Literaturdatenbank
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Refsnider, J. M. (2012). Effects of climate change on reptiles with temperature-dependent sex determination and potential adaptation via maternal nest-site choice. Unpublished thesis , Iowa State University, Ames, Iowa.
Added by: Admin (06 Jan 2014 18:23:06 UTC) |
| Resource type: Thesis/Dissertation BibTeX citation key: anon2012.14667 View all bibliographic details  |
Categories: General Keywords: Schildkröten - turtles + tortoises, Verhalten - ethology, Zeitigung - incubation Creators: Refsnider Publisher: Iowa State University (Ames, Iowa) |
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| Abstract |
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My dissertation provides a comprehensive test of the extent to which maternal nest-site choice behavior may allow reptiles with temperature-dependent sex determination to compensate for the potential skews in sex ratios caused by climate change. In the common-garden experiment described in Chapters 3 and 4, I demonstrated that female choice of shade cover over the nest is a behaviorally plastic characteristic that may allow reptiles with temperature-dependent sex determination to prevent sex ratio skews caused by climate change. Moreover, nests with greater mean daily fluctuation in incubation temperature produced faster hatchlings. This result suggests that if turtles are able to compensate for climate change via adjusting their choice of shade cover over the nest, such adjustment is likely to affect offspring performance. Results of the study described in Chapter 5 indicate that selection of shade cover differs between populations, which I attribute to constraints on availability of shade cover as well as differences in parameters of incubation regime predicted by shade cover at each site. Importantly, for plasticity in choice of shade cover to be expressed, a range of shade cover options must be available in nesting areas from which females can select specific nest sites. In Chapter 6, I show that nest depth in painted turtles appears to be constrained by female body size because smaller females have shorter rear limbs with which to excavate the nest cavity. Moreover, females from a southern population appear to be constructing nests with depths closer to their maximum physical capacity compared to females from a central population. My results suggest that southern females may have less capacity to compensate for a warming climate by constructing deeper nests than females from the center of the species’ range. Finally, in Chapter 7, I found that altering nest depth by two standard deviations from the population mean produced changes only in daily temperature fluctuation, and did not result in differences in sex ratio. Overall, I found that choice of shade cover over the nest site is a behaviorally plastic trait, and although females can adjust selection of shade cover to compensate for environmental conditions, this adjustment affects the performance of offspring produced. Importantly, a range of shade cover options must be available to nesting turtles for this plasticity to be expressed. Nest depth is unlikely to compensate for the effects of climate change on sex ratio skews in turtles, as nest depth is constrained by female body size and the magnitude by which nest depth would have to shift to produce a difference in sex ratios is biologically unfeasible. In conclusion, maternal selection of shade cover over nest sites may be the component of nest-site choice most likely to compensate for potential effects of climate change on sex ratio skew in reptiles with temperature-dependent sex determination
Added by: Admin |