Burness, Gary

Climate change is a major conservation concern, especially for many cold-adapted species. The rate of warming due to climate change will likely outpace adaptive responses, and many populations will likely need to rely on phenotypic plasticity to cope with environmental warming. It is currently unclear whether plasticity in physiological responses to warming will be sufficient to offset the negative consequences of chronic environmental warming in ectotherms. I studied within-generation and transgenerational plasticity in two cold-adapted species of fishes, lake trout (Salvelinus namaycush) and brook trout (S. fontinalis), following temperature acclimation. Adults of both species were acclimated to either cold or warm temperatures and offspring were generated using a fully factorial breeding design, whereby the family thermal histories included crosses made within each temperature treatment and bidirectional crosses between temperatures. Offspring families were subdivided into two groups and acclimated to either warm or cold temperatures, so that offspring thermal experience matched or mismatched that of one or both parents. Offspring metabolic rate and critical thermal maximum during an acute thermal challenge were measured for both species. Limited transgenerational plasticity was detected in both species, but had a lesser effect than within-generationacclimation. In brook trout, the paternal contribution was greater than the maternal contribution. In lake trout, a mismatch in thermal acclimation, where the offspring were cold-acclimated but the parents warm-acclimated, resulted in elevated offspring metabolic rate without a corresponding increase in growth, suggesting that a mismatch in temperatures across generations could be detrimental to offspring. Using RNA-sequencing, transgenerational plasticity was linked to differential gene expression in the liver of lake trout offspring, in that genes were differentially expressed depending on the parental acclimation temperatures. Within-generation warm acclimation had the greatest effect on gene expression profile of offspring, with more genes differentially expressed under conditions of within-generation warm acclimation compared with transgenerational warm acclimation. Although it has been suggested that transgenerational plasticity may help to buffer the impact of warming due to climate change, my work implies that transgenerational plasticity, like within-generation plasticity, will be insufficient for these two species of cold-adapted salmonids to cope with climate change.

Author Keywords: Brook trout, Climate change, Lake trout, Phenotypic plasticity, Thermal tolerance, Transgenerational plasticity

Acoustic communication is vital for mediating interactions between individuals and their environment. From echolocating bats to isolated rodent pups, ultrasonic vocalizations are a useful mechanism for producing localized and cryptic acoustic signals. Flying squirrels have been demonstrated to produce almost exclusively ultrasonic calls which is rare in both squirrels and mammals, though the significance of this acoustic range is unknown. To investigate the context of ultrasonic calls in these gliding mammals, I created phylogenetic comparative analyses to compare ecological and morphological traits against call frequencies. I found that nocturnality, a trait entangled with gliding in squirrels, was related to higher-frequency calls. Furthermore, by comparing all gliding mammals and their non-gliding counterparts, I found that gliding mammals produce significantly higher frequencies than these relatives. This form of cryptic communication is likely used to avoid predation, which was further supported by behavioural experiments wherein flying squirrels used significantly higher frequencies when predation risk increased. While high frequency communication was used by most gliders, I found that ultraviolet-induced photoluminescence, another potential form of crypsis, was strongly associated with nocturnality, with half of the tested gliding mammals showing evidence of this unique colouration. While ultrasonic vocalizations are widespread in echolocating bats and echonavigating mammals, I did not find evidence to support echonavigation in flying squirrels. Instead, I found that ultrasonic vocalizations are used in a variety of social contexts and during solitary foraging and exploration. These combined results demonstrate the unique ecological and evolutionary pressures acting on small-bodied, nocturnal gliding taxa and the resulting cryptic behaviours and communication.

Author Keywords: communication, flying squirrels, gliding mammals, Sciuridae, ultrasound, ultraviolet-induced photoluminescence

I tracked summer movements and activity of snowshoe hares (Lepus americanus) in southwestern Yukon, Canada, during their population cycle (2015–2022) to assess the primary drivers of movement. Hares exhibited variable movement and activity during the cycle, exhibiting increased home range size and higher daily displacement during low population densities. Males exhibited more dramatic increases in their home ranges (>3-fold), and had greater and more variable movement rates and time spent travelling than females. The ratio of predators to hares was highest at low hare densities when hares were moving most, and seasonal activity of hares seemed unrelated to that of predators. Differences between sexes imply that reproductive activities likely were the main driver of hare movement variation rather than food availability. These findings reinforce that, even in highly variable environments, potential rewards associated with successful mate search and reproduction may outweigh the risks associated with reproductive behaviour.

Author Keywords: behaviour, boreal forest, GPS telemetry, home range, movement ecology, predation risk

Due to climate change and managed care, birds may face interacting effects of novel diets and environmental temperatures. I examined how captive zebra finches (Taeniopygia guttata) responded to a 6-month acclimation to either thermoneutral or cool temperatures when provided with saturated or unsaturated fatty acid enriched diets. Body mass was lower on the unsaturated fatty acid diet, but only in cool conditions. Individuals in cool temperatures and saturated fatty acid enriched diets had heavier organs, but pectoralis mass and metabolic rate did not display an effect of diet. While birds on each treatments illustrated similar initial increases in plasma fatty acid unsaturation, composition and concentration of constituent fatty acid varied based on their diet and temperature. Individuals on the unsaturated fatty acid enriched diet and cool treatments had lower survivorship. Collectively, my research will allow researchers to better predict how birds will be impacted by shifting or novel environments.

Author Keywords: chronic acclimation, fatty acids, metabolic rate, Taeniopygia guttata, temperature, unsaturation

Many species of shorebirds depend on stopover sites to rest and refuel during their long-distance migrations. To determine how shorebirds use migratory stopover sites, we tracked three species of shorebirds at two stopover sites in British Columbia, Canada from 2018-2021 during northward and southward migration using automated telemetry. Western Sandpipers (Calidris mauri) stayed longer at the Fraser River Estuary (4-8 days) compared to Tofino (2-6 days). We assessed habitat use of Sanderlings (Calidris alba), Semipalmated Plovers (Charadrius semipalmatus), and Western Sandpipers between beaches and mudflat at the Tofino stopover site. Time spent at the beach and mudflat habitats varied by species, tidal period, time of day, migration period, and human disturbance. This study shows that different stopover sites, and habitats within stopover sites, offer a unique set of characteristics used by birds exhibiting varying migration strategies, highlighting the importance of conserving a diversity of migration stopover locations and habitats.

Author Keywords: habitat use, human disturbance, length of stay, migration, shorebird, stopover site

The influence of stress exposure on the body temperature of vertebrates has been known for nearly two-thousand years. While the proximate mechanisms supporting this phenomenon are well described, the ultimate mechanisms remain enigmatic. In this thesis, I propose a novel hypothesis which states that changes in body surface temperature (henceforth "surface temperature") following stress exposure occur to reduce energetic expenditure toward thermoregulation, thus freeing energy for use in the stress response (hereafter, the "Thermoprotective Hypothesis"). Using a paired experimental design, I first show that black-capped chickadees (Poecile atricapillus, Linnaeus, 1766) exposed to repeated stressors decrease their surface temperatures at low ambient temperatures, and increase their surface temperatures at high ambient temperatures relative to unstressed controls. These changes in surface temperature contribute to a relative reduction in heat loss in the cold, and a relative increase in heat dissipation in the warmth among stress-exposed individuals, thus reducing their energetic demands toward more costly thermoregulatory strategies. Next, I show that stress-induced changes in surface temperature are most pronounced in chickadees that experience naturally-occurring resource-restrictions, suggesting that this response occurs to balance allocation of energy among the stress response and thermoregulation (i.e. a true energetic trade-off ). Third, I show that the magnitudes of chronic, stress-induced changes in surface temperature are highly variable among, and highly consistent within, chickadees, therefore suggesting that this response could hold adaptive significance if such variation among individuals is heritable. Finally, using domestic pigeons (Columba livia domestica, Gmelin, 1789) as a model species, I show that stress-induced changes in surface temperature are highly pronounced at bare tissues with a critical role in thermoregulation for some avian species (the bill), when compared with responses at surrounding bare tissues (the eye region). Together, these findings strongly support the Thermoprotective Hypothesis and suggest that endotherms may trade energetic investment toward thermoregulation with that toward the stress response in resource-limiting environments.

Author Keywords: heat transfer, infrared thermography, stress physiology, surface temperature, thermoregulation, trade-off

In endotherms, physiological functioning is optimized within a narrow range of tissue temperatures, meaning that the capacity to dissipate body heat is an important parameter for thermoregulation and organismal performance. Yet, experimental research has found mixed support for the importance of heat dissipation capacity as a constraint on reproductive performance. To investigate the effects of heat dissipation capacity on organismal performance, I experimentally manipulated heat dissipation capacity in free-living tree swallows, Tachycineta bicolor, by trimming feathers overlying the brood patch, and monitored parental provisioning performance, body temperature, and offspring growth. I found that individuals with an enhanced capacity to dissipate body heat (i.e., trimmed treatment) provisioned their offspring more frequently, and reared larger offspring that fledged more consistently. Although control birds typically reduced their nestling provisioning rate at the highest ambient temperatures to avoid overheating, at times they became hyperthermic. Additionally, I examined inter-individual variation in body temperature within each treatment, and discovered that body temperature is variable among all individuals. This variability is also consistent over time (i.e., is repeatable), irrespective of treatment. Further, I found that individuals consistently differed in how they adjusted their body temperature across ambient temperature, demonstrating that body temperature is a flexible and repeatable physiological trait. Finally, I used a bacterial endotoxin (lipopolysaccharide) to examine the regulation of body temperature of captive zebra finches (Taeniopygia guttata) during an immune challenge. Exposure to lipopolysaccharide induces sickness behaviours, and results in a fever, hypothermia, or a combination of the two, depending on species and dosage. I asked what the relative role of different regions of the body (bill, eye region, and leg) is in heat dissipation/retention during the sickness-induced body temperature response. I found that immune-challenged individuals modulated their subcutaneous temperature primarily through alterations in peripheral blood flow, particularly in the legs and feet, detectable as a drop in surface temperature. These results demonstrate that the importance of regional differences in regulating body temperature in different contexts. Taken together, my thesis demonstrates that heat dissipation capacity can affect performance and reproductive success in birds.

Author Keywords: body temperature, heat dissipation, tree swallow, zebra finch

Natural populations of flowering plants rarely have perfectly uniform distributions, so trends in pollen dispersal should affect the size of the pollination neighbourhood and influence mating opportunities. Here I used spatial analysis to determine the size of the pollination neighbourhood in a stand of the herbaceous, wind-pollinated plant (Typha latifolia; broad-leaved cattail) by evaluating patterns of pollen production and seed set by individual cattail shoots. I found a positive correlation between pollen production and seed set among near-neighbour shoots (i.e., within 4 m2 patches of the stand; Pearson's r = 0.235, p < 0.05, df = 77) that was not driven by a correlation between these variables within inflorescences (Pearson's r = 0.052, p > 0.45, df = 203). I also detected significant spatial autocorrelations in seed set over short distances (up to ~ 5 m) and a significant cross-correlation between pollen production and seed set over distances of < 1 m indicating that the majority of pollination events involve short distances. Patterns of pollen availability were simulated to explore the shape of the pollen dispersal curve. Simulated pollen availability fit actual patterns of seed set only under assumptions of highly restricted pollen dispersal. Together, these findings indicate that even though Typha latifolia produces copious amounts of pollen, the vast majority of pollen dispersal was highly localized to distances of ~ 1 m. Moreover, although Typha latifolia is self-compatible and has been described as largely selfing, my results are more consistent with the importance of pollen transfer between nearby inflorescences. Therefore, realized selfing rates of Typha latifolia should largely depend on the clonal structure of populations.

Author Keywords: clonal structure, correlogram, dispersal curves, pollination, spatial analysis, Typha latifolia

The distribution of animals is rarely random and is affected by various environmental factors. We examined space-use patterns, habitat selection and stress responses of whip-poor-wills to mining exploration activity.To the best of my knowledge, fine scale patterns such as the habitat composition within known home ranges or territories of eastern whip-poor-wills have not been investigated. Using a population at the northern edge of the distribution in an area surrounding a mining exploration site, we tested whether variations in habitat and anthropogenic disturbances influence the stress physiology of individuals. We found no effect of increased mining activity on the stress physiology of birds but found a significant scale-dependent effect of habitat on their baseline and stress-induced corticosterone levels, and we suggest that these are the result of variations in habitat quality. The importance of other factors associated with those habitat differences (e.g., insect availability, predator abundance, and microhabitat features) warrants further research.

Author Keywords: anthropogenic disturbances, Antrostomus vociferus, corticosterone, eastern whip-poor-will, habitat selection, radio-­telemetry

In the face of climate change, the persistence of cold-adapted species and populations will depend on their capacity for evolutionary adaptation of physiological traits. As a cold-adapted Ice Age relict species, lake trout (Salvelinus namaycush) are ideal for studying potential effects of climate change on coldwater fishes. I studied the thermal acclimation capacity and aerobic metabolism of age 2+ lake trout from four populations across four acclimation temperatures (8ºC, 11ºC, 15ºC, and 19ºC). One population had marginally significant higher active metabolic rate (AMR) and metabolic scope across all temperatures. There was no interpopulation variation for critical thermal maximum (CTM), standard metabolic rate (SMR), or thermal acclimation capacity. Acclimation resulted in a 3ºC increase in thermal tolerance and 3-fold increase in SMR for all populations. At 19ºC, SMR increased and AMR declined, resulting in sharply reduced metabolic scope for all populations. The limited intraspecific variation in thermal physiology suggests that climate change may threaten lake trout at the species rather than population level.

Author Keywords: Climate Change, Lake Trout, Metabolic Rate, Salvelinus namaycush, Temperature, Thermal Acclimation