Lac Hertel

Fussmann Lab
Department of Biology

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Felipe Dargent

Felipe Dargent

PhD3 Student McGill Biology
(funded through a Vanier Canada Graduate Scholarship)
BSc Geography
Pontificia Universidad Católica del Perú
Co-supervisor: Prof. Marilyn Scott
Stewart Biology Building, W3/2
Phone: 514-398-3153
e-mail: felipe.dargent@mail.mcgill.ca

My research with doctors Fussmann and Scott has two main axes: the evolution of host defences against infection and the ecological interactions of parasites within a host.

Resistance and tolerance, the two main component of host antipathogen defence, trade off with each other leading to two conceptually different mechanisms through which the host can decrease the parasite burden or reduce the fitness decreasing effects of a given burden. Although well explored in plants, these mechanisms have been scarcely studied in animals due to practical and conceptual complications for measuring such mechanisms. By comparing parasite population dynamics and an array of host health indicators through different generations I will assess the rate and nature of the evolution of host's defence.

My experimental system uses guppies (Poecilia reticulata) reared in the lab from wild caught populations in the northern range of Trinidad island, and Gyrodactylus turnbulli, a naturally occurring guppy Monogenean ectoparasite. I will assess the evolution of guppy defence against Gyrodactylus turnbulli with populations from the same stream that differ either in natural parasite levels (none and high) or predation regime (low predation and high predation).

In order to have a clearer understanding of the impacts of Gyrodactylus sp. in a natural setting I will focus on parasite community ecology. I will assess the community ecology of various guppy parasites to understand how different parasite species may facilitate, exclude each other or coexist in the same host through immune response activation, energy diversion, resource partitioning, priority effects or density dependent effects. The main interacting parasites for this research will be G. turnbulli, G. bullatarudis, G. pictae, Ichtyophthirius and Camellanus.

This research is funded by a Tomlinson Fellowship and an NSERC Special Research Opportunity Grant (to Fussmann, Hendry, Scott, Bentzen) and linked to the NSF-funded, Trinidadian whole-ecosystem project "From Genes to Ecosystems: How do Ecological and Evolutionary Processes Interact in Nature."

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Monica Granados

Monica Granados

PhD2 Student McGill Biology
MSc University of Toronto
Co-supervisor: Dr. Stéphane Plourde (Fisheries and Oceans Canada)
Stewart Biology Building, W6/13
Phone: 514-398-6725
e-mail: monica.granados@mail.mcgill.ca

The consequence of omnivory in food webs has a contentious history. Food web simulations by Pimm and Lawton in 1978 indicated the percentage of stable food webs with omnivory should be low. Yet, omnivory is prolific in real food webs. Reconstructions of terrestrial and marine ecosystems generated reticulate webs replete with omnivory. The disparity between real and simulated webs was reconciled in 1997 with the identification of weak interaction strength as the mechanism for the maintenance of omnivory. In simple, tri-trophic food webs with an omnivore, consumer and basal resource, weak omnivory reduces the attack rate on the consumer and reduces the growth rate of the basal resources resulting in increased stability.

While the current consensus is that the presence of omnivory is stabilizing, the consequence of introducing omnivory to a resident food web remains unknown. My research is motivated by the introduction of the blue mussel, Mytilus edulis, into the water column for aquaculture. Aquaculture transplants mussels from their natural benthic habitat to suspended lines consequently increasing the interaction rate between mussels and zooplankton. In this modified food web, mussels are omnivores consuming and competing with zooplankton for a common phytoplankton resource. For the first chapter of my thesis I performed experiments dissecting and manipulating the strength of predation and omnivory in an experimental food web consisting of a mussel, zooplankton and phytoplankton. The results were consistent with theoretical predictions - weak interactions promoted the persistence of zooplankton, whereas strong interactions drove zooplankton towards extinction. The experiment however, also revealed that the strength of omnivory and predation are not independent. The availability of algae, as a consequence of reducing omnivory, increased the rate of mussel predation on zooplankton.

My current research continues to investigate how omnivory mitigates stability. Presently I am performing experiments with ciliate communities to record the dynamics of consumer-resource oscillators along an omnivory gradient. I will also be conducting experiments to determine 1. the consequences of introducing omnivory to a predator-prey community and 2. how omnivory affects rates of invasion spread.

The results from these experiments will be coupled with models and metanalyses to elucidate the consequences of the propagation of omnivory.

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Caolan Kovach-Orr

Caolan Kovach-Orr

PhD3 Student McGill Biology
BSc Rutgers University, New Jersey
Stewart Biology Building, W6/13
Phone: 514-398-6725
e-mail: caolan.kovach-orr@mail.mcgill.ca

As ecologists, we are ultimately interested in understanding the factors that influence community establishment, stability, and persistence. For this reason, the effect of species diversity on community dynamics has been the subject of a great deal of research; however, there have only been limited investigations into how changing the amount of variation within species affects community interactions. Recent theoretical and empirical experiments have shown that increasing intraspecific variation has the potential to significantly enhance community stability.

Within species, there are two sources of adaptive trait variation that may act separately or in concert: genetic diversity and phenotypic plasticity. Genetic diversity, the presence of different alleles that encode different phenotypes, can potentially promote population level stability (of a single species) while allowing individual genotypes' populations to fluctuate asynchronously. Phenotypic plasticity involves individuals with the same genes expressing different traits in response to different environmental cues, potentially enhancing stability within a single genetic strain. For example, inducible defences can enhance strain level stability by reducing the efficiency of the predator.

My research combines theoretical and empirical studies to model the interaction of the different sources of intraspecific variation and their direct effects on community dynamics. This can be accomplished using planktonic food webs because a kairomone released by the carnivorous rotifer, Asplanchna brightwelli, induces successive generations of Brachionus calyciflorus to develop defensive posterolateral spines. Using genetically distinct and asexually reproducing strains of Brachionus, I am assessing how genetic diversity and phenotypic plasticity affect and interact to affect community dynamics.

By researching how genetic diversity and phenotypic plasticity contribute to community stability, I hope to make progress towards determining the importance of intraspecific variation within ecological communities.

My research is part of a collaborative project with the "Chemostat Group" at Cornell University (Dept. of Ecology and Evolutionary Biology) and funded by the James S. McDonnell foundation.

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Etienne Low-Décarie

Etienne Low-Décarie

PhD3 Student McGill
(funded through an NSERC PGS-D Postgraduate Scholarship)
BSc McGill
Co-supervisor: Prof. Graham Bell
Stewart Biology Building, W6/13
Phone: 514-398-6725
e-mail: etienne.low-decarie@mail.mcgill.ca

I am currently an M.Sc. student in the labs of Dr. Gregor Fussmann and Dr. Graham Bell. I am studying evolutionary and ecological response of phytoplankton to rising CO2.

The exponential growth of atmospheric CO2 through its link to global climate change is alarming scientists around the world. However, very few studies have looked into its direct effect on organisms. CO2 is generally seen as a fertilizer for photosynthetic organisms, not as a pollutant. But by stimulating the growth of some organisms, the rise in CO2 may lead to the extinction of many other organisms that would be outcompeted in the high CO2 environment. Furthermore, evolution in response to this rise in CO2 might invalidate most predictions of organism response to rising CO2.

I am using communities of microscopic photosynthetic organisms, micro-algae/phytoplankton, to investigate both the ecological and evolutionary response of organisms and communities to rising CO2. Algae are important absorbers of CO2 and producers of oxygen. Due to their small size and rapid reproduction, they allow for ecological studies at a reasonable geographic scale and evolutionary studies at reasonable time scales.

For more details on my research please visit
http://etienne.webhop.org

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Michael Pedruski

Michael Pedruski PhD3 Student McGill Biology
(funded through an NSERC PGS-D Postgraduate Scholarship)
MSc Queen's University, Kingston
Co-supervisor: Prof. Andrew Gonzalez
Stewart Biology Building, N3/15
Phone: 514-398-3265
e-mail: michael.pedruski@mail.mcgill.ca

One of the most fascinating aspects of biotic life must surely be the immense diversity that characterizes it at almost every spatial scale. From well researched environments such as rainforests and coral reefs, to seemingly mundane habitats such as melt-water pools on urban soccer fields, the diversity of living organisms is often incredible. It seems only natural that in the face of such diversity we should ask how it arose, how it is maintained, and what would happen if it wasn't.

Competitive coexistence provides an intriguing problem in biodiversity research. While much research has suggested that species should not be able to coexist with other species that have the same niches or limiting resource, this contrasts with frequent observations of similar species co-ocurring. Recently, much debate has erupted between proponents of neutral and niche based theories of competitive coexistence over the extent to which these models are representative of natural communities. There is, however, increasing recognition that when considered in a framework of equalizing and stabilizing mechanisms (where equalizing mechanisms minimize fitness differences between competitors, and stabilizing mechanisms focus intraspecific competition relative to interspecific competition) neutral communities simply represent the extreme case of communities maintained by equalizing mechanisms alone, whereas niche structured communities involve both equalizing and stabilizing mechanisms. As such, the more pertinent question may not be the prevalence of neutral or niche structured communities, but rather the relative importance of equalizing and stabilizing mechanisms in competitive coexistence.

Over the course of my PhD at McGill under the supervision of Andrew Gonzalez and Gregor Fussmann I plan to conduct a series of experiments and theoretical studies in which I will manipulate the relative strength of equalizing and stabilizing mechanisms under resource competition in a freshwater diatom model system. I intend to examine how changing the relative importance of equalizing and stabilizing mechanisms alters the structure and function of the model communities. Furthermore I hope to investigate how evolutionary dynamics alters the balance between equalizing and stabilizing mechanisms given initial differences in their relative importance, and experimental variation in environmental constraints.

Through this research I hope to provide novel insights on the different ways that equalizing and stabilizing mechanisms can affect biotic communities, and ultimately elucidate the roles they play in nature.

Visit Paradox of Plankton for more on this project.

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Felipe Pérez-Jvostov

Felipe P$eacute;rez-Jvostov

PhD3 Student McGill Parasitology
Co-supervisor: Prof. Marilyn Scott
Stewart Biology Building, W6/13
Phone: 514-398-6725
e-mail: felipe.perezjvostov@mail.mcgill.ca

The beauty of nature relies on its complexity. Ecological systems, with their multi-species levels and tangled interactions have always been of interest to scientists; however, parasitism which has been recognized as a major driver of ecological and evolutionary forces, has been, until recently, largely neglected. The Trinidadian guppy (Poecilia reticulata) undergoes high and low predation regimes throughout its geographical range. These localities differ mainly in their primary production and predatory fauna. Infection levels with the monogenean parasite Gyrodactylus sp. also differ among populations; fish from high predation areas tend to have higher infection levels than those from low predation areas. This results in questions about the ecological importance of parasitism-predation interactions and how species respond to them.

In fall 2008, I started my MSc. in Parasitology under the supervision of Dr. Marilyn Scott and Dr. Gregor Fussmann, studying the Trinidadian system, where predation regime and parasite-host relationships interact with one another under natural conditions. In the field, I experimentally manipulate natural infections of Gyrodactylus on guppies of different predation regimes and analyze how the guppies differ in their ecological response to the infection. This is a great opportunity to study the dynamics between two main ecological interactions: predation and parasitism.

This research is funded by an NSERC Special Research Opportunity Grant (to Fussmann, Hendry, Scott, Bentzen) and linked to the NSF-funded, Trinidadian whole-ecosystem project "From Genes to Ecosystems: How do Ecological and Evolutionary Processes Interact in Nature."

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Sébastien Portalier

Sébastien Portalier

PhD3 Student McGill Biology
Co-supervisor: Prof. Michel Loreau
Stewart Biology Building, W3/1
Phone: 514-398-6697
e-mail: sebastien.portalier@mail.mcgill.ca

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.

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Christina Tadiri

Christina Tadiri

PhD1 Student McGill Biology
BSc Biology McGill University
Stewart Biology Building, W3/2
Phone: 514-398-3153
e-mail: christina.tadiri@mail.mcgill.ca

In September 2012, I started as a PhD student working on parasite-host interactions in metacommunities.

I am using the guppy-Gyrodactylus system in the McGill Biology Phytotron.

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