Literaturdatenbank
Literaturdatenbank |
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Janzen, F. J. (1995). Experimental evidence for the evolutionary significance of temperature dependent sex determination. Evolution, 49(5), 864–873.
Added by: Sarina Wunderlich (30 Jun 2012 22:01:07 UTC) |
| Resource type: Journal Article BibTeX citation key: Janzen1995a View all bibliographic details  |
Categories: General Keywords: Chelydra, Chelydra serpentina, Chelydridae, Schildkröten = turtles + tortoises, Zeitigung = incubation Creators: Janzen Collection: Evolution |
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| Abstract |
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The evolutionary significance of sex-determining mechanisms, particularly temperature-dependent sex determination (TSD) in reptiles, has remained unresolved despite extensive theoretical work. To investigate the evolutionary significance of this unusual sex-determining mechanism, I incubated eggs of the common snapping turtle (Chelydra serpentina) at a male-producing temperature (26⚬C), a female-producing temperature (30⚬C), and an intermediate temperature that produced both sexes about equally (28⚬C). Laboratory experiments indicated that two performance variables, but no morphological measurements, were significantly influenced by incubation temperature (P ≤ 0.05): hatchlings from cooler incubation treatments swam faster than turtles from warmer incubation treatments, and hatchlings from 28⚬C exhibited a greater propensity to run than did individuals from 26⚬C and 30⚬C. In the field, hatchlings from the all-male and all-female producing temperatures had significantly higher first-year survivorship than did consexuals from the incubation temperature that produced both sexes (G = 6.622, P = 0.03). Significant directional selection was detected on propensity of hatchlings to run (β' = -0.758, P = 0.05): turtles that tended to remain immobile had a higher probability of first-year survivorship than did individuals that moved readily. Thus, the effects of the gender x incubation temperature interaction on survivorship of hatchling turtles observed in the field experiment may have been mediated by temperature-dependent antipredator behavior. These results provide a possible functional explanation for the evolutionary significance of TSD in turtles that is consistent with predictions of theoretical models.
Added by: Sarina Wunderlich |