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Dr.
Craig F. Purchase Evolutionary
Ecology of Fishes Research
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Research
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As an evolutionary ecologist I am interested in how
organisms have adapted to their environment, as a result of interactions with
individuals of their own and other species, and with abiotic conditions. Within
this context, I conduct research on fishes. Fishes are good study organisms;
they are the most specious of all vertebrates, they exhibit a huge diversity in
morphology, remarkable variability in how and where they live, and they have
social and economic value that enables certain types of research that would
otherwise be impossible.
My group does different types of research: (1) we do “environmental
monitoring” sort of things where we measure characteristics of wild fish
populations (e.g., juvenile densities, adult “health” – size/colour/shape/energy), and (2) using gametes collected from
wild fish, we do lab experiments, where we manipulate the conditions of fertilization
(and monitor sperm performance or fertilization success) or incubation (and
monitor offspring performance).
Our research is relevant for diverse fields, including: evolutionary biology, ecology, invasive species,
biodiversity, conservation biology, toxicology, and fisheries productivity.
Areas
of concentration
Fish reproductive biology: I have a
general interest in reproductive biology and I use reproductive traits as tools
for questions related to plasticity and adaptation. Recent work has included
spawning site selection, courtship behaviour,
temporal/spatial variation in egg size-number tradeoffs, egg quality, ovarian
fluid, sperm morphology and quality, sperm behaviour,
sperm competition, fertilization variability, embryo development under
different conditions, and hatch characteristics.
Phenotypic plasticity: Phenotypic
plasticity occurs when a single genotype produces different phenotypes when
exposed to different environments. The shape of this response is known as a
reaction norm. This plasticity can be adaptive, neutral, or maladaptive
depending on the trait and context. Just about any trait can be plastic (e.g.,
escape behaviour, gut length, pigmentation, spine
length, growth rate, maturation age, fish swimming speed, sperm swimming
speed), and my research has investigated many different sources of
environmental variation and responses to it. Two particularly interesting areas
of work are plasticity in plasticity (how the phenotype produced to one
environmental cue depends upon something else), and transgenerational
plasticity (how parental experience affects offspring).
Local adaptation: Within a species,
populations often adapt to local conditions if (1) there is an environmental
gradient that is selectively important, (2) variability in the trait in
question which is heritable, and (3) at least some degree in reproductive
isolation from other populations. Such adaptation constitutes within-species
genetic variation that is ecologically important, as it may influence overall
species productivity and resilience to extinction. Local adaption among
populations is well documented for a wide variety of traits, including growth
rates, energy assimilation efficiency, maturation age, egg size, and swimming
performance. Hybridization between locally adapted populations destroys
intra-specific biodiversity, as does hybridization between related species. I am
interested in causes and consequences of such hybridization.
Life history variability: Much of my
earlier work focused on life history variability. Life history traits directly influence an organism’s
ability to pass genes to the next generation and greatly affect yield in
harvested populations. Traits like maturation age and reproductive investment
vary widely among- and within-species, and are influenced by both genetics and
environment. Understanding this variation is therefore critical for
conservation and resource management. I investigate within-species life history
variability of fishes at different levels: among populations, generations,
families, sexes and individuals.
Invasion biology: Invasive organisms
are becoming an increasing threat to biodiversity. My group has been conducting
a variety of studies on brown trout, which are labeled as one of the world’s
top 100 worst invaders. Invasive species by definition cause concern outside of
their native distribution to other species. Less obvious to the public are
ecological and evolutionary problems caused when non-native populations of a
given species are either purposely or accidentally released into the range of
conspecifics. These “invading” individuals can interbreed with native fish and
genetically pollute local adaptation. Stocking from hatcheries and escapes from
aquaculture are common sources of this problem. I am interesting in the
reproductive biology of invasive fishes.
Conservation biology: Within the
context above, some of my research has direct conservation implications. Of
particular concern is how the loss of local adaptation within a species affects
the long-term existence and/or productivity of the species as a whole. As in
the business world, this is known ecologically as the portfolio effect. Most of
my interest in this area focuses around reproduction.
Funding
My research program at Memorial University has
received funding through the following sources:
· Memorial
University
· Natural
Sciences & Engineering Research Council of Canada
· Canada
Foundation for Innovation
· Newfoundland
& Labrador Research & Development Corporation
· Newfoundland
& Labrador Department of Environment & Conservation
· Fisheries
and Oceans Canada
· Salmonid
Association of Eastern Newfoundland
· Ireland
Canada University Foundation
· Atlantic
Salmon Conservation Foundation
· My
students also received support from many additional sources
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