Available online at www.sciencedirect.com Fighting strategies in two species of fig wasp JAMIE C. MOORE * , DARREN J. OBBARD * , CAROLINE REUTER †‡, STUART A. WEST * & JAMES M. COOK †‡ *Institute of Evolutionary Biology, University of Edinburgh yDivision of Biology, Imperial College London zSchool of Biological Sciences, University of Reading (Received 5 August 2007; initial acceptance 28 September 2007; final acceptance 9 January 2008; published online 20 May 2008; MS. number: 9484) Although theory exists concerning the types of strategies that should be used in contests over resources, empirical work explicitly testing its predictions is relatively rare. We investigated male fighting strategies in two nonpollinating fig wasp species associated with Ficus rubiginosa figs. In Sycoscapter sp. A, males did not assess each other before or during fights over mating opportunities. Instead, fights continued until the loser reached an energetic cost threshold that was positively correlated with its body size (fighting abil- ity) and retreated. In Philotrypesis sp. B, prefight assessment was indicated, with males attacking competi- tively inferior rivals to remove them from the competitor pool (they then continued to do so until they reached a cost threshold that was again positively correlated with body size). Using data on species ecology, we discuss our findings with respect to theory on when different fighting strategies should evolve. We argue that the type of strategy used by a fig wasp species is determined by its relative benefits in terms of inclusive fitness. Ó 2008 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved. Keywords: Ficus; fig wasp; fighting strategy; opponent assessment; Philotrypesis; Sycoscapter Contests over resources are common in nature (Huntingford & Turner 1987). Resources contested for include food (Blanckenhorn 1991), mates (West et al. 2001), oviposition sites (Moore & Greeff 2003) and territories (Kemp & Alcock 2003). Behaviour varies from nonviolent ritualized displays (e.g. Davies 1978) to fatal fighting (e.g. Hamilton 1979). There may be distinct phases in which different behaviours are used (e.g. Clutton-Brock & Albon 1979), and behaviour may be modified in the light of information acquired about the opponent (e.g. Pratt et al. 2003). A challenge to evolu- tionary biologists is to explain why this diversity occurs. Theory indicates that the costs individuals should risk to ob- tain resources (the likely severity of contests) will increase with resource value in terms of future expected fitness (Enquist & Leimar 1990), a prediction receiving empirical support (West et al. 2001). Indirect fitness benefits through relatives can also be important, with, depending on popula- tion structure, individuals potentially selected to be altruistic (Hamilton 1964) or spiteful (Gardner & West 2004) to rivals. In addition, theory predicts different types of strategy. In extended contests, these may be divided into three categories. (1) Strategies not involving opponent assessment: such strategies are predicted to evolve when individuals risk high costs to obtain resources that have high future expected fitness value (Enquist & Leimar 1990). The pro- pensity to contest resources may be independent of the in- dividual’s own phenotype, or may increase with fighting ability (e.g. McNamara & Houston 2005). The fighting ability of an individual is generally termed its resource- holding potential, or RHP (Maynard Smith & Parker 1976). (2) Strategies involving opponent assessment in which the most costly contests are between evenly matched rivals: in these, individuals use cues associated with RHP to assess opponents and retreat if it becomes apparent Correspondence and present address: J. C. Moore, Institute of Evolution- ary Biology, School of Biological Sciences, University of Edinburgh, Ash- worth Laboratories, Kings Buildings, West Mains Road, Edinburgh EH9 3JT, U.K. (email: jamie.moore@ed.ac.uk). C. Reuter and J. M. Cook are at the School of Biological Sciences, University of Reading, Whiteknights, Reading RG6 6AS, U.K. 315 0003e 3472/08/$34.00/0 Ó 2008 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved. ANIMAL BEHAVIOUR, 2008, 76, 315e322 doi:10.1016/j.anbehav.2008.01.018