Sherise Vialva MSc Candidate, Colautti Lab Exploring co-occurrence patterns and the impact of Climate Change on the Competitive Dynamics between Alliaria petiolata and Vincetoxicum rossicum My research looks at the interaction between two invasive plant species, Alliaria petiolata and Vincetoxicum rossicum, and how co-occurrence and competition may be affected by climate change. I conducted a field survey across Southern Ontario to determine if these species naturally co-occur and what environmental conditions possibly lead to one dominating over the other.
The results from the field survey found that both species naturally co-occur, leading me to conduct a field experiment to further investigate their interactions. The objective of this experiment was to examine how climate change may affect the interactions between Alliaria petiolata and Vincetoxicum rossicum. And to determine how this change could impact the abundance of both species, as well as their ability to spread in the future. My results suggest that climate warming may increase the fitness for both species, which may lead to greater spread and abundance in the future. However, this benefit from warming appears to be greater for each species when they are grown alone rather than together. This suggests that the presence of one species negatively affects the other. More research is needed to understand how these interactions will impact native plant communities. And on developing management strategies to better control the future spread of both species in a warmer climate. Allochronic speciation with gene flow? Genomics of parallel breeding time divergence among storm-petrels (Hydrobatidae) Parallel evolution, in which similar phenotypes arise among independent lineages, provides strong insights into the mechanisms and constraints on evolution. However, whether the same genomic regions underly the evolution of parallel traits is often unclear. Storm-petrels (Procellariiformes: Hydrobatidae), a cosmopolitan family of island-breeding seabirds, provide a useful case study for parallel evolution. Several sister races of storm-petrels have independently diverged in breeding season – an example of parallel allochronic divergence. I am using low-coverage whole-genome sequencing to disentangle the origins of repeated breeding time switches in storm-petrels. I am examining allochronic sister races in the band-rumped storm-petrel species complex (Hydrobates spp.), as well as an allochronic species pair from Guadalupe Island, Mexico: Townsend’s (H. socorroensis) and Ainley’s storm-petrels (H. cheimomnestes). Firstly, I am using outlier analyses to determine whether the same genomic regions differentiate sympatric population pairs. Secondly, I am assessing the role of adaptive introgression in promoting parallel evolution and inspecting the overlaps between introgressed regions and genomic outliers. Preliminary results confirm that allochronic populations arose in parallel across the breeding range. Moreover, the identification of outliers and evidence for widespread introgression among seasonal populations suggest that gene flow may have facilitated parallel divergence in the storm-petrels. The use of annotated genome databases will complement these results by matching potential gene functions to the outliers, which will further improve our understanding of the drivers of population divergence and adaptation.
Patterning the meristems - the development and evolution of the floral ground plan Despite the seemingly infinite morphological diversity, all flowers are highly organized structures. The overall pattern, or the floral ground plan, is determined at the earliest developmental stage in making a flower by the floral meristem. Knowledge of how different floral ground plans are established and evolved is critical for our understanding of flower diversification as well as genetic engineering of crop species. Although comparative analyses have revealed many evolutionary trends in the floral ground plan during angiosperm diversification, the molecular mechanisms underlying these evolutionary transitions remain largely known. Using Aquilegia and Mimulus, two charismatic emerging model systems for evo-devo studies, I demonstrate how developing new model systems can help us understand key aspects of the floral ground plan that cannot be addressed by previously established model systems.
Beetlejuice, Beetlejuice, Beetlejuice: The role of antimicrobial secretions in competition in the burying beetle, Nicrophorus orbicollis An organism’s ability to survive and reproduce is often related to its ability to compete for resources. Competition can be intense for organisms that rely on temporally or spatially limited or unpredictable resources. Carrion is often both limited and unpredictable, and is particularly valuable because it is nutrient rich. Animals that use carrion face intense competition from microbes, which can make the carcass unpalatable or inhospitable. I investigated adaptations to competition with microbes in the burying beetle, Nicrophorus orbicollis. Burying beetles require vertebrate carcasses to reproduce, and use anal secretions containing antimicrobial components and beneficial gut microbes to protect a carcass during breeding. Anal secretions can delay carcass decay and prevent pathogenic competitor microbes from colonizing the carcass during larval rearing. However, the proximate mechanisms by which these antimicrobial effects occur, whether through endogenous immune defenses of the beetle and/or direct competition between gut and carcass microbes, remains unknown. Fungal gut symbionts from the genus Yarrowia might play a critical role in competition with harmful carrion consuming microbes, and until now the direct effects of fungal gut symbionts on competition between burying beetles and carcass microbes have not been tested. I determined the competitive consequences of experimentally disrupting fungal symbionts from the gut microbiome of N. orbicollis by measuring treatment effects on carcass preparation behaviours, anal secretion antimicrobial potency, and carcass decomposition rate. Results demonstrate the importance of the gut microbiome in behavioural plasticity, but suggest that fungal microbial symbionts might not contribute to the antibiotic properties of anal secretions, or impact the rate of carcass decomposition. Our findings contribute to our understanding of symbiotic relationships with gut microbes, and the complex strategies some organisms use to compete for scarce resources.
Machine learning and genomics: Using neural networks for population assignment of a threatened seabird Population genomics is aiding researchers in uncovering more information about non-model organisms, and has aided in the development of species and population-specific conservation plans. For many species, effective conservation remains difficult due to low population genetic structure and difficulty in accurately assessing potential threats. The Leach’s storm-petrel (Hydrobates leucorhous) is a migratory pelagic seabird that breeds in large colonies throughout the North Pacific and Atlantic Oceans. In the past 50 years, Atlantic populations have declined by an estimated 54%. Several potential threats, ranging from offshore structures to increased predation from gulls, have been identified, however determining the impact of these widely distributed threats on specific colonies remains difficult due to the species low genetic structure and migratory behaviour. Where previous population assignment studies on this species have failed, I aim to use a combination of genomic data and novel machine learning methods to investigate the genetic structure of Atlantic Leach’s Storm-Petrels and assign individuals of unknown origin to their respective breeding colonies. Using DNA collected from over 300 individuals from 11 different populations, as well as 84 deceased individuals of unknown origin, I attempted to use the novel neural network popfinder to generate colony of origin predictions and determine what threats appear to be the most pertinent to specific colonies.
Full Professor, Department of Cellular & Molecular Medicine Faculty of Medicine, University of Ottawa The SMC5/6 complex: Folding chromosomes back into shape when genomes take a break High-level folding of chromatin is a key determinant of the shape and functional state of chromosomes. During normal cell division cycles, structural maintenance of chromosome (SMC) complexes ensure the large-scale folding of chromatin into visible chromosomes. While it is known that cancer cells experience important changes in genome architecture, it is still unclear if mutations in core regulators of chromosome structure can lead to cancer-promoting loss in genome stability. To address this question, we conducted a systematic analysis of mutations affecting a global regulator of chromosome biology –the SMC5/6 complex– in cancer genomics cohorts. Analysis of 64,959 cancer samples spanning 144 tissue types and 199 different cancer genome studies revealed that the SMC5/6 complex is frequently altered in breast cancer patients. Patient-derived mutations targeting this complex associate with strong phenotypic outcomes such as loss of ploidy control and reduced overall survival. Remarkably, the phenotypic impact of several patient mutations can be observed in a heterozygous context, hence providing an explanation for a prominent role of SMC5/6 mutations in breast cancer pathogenesis. Overall, our findings suggest that genes encoding global effectors of chromosome architecture can act as key contributors to cancer development in humans.
Drew Sauve, PhD Candidate, Friesen Lab Environmental correlates of early-life growth, natural selection, and components of phenotypic variation in a long-term experimental study system of black-legged kittiwakes In the face of global environmental change, the ability to predict adaptation has become a priority. To make predictions of adaptation, we must understand how environmental factors shape phenotypic expression, natural selection, and genetic variation. In my dissertation, I explore the effects of environmental variability on phenotypes, selection, and genetic variation using pedigrees, nestling growth traits, and nestling survival data from three long-term seabird monitoring programs. In most chapters, I focus on a Northeastern Pacific population of black-legged kittiwakes Rissa tridactyla. First, I use a sliding window approach to analyze three long-term seabird datasets. I use these analyses to identify specific periods of environmental variation that correlate with growth, assess changes in environmental predictors across years, and predict future growth under climate change. My findings reveal specific breeding season periods that are strongly associated with growth. These associations suggest warmer conditions may result in poorer growth for two of the three species studied. Further, windows of environmental influence change between historical and contemporary periods, emphasizing the need to investigate how such changes might affect adaptation to changing environments.
In my final chapters, I use kittiwake food supplementation experiment data to examine the relationship between food conditions, the variability of selection strength, and variance components of nestling kittiwake size traits. I find that natural selection is strongest in early ontogeny, in non-food supplemented nestlings, and for the youngest nestlings in a brood. Selection magnitude varies among years, but annual variation in magnitude was similar for all treatment and hatching order groups. Warming conditions have mixed effects on selection that depend on food supplementation and hatching order. Finally, using pedigree data, I find higher annual variance and additive genetic variance in non-food supplemented nestlings, suggesting potential cohort effects and increased evolutionary potential in non-food supplemented nestlings. Together, my results help fill and identify gaps in our understanding of the ability of natural populations to adapt to ongoing climate changes. Dr. Hilary Dugan, Assistant professor at the Center for Limnology at the University of Wisconsin – Madison. A Winter's Tale of Wisconsin Lakes Historically, limnologists have dedicated their efforts to studying lakes in the summer, while overlooking winter. Winter field work is challenging. Most lakes in the United States and Canada, however, freeze over for at least part of the winter. A bias for summer research has left gaps in knowledge on lake chemistry and biology under ice. More pressingly, with anticipated changes in environmental conditions, there is a need for information on how lakes and reservoirs function in the winter for a more complete understanding of lakes. This knowledge is also critical to future management of freshwater resources in a future with shorter winters and less lake ice. This talk will focus on what we’ve learned from winter limnological research taking place on Wisconsin lakes, and will include recent results from a a whole-lake manipulation where we removed all of the snow from the surface of a north temperate bog lake in northern Wisconsin.
Andrew Le, MSc Candidate, Colautti Lab Exploration into the “blackbox” of Vincetoxicum rossicum’s allelopathy Secondary metabolites may directly inhibit the growth of native plants or act indirectly by altering soil microbial communities. Vincetoxicum rossicum is an invasive vine known to exudate such a metabolite, (-)-antofine. Although (-)-antofine has been shown to exhibit antimicrobial properties, whether the chemical is ecologically relevant is unclear. The objective of this study was to assess how (-)-antofine production relates to the abundance of V. rossicum in different habitats. Soil cores were collected across twelve meadow and nine understory sites covering replicated gradients (n=8) of V. rossicum at Rouge National Urban Park, Canada. In total 1344 soil samples were analyzed using Liquid Chromatography – Mass Spectrometry to measure the (-)-antofine concentration. V. rossicum and (-)-antofine patterns were compared using linear-mixed effect models with site as a random effect to control for site level differences in (-)-antofine.
Our results show that (-)-antofine concentration was higher in areas where V. rossicum is more abundant (P < 0.05). The same held true in both meadow (P = 0.049) and understory (P < 0.05) habitats. As site was used as a random effect, this suggests that the abundance of (-)-antofine is not dependant on site but on the density of V. rossicum. This may suggest that V. rossicum ability to invade a wide range of habitats is due to (-)-antofine exudation. As (-)-antofine has anti-microbial properties, V. rossicum invasion success may involve changes in plant-soil interactions. Our research indicates that (-)-antofine may be an important factor in the invasive success of V. rossicum. Jason C. L. Brown, Department of Biological Sciences, University of Toronto Scarborough (UTSC) An animal physiologist’s foray into the scarcely inhabited world of plant aging Despite the fact that my graduate research was focused on mitochondrial metabolism in hibernation and daily torpor in mammals, and despite the fact that, in my teaching-focused role at UTSC, I instruct students in animal physiology and vertebrate endocrinology, when I was tasked with carving out a research niche in which I could supervise undergraduate students, I decided to enter the realm of plant aging, which is seemingly an area of focus for only a handful of researchers around the world. I was inspired to undertake such research after reading a book about life history strategies in plants. The book talked at length about the ecological and evolutionary pressures that favour the annual vs. perennial condition in plants but entirely neglected that physiological adaptations must accompany any changes in life history strategy within plant lineages. To this end, my research program has focused on physiological differences between annual and perennial species, with a particular emphasis on the oxidative theory of aging. To date, we have shown that the leaves of perennials are more resistant to oxidative damage from exogenous H2O2 than those from annuals. We have further shown that perennials have higher antioxidant levels in their seeds, leaves, and roots compared to annuals, and that perennials are able to repair oxidative damage to their chlorophyll faster than annuals. Additionally, we have demonstrated that perennials do not limit their concentration of chlorophyll b, despite its increased susceptibility to oxidative damage, but these plants have altered the amino acid sequence of one of their chlorophyll-binding proteins (CP24), thereby making it more stable and better able to fulfill its role in minimizing photosynthetic ROS production. Recently, we also began investigating several lines of early-flowering flax, expecting that they would be more susceptible to oxidative stress given their shorter lifespan. To the contrary, they exhibited significantly higher catalase levels, which complicates our understanding of plant aging.
Natasha Neves, MSc Candidate, Orihel Lab Effects of microplastics on benthic macroinvertebrates in a limnocorral experiment The response of freshwater benthic macroinvertebrates to microplastics (< 5 mm) under environmentally relevant conditions is not well understood. The objective of the present study was to determine effects of a microplastic particle mixture (polystyrene, polyethylene terephthalate, and polyethylene) on benthic invertebrates under an environmentally relevant gradient of microplastic pollution. Twelve open-bottom limnocorrals were deployed in the littoral zone of a boreal lake at the International Institute for Sustainable Development – Experimental Lakes Area in Ontario, Canada in June 2022. Pre-colonized leaf litterbags (5x3 mm mesh size) were added to the limnocorrals and sampled after 5 and 8 weeks of microplastic exposure to characterize the benthic invertebrate community. Results will elucidate a concentration-response relationship between microplastics and benthic invertebrates at the organismal (body size), population (species abundance), and community (diversity, evenness) levels. This study will help to identify thresholds in microplastic pollution that could be hazardous to freshwater benthic invertebrates.
Lisa Cicchetti, MSc Candidate Grogan Lab Evolved tolerance to road salt among wild populations of Daphnia Snowmelt and rain carry road salt from paved surfaces through the watershed via runoff and groundwater and increase the salinity of lakes, often measured as chloride concentration (Cl- mg/L). Salinization negatively impacts freshwater organisms, including Daphnia pulicaria, a ubiquitous crustacean zooplankton grazer that is integral to healthy ecosystems. Daphnia are sensitive to environmental changes, but studies have shown they are capable of rapid evolution. We investigated intraspecific variation in salt sensitivity among D. pulicaria collected from 10 lakes in southeastern Ontario to understand how wild Daphnia respond to salt pollution. Acclimation can also influence tolerance, so we tested the effect of acclimation on acute 48-hour salt tolerance for Daphnia grown at low (18 mg Cl-/L) and high (218 mg Cl-/L) Cl-. Our results indicate that acclimation to salt does not significantly impact tolerance. Our common garden experiments testing acute toxicity of salt on Daphnia from lakes ranging from <1 mg Cl-/L to 271 mg Cl-/L show a wide range of salt tolerances for wild Daphnia. Daphnia from Presqu’ile Bay, Lake Ontario (26.2 mg Cl-/L) and Lake Wilcox (194 mg Cl-/L) have higher salt tolerances of 2222 mg Cl-/L and 2344 mg Cl-/L, respectively, compared to Daphnia from unimpacted lakes (1277 – 1617 mg Cl-/L). This indicates that D. pulicaria may have adapted to localized road salt pollution. Understanding the factors contributing to robust tolerance to road salt will help inform decisions regarding freshwater ecosystem conservation.
Dr. Josh Neufeld, University of Waterloo Professor, University Research Chair Shedding light on the evolution of anoxygenic phototrophy through cultivation of Boreal Shield lake bacteria Phototrophic members of the Chloroflexota phylum are enigmas in the evolution of phototrophy because of their unusual photosynthetic reaction centre and antenna complex pairing. Through a “failed” cultivation experiment from an iron-rich Boreal Shield lake, we recovered and characterized a novel new species, “Ca. Chlorohelix allophototropha”, with unexpected features relevant to the evolution of phototrophic bacteria. This talk will present genome, physiology, and ecology data to demonstrate that this phylogenetically distinct phototroph can be among the most active populations in illuminated anoxic waters of Boreal Shield lakes, which number in the millions globally. Our results establish Chloroflexota phylum members as unique among known anoxygenic phototrophs, providing new context for understanding the origins of phototrophic life on Earth. Dr. Graeme Howe, Assistant Professor Queen's University, Department of Chemistry Genome mining for "extremozymes" - Extremophiles as sources of novel biocatalysts Directed evolution has enabled the development of extremely useful biocatalysts that have, in some cases, supplanted traditional organic chemistry in the industrial production of value-added commodity chemicals. Generally, mutations introduced into a protein scaffold to increase catalytic efficiency are accompanied by a compensatory destabilization of the enzyme. To circumvent this issue and allow a more thorough exploration of sequence space around naturally occurring enzymes, we have turned to sequence similarity networks (SSNs) to mine the genomes of thermophilic microorganisms to identify novel thermostable variants of enzymes with potential industrial utility. These networks allow for the exploration of whole protein families and the interrelatedness of every member sequence through an ‘all-by-all’ BLAST. Through the iterative construction of SSNs with varying sequence identity cutoffs, we have produced networks of putative isofunctional clusters that allow a single sequence with known catalytic function to reveal the role of thousands of unannotated PETase-like genes.
Our initial efforts in this arena have focused on the search for new thermostable plastic-degrading enzymes as a part of the OpenPlastic consortium’s efforts to develop a circular plastics economy. Following the initial discovery of a cutinase-like enzyme from Ideonella sakaiensis that degrades polyethylene terephthalate (PET), there has been an explosion in research revolving around the biocatalytic degradation of PET and other plastics. While several engineered PETases have emerged that are sufficiently stable and catalytically efficient for industrial PET degradation, we opted to direct our initial efforts to exploit the wealth of PETase sequence-function relationships to mine the genomes of extremophiles for new PETases as starting points for further engineering efforts. Using the I. sakaiensis enzyme as a seed sequence, SSNs were constructed that led to the identification of 10 putative PETases from bacteria with optimal growth temperatures ranging from 50 °C to 80 °C. This presentation will detail our efforts to characterize these enzymes and their potential utility in the degradation of PET plastics. Similar bioinformatics-driven approaches to identify and characterize thermostable enzymes that degrade polyamides and polyurethanes will also be presented. Michael Vermeulen, PhD candidate Babak/Craig Lab The Vanishing Y: Exploring the role of mosaic loss of chromosome Y in neurodegeration and cancer As men age they experience a gradual loss of the Y chromosome (LOY) in their cells, specifically within immune cell-types. Recent, large-scale epidemiological surveys have found
approximately 70% of men older than 70 years of age have a detectable loss of their Y chromosome. Furthermore, a range of association studies have linked LOY to several age-related diseases including heart disease, Alzheimer’s, cancer, and macular degeneration. Also, we know that LOY is one of the most common chromosomal aberrations observed in male cancers (occurring in about ~28% of primary tumors). Despite the frequency of LOY and its association with disease, relatively little is known about its mechanisms and its role in disease pathology. Although recent mouse studies suggest LOY can directly cause disease, we still don’t know if it directly causes disease or is a passenger biomarker of degrading genomic instability. My Master’s research aimed to better understand LOY in brain tissue, with a specific interest in the cell-types LOY tends to accumulate in. We found that LOY is particularly common in the microglia, the main immune cell in the brain and a cell-type with important roles in neurodegerative processes. My PHD research investigates the role of LOY in cancer, and its potential use as a therapeutic target. We plan to use CRISPR-cas9 editing systems to engineer isogenic cell lines differing only by the presence of the Y chromosome. We will then test for LOY-specific genetic vulnerabilities using CRISPR loss-of-function screens with the goal of highlighting potential weaknesses in LOY cells that could be exploited as a cancer therapy. Dr. Zoe Panchen The blossoming of the Arctic: Natural history records as a resource to study plant responses to climate change The Arctic is experiencing some of the most dramatic changes in climate with temperatures rising at treble the rate of the global average. Phenology, the timing of natures seasonal events, is often related to temperature and, as the climate warms, Arctic flowering and fruiting times are generally shifting earlier. Natural History records of pressed plants (herbarium specimens) are often collected in flower or fruit and offer a snap shot of flowering and fruiting times over the past century or more. Herbarium specimens are thus an excellent resource for predicting how plants will respond to climate change. In this talk, I will discuss how Arctic plants are responding to climate change, focusing on findings from my Nunavut plant phenology research using herbarium specimens and long-term phenology monitoring. I will conclude my presentation by describing my current research on evolutionary and life history trait patterns in Arctic plant phenological responses to climate change.
Investigating pollen capture, production, and size strategies in wind-pollinated flowering plants The flowering plants (angiosperms) have evolved a wide diversity of pollination strategies, from complex interactions with specialized animal pollinators to strategies that are entirely abiotic, relying on fluid currents like wind or water to transport pollen from stamen to stigma. Compared to animal pollination, abiotic strategies like wind pollination have long been considered inefficient, evolving when animal pollination becomes unreliable. Traits commonly associated with wind-pollinated plants are thought to reflect this apparent inefficiency and low probability of successful pollen transfer. Compared to animal-pollinated species, which tend to have large showy flowers design to attract animal pollinators, wind-pollinated plants tend to make many small, inconspicuous flowers that produce large volumes of pollen and often have just one ovule. These traits may represent a strategy to mitigate inevitable pollen losses – or they may represent innovative adaptations to maximize pollen capture in a unique pollination system. For example, packaging just one ovule per flower might not be because the probability of multiple grains landing on a given stigma is unusually low. Instead, having many small, relatively inexpensive flowers may allow wind-pollinated plants to maximize their pollen capture by maximizing the area they sample in space, at minimal floral costs. Similarly, pollen production strategies in wind pollinated plants may not simply reflect low probability of pollen capture by stigmas. Instead, these may be the result of a complex balance of selection on pollen size and number imposed by transport through wind and subsequent competition between pollen grains for limited ovules. In my research, I’m broadly interested in understanding the strategies wind-pollinated plants use to facilitate successful pollination from both male and female fitness perspectives, despite the inherent stochasticity in wind pollination.
Effects of turbidity and nutrients on zooplankton community structure: a mesocosm study Freshwater ecosystems make significant contributions to biodiversity and provide ecosystem services of value to humans. However, freshwater habitats are among the most threatened globally. Among the many ways that humans are altering freshwater ecosystems, elevated turbidity from suspended clay-sized sediments remains relatively under-explored, with much research limited to controlled single-species laboratory studies or community-level studies in oligotrophic environments. Sediments can adsorb nutrients and simultaneously deliver nutrients to freshwater systems, resulting in turbidity and nutrients simultaneously acting as stressors in lakes. Zooplankton play an important role in aquatic ecosystems, transferring energy from lower to higher trophic levels, and are excellent indicators of freshwater ecosystems. With the objective of exploring the causal relationships between turbidity and nutrients on zooplankton communities, I conducted a mesocosm experiment at the Queen’s University Biological Station. Using 60 mesocosms, I established two 30-increment turbidity gradients, one at ambient (mesotrophic-eutrophic) and one at high (eutrophic-hypereutrophic) nutrient levels. I stocked the mesocosms with a diverse zooplankton community and measured community-level responses (abundance, biomass, and diversity) after 6 weeks. I found no change in total zooplankton abundance or biomass, and no interaction between turbidity and nutrients. Rotifer abundance and biomass declined with turbidity, which correlated with a decline in the concentration of cryptophytes, a preferred food source for rotifers. Cladocera abundance increased with turbidity and there was no change in biomass, indicating compensatory responses within the cladocera community. Changes in the abundance of specific cladocera species further support the presence of compensatory dynamics in response to turbidity. In contrast with my findings, past laboratory studies and oligotrophic community studies found that turbidity had no impact on rotifer abundance and caused a decline in Cladocera abundance. In drawing different conclusions from previous studies, my research provides insights to how a highly diverse zooplankton community in nutrient-rich conditions respond to turbidity, and the potential for nutrients to alter the effects of turbidity on zooplankton communities.
Dr. Liana Burghardt Assistant Professor, Plant Sciences Department Pennsylvania State University Evolving together, evolving apart: Measuring the fitness of rhizobial bacteria in and out of symbiosis with leguminous plants The nitrogen-fixing symbiosis between legumes and rhizobia represents fertile ground to study the evolution and ecology of beneficial plant-microbe interactions. In facultative relationships where both partners can live independently, soil selection patterns can influence the process of host adaptation and vice versa. This talk will describe a twist on an ‘evolve and resequence’ methodology we developed to measure the relative success of scores of co-existing rhizobia isolates in host and nonhost environments. Our team of researchers has measured Sinorhizobium strain fitness in nodules of Medicago legume hosts and as free-living saprophytes in the soil. By synthesizing results from multiple experiments, we examine patterns of rhizobial fitness correlations within and between host and non-host environments. We found 1) only between host species do we observe negative fitness correlations (evolutionary constraint), 2) that in soil mesocosms, temperature and salinity influence isolate-level selection more strongly than other soil characteristics, and 3) that adaptation to nonhost soil environments is unlikely to constrain or undermine rhizobial adaptation to host environments. Our results suggest it may be possible to leverage host genetic variation to manipulate rhizobial communities and optimize rhizobial fitness without undermining the soil survival of rhizobia and that co-occurring Medicago species may function to maintain rhizobial diversity in soils.
DR. LEIGH MCGAUGHEY The Great River Rapport: A collaborative approach to assessing and communicating the ecological health of the Upper St. Lawrence River Born out of the question “What is the health of the St. Lawrence River?” the River Institute, in partnership with the Mohawk Council of Akwesasne, initiated an ecosystem health report on the river. Framed in the Ohén:ton Karihwatéhkwen (Words that come before all else), the project is a science-based, ecosystem health report informed by community-driven research questions. The Great River Rapport engages Indigenous partners, community members and groups, academics, students, and government agencies to produce scientific findings, and translate science into compelling stories and formats that motivate action. It also performs the role of identifying data gaps for future research. Through a participatory approach, a suite of 35 ecological indicators have been selected to reflect the health of the river system. Progress on the project to date will be shared, along with key findings from a selection of the fish indicators (see www.riverrapport.ca). Assistant Professor and Canada Research Chair in Plant Cell Biology Department of Cell and Systems Biology, University of Toronto Building the plant cell wall from the inside out The plant cell wall is a polysaccharide-based extracellular matrix that surrounds and protects all plant cells. Since plants are constantly growing and developing within the confines of their cell walls, plant cells must be in constant communication with their cell walls. Furthermore, cell walls are a critical line of defense between plant cells and their environment; changes to the cell wall are often early warning signs of pathogen attack or abiotic stress, and plants fortify their cell walls in response to these stresses. This ongoing communication between the plant cells and their cell walls is collectively called “cell wall signaling”. The McFarlane Lab at The University of Toronto studies the molecular mechanisms of cell wall signaling and responses, including cell wall secretion and remodeling. We have recently characterized two different pathways that affect cell wall matrix polysaccharide synthesis at the Golgi apparatus. Interestingly, these cell wall synthesis defects result in changes to Golgi structure and function including inappropriate cell wall synthesis, secretion, and/or remodelling. These cellular phenotypes ultimately result in defects in coordinated cell growth and loss of tissue integrity, resulting in dramatic consequences for plant growth and development
University of Rochester The evolutionary history of Drosophila simulans Y chromosomes reveals molecular signatures of resistance to sex ratio meiotic drive The recent evolutionary history of the Y chromosome in Drosophila simulans, a worldwide species of Afrotropical origin, is closely linked to that of X-linked meiotic drivers (Paris system). The spread of the Paris drivers in natural populations has elicited the selection of drive resistant Y chromosomes. To infer the evolutionary history of the Y chromosome in relation to the Paris drive, we sequenced 21 iso-Y lines, each carrying a Y chromosome from a different location. Among them, 13 lines carry a Y chromosome that is able to counteract the effect of the drivers. Despite their very different geographical origins, all sensitive Y’s are highly similar, suggesting that they share a recent common ancestor. The resistant Y chromosomes are more divergent and segregate in 4 distinct clusters. The phylogeny of the Y chromosome confirms that the resistant lineage predates the emergence of Paris drive. The ancestry of the resistant lineage is further supported by the examination of Y-linked sequences in the sister species of D. simulans, D. sechellia and D. mauritiana. We also characterized the variation in repeat content among Y chromosomes and identified two simple satellites ((AAACAAT)n and (AATGG)n) associated with resistance. Altogether, the molecular polymorphism allows us to infer the demographic and evolutionary history of the Y chromosome and provides new insights on the genetic basis of resistance.
Conner Elliot PhD Student, Tufts lab Biotelemetry provides new insights about the migration of adult walleye in Lake Ontario Walleye (Sander vitreus) populations throughout the Laurentian Great Lakes complete annual migrations between spawning and foraging habitats. Until recently, information regarding these migrations was collected using fisheries-dependent data, which can be biased based on fishing effort. Advances in tracking technology and electronic tagging techniques now provide the tools to collect fisheries-independent information about highly mobile species. This thesis examined the timing, extent, and patterns of migration for adult walleye that spawn in the Bay of Quinte and migrate through eastern Lake Ontario. The within-individual repeatability of these annual migrations was determined to be high at the temporal, spatial, and combined spatiotemporal levels. Tagging fish with a combination of acoustic transmitters and pop-off data storage tags (pDSTs) provided insights into the benefits and limitations of each method and identified a novel diving behaviour for this species. Combining the data from both methods provided an overview of the seasonal temperatures, depths, and activity levels experienced by these fish across an entire annual migration. There were sex-based differences in the timing, extent, area use, and vertical activity rates during the annual migration, as well as the number of dives per day during the summer. For most studies, acoustic transmitters can provide estimates of thermal and depth preferences, but they also have important limitations that were identified in this study. This thesis improves our understanding of migratory behaviour in freshwater fish, and the degree to which they are able to repeat these behaviours. It outlines the benefits and limitations of new methods that can be used to collect high-resolution data throughout the year. Future studies should examine the drivers behind these movements, and the mechanisms that these fish use to navigate across large inland waterbodies.
Dr. Molly Stanely University of Vermont Chacterizing a unique subset of taste cells in Drosophila melanogaster All animals must continually make important feeding decisions. Chemosensory neural circuits, such as those for taste and smell, play a key role in directing feeding behaviors. The sensing of food chemicals by specialized sensory taste cells (gustation) helps animals evaluate potential food sources to encourage consumption of nutritive compounds while avoiding potentially harmful compounds. While the cellular and molecular mechanisms for encoding some taste modalities are relatively well-understood, such as ‘sweet’ and ‘bitter’, other taste modalities are more complex, such as ‘salty’ and ‘umami’. The fruit fly, Drosophila melanogaster, offers unparalleled genetic tools to answer neurobiological questions and I have recently used this model organism to help uncover the molecular and cellular mechanisms of salt taste and feeding. While creating a comprehensive map of taste cells on the fly labellum for this project, a unique subset of chemosensory cells with an unknown function were identified. In this seminar, I will share recent work that aims to characterize the activation profile of these taste cells and understand the functional impact of these sensory cells on feeding behaviors.
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