Department of Biology
Lab Members - Graduate Students
The topic of my PhD thesis is to model the evolution of food webs. It involves developing mathematical and computer models that represent food webs in which species are engaged in biotic interactions (like predator - prey, and competition) and exposed to the effects of important abiotic factors (e.g. gravity, light intensity). The food web structure is also affected by species evolution through time.
In summary, this approach tries to build more realistic food web models that include the effects of both environmental factors and evolution through some of the fundamental characteristics of species, such as their body size.
The models are then applied to investigate exciting and somewhat untracked issues. For example, the models investigate why, in pelagic food webs, predators usually have a larger body size than their preys, and why this pattern is not as obvious in continental food webs (in which predators can be smaller than their preys). Another aspect explored is the structure of food webs along the vertical dimension of space (especially in aquatic ecosystems) and the relative influence of several physical factors (such as light availability, gravity, turbulence) on this structure.
PhD Candidate McGill Biology
Funded through an NSERC PGS-D
Co-supervisor: Prof. Marilyn Scott
BSc Biology McGill University
Stewart Biology Building, W3/2
My research aims to investigate how evolutionary and ecological dynamics interact at a broad scale by determining how evolved host heterogeneity in resistance to parasites may impact epidemic dynamics in metapopulations using Gyrodactylus spp. as a model system. Parasites and infectious disease are both major contributors to species decline and therefore have important implications for conservation and the management of natural ecosystems. Although connectedness and migration among populations is known to promote species persistence over a larger metapopulation, such dispersal can also act as an agent for disease transmission, through continued introduction of susceptible hosts to infected populations and through introduction of parasites to naÔve host populations within the metapopulation.
My research explores the interaction of evolutionary and ecological dynamics by determining whether host heterogeneity impacts parasite dynamics at the individual, subpopulation and metapopulation level using Gyrodactylus spp. and guppies as a model system.Thus far, I've conducted lab-based research which explores how host sex and host population sex ratios affect parasite dynamics at a host individual- and population level, and another experiment which examines how asynchrony in parasite introductions affect host and parasite dynamics. For my final experiment, I plan on studying how rapid evolution of resistance to parasites impacts host-parasite dynamics using fish reared in the lab with and without parasites. I am also working with collaborators at the University of Alberta to develop a mathematical model for describing this host-parasite system and can predicting longer-term dynamics under various conditions.
The highly-controlled laboratory setting and multi-level analysis of this system combined with theoretical models will not only lead to a better understanding of host-parasite eco-evolutionary interactions at the metapopulation scale, but also provide concrete applications to conservation strategy and disease management in wildlife resources. The scope and scale of this project, particularly with a vertebrate system is unprecedented, and will provide a unique set of that can direct which future work in the field of host parasite relations and metapopulation ecology.
MSc Student McGill Biology
Stewart Biology Building, W3/2
Phytoplankton are sometimes called "The Forest of the Sea" because they are the most important primary producers of aquatic systems. I am currently looking at the effect of increasing CO2 levels in the atmosphere on communities of these organisms, which are at the base of aquatic ecosystems.
I am using an experimental dock located on Lake Hertel in McGill University's Gault Nature Reserve. The dock contains holes which accommodate 2500 L plastic bags that enclose parcels of the lake, called mesocosms. Apart from CO2 enrichment, I am also adding nitrogen and phosphorus to mimic agricultural runoff which can exacerbate the effects of carbon dioxide. The phytoplankton communities are quantified using a Fluoroprobe which allows me to quickly measure biomass of four different groups of phytoplankton: green algae, blue-green algae (cyanobacteria), diatoms and cryptophytes.
The goal of the research is to get an insight into the dynamics of phytoplankton communities with respect to nutrient limitation. This will allow us to infer how communities, including the larger non-photosynthetic organisms such as zooplankton and fish will react to the high CO2 levels in the atmosphere.
PhD Student McGill Biology
Funded through an NSERC postgraduate scholarship and an Écolac NSERC-CREATE fellowship
Co-supervisor: Prof. Beatrix Beisner
BSc & MSc Biology Université de Montréal
Stewart Biology Building, W6/13
Anthropogenic disturbances to inland waters such as climate warming and land-use intensification can affect organisms' properties and acitivities (traits), altering aquatic communities and food web structure. Some of the most critical responses of organisms to such environmental perturbations are a decrease in body size as well as altered vital rates (e.g. growth, feeding, metabolism).
The overall objective of my PhD project is to assess how zooplankton traits intimately linked to ecosystem functioning are affected by combinations of anthropogenic stressors. More specifically, I will (1) quantify variation in zooplankton size structure and trophic interactions (with algae) under multiple stressors, and (2) assess their feedbacks on food web regulating processes (top-down vs. bottom-up effects) and, consequently, ecosystem functioning. Using lake and pond mesocosm platforms, I plan on monitoring zooplankton responses and feedbacks under two sets of environmental disturbances: (i) agricultural herbicide, insecticide and fertilizer, and (ii) warming and basal resource availability/quality.
I believe that improving our ability to predict organismal responses and effects is crucial to efficiently detect impending impacts on perturbed freshwater ecosystems that appear to be functioning normally, as trait variation can precede (or sometimes buffer against) whole ecosystem changes.
If you want to know more about my previous work, visit https://www.researchgate.net/profile/Marie_Pier_Hebert
Naíla Barbosa da Costa
PhD Student Université de Montréal Biologie
Funded through an Écolac NSERC-CREATE fellowship
Supervisor at UdeM: Prof. Jesse Shapiro
MSc Ecology Federal University of Minas Gerais (UFMG)
Pavillon Marie-Victorin (UdeM), E223
Microorganisms compose the most abundant, ubiquitous and diverse group of organisms in the world. Microbial communities can rapidly adapt to different environmental constraints but the evolutionary mechanisms of their differentiation are still not clear. During my PhD I intend to contribute to a better understanding of the ecological and evolutionary processes underlying the genetic differentiation in aquatic bacterial communities subjected to different chemical stressors and also in cyanobacterial communities naturally exposed to phage that act as predators.
PhD Candidate, McGill, Natural Resource Sciences (NRS)
Funded through NSERC CGSD and W. Garfield Weston Award for Northern Research
Supervisor in NRS: Prof. Chris Buddle
BSc Biology Carleton University
MSc Biology McGill University
Research interests: community ecology, entomology, ecological networks
My research is about how biodiversity is distributed across trophic levels. To understand the concept of trophic biodiversity structure, imagine an ecological community as being like a building with many floors. The first floor is the plant species, the second floor is the herbivore species, the third floor is the species that eat herbivores, up to the floor of top predator species. The square-footage of each floor is the number of species belonging to that floor. What Iíd like to know is how the buildings Iíve described are shaped. Are they shaped like Aztec pyramids? Office buildings? Something less expected? What determines their shape? How does a buildingís shape determine the goings-on (ecosystem functions) in that building?
Over the course of my PhD, Iím approaching these questions about trophic biodiversity structure from a number of directions. Iíve completed a meta-analysis of 72 large food webs, describing their trophic structure and the determinants of that structure. I found that food webs have a trophic biodiversity structure that is generally, but not always, pyramid shaped. In the summer of 2016 I collected invertebrates from the tundra of the Yukon, Canada, and found that the trophic structure of the invertebrate communities varied with latitude. In the summer of 2017 I returned to the Yukon tundra to carry out experiments with spiders, investigating the relationship between predator diversity and prey abundance. Finally, Iím currently testing some predictions of evolutionary food web models, in regards of the role of body size in the evolution of trophic strategy.