Intermorph breeding and the potential for reproductive isolation in polymorphic mole salamanders (Ambystoma talpoideum) |
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Authors: | Howard H Whiteman John D Krenz Raymond D Semlitsch |
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Institution: | (1) Department of Biological Sciences, Murray State University, Murray, KY 42071, USA;(2) Savannah River Ecology Laboratory, Drawer E, Aiken, SC 29802, USA;(3) Department of Biological Sciences, Minnesota State University, Mankato, MN 56001, USA;(4) Division of Biological Sciences, University of Missouri, Columbia, MO 65211, USA |
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Abstract: | The study of reproductive isolation as a prerequisite to sympatric speciation has been limited by the focus on species that
have already experienced such isolation. However, a complete understanding of how such processes evolve depends on observing
taxa before they complete the speciation process. We studied the potential for sexual isolation in the polyphenic mole salamander,
Ambystoma talpoideum, using a series of laboratory and field experiments. This species consists of aquatic paedomorphic adults and terrestrial
metamorphic adults which are exhibited by both sexes and which mate in the same aquatic habitat. Previous field studies on
this species suggested that intermorph breeding would be less common during the winter months, because paedomorphic adults
begin breeding in early autumn and thus may have less energy available for reproduction in the winter. Laboratory experiments
conducted during the winter showed that the mating behavior of paedomorphic males occurred at a much lower frequency than
that of metamorphic males. In contrast, field experiments that best mimicked natural conditions revealed symmetric intermorph
breeding and included multiple paternity shared among males of each morph. This and other studies suggest that there is little
evidence of sexual isolation among morphs based on behavioral interactions alone. However, the potential for partial isolation
still occurs because of temporal and spatial differences in the frequencies of each morph in nature. Our results suggest that
further studies on this system, and other similar polyphenisms, may provide valuable insight into the mechanisms that underlie
the evolution of reproductive isolation. |
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Keywords: | Reproduction isolation Reproductive success Polyphenism Facultative paedomorphosis Salamander |
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