Fraser Lab

Evolutionary Conservation Biology

We live in an age of ever-increasing human impacts to natural ecosystems. To use natural resources more sustainably, and to slow the rate of loss of biodiversity, we therefore need to understand how organisms diverge and adapt to their environments, how this diversity is maintained, and how human activities alter this diversity. Research in the Fraser Lab involves testing fundamental hypotheses about evolutionary processes underlying the origin and maintenance of biodiversity below or at species levels, by combining field, laboratory and molecular studies of natural populations. My students and I then apply this knowledge towards more effective biodiversity conservation, fish and wildlife management, and more environmentally sustainable aquaculture.

Understanding the processes that drive population divergence

What processes drive population divergence? A first aspect of our research uses sympatric, evolutionarily-young populations of migratory salmonid fishes to test hypotheses regarding the relative roles of selective and historical factors in driving the initial stages of population divergence. This involves a combination of modern molecular tools, new population genetic analyses (e.g. assignment tests, asymmetric gene flow, genetic admixture), diverse population phenotypic data (e.g. morphology, migratory behaviour, habitat selection, breeding time), and common-garden experimentation.

To date, the research has illustrated how population phenotypic and genetic differentiation can arise through interactions between historical events and selection. In collaboration with Dr. Louis Bernatchez (Université Laval), information generated from this work is being applied towards recognizing, conserving and prioritizing diversity below species levels, as well as the processes that generate and maintain it. The research has also contributed to the development of a co-management committee between First Nations people and governmental agencies that protect population diversity, with the goal of maintaining sustainable northern fisheries practices.

Genetics in species reintroductions and population monitoring

Why are some species reintroductions successful and others unsuccessful? A second research initiative involves evaluating the potential influence that genetic factors can have on enhancing or hindering species reintroduction efforts. In part, this involves using archival DNA samples to evaluate the roles of standing genetic diversity from sources, inbreeding, low effective population size, genetic depensation or processes beyond source and reintroduced populations (e.g. gene flow) as factors contributing to reintroduction successes or failures. Such historical examinations of population genetic differentiation and connectivity over time can be very useful for aiding reintroduction efforts, particularly with respect to the choice of source population and the scale at which efforts should be made.

With Dr. Michael Hansen (Danish Institute for Fisheries Research), we continue to address how monitoring of population genetic metrics, such as effective population size and temporal gene flow, can provide insights into demographic and evolutionary processes in natural or captive populations that are difficult to obtain using traditional methods. With the Ecosystem Sciences Division of the Department of Fisheries and Oceans (DFO, Ottawa), we are also applying population and quantitative genetics to the demand for improving species reintroduction projects.

Fitness consequences of hybridization between artificially-selected and wild organisms

There are growing concerns over the potentially negative fitness consequences of hybridization between artificially-selected and wild organisms. Such hybridization could both alter the genetic makeup of the wild organism and/or result in reduced fitness in the offspring, a process known as outbreeding depression. Theory predicts greater reductions in hybrid fitness should be accrued as population divergence increases. Yet, this has rarely been tested in nature despite its relevance to domestication risk assessment. With collaboration from Dr. Patrick O’Reilly (DFO, Halifax), Dr. Jeff Hutchings (Dalhousie University), Dr. Paul Bentzen (Dalhousie University), Adam Cook (PhD student, Dalhousie), Paul Debes (PhD student, Dalhousie) and Matthew Morris (BSc student, Dalhousie; now at U. of Calgary), a third research initiative addresses three fundamental questions regarding the fitness consequences to wild salmon populations resulting from hybridization with escaped farmed salmon:

1) Does population divergence influence farmed-wild hybrid fitness? This experiment involves comparing the fitness performance of wild salmon from ecologically and genetically divergent populations with farmed salmon and their F1, F2 and backcross hybrids, under common environmental conditions.

2) Does hybridization alter or reduce phenotypic responses to environmental change or stressors? This experiment involves comparing the fitness performance of wild salmon and farmed-wild hybrids across environmental gradients (e.g. pH, food availability, salinity) that typify the range of natural conditions in the wild.

3) What is the duration of outbreeding depression in species such as salmon? This experiment compares the fitness performance of an F3 generation of farmed salmon, one wild population, and seven inter-population hybrids. Such research takes more than a decade to complete in species such as Atlantic salmon, but is sorely needed to evaluate concerns over outbreeding depression between distinct populations (whether wild or wild and farmed).

Experimental approaches to evaluating the relative risks of inbreeding and outbreeding

As populations are increasingly fragmented by human activities, they decline and become smaller in size. Small, endangered populations are especially susceptible to inbreeding depression and a loss of genetic diversity. Information is sorely needed on whether it is better to mix such small fragmented populations to avoid inbreeding depression and thus genetically ‘rescue’ populations, or whether the benefits of mixing are outweighed by potential outbreeding depression. With collaboration from Aimee Houde (MSc, Dalhousie University), Dr. Patrick O’Reilly (DFO, Halifax) and Dr. Jeff Hutchings (Dalhousie), a fourth research aspect addresses a fundamental question regarding the joint impacts of inbreeding and outbreeding depression in natural populations:

4) Under what conditions is genetic rescue successful? This experiment involves reciprocal transplants in the wild using three endangered salmon populations. The survival of genetically-known inbred and outbred within-population crosses, as well as multigenerational hybrid crosses between populations, will be compared to investigate tradeoffs between inbreeding and outbreeding in species rehabilitation.

Relationships between accessibility and the status of exploited populations

Harvesting and exploitation can have profound impacts on the ecology, genetics and life history characteristics of natural populations. A final research objective evaluates the degree to which such impacts may be manifested in relation to how accessible populations are to humans. A collaborative project is underway with Anthony Heggelin (BSc student, Dalhousie University), Dave Hardie (Postdoctoral Fellow, Dalhousie) and Dr. Jeff Hutchings (Dalhousie), wherein we are examining relationships between the health of fish populations in lakes (e.g. abundance, size-at-age relationships, habitat quality) and accessibility in Nova Scotia. The research will facilitate more informed management decisions regarding fisheries practices in wilderness areas and parks.

Current and past research project partners or sponsors:

Natural Sciences and Engineering Research Council of Canada (NSERC)
Department of Fisheries and Oceans Canada (DFO)
Ontario Ministry of Natural Resources (OMNR)
Société de la faune et des parcs du Québec (FAPAQ)
Société des établissements de plein air du Québec (SEPAQ)
Ministère des ressources naturelles, Québec
Department of Inland Fisheries, Nova Scotia
Grand Council of the Crees of Québec
Cree Regional Authority
Cree Nation of Mistissini, Québec
Cree Trapper’s Association, Mistissini, Québec
Atlantic Salmon Federation
Ecology Action Centre, Halifax, Nova Scotia
Trout Unlimited Canada
Trout Nova Scotia
Mountain Equipment Co-op
Eeyou Nemess Corporation
Barrette Chapais LtD
Osprey Excursions Reg’D, Mistissini, Québec
Camp Louis Joliet, Mistissini, Québec
Fonds Ecologique Anne Vallee
Fonds Richard Bernard