Evol Ecol Res 12: 507-522 (2010)     Full PDF if your library subscribes.

Sexual conflict over habitat selection: the game and a test with small mammals

Douglas W. Morris and Jody T. MacEachern

Department of Biology, Lakehead University, Thunder Bay, Ontario, Canada

Correspondence: D.W. Morris, Department of Biology, Lakehead University, Thunder Bay, Ontario P7B 5E1, Canada.
e-mail: douglas.morris@lakeheadu.ca


Background: Sexual conflict arises when the evolutionary strategies of reproduction by one sex differ from those of the other. The differences in evolutionary strategies are often associated with sexually antagonistic selection and an arms war of adaptation and counter-adaptation between the sexes. The selection gradient will disappear, and resolve the conflict, if fitness trade-offs between the sexes allow them to achieve equal fitness.

Questions: Does density-dependent habitat selection resolve sexual conflict? Can we use the sex ratio in a habitat to assess sexual conflict?

Mathematical methods: Isodar theory, two-by-two matrix games, and computer simulation.

Field methods: Manipulation of food supplements provided to a controlled population of meadow voles (Microtus pennsylvanicus) living in rodent-proof interconnected field enclosures. Use of remote antennae to monitor habitat use by radio-frequency identification-tagged male and female voles.

Key assumptions: Sexual conflict occurs in meadow voles. Relative use of interconnected habitat enclosures by male and female voles can evaluate habitat-dependent sexual conflict. All individuals have equal effects on resource consumption. Fitness is equalized between habitats by population density. Female fitness is increased by mate choice and reduced by male harassment. Male fitness depends on mating success and female fitness.

Conclusions: When male and female fitness varies between habitats, density- and sex-dependent habitat selection resolve sexual conflict. The sexual conflict game is typified by dominant strategies for both males and females that create local differences in sex ratio. Sex ratios of meadow voles using five enclosures confirmed the theory’s predictions. The local sex ratio was male biased (there were always more males using an enclosure than females) even though the global sex ratio was 1 : 1.

Keywords: fitness, habitat selection, isodar, matrix games, sex ratio, sexual conflict, voles.

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