November 23, 2018
Wing shape of birds is thought to be under strong selective pressures that reflect their need to fly efficiently, exploit habitat effectively, and survive as predator or prey. Wing shape plays a vital role in determining overall flight performance. Low aspect ratio wings (short and blunt) increase take-off speed, which could result in increased predator avoidance. High aspect ratio wings (long and pointed) and low wing loading (large wings compared to body) reduce the energetic costs of flight, which could ultimately increase the overall rate of migration. Most migratory songbirds have differential migration patterns; males arrive at breeding areas before females and older birds arrive before younger birds. If this is facilitated by differences in wing shape, I predict sex and age-related differences in wing shape. I tested these predictions using 20 species of Nearctic-Neotropical migratory birds captured in Long Point, Ontario.
Animals that provide parental care to their offspring often face behavioural trade-offs. Hormones have been implicated in mediating these trade-offs, with androgens often promoting aggressive behaviours at the expense of reduced nurturing behaviour. Conversely, prolactin can promote nurturing behaviour but may reduce aggressive behaviours. We tested the effects of these hormones on parental care in bluegill sunfish, a species in which males build nests and provide sole parental care to the offspring. Immediately after spawning, parental males received one of five hormone manipulations: (1) placebo; (2) 11-ketotestosterone (11-KT); (3) flutamide, an androgen receptor antagonist; (4) prolactin; or (5) bromocriptine, a prolactin-release inhibitor. We found that prolactin-treated males exhibited significantly more nurturing behaviours, whereas 11-KT-treated males exhibited more aggressive behaviours relative to the other treatments. We discuss the hormone-mediated trade-offs during parental care in bluegill sunfish.
November 16, 2018
Anthropogenic changes are causing shifts within ecological communities and subsequently food web structure. In terrestrial and aquatic systems, top-down and bottom-up effects in food webs have been known to cause consistent shifts in community structure and community body size. In soil detrital systems where microarthropod communities are key in carbon and nutrient cycling, community level responses to environmental shifts are understudied. Within the soil detrital microarthropod community, Collembola, commonly known as springtails, are a mid-trophic group susceptible to both top-down and bottom-up forces. To evaluate these effects my study exposed soil dwelling Collembola communities to treatments of warming, nutrient addition and predator addition, to induce top-down and bottom-up effects in both field and lab conditions. Community responses to these treatments reflect potential future responses to anthropogenic change and that may affect decomposition dynamics and carbon storage in soils.
Shade-grown coffee plantations provide wintering Neotropical migrants with an alternative to primary growth forest which is disappearing throughout most of their range. However, it remains unclear whether plantations can provide enough structure to maintain viable wintering populations of many species. We studied Swainson’s Thrush (Catharus ustulatus) wintering in two different sites in the Colombian Andes that consisted of a mixture of montane forest and shade-grown coffee plantation. In comparing the two habitats we looked at several factors that are indicative of habitat quality, such as age/sex hierarchies, home range sizes, density, and migration timing. We also used stable isotopes (δ 13C and δ 15N) to better understand dietary differences between habitats. My research aims to determine whether wintering Neotropical migrants benefit from this agroecosystem and find ways to improve shade-grown coffee practices in the future.
November 9, 2018
Harmful algal blooms are on the rise globally, in which there is a demand for improved historical context and monitoring efforts. This research aims to develop tools for accurate surface chlorophyll- a (chl- a) retrieval (a proxy for algae) within inland lakes as a basis for improved scientific understanding of algal blooms. Landsat satellite images (4-5 TM, 7 ETM and 8 OLI) were used to create a ±30 year predictive model (1984 to 2017), for the following ecoregions: polar, boreal forest, temperate forest, temperate steppe, temperate desert, subtropical humid forests, and tropical moist forests. Regression analyses for 82 algorithms were conducted to determine best fit models (linear, exponential, logarithmic, power) for chl-a and interfering signals of true water colour, total suspended solids, and turbidity to top of atmospheric reflectance. These algorithms were used to assess the usefulness of chl-a predictions within both a regional, and global context.
November 2, 2018
Even though they are hyperdiverse, high biomass, and a vital food source for vertebrate species, soil arthropods are not well understood because they are difficult to directly observe. Many soil-dwelling arthropods (e.g. Coleptera, Diptera) only live in soil for part of their life cycles, emerging when they reach maturity. Along with predatory arthropods on the soil surface, these emergent arthropods connect the soil system to the above-ground food web. In peatlands, soil organisms are exposed to high levels of methylmercury, a neurotoxin, which is shown to bioaccumulate and biomagnify in food webs. My study will examine the diversity of soil-dwelling arthropods and assess arthropod methylmercury content across two peatland sites in central Ontario. Identifying which arthropods have high methylmercury content could help us understand cascading effects of mercury on the environment and for the organisms which feed on arthropods, such as birds.
October 26, 2018
Both freezing and drought stress cause cellular dehydration in plants and elicit similar physiological responses. We examined how spring freezing influences the summer drought tolerance of 6 graminoid (Agrostis stolonifera, Arrhenatherum elatius, Bromus inermis, Festuca rubra, Lolium perenne, Poa compressa), 2 forb species (Plantago lanceolata, Securigera varia) and intact plant-soil mesocosms collected from an old field. In terms of total dry biomass, we found that there were indications of cross-acclimation between freezing and drought stress for Agrostis stolonifera, Bromus inermis, Lolium perenne, Poa compressa and Plantago lanceolata. The decline in biomass under drought was lowest for the plants previously exposed to freezing. In our mesocosm experiment, there was no significant interaction between freezing and drought for total aboveground biomass, despite significant main effects. Overall, our results indicate that there is variation in cross-acclimation responses among species and the latter does not necessarily translate to community level effects.
The degree to which animals move on one scale may be closely related to their other movement patterns. If individuals are prone to movement on multiple different scales, behaviours such as exploration and migration distance may show a consistent relationship. I will assess the relationship between exploratory behaviour and migration distance in a population of song sparrows (Melospiza melodia) using a novel environment test to quantify exploration and stable isotope analysis of claw samples to infer latitudinal migration distance. I will also investigate potential genetic and hormonal mechanisms that may drive this relationship. Preliminary results show variation in exploration levels and migration distance within the population and indicate a positive relationship between the two movement behaviours. A relationship between exploration and migration may suggest a movement syndrome involving the two behaviours and would present important insight into the evolution and consequences of these movements.
|DATE||FIRST SPEAKER||SECOND SPEAKER|
|Nov. 23||Jessica Deakin (PhD entry)||Adriano Pereira da Cunha (PhD exit)|
|Nov. 30||Matthew Meehan (PhD entry)||Emma Churchman (MSc entry)|
|Dec. 7||Aleksey Paltsev (PhD exit)||Dr. Wei Zhang|
|Jan. 11||Dong Lee (MSc entry)||Rebecca Howe (MSc entry)|
|Jan. 18||Curtis Lubbe (PhD exit)||Andrew Beauchamp (PhD entry)|
|Jan. 25||Kaelyn Bumelis (MSc exit)||Madelaine Anderson (MSc entry)|
|Feb. 1||Alix Thoreau (PhD entry)||No second speaker|
|Feb. 8||Olivia Colling (MSc exit)||No second speaker|
|Feb. 22||Reading Week|
|Mar. 1||Aida Parvizi (MSc exit)||Melissa Lucas (PhD exit)|
|Mar.8||Samuel Rycroft (MSc entry)||Christine Scharf (MSc exit)|
|Mar. 15||Rose-Lynne Savage (MSc entry)||Kyra Simone (MSc exit)|
|Mar. 22||Spencer Heuchan (PhD entry)||Caitlin Lyons (MSc exit)|
|Mar.29||Babak Ataei Mehr (PhD exit)||Anna Chernyshova (MSc exit)|
|Apr. 5||Corrine Genier (MSc exit)||Farhaan Kanji (MSc entry)|
|Apr.12||Jennifer Blythe (MSc exit)||Pilar Caicedo (MSc entry)|