Literaturdatenbank
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Baumgardt, L. L. (1997). Temperature-dependent sex determination: Factors affecting sex allocation in a northern population of snapping turtles. Unpublished thesis , University of North Dakota, Grand Forks.
Added by: Admin (06 Jan 2014 18:24:02 UTC) |
| Resource type: Thesis/Dissertation BibTeX citation key: anon1997a View all bibliographic details  |
Categories: General Keywords: Chelydra serpentina, Chelydridae, Habitat - habitat, Nordamerika - North America, Schildkröten - turtles + tortoises, Zeitigung - incubation Creators: Baumgardt Publisher: University of North Dakota (Grand Forks) |
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| Abstract |
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Sex in the snapping turtle (Chelydra serpentina) is fated by egg temperature during incubation by a process called temperature-dependent sex determination (TSD). Natural nests of C. serpentina were manipulated to determine if different clutches incubated together under lab and field conditions would result in equivalent sex ratios among clutches. The plasticity in sex ratio among clutches from both treatments suggests that not only does heritability of sex expression operate in the lab for this TSD population, but also under field conditions where nest temperatures and moisture conditions fluctuate throughout the nesting season. This implies this population of C. serpentina may be able to adapt to changing climatic conditions via natural selection. Two models were constructed using air temperature and/or precipitation data during the nesting season to predict annual snapping turtle sex ratios for a 30-year period. Consequently, long-term trends in sex ratio were predicted over ecological time. Comparison of extrapolated sex ratios, using projections based on the two models, revealed that nest temperature was estimated accurately by combining air temperature with precipitation. Projections from one model in conjunction with sex ratio data from the field suggest that northern TSD population embryo mortality substantially affects recruitment. Further, this mortality differentially affects recruitment of males much more than females. Over ecological time, such differential mortality of males tends to equilibrate an otherwise male-biased pattern of sex determination resulting from eggs incubating at predominantly male-determining nest temperatures. If sex ratio does equilibrate, it probably is not the result of annual, equitable allocation of sex; rather, it likely occurs over many years of alternating highly skewed ratios. Finally, global warming scenarios of various magnitude are used to predict how the sex ratio in this northern population of snapping turtles will respond to simplified projections of climate change.
Added by: Admin |