Both Geography and Ecology Contribute to Mating Isolation in Guppies
Date
2010-12
Authors
Schwartz, Amy K.
Weese, Dylan J.
Bentzen, Paul
Kinnison, Michael T.
Hendry, Andrew P.
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Abstract
Local adaptation to different environments can promote mating isolation - either as an
incidental by-product of trait divergence, or as a result of selection to avoid maladaptive mating.
Numerous recent empirical examples point to the common influence of divergent natural selection on
speciation based largely on evidence of strong pre-mating isolation between populations from
different habitat types. Accumulating evidence for natural selection's influence on
speciation is therefore no longer a challenge. The difficulty, rather, is in determining the
mechanisms involved in the progress of adaptive divergence to speciation once barriers to gene flow
are already present. Here, we present results of both laboratory and field experiments with
Trinidadian guppies (Poecilia reticulata) from different environments, who do not show complete
reproductive isolation despite adaptive divergence. We investigate patterns of mating isolation
between populations that do and do not exchange migrants and show evidence for both by-product and
reinforcement mechanisms depending on female ecology. Specifically, low-predation females
discriminate against all high-predation males thus implying a by-product mechanism, whereas
high-predation females only discriminate against low-predation males from further upstream in the
same river, implying selection to avoid maladaptive mating. Our study thus confirms that mechanisms
of adaptive speciation are not necessarily mutually exclusive and uncovers the complex
ecology-geography interactions that underlie the evolution of mating isolation in nature.
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Citation
Schwartz, Amy K., Dylan J. Weese, Paul Bentzen, Michael T. Kinnison, et al. 2010. "Both Geography and Ecology Contribute to Mating Isolation in Guppies." Plos One 5(12): 15659-e15659. doi:10.1371/journal.pone.0015659