Demographic effects of temperature-dependent sex determination: will tuatara survive global warming?

(Image courtesy of http://phys.org/news/2013-11-encounters-tuatara.html)

Sphenodon guntheri is one of two extant species found in the Family Rhynchocephalia (Tuatara) nestled within Lepidosauria. Like the majority of Lepidosauria, they are temperature-dependent sex determinant species. Their species is threatened due to restriction to New Zealand. They are unique in that they are the only remnants of ancient radiation. They are incredibly valuable for scientists' understanding of ancient tetrapods. With a small, declining population and seclusion to a small area, means there is limited genetic variation. This particular species also has a low reproduction rate and does not reach sexual maturity until 15 years of age! According to the report, they only lay 3-8 eggs every 9 years!
Due to the temperature-dependent sex determination, global warming is predicted to be having an impact on this species, as well as many Reptilia. Because of slowness of adaptation in sexual behavior and the already male bias, sex ratio in the species, the scientists in this study predicted they would not be able to adapt in time to rapid climate change, in order to achieve a stable ratio. In this article, the scientists analyze the demographics of tuatara in North Brother Island, New Zealand, and the impact of male bias on survival of the population. The data collected was entered into a Population Viability Analysis in order to determine at which male ratio, would lead to population extinction.
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Results: Most of the populations measured showed a male-favored sex ratio at around 60%, smaller populations, however, were as high as 75%! The information collected from the Population Viability Analysis (PVA), showed that the species would reach a point of no return at around 85%.
Global warming is not just a problem for crops, loss of polar ice caps, rising oceans, but it is directly affecting animals as well! Most Reptiles have temperature-dependent sex determination, and if they cannot adapt to warming climates, they will either end up producing all males, or all females, leaving limited/none genetic variation, and eventual extinction.

WORK CITED: Mitchell, Nicola, Fred Allendorf, Susan Keall, Charles Daugherty, and Nicola Nelson. "Demographic Effects of Temperature-Dependent Sex Determination: Will Tuatara Survive Global Warming?" Global Change Biology 16.10 (2010): 60-72. EBSCO. Web. 8 Apr. 2015. <http://eds.b.ebscohost.com.nuncio.cofc.edu/eds/pdfviewer/pdfviewer?sid=bcc639a0-8eb6-4f01-9d4b-a0488896dcaa@sessionmgr110&vid=7&hid=108>.