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Adaptive significance of vertical migration behaviour of Skistodiaptomus oregonensis Ghan, David
Abstract
I have studied the adaptive significance of vertical migration of zooplankton in 2 populations of the copepod Skistodiaptomus oregonensis that migrate and 2 populations that do not migrate. Vertical migration of the copepods is associated with the presence of pelagic sticklebacks. This observation is consistent with the hypothesis that the adaptive benefit of vertical migration by S. oregonensis is to avoid stickleback predators. The alternative hypotheses including avoidance of juvenile sockeye predators, foraging efficiency, bioenergetic efficiency, or combined foraging/bioenergetic efficiency are not supported by the comparisons of migratory behaviour of S. oregonensis in the 4 lakes. Both the depth and timing of S. oregonensis migration are consistent with the hypothesis that copepods are avoiding predation by sticklebacks. Light intensities at the depth at which S. oregonensis reside during the day are sufficiently low to reduce predation risk from visual foraging stickleback and the timing of ascent at dusk and descent at dawn are such that S. oregonensis remain at light intensities that reduce risk from stickleback. S. oregonensis are at the surface at dusk and dawn at the time that juvenile sockeye feed in the surface habitat. Vertical migration appears to be a trade-off with resource acquisition. Phytoplankton are less concentrated in the deep habitat where S. oregonensis reside during the day. Furthermore, migrating copepods contain less phytoplankton as food in their guts than do non-migrating individuals. In vertical columns in the laboratory, the presence or absence of sticklebacks does not influence the vertical distributions of S. oregonensis collected from lakes with either migratory or non-migratory populations. This indicates that the migration phenotype is fixed rather than being a flexible behaviour induced by environmental cues. I developed a dynamic optimization model to predict the optimal depth decisions for S. oregonensis based on depth dependent lake food and temperature conditions, fish abundance and predation rates, and S. oregonensis bioenergetics. The model predicts that vertical migration should occur to avoid sticklebacks under a broad range of modelled conditions, but with a fitness cost due to feeding opportunity costs. This demonstrates quantitatively that it is tenable to hypothesize that vertical migration involves a tradeoff between stickleback avoidance and feeding opportunity. Taken together, these results are consistent with the view that different migration behaviours in these populations are a result of divergent evolution driven by environmental variation affecting the optimal solution to the predation risk/resource acquisition trade-off.
Item Metadata
Title |
Adaptive significance of vertical migration behaviour of Skistodiaptomus oregonensis
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
1997
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Description |
I have studied the adaptive significance of vertical
migration of zooplankton in 2 populations of the copepod
Skistodiaptomus oregonensis that migrate and 2 populations that
do not migrate. Vertical migration of the copepods is associated
with the presence of pelagic sticklebacks. This observation is
consistent with the hypothesis that the adaptive benefit of
vertical migration by S. oregonensis is to avoid stickleback
predators. The alternative hypotheses including avoidance of
juvenile sockeye predators, foraging efficiency, bioenergetic
efficiency, or combined foraging/bioenergetic efficiency are not
supported by the comparisons of migratory behaviour of S.
oregonensis in the 4 lakes.
Both the depth and timing of S. oregonensis migration are
consistent with the hypothesis that copepods are avoiding
predation by sticklebacks. Light intensities at the depth at
which S. oregonensis reside during the day are sufficiently low
to reduce predation risk from visual foraging stickleback and the
timing of ascent at dusk and descent at dawn are such that S.
oregonensis remain at light intensities that reduce risk from
stickleback. S. oregonensis are at the surface at dusk and dawn
at the time that juvenile sockeye feed in the surface habitat.
Vertical migration appears to be a trade-off with resource
acquisition. Phytoplankton are less concentrated in the deep
habitat where S. oregonensis reside during the day. Furthermore,
migrating copepods contain less phytoplankton as food in their
guts than do non-migrating individuals.
In vertical columns in the laboratory, the presence or
absence of sticklebacks does not influence the vertical
distributions of S. oregonensis collected from lakes with either
migratory or non-migratory populations. This indicates that the
migration phenotype is fixed rather than being a flexible
behaviour induced by environmental cues. I developed a dynamic
optimization model to predict the optimal depth decisions for S.
oregonensis based on depth dependent lake food and temperature
conditions, fish abundance and predation rates, and S.
oregonensis bioenergetics. The model predicts that vertical
migration should occur to avoid sticklebacks under a broad range
of modelled conditions, but with a fitness cost due to feeding
opportunity costs. This demonstrates quantitatively that it is
tenable to hypothesize that vertical migration involves a tradeoff
between stickleback avoidance and feeding opportunity.
Taken together, these results are consistent with the view
that different migration behaviours in these populations are a
result of divergent evolution driven by environmental variation
affecting the optimal solution to the predation risk/resource
acquisition trade-off.
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Extent |
6540981 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-03-30
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0087773
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
1997-05
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Item Media
Item Citations and Data
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.