Evol Ecol Res 13: 105-111 (2011)     Full PDF if your library subscribes.

The cost of males in non-equilibrium populations

Curtis M. Lively

Department of Biology, Indiana University, Bloomington, Indiana, USA

Correspondence: C.M. Lively, Department of Biology, Indiana University, Bloomington, IN 47405, USA.
e-mail: clively@indiana.edu


Question: What is the cost of producing males in non-equilibrium sexual species?

Background: Asexual reproduction is generally associated with non-equilibrium (r-selected) species, while sexual reproduction is generally associated with equilibrium (K-selected) species.

Mathematical methods: The cost of males per reproductive time step was calculated as the ratio of the per-capita growth rate of an asexual population relative to the per-capita growth rate of a sexual population.

Key assumptions: Sexual and asexual individuals are ecologically similar. Sexual females produce males, which do not contribute to the per-capita birth rate, whereas asexual females produce only female offspring. All else is equal.

Conclusion: The cost of males per reproductive time step approaches two-fold in non-equilibrium populations where the birth rate is much greater than the death rate. In contrast, the cost of males per time step can be much less than two-fold in iteroparous populations at equilibrium. These results are consistent with the distribution of parthenogenesis in natural populations.

Keywords: cost of males, K-selection, maintenance of sex, non-equilibrium populations, r-selection.

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