Evol Ecol Res 5: 867-881 (2003)     Full PDF if your library subscribes.

Condition-dependent sexual selection can accelerate adaptation

Patrick D. Lorch,* Stephen Proulx,‡ Locke Rowe and Troy Day§

Department of Zoology, University of Toronto, Ramsay Wright Labs, 25 Harbord Street, Toronto, Ontario, M5S 3G5, Canada

Address all correspondence to Patrick D. Lorch, Department of Biology, University of North Carolina, Chapel Hill, NC 27599-3280, USA.
e-mail: plorch@email.unc.edu


Sexual selection is responsible for much of the spectacular natural diversity of mating traits. It is unclear, however, how this powerful evolutionary force affects the evolution of traits unrelated to mating. Four recent theoretical studies have argued that sexual selection might increase the rate of adaptation, but each relies on the assumption of a substantial positive covariance between male condition (non-mating fitness) and display. Here we demonstrate, with an explicit genetic model, that sexual selection itself can easily lead to the evolution and maintenance of this covariance. This process occurs through the evolution of condition-dependent male display and the resultant transfer of genetic variance for condition into variance in male display. We also track the effect of the covariance between condition and display on the rate of adaptation. Our results demonstrate a powerful synergy between natural and sexual selection that can elevate population mean fitness. Moreover, this synergy can greatly accelerate the rate of adaptation, making the feedback between natural and sexual selection a particularly potent force in changing environments. This has important implications for several key evolutionary processes, including the evolution of sex, sexual conflict and speciation.

Keywords: Fisher process, good genes, individual-based model, simulation.

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