Evol Ecol Res 9: 1119-1129 (2007)     Full PDF if your library subscribes.

The twofold cost of sex unfolded

Helen Olofsson* and Per Lundberg

Department of Ecology, Section of Theoretical Ecology, Ecology Building, Lund University, SE-223 62 Lund, Sweden

Address all correspondence to: H. Olofsson, Department of Biology, University of North Carolina at Chapel Hill, CB#3280, Coker Hall, Chapel Hill, NC 27599, USA.
e-mail: helen.olofsson@unc.edu


Question: Considering ecological factors and life history, how easy is it for sexual reproduction (as a strategy) to invade and persist in a population where all individuals are reproducing asexually?

Mathematical method: We use a population growth equation that despite its simplicity captures several relevant ecological parameters: age-specific survival, differential birth rates, as well as both within-strategy and between-strategy competition. We perform invasion analysis to reach conclusions about the stability of the two evolutionary strategies.

Key assumptions: Sexual and asexual reproduction can be thought of as a strategy game. Instead of focusing on the genetic advantages of sexual reproduction, we explore the ecological and demographic conditions under which the two main reproductive strategies are maintained.

Conclusions: From an ecological point of view, sexual reproduction remains enigmatic only if the sexual strategy implies monogamy, there are no ecological interactions between the alternative reproductive strategies, and the life histories of both asexual and sexual strategies are limited to semelparity. Relaxation of those very restrictive ecological conditions allows for the co-existence of sexual and asexual reproduction as well as mutual invasion of the two strategies.

Keywords: co-existence, evolution of sex, invasion, life history, population dynamics.

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