University of Groningen Male-male competition and speciation Dijkstra, P. D.; Seehausen, O.; Pierotti, M. E. R.; Groothuis, Ton Published in: Journal of Evolutionary Biology DOI: 10.1111/j.1420-9101.2006.01266.x IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite from it. Please check the document version below. Document Version Publisher's PDF, also known as Version of record Publication date: 2007 Link to publication in University of Groningen/UMCG research database Citation for published version (APA): Dijkstra, P. D., Seehausen, O., Pierotti, M. E. R., & Groothuis, T. G. G. (2007). Male-male competition and speciation: aggression bias towards differently coloured rivals varies between stages of speciation in a Lake Victoria cichlid species complex. Journal of Evolutionary Biology, 20(2), 496-502. DOI: 10.1111/j.1420-9101.2006.01266.x Copyright Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons). Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. Download date: 10-02-2018 doi: 10.1111/j.1420-9101.2006.01266.x Male–male competition and speciation: aggression bias towards differently coloured rivals varies between stages of speciation in a Lake Victoria cichlid species complex P. D. DIJKSTRA,* O. SEEHAUSEN, M.E.R. PIEROTTIà &T.G.G.GROOTHUIS* *Department of Behavioural Biology, University of Groningen, AA Haren, the Netherlands Aquatic Ecology and Evolution, Institute of Zoology, University of Bern, Bern, Switzerland, and EAWAG Ecology Research Centre, Kastanienbaum, Switzerland àDepartment of Biological Sciences, Molecular and Evolutionary Ecology Group, University of Hull, UK Keywords: Abstract aggression; Sympatric speciation driven by sexual selection by female mate choice on a haplochromine cichlid; male trait is a much debated topic. The process is problematic because of the Lake Victoria; lack of negative frequency-dependent selection that can facilitate the invasion male-male competition; of a novel colour phenotype and stabilize trait polymorphism. It has recently sexual selection; been proposed that male–male competition for mating territories can generate sympatric speciation. frequency-dependent selection on male colouration. Rare male cichlid fish would enjoy a fitness advantage if territorial defenders bias aggression towards male cichlid fish of their own colour. We used blue (ancestral type) and red phenotypes of the Lake Victoria cichlid species complex Pundamilia. We tested the aggression bias of wild-caught territorial blue male cichlid fish from five separate populations for blue vs. red rival male cichlid fish using simulated intruder choice tests. The different populations vary in the frequency of red male cichlid fish, and in the degree of reproductive isolation between red and blue, reflecting different stages of speciation. Blue male cichlid fish from a population that lack red phenotypes biased aggression towards blue stimulus male cichlid fish. The same was found in two populations where blue and red are reproductively isolated sister species. This aggression bias may facilitate the invasion of a novel colour phenotype and species coexistence. Blue male cichlid fish from two populations where red and blue are hybridizing incipient species biased aggression towards red stimulus male cichlid fish. Thus, after a successful invasion of red, aggression bias alone is not likely to generate frequency dependence required to stabilize the coexistence of phenotypes. The findings show that aggression bias varies between stages of speciation, but is not enough to stabilize the process of speciation. research: in classical theoretical scenarios of sympatric Introduction speciation, sexual selection plays a secondary role, if any Empirical research on potential mechanisms of sympatric (Maynard Smith, 1966; Bush, 1975; Rosenzweig, 1978; speciation has concentrated primarily on disruptive Kondrashov & Mina, 1986; for review see Coyne & Orr, natural selection through competition for ecological 2004). Different speciation models have demonstrated resources leading to the evolution of ecological special- the theoretical feasibility that selective mating exerting ization and reproductive isolation (Filchak et al., 2000; sexual selection can cause sympatric speciation (Lande & Schluter, 2000; Turelli et al., 2001; Rundle & Nosil, 2005). Kirkpatrick, 1986; Turner & Burrows, 1995; Payne & This partly reflects the developments in theoretical Krakauer, 1997; van Doorn et al., 1998; Higashi et al., 1999; Kawata & Yoshimura, 2000; van Doorn & Weiss- ing, 2001). Many of these models were inspired by the Correspondence: Peter D. Dijkstra, Department of Behavioural Biology, University of Groningen, PO Box 14, 9750 AA Haren, the Netherlands. explosive speciation of haplochromine cichlids in Lake Tel.: +31-50-3637850; fax: +31-50-363520; Victoria and Lake Malawi (Kocher, 2004). Closely related e-mail: [email protected] haplochromine cichlid species typically differ markedly in ª 2006 THE AUTHORS 20 (2007) 496–502 496 JOURNAL COMPILATION ª 2006 EUROPEAN SOCIETY FOR EVOLUTIONARY BIOLOGY Male–male competition and speciation in Lake Victoria cichlid fish 497 colouration but little otherwise (Bouton et al., 1997; feeding strategies while enhancing competition among Seehausen & Bouton, 1997; Albertson et al., 1999; species with a similar specialization. The role of aggres- Genner et al., 1999a; Allender et al., 2003). This colour sion in sexual selection and speciation has only recently variation in male cichlid fish is associated with variation been fully appreciated (van Doorn et al., 2004; Mikami in female mate preferences (Seehausen & van Alphen, et al., 2004; Seehausen & Schluter, 2004; Dijkstra et al., 1998; Knight & Turner, 2004). 2005, 2006). More recent theoretical investigations indicate that Here we tested for aggression biases in wild-caught sympatric speciation by sexual selection alone requires territorial blue male phenotypes of the Pundamilia species stringent conditions (Turelli et al., 2001; Arnegard & complex from Lake Victoria towards either red (Punda- Kondrashov, 2004; van Doorn et al., 2004; Kirkpatrick & milia nyererei) or blue (Pundamilia pundamila) rivals using Nuismer, 2004). A fundamental problem is the initial simulated intruder choice tests. Red and blue phenotypes hurdle for a novel male phenotype to invade a popula- are anatomically similar that behave like reproductively tion against the predominant female preference. Also, isolated species in some locations, and like hybridizing the coexistence of incipient species, both during and after incipient species in other locations (Seehausen, 1996, the evolution of reproductive barriers, is problematic 1997). Blue phenotypes have a lake-wide distribution (van Doorn et al., 2004). Successful invasion requires a whereas red phenotypes have a patchy distribution and fitness advantage for a novel male phenotype, but always co-occur with blue phenotypes. Among the maintenance of a trait polymorphism requires that this members of the Pundamilia complex, the blue form has advantage is negatively frequency dependent (van Doorn the highest record of sympatric occurrences with other et al., 2004). Male–male competition for access to mating members of the Pundamilia complex (Seehausen, 1996; territories could generate such frequency dependence in Seehausen & van Alphen, 1999). It seems therefore likely sexual selection when exerting selection on the same that blue represents the ancestral state and that blue traits that are involved in female mate choice (van Doorn populations have been invaded repeatedly and indepen- et al., 2004; Mikami et al., 2004; Seehausen & Schluter, dently by red phenotypes during speciation (Seehausen, 2004). For example, if territorial defenders bias aggres- 1997; Seehausen & van Alphen, 1999; Seehausen & sion towards phenotypes coloured like themselves, rare Schluter, 2004). male phenotypes would receive less aggression, possibly In this study we have taken advantage of the fact that resulting in a higher chance of rare male types to blue Pundamilia populations exist that differ in the establish a high-quality territory. If female cichlid fish frequency of red male cichlid fish, as well as in the assess prospective mates by not only colour but also degree of gene-flow between red and blue phenotypes territory quality (e.g. territory size, see Maan et al., 2004; (Seehausen, 1997). We take these population types as P.D. Dijkstra et al. unpublished), they may face a conflict representing different stages of speciation, allowing us to between species recognition and preference for mates ask whether the direction and strength of an aggression with a high-quality territory. This effect could bestow an preference in blue male cichlid fish depends on speciation initial fitness advantage upon rare male cichlid fish stage. Firstly, we measured aggression preference in wild- facilitating the propagation of their genes in the popu- caught male cichlid fish from a location with a single