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Widemo (1998) - Alternative(2)

Widemo (1998) - Alternative(2) - A NIMAL BEHAVIOUR 1998 56...

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ANIMAL BEHAVIOUR, 1998, 56, 329–336 Article No. ar980792 Alternative reproductive strategies in the ruff, Philomachus pugnax : a mixed ESS? FREDRIK WIDEMO Section of Animal Ecology, Department of Zoology, Uppsala University and Department of Zoology, Norwegian University of Science and Technology, Trondheim (Received 26 March 1996; initial acceptance 13 July 1996; final acceptance 28 November 1997; MS. number: 5206R) ABSTRACT In the ruff, there are two alternative male reproductive strategies. The majority of males of this lekking bird attempt to establish and defend territories on leks, and are referred to as Independents. Other males, referred to as Satellites, forego this behaviour and instead attempt to get access to the territories defended by Independents by acting submissively. The system is thought to be an example of a mixed evolutionarily stable strategy (ESS), where the two strategies have equal fitness payoffs and are maintained by negative frequency-dependent selection. Satellites visited leks at the same time as females, and were associated with territory-holding Independents which were successful in attracting females. This appeared to be an effect both of Satellites following females, and of females being attracted to Independents that dominated submissive Satellites. Males pursuing the two strategies benefited from the presence of each other, at least to some extent. In this study, Satellites got fewer copulations than expected by their proportion in the population. Satellites on leks might have increased longevity or reproductive life span, and gained copulations off leks and while migrating, to compensate for their low observed mating success on leks. The Satellite strategy may be a low-cost, low-benefit strategy, which may have equal average lifetime reproductive success as the territorial strategy. 1998 The Association for the Study of Animal Behaviour Animal mating systems show a remarkable variation between species, and some species even show plasticity in reproductive behaviours between, and within, popula- tions ( Emlen & Oring 1977 ). Distinct alternative male mating behaviours also sometimes co-occur within populations (e.g. Austad 1984 ; Gross 1984 ; Shuster 1989 ; Zimmerer & Kallman 1989 ). Authors have extensively applied game theory and the concept of evolutionarily stable strategies (ESS; Maynard Smith 1982 ) to alternative reproductive behaviours while attempting to explain how the strategies are maintained. Here, I define a strategy as a genetically based programme that governs the allocation of the somatic and reproductive effort of an organism. Thus, the strategy functions as a decision rule between alternative phenotypes, which are referred to as tactics ( Gross 1996 ). Evolutionarily stable strategies may be divided into pure, conditional and mixed strategies ( Maynard Smith 1982 ; Gross 1985 ). In a pure ESS, all individuals adopt the same genetically fixed tactic.
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