Climate change and land use change impacts on pollinators
Presented by Peter Soroye
Dec 3rd 12:30 – 1:30 PM ET
(email for Zoom link)
Pollinators, including bumblebees (Bombus), are declining in range size and abundance across their ranges across North America and Europe, linked in large part to rapid recent climate change and changes in human land use. Niche theory and physiology suggest that species’ physiological limits might define whether they persist in some areas and may help to inform predictions on climate change effects. Using a spatially explicit index for calculating species’ exposure to thermal and precipitation limits across their ranges and a comprehensive occurrence dataset of North American and European bumblebee species, we test whether a species’ or communities’ proximity to thermal or precipitation tolerance limits predicts local extinction, colonization, occupancy, and species richness change, and how these climate change-related biodiversity responses interact with changing land use.
Peter Soroye is a PhD Student in Biology working with Prof Jeremy Kerr at the University of Ottawa. Peter is a conservation biologist studying the impacts of climate change and land use change on biodiversity across the globe, with the goal of informing conservation management and policy to find more effective ways of protecting species and reversing declines of biodiversity. In February 2020, Peter published the first chapter of his PhD research in the journal Science, which was focused on a novel mechanism for predicting climate change related extinction risk in bumblebees.
Deciphering mechanisms of transcription regulation and their role in the biological embedding of experience
Presented by: Dr Maria Aristizabal
November 19th at 12:30pm EST
Transcription is essential for life and in eukaryotes it is performed by one of several RNA polymerases (RNAP). Of these, RNAPII is responsible for the synthesis of all mRNAs and many non-coding transcripts, an activity that requires the integration of general and gene-specific signals. However, how these activities are coordinated and contribute to the response to environmental contexts remains poorly understood, despite a clear significance in the adaptation, health and survival of all organisms. Furthermore, the extent to which genetic variability affects transcription and thus modulates individual differences in the response to challenge is unclear. In this presentation, I will discuss two distinct but interconnected projects examining the molecular mechanisms by which organism respond to nutritional information. The first project leverages the unique advantages of the yeast model system and focuses on Cdk8, the kinase subunit of the Mediator transcription co-activator complex. Here, I focus on a new kinase-substrate relationship that directly linked Cdk8 to the regulation of metabolism. The second project uses fruit flies and shows that the response to nutritional stimulus is sex-specific.
We are showered every day with the gifts of the Earth and yet we are tied to institutions which relentlessly ask what more can we take? Drawing upon both scientific and indigenous knowledges, this talk explores the covenant of reciprocity, how might we use the gifts and the responsibilities of human people in support of mutual thriving in a time of ecological crisis.
Robin Wall Kimmerer is a mother, scientist, decorated professor, and enrolled member of the Citizen Potawatomi Nation. She is the author of Braiding Sweetgrass: Indigenous Wisdom, Scientific Knowledge and the Teaching of Plants, which has earned Kimmerer wide acclaim. Her first book, Gathering Moss: A Natural and Cultural History of Mosses, was awarded the John Burroughs Medal for outstanding nature writing, and her other work has appeared in Orion, Whole Terrain, and numerous scientific journals. She tours widely and has been featured on NPR’s On Being with Krista Tippett and in 2015 addressed the general assembly of the United Nations on the topic of “Healing Our Relationship with Nature.” Kimmerer lives in Syracuse, New York, where she is a SUNY Distinguished Teaching Professor of Environmental Biology, and the founder and director of the Center for Native Peoples and the Environment, whose mission is to create programs which draw on the wisdom of both indigenous and scientific knowledge for our shared goals of sustainability.
As a writer and a scientist, her interests in restoration include not only restoration of ecological communities, but restoration of our relationships to land. She holds a BS in Botany from State University of New York Environmental Science and Forestry (SUNY ESF), an MS and PhD in Botany from the University of Wisconsin and is the author of numerous scientific papers on plant ecology, bryophyte ecology, traditional knowledge and restoration ecology. She lives on an old farm in upstate New York, tending gardens both cultivated and wild.
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Ecological contexts of balancing selection in nature
Presented by: Dr Lauren Carley
November 5th at 12:30pm EST
How genetic variation is maintained in the face of persistent natural selection is a central question in evolutionary biology. Neutral models of mutation-selection balance are possible, but do not explain intermediate-frequency polymorphisms that have been observed in many populations and species. An alternative explanation is balancing selection, in which natural selection actively maintains polymorphisms at higher than neutral levels over space and/or time. This phenomenon is frequently invoked, but rigorous tests demonstrating balancing selection operating in nature are scarce, particularly on complex traits, which frequently display high levels of variation. Moreover, balancing selection is an evolutionary process that may be generated by a variety of mechanisms, including overdominance, spatial and temporal variation in selection, frequency-dependent selection, and antagonistic pleiotropy, which may result from diffuse and/or multivariate ecological interactions.
Focusing on a biochemical polymorphism in the wildflower Boechera stricta (Brassicaceae), we use tractable genetic tools in field and greenhouse experiments to elucidate the molecular underpinnings of ecological plant-herbivore interactions and fitness in nature. Further, we use population modeling to investigate the role of ecological variation and covariance in determining lifetime fitness. Together, these approaches suggest that variation in secondary metabolic profiles in B. stricta may persist at present due to balancing selection, and may continue to persist in the future under a range of varying environmental scenarios, offering an integrated perspective on the forces contributing to the maintenance of natural variation.
A broad-scale test of dispersal constraints on the northern range limit of a Pacific coastal dune plant
Presented by: Mike Dungey from Queen’s University
October 29th from 12:30pm – 1:30pm EST
Species are expected to occur where environments allow populations to achieve self-replacement and be limited where biotic and abiotic conditions shift outside their recognized niche. However, many systems lack the declines in fitness towards their range edges expected under niche limitation and even show persistence beyond them, suggesting a role of dispersal limitation in maintaining species’ ranges. For species that exist within patchy environments, dispersal limitation can occur through an increase in the heterogeneity of suitable habitat, as opposed to absolute dispersal barriers. Reductions in habitat patch abundance and size, and higher isolation between patches can increase the cost of dispersal along a gradient, with a range limit forming where colonization can no longer match stochastic patch extinction. We tested the predictions of this hypothesis across the northern range of a Pacific coastal dune endemic, Camissoniopsis cheiranthifolia (Onagraceae). This species occurs in patchy dune habitat, and previous studies of beyond-range transplants strongly suggest that dispersal constraints could limit its northern range. By surveying all coastal dune habitat in the northern half of the species’ range, and quantifying habitat suitability and occupancy and at > 7000 randomly distributed 5×5 m plots, we tested the predictions that towards the northern range limit: (1) availability of suitable habitat decreases, (2) distances between habitat patches increases, and (3) occupancy of suitable habitat patches decreases. Our results suggest that available, suitable habitat for C. cheiranthifolia declines with increasing proximity to the range limit, despite an increase in coastal dune systems across the species northern range. These results suggest that dispersal constraints through reduced dispersal success may play a role in maintaining this species stable range limit.
Population genomic structure and hybridization of Glaucous Gull (Larus hyperboreus) in the Canadian Arctic
Presented by: Emma Lachance Linklater
October 22nd at 12:30pm – 1:30pm EST
Climate change poses a significant threat to the future of Arctic ecosystems. To effectively conserve Arctic species, genetically differentiated populations must be defined for genetic variation to be appropriately managed. This project examines population genomic differentiation in Glaucous Gull (Larus hyperboreus) – a circumpolar Arctic species – and assesses hybridization between Glaucous Gull and three closely-related species. Glaucous Gull is a valuable species, both biologically and culturally. As apex predators, Glaucous Gulls develop high levels of toxins in their tissue and are, therefore, excellent bioindicators of the long-range transport of contaminants in the Arctic. Glaucous Gulls also hybridize with other white-headed gull species where breeding ranges overlap. Although the IUCN currently lists Glaucous Gull as Least Concern, declines have been reported across their range in Arctic Canada. Currently no finescale population genetic information exists for this species, and management units have not been delineated. Double digest restriction-site associated DNA sequencing was conducted on 62 Glaucous Gull, 18 American Herring Gull (L. smithsonianus), 6 European Herring Gull (L. argentatus), and 15 Glaucous-winged Gull (L. glaucescens) sampled across the North American and European Arctic. Despite the geographic distance between sampling locations, STRUCTURE and discriminant analysis of principal components (DAPC) suggest only weak population differentiation between European and Canadian colonies of Glaucous Gull. Interspecific analyses using 2145 loci show that Glaucous Gull and Glaucous-winged Gull are genetically distinct species but that Glaucous Gull and the two species of Herring Gull are only weakly differentiated. Several sampled individuals may represent hybrids between Glaucous Gull and other species. Detailed information on population genetic structure and hybridization will help conservation practitioners effectively manage the long-term persistence of Glaucous Gull populations. Proactive management strategies for this species will benefit both Glaucous Gull and the entire Arctic ecosystem.
Testing for convergent evolution in semi-aquatic Anolis lizards
Oct. 15th at 12:30 – 1:30pm ET
Anolis lizards are a textbook example of convergent evolution. Independent anole lineages on each of the Greater Antillean islands have converged on the same six ‘ecomorphs’, categories encompassing morphology, ecology, performance, and behaviour. However, the majority of anole species, including those found on continental Central and South America, do not fit neatly into these categories. Of these ‘non-ecomorph’ anoles, there are twelve species which are always found within metres of neotropical streams, swim and dive to escape predators, and consume aquatic prey. Given the prevalence of convergence in anoles, we might expect these semi-aquatic species (that include 6 phylogenetically independent lineages) to exhibit broadscale convergence; yet previous work did not find evidence of morphological similarity between these lizards. To determine if semi-aquatic anoles should be considered a new ecomorph, I conducted a comprehensive study of their morphology, swimming performance, and underwater behaviours. In addition to finding multi-modal evidence of convergence, we also discovered a novel convergent respiratory behaviour that we have called ‘rebreathing’.
Making sound decisions: Singing mice as integrative models for adaptive display
Presented by: Dr. Steve Phelps from the University of Texas
October 8th 12:30-1:30pm ET
By their very nature, animal displays are among the most conspicuous of all behaviors. They are designed to be noticed, but not without cost. The trade-offs between costs and benefits of conspicuous displays are influenced by state variables, like an individual’s reproductive status or energy balance; contextual variables, like the presence or absence of a given audience; and idiosyncratic contingencies that are unique to the ecological circumstances of an individual and must be learned through experience. While such trade-offs have been well explored theoretically, we know surprisingly little about the mechanisms by which animals match display effort to such diverse concerns. Work with singing mice illustrates some of the many neural and hormonal mechanisms by which these considerations are balanced against one another to optimize display effort.
Models of adaptation to climate change with complex life histories
Climate warming has been the epitome of rapid global environmental changes induced by anthropogenic activities. The need to predict species responses to these challenges has been a strong motivation to develop the theory of adaptation to rapid and ongoing environmental changes. Early theory provided strong conceptual insights based on simple models, notably assuming non-overlapping generations. However, many organisms, some of major conservation or agronomic interest, have complex life histories structured in different ages and stages. I will present some of the work we have done to integrate life history in models of adaptation to changing environments. These models strongly emphasize the link between ecological and evolutionary dynamics. We demonstrate in particular how changing environments can trigger eco-evolutionary feedback loops with major consequences both on life history and on the fate of populations.
“Now, here, you see, it takes all the running you can do to keep in the same place. If you want to get somewhere else, you must run at least twice as fast!”
Direct and indirect effects of host food quality on host life history, host susceptibility to parasitism, and parasitoid life history
Thursday September 24th from 12:30-1:30 pm
Ecological communities are complex, comprising species and environmental factors that are so entangled in their effects on one another that ecologists and evolutionary biologists will forever be mystified by how they are assembled and function. Against such complexity, we have come to understand that autotrophic resources can have large cascading impacts on higher trophic levels via direct interactions (the effect of one species or environmental factor on another). However, because of indirect interactions (between species or environmental factors that are mediated through direct interactions with other species or factors), the relationships and dynamics we expect in natural communities are often not observed. In this thesis, I investigate how food resources directly impact consumer life histories and how this direct interaction indirectly impacts tertiary consumers in an experimental resource-host-parasitoid community. I address the direct and indirect effects of host food quality on primary and secondary consumer life histories in two highly replicated experimental life history assays. In the first assay, I ask whether variation in host life history traits in response to food quality is consistent within and across stages of host development. Importantly, throughout juvenile development, many organisms develop through several stages of growth that can have different interactions with their environment. For example, some parasitoids typically attack larger instars, whereas larval insect predators typically attack smaller instars. Interestingly, most studies lump all juvenile stages together, which ignores these ecological changes over juvenile development. Using a cross-sectional experimental approach combined with a stage-structured population model to estimate instar specific host vital rates, I show that food quality effects on host vital rates, growth and development are not consistent throughout ontogeny, suggesting host food quality may cascade to impact host susceptibility to parasitism and parasitoid life histories. In the second study, I ask whether host food quality indirectly cascades to impact host susceptibility to parasitism and parasitoid life histories. Using a similar cross-sectional approach, I show host food quality indirectly impacts host susceptibility to parasitism but has little to no effect on parasitoid life histories. Overall, my research shows that, despite large effects on host life histories, host food quality effects are markedly reduced in parasitoids in this system, emphasizing the need to consider specific species life histories when characterizing resource-host-parasitoid community relationships and dynamics, and whether or not resources cascade to impact higher trophic consumers.