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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.
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.
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My current core interests connect these fields. A big
focus is gamete ecology, much (but not all) of which includes plasticity of
sperm performance to abiotic conditions (including natural and unnatural
stress), biotic conditions (post-copulatory cryptic female choice of sperm via
female secretions), their interactions, and how these patterns may differ among
locally adapted populations.
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The cartoon (and description) below attempts to
capture this work.
Other
key areas
In addition to my primary areas of concentration
(described above), I maintain an interest in all aspects of fish biology and
have published in areas as far ranging as quantification of bycatch from
commercial fisheries, ideal free distribution theory, morphology, aquaculture
production, mercury bioaccumulation, behaviour,
maximum sustainable fisheries yields, to seminal fluid chemistry.
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. Again,
most of my interest in this area focuses around reproduction.
Funding
My research program at Memorial University has
received funding through the following sources:
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Memorial University
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Natural Sciences & Engineering Research Council of
Canada
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Canada Foundation for Innovation
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Newfoundland & Labrador Research & Development
Corporation
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Newfoundland & Labrador Department of Environment
& Conservation
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Fisheries and Oceans Canada
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Salmonid Association of Eastern Newfoundland
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Ireland Canada University Foundation
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Atlantic Salmon Conservation Foundation
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My students also received support from many additional
sources
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