Gene flow and local adaptation in a sunfish-salamander system |
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Authors: | Andrew Storfer |
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Institution: | (1) Center for Ecology, Evolution and Behavior T.H. Morgan School of Biological Sciences 101 T.H. Morgan Building, University of Kentucky Lexington, KY 40506-0225, USA, US |
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Abstract: | There is increasing evidence that populations may not be well adapted to their local environments, and as a result, recent
interest has focused on understanding factors that constrain adaptive evolution. This study presents data suggesting gene
flow may constrain the ability of larvae of the streamside salamander Ambystoma barbouri to avoid predation by fish via escape behavior and life history tactics. Streamside salamander larvae face conflicting selection
pressures in different streams. Some streams are ephemeral, where larvae should be active to feed, grow, and reach metamorphosis
before stream drying. Other streams contain predatory fish, where larvae should be generally inactive to avoid predation.
Previous work has shown that streamside salamander larvae exhibit ineffective antipredator behavior by having inappropriately
high activity levels with fish, resulting in high predation in laboratory and field experiments. This study investigated the
possibility that gene flow from larvae in ephemeral habitats may reduce the escape performance of larvae from populations
with fish and alter their life history characteristics to increase their susceptibility to fish predation. I assayed escape
behavior (speed, acceleration, and duration of escape) and life history characteristics (hatching date, size, stage) associated
with predator avoidance among laboratory-reared larvae from four populations. As predicted, two populations (one with fish
and the other fishless and ephemeral) connected by gene flow were not significantly different in almost all assays. In contrast,
larvae from an isolated population with fish had significantly stronger escape behaviors and delayed hatching than both an
isolated population that lacked a history of fish co-occurrence and the population with fish but gene flow from a fishless
population. These results support theory suggesting that gene flow can constrain adaptive evolution.
Received: 22 February 1999 / Received in revised form: 4 April 1999 / Accepted: 26 April 1999 |
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Keywords: | Gene flow Local adaptation Life history Ambystoma barbouri |
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