effective population sizes, lower migration rates, lacked source-sink dynamics, and appeared to be in migration-drift equilibrium, indicative of a temporally stable population structure. A clustering analysis identified a series of block faults as a common barrier to dispersal for both garter snakes, and ecological correlates were found to be more similar among response variables than within species. I then compared degree of genetic differentiation at quantitative traits with that at neutral markers to infer strength of selection and adaptive divergence between two ecotypes of T. elegans. Selection on most traits was relatively weak, but strong diversifying selection was found for background coloration, total number of ventral scales and number of infralabials. Overall, my research documented ecological and evolutionary processes associated with population differentiation in a metacommunity and respresents an important contribution toward the unification of ecology and evolutionary biology. / Graduation date: 2005

Climate change is putting the Earth’s biodiversity in serious jeopardy. UBC’S Biodiversity Research Centre is aiming to understand the impact of this shift.

I describe the natural history and reproductive behaviours of the Emei Moustache Toad (Leptobrachium boringii), testing the hypotheses that the species exhibits resource defense polygyny, and that combat, and paternal care lead to the evolution of male-biased sexual size dimorphism. In this study I document combat behaviour and paternal care for the first time in this species. Between February and March of 2011 and 2012, 26 female and 55 male L. boringii from Mount Emei UNESCO World Heritage Site, Sichuan, China, were observed throughout the breeding season. Prior to the breeding season, males grow 10-16 keratinized maxillary spines, which fall off once the season has ended. Throughout this time, males construct and defend aquatic nests where they produce advertisement calls to attract females. In a natural setting, I documented 14 cases involving a total of 22 males where males used their moustaches for aggressive interaction, and nest take over was observed on seven occasions. Despite my predictions, neither male body size nor body condition significantly affects the outcome of an aggressive interaction, though this may be representative of a low sample size. Males were also observed to possess injuries resulting from combat. Combat trials conducted in artificial nests demonstrated heightened aggression from resident males towards intruders. Genetic analysis using microsatellite markers revealed several cases of multiple paternity, both within nest and within clutch, indicating that some alternative male reproductive strategy, such as satellite behaviour is occurring. Larger males were observed to mate more frequently, and in multiple nests, suggesting that females are selecting for larger males, or that larger males are more capable of defending high quality territories. Males showed evidence of paternal care behaviours by remaining with the nests once females had left, moving throughout the nest cleaning, touching the eggs, and blowing bubbles into the centre of the doughnut-shaped egg masses. From this study I conclude that the male biased sexual size dimorphism in L. boringii is likely the result of both combat and paternal care behaviours creating a selection pressure on male body size.

[Truncated abstract] This study describes the results of a four and a half year investigation examining local regulation of ion transport through pumping epithelial cells. The study focussed on the standard isolated toad skin preparation, made famous by Hans Ussing. Originally, the objective was to perform some simple manipulations on the isolated toad skin, a standard and well-tested epithelial layer, which, according to the literature, was a well-behaved and stable preparation. The purpose of doing these toad skin experiments was to gain familiarity with the experimental techniques, such as measuring the open-circuit voltage (Voc) and the short-circuit current (Isc) across an epithelium. In the process, the experimental information that was obtained was to assist in the development and refinement of a mathematical model of a single pumping epithelial cell . . . Finally, it should be emphasised the toad skin was a convenient tissue model for exploring more general issues such as: (i) how pumping epithelial cells may adjust to changes in the extracellular environment by locally regulating their membrane conductances; (2) how the topology of a cell can influence its function (i.e. the topology can determine whether a cell is optimised for salt transport or water transport). (3) how different cells, with different functions, may be positioned in apposition in a pumping epithelial tissue so that gradients generated by one cell type can be utilised by another. From a broader perspective, it is likely that such issues are also applicable to other pumping epithelia, and ultimately, may assist in understanding how these epithelia function.

The endangered Western Leopard Toad (Amietophrynus pantherinus) is endemic to the winter-rainfall parts of the Western Cape, areas which are also favoured for human settlement. Residents in the Noordhoek area witnessed many toads being killed on roads during their annual migration to breeding ponds. Concerned citizens mobilised a volunteer group to mitigate this threat to the species. Toad NUTS (Noordhoek Unpaid Toad Savers), a well-established and successful citizen science group is explored as a case study of how environmental citizenship emerges in a citizen science group. This research has three research goals. Firstly to probe the enabling and constraining factors shaping the Toad NUTS practices, secondly to investigate the learning dynamics in the citizen science group and thirdly to understand how participation in citizen science develops environmental citizenship. Practice architectures theory (Kemmis & Grootenboer, 2008) was used to explore how cultural-discursive, economic-material and social-political arrangements shape the practices of the Toad NUTS group. The Toad NUTS group was identified as a community of practice, therefore Lave and Wenger’s (1991) communities of practice theory was used to better understand the social learning processes within the group. The Global Citizenship Education international policy document was used to capture the aims of citizenship education as it relates to environmental issues and identifies the competencies that citizenship education initiatives should develop. The practices of the Toad NUTS group were investigated for evidence of the goals and competencies identified in the Global Citizenship Education policy documents of environmental citizenship. Data was generated through documentary research, surveys, a questionnaire, semi-structured interviews and observations. The data was stored, organised and analysed using NVivo data management software in three phases corresponding to the three research goals. With respect to Goal 1, the evidence suggested that there are various shaping arrangements of cultural-discursive, material-economic and social-political configurations which influence Toad NUTS practices. Volunteers must learn to navigate these arrangements in order to successfully implement conservation strategies. The shaping features identified were the WhatsApp group communication system used by volunteers; public awareness and education strategies; equipment, material and funding required for implementing the group’s practices; power balances and exchanges between stakeholders in the conservation field; bureaucratic processes and scientist-lay person exchanges. Very important for facilitating social-political connections to various stakeholders, is the membership Toad NUTS enjoys on the Western Leopard Toad Conservation Committee. With respect to Goal 2, four interconnected components of learning were investigated. These were: learning as belonging, learning as doing, learning as meaning-making experience and learning as becoming. Members learn by doing things together like training, patrolling and deliberating problems in the field. They learn by exploring what is collectively known from past and unfolding experiences. Evidence showed that learning deepens as Toad NUTS members perceive their praxis as meaningful and their identities evolve as their knowledge and experience grows. This strengthens members’ sense of belonging and identification with the Toad NUTS group. In time the group develops a reputation and the wider community acknowledges the expertise and knowledge that resides with the group. With respect to Goal 3, it was found that volunteers who have a predisposition for environmental citizenship are more likely to join a citizen science group. Although volunteers care about nature and want to make a difference, it is after gaining access to the embedded knowledge and knowledge processes of the citizen science group that they realise meaningful sustainable solutions to the issue(s) that the project is concerned with. It was found that knowledge paired with reasoned practice enables the agency of volunteers to bring about positive and meaningful change in the local environment. If facilitated carefully, citizen science can make positive contributions to the field, in this instance, conservation, while allowing volunteers to exercise environmental citizenship engaging in participative governance with regard to the project.

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Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal