Friday Philosophicals

The Laurentian Great Lakes face numerous threats such as increases in contaminant loads, invasive species, overfishing, loss of habitat, and climate change, which has led to changes in food webs and detrimental impacts on the health of many species. Stable isotope analyses (δ¹³C and δ¹⁵N) of consumer tissues and their prey provide a valuable tool to examine diet, relative trophic position, and the contribution of benthic vs. pelagic nutrients. Egg volume, indicative of energy content and maternal investment in each offspring, has important fitness implications and has been previously correlated with stable isotope dietary markers. This information can be used to better evaluate the effects of current and predicted environmental perturbations. My project will examine the sources of nutrients, trophic ecology, and egg volume trends of two colonial waterbirds, the double-crested cormorant (Nannopterum auritum) and ring-billed gull (Larus delawarensis), from data collected across the Great Lakes in 2022 and 2023.

Plants can modulate their root architecture to maximize soil water and nutrient capture in different environments. The two main root architecture categories, taproot and adventitious root systems, are characterized by contrasting patterns in root branching and distribution, which influence resource acquisition. For over-wintering plants, variation in root architecture can have important implications for frost exposure and sensitivity to frost. I will first examine the differences of these root architectures within Plantago lanceolata, a model tap-rooted species, in driving trade-offs or shared benefits for responses to nutrient limitation, water limitation and soil frost using a novel root injury technique that can produce an adventitious rooted phenotype. I will examine the responses of this species both alone in pots and in competition with other species in the field. Thereafter, I will extend the root injury technique and analyses to a greater range of species to expand the generality of my findings.

The sheer amount of whole-genome sequences (WGS) becoming available allows us to better understand the evolution of different wild species. Here, we sequenced high-quality long-read assemblies of three wild sheep (bighorn, Ovis canadensis; thinhorn: Dall, O. dalli dalli and Stone, O. d. stonei) and short-read sequences of sheep-like fossils. We analyzed the demographic history of extant bighorn and thinhorn individuals by mapping WGS to these high-quality assemblies. The demographic histories of Dall and Stone presented differences, and distinguishing between these subspecies is crucial as Stone also shares ancient hybridization patterns with bighorn. Moreover, we also mapped extant and extinct sheep WGS to the domestic sheep reference genome. We observed a striking result: a fossil from the Natural Trap Cave/USA presents similarities to both extant bighorn and thinhorn sheep. Our findings illustrate the power of WGS in detecting ancient genomic signatures and unravelling the evolutionary history of North American wild sheep.

The largest and most conspicuous fungi, the macrofungi, include many species of ecological and human significance because of their roles in nutrient cycling, mycorrhizal associations with plants, and medicinal and culinary values. Despite their global significance, relatively little is known about the biogeography and conservation needs of macrofungi compared to vascular plants and wildlife. This lack of knowledge is particularly striking in Ontario’s Carolinian Zone, which is one of the most biologically diverse and densely populated regions in Canada. To address this knowledge gap, Dr. Greg Thorn’s lab is undertaking a study of the systematics and biogeography of the Carolinian mushroom fungi (Agaricomycetes). My project focuses on the composition of the macrofungus communities of three municipalities in this region using a combination of historical collection data, field collections, and citizen science. The objectives are to prepare inventories of the macrofungi of each municipality and begin to assess their conservation needs.

Introducing outbred individuals into smaller, inbred populations, termed genetic rescue, is a commonly proposed method for alleviating populations of the stresses associated with inbreeding depression. An inbred population of bighorn sheep that was isolated for over 60 years underwent a series of three introductions aiming to relieve the population of inbreeding depression. These admixture events led to the development of a robust herd in good health with increased genetic diversity, relative to diversity measures before the translocations, as well as a 2-week shift in breeding dates. But, in 2016, an outbreak of Mycoplasma ovipneumoniae swept through the population, causing an 85% decrease in population size in less than one year. Despite good health and high levels of genetic diversity in this population, it experienced severe mortality from this outbreak. This project will investigate the long-term genomic effects of this genetic rescue, specifically on phenology and epizootic pneumonia survival.

The sedentary stages (i.e., egg and pupa) of insects may suffer more negative effects following heatwaves, and previously I showed that heat stress during pupal development reduces mating frequency in the true armyworm (Mythimna unipuncta). This suggests the pheromone-mediated communication system was affected. I compared the calling behaviour of females heat stressed during pupal development with controls but found no significant differences. I also compared the content of male hairpencils using gas chromatography and found that heat stress increased the average fluctuating asymmetry of male hairpencils. Future experiments will quantify female pheromone production, as well as the ability of the antennae of both sexes to detect conspecific pheromone using electroantennography. The findings will add to our understanding of the impacts of climate change on pheromone-mediated communication, which could have considerable importance with respect to the use of pheromone traps in pest management programs.