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 twenty-four month research fellowship by Dr. Lisa Schwanz to work with Dr. Christopher Johnson at James Cook University in Australia.
Offspring sex ratios vary remarkably among populations and individuals. Sex ratio theory is a cornerstone of evolutionary biology that aims to explain the diversity of offspring sex ratios. The theory has seen remarkable success, predicting offspring sex ratios in a multitude of biological scenarios, thus establishing natural selection as an important mechanism in the evolution of reproductive diversity. The importance of offspring sex ratios extends beyond theory to nearly every aspect of population biology, including social behavior, population dynamics and conservation. Sex ratios of birds and mammals have not been as successfully predicted as in other taxa, and remain the next great challenge for sex ratio theory. This research will build on recent conceptual advances by investigating mammalian sex ratios at an adaptive and mechanistic level in a native Australian mammal of conservation interest. The primary objective of the research is to simultaneously test a recent mechanistic hypothesis for sex ratio biases in mammals and examine how multiple environmental conditions impact maternal fitness through offspring sex. Specifically, the research will take advantage of the marsupial biology of the Tammar wallaby to test for the roles of maternal blood cortisol and glucose in offspring sex and untangle the potentially simultaneous operation of selective pressures associated with two hypotheses of sex allocation, the Trivers-Willard and Local Resource Competition hypotheses. The fitness consequences of offspring sex will be revealed through cross-fostering of offspring by sex, a technique that has never been published in mammalian sex ratio research. This research will advance the two frontiers of research in mammalian sex ratios ? the adaptive explanations and the proximate mechanisms. By integrating physiological assays with field observational data and field manipulations in wild marsupial populations, this research will address an important question at the interface of ecology and evolutionary biology.
This postdoctoral fellowship will involve collaboration with multiple researchers and institutions in Australia and form the basis for long-term research collaborations between US and Australian scientists. The results of the research will provide a greater understanding of the occurrence and nature of offspring sex ratios in mammals, and have strong implications for conservation (e.g. captive breeding) and pest management. In addition, the study will involve training of Australian students and non-academic volunteers in field research and experimental science.
