International Research Fellowship Program: Population Sex Ratio Bias: Influences of Climate and Consequences for Extinction Risk

Grayson Kristine L, Richmond VA

Investigators

Abstract

0965096 Grayson The International Research Fellowship Program enables U.S. scientists and engineers to conduct nine to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad. This award will support a sixteen-month research fellowship by Dr. Kristine L. Grayson to work with Dr. Nicola J. Nelson at Victoria University in New Zealand. Understanding the ecological impacts of climate change is an urgent research priority. The ability of temperature to dramatically impact population dynamics is particularly apparent in species with temperature-dependent sex determination (TSD). Even small shifts in climate have the potential to alter nest temperatures and bias the sex ratio of an entire population. This research project measures the influence of climate on population structure in a reptile species with TSD, the tuatara (Sphenodon punctatus), and determines if a biased sex ratio amplifies the risk of extinction. First, they are using small island populations of tuatara across northern New Zealand to measure current population sex ratios across a natural latitudinal gradient. The variation in population structure across islands is being examined in relation to 1) past temperature regimes, 2) available thermal nesting microhabitats, and 3) female condition and fecundity. Second, they are using an experimental approach to determine the interactions and behavior altered by a male-biased sex ratio over the short-term and the impact on female morphology and condition over the long-term. Finally, they are combining their data with long-term population data from the tuatara research group to inform a projection matrix model. This model will allow them to explore theoretical questions about the links between a biased sex ratio and population processes, as well as generate realistic estimations of tuatara population viability. Their research tests hypotheses about the influence of rising air temperatures and available thermal nesting habitats on the degree of adult sex ratio bias across natural populations. They use a species with Type Ib TSD, where warmer nests produce male offspring, to test theoretical predictions about the role of population sex ratio in linking individual interactions and the social system to the growth, decline, or extinction of a population. In addition, their population data will provide much needed information to guide the conservation of important remnant populations of tuatara, a threatened species of evolutionary, cultural, and international significance. This fellowship also includes opportunities to support local primary science education through the Spinyback Trust and work with the northern island tribes of the Mâori.