Conservation of salmonid
biological diversity in the Pacific Northwest has focused on
recognizing fundamental units of intraspecific genetic diversity
that reflect population structure in relation to reproductive
isolation. Intraspecific diversity has been defined at broad
levels with formal terms, such as subspecies and evolutionary
significant units (ESU), but increasingly sophisticated molecular
techniques can detect population structure at an even finer
scale. Understanding fine-scale population structure and evolutionary
relationships among populations is fundamental for preserving
current and future ecological and evolutionary processes.
In the Pacific Northwest, small populations of coastal cutthroat
trout (Oncorhynchus clarki clarki) are commonly the
only salmonid species present in headwater streams above barriers
to anadromy. Headwater streams are highly dynamic in space
and time, and natural environmental events, such as floods,
drought, channel desiccation, landslides, and debris flows,
are common. Coastal cutthroat trout are adapted to natural
stochastic processes but remain sensitive to habitat alteration,
and therefore, this native salmonid can be used as an indicator of ecosystem integrity.
Because populations isolated above barriers to anadromous
fishes are not influenced by fluctuations in the marine environment,
they may be direct indicators of the effects of landscape
alteration.
To persist in isolated headwater environments, coastal cutthroat
trout populations must maintain genetic heterogeneity in spite
of demographic and environmental fluctuations. Factors, such
as founder effects, bottlenecks, and genetic drift, reduce heterogeneity
and disproportionately affect small populations with little
or infrequent gene flow. Genetic population structure is shaped
by historical biogeographic events, spatial environmental heterogeneity,
life-history differences and/or differential levels of human-mediated
habitat manipulation. Characterizing genetic structure within
populations will provide insight into the effects of historical
and current processes on isolated coastal cutthroat trout populations.
In this study, environmental variables that are related to genetic
heterogeneity will be identified. Results of this study will
give fisheries and forest managers insight into the genetic
population structure and the relative effects of landscape variables
on genetic diversity and population viability of coastal cutthroat
trout. Specific objectives include:
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Determine how coastal cutthroat trout genetic diversity
is organized among isolated headwater streams throughout western Oregon
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Investigate
how landscape variables relate to coastal cutthroat trout
genetic diversity in western Oregon headwater basins |
