McCullough and Emlen • The research bias is unfortunate but also unsurprising 799 Telmatochromis temporalis; albeit, in this species, the sexes pronouncedly What is the role of competition among differ in aggressiveness ( Winkelmann et al. 2014). pairs in speciation?: a comment on Third, Tinghitella et al. (2018) underscore recent theoretical Tinghitella et al. and empirical results that also more directly support a role for male competition in speciation. Here, a particularly important Topi K. Lehtonen group has been cichlid fishes ( Tinghitella et al. 2018). Socially School of Biological Sciences, Rainforest Walk 25, Monash monogamous species have not been as commonly considered, University, Victoria 3800, Australia although both sexes of, for example, Amphilophus sagittae, a color- assortatively mating biparental cichlid, bias aggression towards Competition for limited resources is a major source of divergent homotypic individuals (Lehtonen 2014). Interestingly, such a selection, which fuels speciation processes. Tinghitella et al. (2018) bias is arguably the most commonly considered mechanism that focus on empirical and theoretical evidence that supports the role can promote phenotypic divergence in the context of aggression of competition among males in speciation. They observe that the between males (Tinghitella et al. 2018). Moreover, evidence from research field has to date been dominated by speciation mecha - socially monogamous cichlid fish ( Lehtonen et al. 2015) and birds nisms in sympatry. Nonetheless, both empirical and theoretical (Newton 1994), including those with assortatively mating color findings suggest that competition for mates is most likely to contrib - morphs (Pearce et al. 2011), suggests that selection from inter- ute to speciation when it interacts with divergent ecological selec- specific competition can influence the success of different (com - tion pressures (Tinghitella et al. 2018). petitive) phenotypes. Indeed, Tinghitella et al. (2018) note how Although Tinghitella et al. (2018) refer to “male competition” interspecific interactions drive habitat segregation between several and “female mate choice,” to reflect how sex roles are most often bird species. represented in the literature, they also insightfully note that their Similar to the conceptual links between male competition and conclusions should apply to “competitors” and “choosers,” regard- competition among pairs, the latter might be seen just as a spe- less of sex. In parallel, many of the same processes may also be rel- cific case of intra and interspecific competition, or reproductive evant for socially monogamous species in which both sexes in a pair interference (sensu Grether et al. 2013). Avoiding getting caught together compete with other pairs for reproductive opportunities. up in semantics, however, can help move the field forward. This To demonstrate this, I consider below each of the 3 major sources is exactly what Tinghitella et al. (2018) have done, especially of compelling evidence, as singled out by Tinghitella et al. (2018), by showing how the role of sexual selection in speciation is not that male competition is a “potent evolutionary force capable of only about mate choice, but that competition for mates is also driving divergence.” important. First, Tinghitella et al. (2018) observe that in some mat- ing systems, variance in reproductive success is tightly linked Address correspondence to T.K. Lehtonent. E-mail: email@example.com to competitive interactions among males. Similarly, in many socially monogamous species, the success of a pair in competi- Received 15 November 2017; accepted 22 November 2017; editorial deci- tion for limited reproductive resources defines reproductive suc - sion 20 November 2017; Advance Access publication 19 January 2018 cess (Newton 1994; Pearce et al. 2011; Lehtonen et al. 2015). doi:10.1093/beheco/arx175 Here, species in which the sexes share discrete, competitively rel- evant phenotypes, such as the Gouldian finch, Erythrura gouldiae Editor-in-Chief: Leigh Simmons (Pearce et al. 2011), and cichlid fishes of the genus Amphilophus (Lehtonen 2014), are particularly interesting. Importantly, repro- ductive performance may peak when the mates in a pair have REFERENCES the same phenotype (Burtka and Grindstaff 2015 ). Individuals Burtka JL, Grindstaff JL. 2015. Similar nest defence strategies within pairs with the same/similar (competitive) phenotypes benefitting from increase reproductive success in the eastern bluebird, Sialia sialis. Anim pairing up with each other should result in a link between the Behav. 100:174–182. (competitive) phenotype and mate choice. Such a link, in turn, Grether GF, Anderson CN, Drury JP, Kirschel AN, Losin N, Okamoto is expected to increase the probability of speciation (Tinghitella K, Peiman KS. 2013. The evolutionary consequences of interspecific aggression. Ann N Y Acad Sci. 1289:48–68. et al. 2018). Lehtonen TK. 2014. Colour biases in territorial aggression in a Neotropical The second source of empirical evidence highlighted by cichlid fish. Oecologia. 175:85–93. Tinghitella et al. (2018) is the similarity between mate competition Lehtonen TK, Sowersby W, Wong BBM. 2015. Heterospecific aggression and competition for ecological resources, suggesting that the former bias towards a rarer colour morph. Proc R Soc B. 282:20151551. can also be important in speciation. Similarly, as indicated above, Newton I. 1994. The role of nest sites in limiting the numbers of hole- nesting birds: a review. Biol Conserv. 70:265–276. the reproductive success of social pairs is commonly defined by their Pearce D, Pryke SR, Griffith SC. 2011. Interspecific aggression for performance in competition with other pairs for limited (reproduc- nest sites: model experiments with long-tailed finches ( Poephila acuti- tive) resources (Newton 1994; Pearce et al. 2011; Lehtonen et al. cauda) and endangered Gouldian finches ( Erythrura gouldiae). The Auk. 2015). For example, in many birds, nest cavities represent a criti- 128:497–505. Tinghitella RM, Lackey ACR, Martin M, Dijkstra PD, Drury JP, Heathcote cal, defendable, and limiting reproductive resource that is frequently R, Keagy J, Scordato ESC, Tyers AM. 2018. On the role of male under intense intra and interspecific competition ( Newton 1994; competition in speciation: a review and research agenda. Behav Ecol. Pearce et al. 2011). Such competition among pairs may also drive 29:783–797. habitat choice, resulting in divergent ecological selection pressures. Winkelmann K, Genner MJ, Takahashi T, Rüber L. 2014. Competition- This is seen, for example, in a biparental Lake Tanganyika cichlid, driven speciation in cichlid fish. Nat Commun. 5:3412. Downloaded from https://academic.oup.com/beheco/article-abstract/29/4/799/4786627 by Ed 'DeepDyve' Gillespie user on 11 July 2018
Behavioral Ecology – Oxford University Press
Published: Jan 19, 2018
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