Sex and ageing: Inter- and intrasexual reproductive trade-offs mediated by ecology, energetics and oxidative stress


Trade-offs are a central theme in evolutionary biology. Organisms have limited resources that must be partitioned among different organs, functions and/or stages of life. With the evolution of sexual reproduction in the eukaryotic lineage, a fundamental trade-off between gamete size and number leads almost inexorably to the evolution of two very different reproductive strategies, those of males and females. At the heart of the divergence between the sexes is differential energy allocation where females tend to invest more in egg production than males do in sperm production. However competition for mates also comes with costs. The sex-specific routes of optimizing reproductive fitness often lead to sexual conflict. Within males, trade-offs between pre- and post-mating episodes of sexual selection can generate selection of different reproductive tactics. At a basic level energy expenditure and the generation of reactive oxygen species may play a role in mediating these trade-offs. I will present data on two separate model systems: North American garter snakes and Australian painted dragon lizards. In garter snakes, I will show data supporting sex-specific differences in ageing. In painted dragons, I will present data on different male morphs with different mating strategies which may lead to different ageing rates in the wild.


I received my PhD from Oregon State University working on postcopulatory sexual selection and sexual conflict in garter snakes. I am also very interested in the energetics of courtship and mating and during my first postdoc started to think more holistically about how energy allocation toward sexual competition and reproduction more generally might affect reproductive tactics and other life history traits such as life span. In my current postdoc at the University of Sydney working on sperm-egg interactions in cane toads, I have come to appreciate how geographic variation across a species' range can be harnessed for intraspecific comparative studies. These experiences have lead to my current fascination with environmental drivers of geographic variation in, and the physiological underpinnings of sexual selected and life history traits.

Key Papers

Rollings, N., E. J. Uhirg, R. J. Krohmer, H. L. Waye, R. T. Mason, M. Olsson, C. M. Whittington & C.R. Friesen. 2017. Age-related sex differences in body condition and telomere dynamics of red-sided garter snakes. Proceedings of the Royal Society B: Biological Sciences.

Friesen, C. R., D. R. Powers, and R. T. Mason. 2017. Using whole-group metabolic rate and behaviour to assess the energetics of courtship in red-sided garter snakes. Animal Behaviour

Friesen, C. R., D. R. Powers, P. E. Copenhaver, and R. T. Mason. 2015. Size dependence in non-sperm ejaculate production is reflected in daily energy expenditure and resting metabolic rate. Journal of Experimental Biology 218:1410-1418.

Date & time

1–2pm 19 September 2017


Gould Seminar Room (Rm 235), Bldg 116, Gould Building, Daley Road, ANU


Christopher Friesen, University of Sydney


 Megan Head
 6125 5082

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