Investigating the interaction between inter-locus and intra-locus sexual conflict using hemiclonal analysis in Drosophila melanogaster
January 21st 12:30 – 1:30 pm ET
Divergence in the evolutionary interests of males and females leads to sexual conflict. Traditionally, sexual conflict has been classified into two types: inter-locus sexual conflict (IeSC) and intra-locus sexual conflict (IaSC). IeSC is modeled as a conflict over outcomes of intersexual reproductive interactions mediated by loci that are sex-limited in their effects. IaSC is thought to be a product of selection acting in opposite directions in the two sexes on traits with a common underlying genetic basis. While in their canonical formalisms IaSC and IeSC are mutually exclusive, there is growing support for the idea that the two may interact. Empirical evidence for such interactions, however, is limited. We investigated the interaction between IeSC and IaSC in Drosophila melanogaster. Using hemiclonal analysis, we sampled 39 hemigenomes from a laboratory-adapted population of D. melanogaster. We measured the contribution of each hemigenome to adult male and female fitness at three different intensities of IeSC obtained by varying the operational sex-ratio. Subsequently, we estimated the intensity of IaSC at each sex-ratio by calculating the intersexual genetic correlation for fitness and the proportion of sexually antagonistic fitness-variation. Additionally, we also measured a suit of male and female traits associated with sexual conflict in D. melanogaster. Our results indicate a statistically non-significant trend that suggests that increasing the strength of IeSC ameliorates IaSC in the population, a pattern that might be driven by positive genetic correlations between female resistance traits and male fitness.
Dr. Blake Jones
Bennington CollegeUnderstanding complex sociality: Field-based and meta-analytic approaches
Jan 14th 12:30 – 1:30 pm ET
Welcome back! We kick off the Winter EEB Seminar Series next week with Dr. Blake Jonesfrom Bennington College, hosted by the Bonier lab. Dr. Jones studies the underlying mechanisms of development, sociality, learning, and memory in free-living animals. His research integrates theories and techniques from climate-science, ecology, physiology, genetics, and cognitive neuroscience. Tune in next Thursday at 12:30 pm to hear about his work on manakins, social hierarchies, and mate choice copying! ABSTRACT Complex sociality has evolved across the animal kingdom. As such, biologists as early as Darwin have focused on the ultimate aspects of complex social behaviors, such as cooperation and social learning. More recently, integrative approaches in biology have led to a growing understanding of the proximate mechanisms of sociality in a number of diverse taxa. Here, I highlight a few examples of field-based and meta-analytical approaches to better understand how complex social behaviors are mediated and modulated. First, social classes are a common feature of cooperative animal societies, but what determines an individual’s place within the social hierarchy? My colleagues and I investigated this question in the lance-tailed manakin (Chiroxiphia lanceolata), a cooperative bird species with a complex social hierarchy. We found that glucocorticoids, hormones associated with the physiological stress response, positively correlated with and predicted current and future social status. Likewise, we found a similar predictive link between future social status and the dynamics of telomeres, repetitive sequences of non-coding DNA at the ends of chromosomes. Second, female mate choice is a critical component of sexual selection and can be influenced by social information. Female mate choice copying occurs when one female copies the apparent mate choice of another female and has been documented in numerous taxa. Though this social phenomenon has the potential to influence patterns of sexual selection, how widespread is it? And, what are the individual and environmental factors that modulate its effect? We used a meta-analytical approach to discover that mate-choice copying is exhibited across taxa and is strongly influenced by factors both intrinsic and extrinsic to the individual.
Blake’s work aims to uncover the genetic and physiological underpinnings of complex sociality, cognition, and development in free-living animals. He uses integrative and comparative approaches in the lab and the field to address questions at the forefront of organismal biology. His work is highly collaborative, involving researchers and undergraduates from throughout the US as well as Brazil and Australia. Blake’s work has been funded by multiple National Science Foundation awards, The Nature Conservancy, the Society for Integrative and Comparative Biology, and the American Ornithological Society. He routinely publishes in peer-reviewed, international scientific journals, including Animal Behaviour, Frontiers in Ecology and Evolution, General and Comparative Endocrinology, Hormones and Behavior, and Oecologia. Blake’s teaching style focuses on critical thinking and first-hand experience in the lab and the field. He draws on his diverse experience in research, conservation, field biology, veterinary medicine, art, music, and photography to make biology easily accessible. B.S., James Madison University; Ph.D., University of Memphis; Visiting Research Scholar, Curtin University (Perth, Australia); Postdoctoral Scholar, Florida State University. Blake joined Bennington College in 2020.
The choice of “who to mate with” has profound consequences for organisms and populations alike, determining not only phenotypes and trait expression within an individual, but the ecology, genetics, and evolutionary trajectories of populations and species. In plants, mate choice falls into a few main categories of reproductive modes, including preferential mating with oneself (self-fertilization), avoiding mating (asexual reproduction), or avoiding mating with different species. Mating habits thus shape patterns of genomic variation, gene flow, and speciation and are key to the astounding biological diversity that we see in the world. My research integrates field ecology, population genetics, and theory to address two main questions: 1) What are the ecological and genomic consequences of mate choice? and 2) How does mate choice influence speciation? I will present two stories of mate choice in wild plant populations. First, I explore the impacts of asexuality, hybridization, and self-fertilization on the evolution of sex in the North American wildflower Boechera. Second, I discuss a population genetic model that predicts the breakdown of reinforcement in wild maize and teosinte due to sexual conflict between a female mating barrier allele and a male compatibility allele. The interplay between these two phenomena highlights the tension between the costs and benefits of hybridization. My work shows how plant diversity is shaped by the influence of mating habits on both trait evolution and speciation, and future work will continue to explore the micro- and macroevolutionary consequences of mate choice.
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.
note: EEB attendees do not need to register via the public link; instead, you can join as usual by clicking the Zoom link in the emailed ad. If you do not receive EEB links, you can join the event by registering through the link above
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’.