Close encounters of the three morphs: Does color affect aggression in a polymorphic lizard?

Abstract

Color polymorphism is genetically controlled, and the process generating and maintaining morphs can affect speciation/extinction rates. Color badges are useful signals in intraspecific communication because they convey information about alternative strategies and can potentially decrease unnecessary conflicts among different color morphs. Competition and aggressive interactions among color morphs can contribute to polymorphism maintenance. This could lead to an uneven spatial distribution of morphs in a population because the local frequency of each morph establishes the intensity of the competition and the fitness of each male. We used a polymorphic lizard, Podarcis muralis, to assess if aggression varies among morphs under two contrasting hypotheses: a heteromorphic versus homomorphic aggression. We used laboratory mirror tests after lizard color manipulation, and we verified the consistency of results with an analysis of the spatial distribution of morphs in a wild population. Both the experiments confirmed that aggression is more common during homomorphic than heteromorphic contests. The adoption of alternative behavioral strategies that minimize risks and costs could facilitate the stable coexistence of the phenotypes and reduce competition. A bias in aggression would advantage rarer morph, which would suffer less harassment by common morphs obtaining a fitness advantage. This process would be negatively‐frequency‐dependent and would stabilize polymorphism, possibly contributing to sympatric speciation.

Throat color polymorphism is related to differences in aggression in the Aegean wall lizard

“…Alternative behavioral strategies associated with genetically-based color polymorphisms are common in lizards (Sinervo and Lively, 1996; Robson and Miles, 2000; Stuart-Fox et al, 2020; Brock et al, 2022a). Some lizard color morphs with alternative behavioral strategies exhibit different levels of aggression (Bastiaans et al, 2013; Abalos et al, 2016; Yewers et al, 2016; Brock et al, 2022a), and certain color morphs even exhibit morph aggression bias where they adjust their aggressive behaviors depending on the morph with which they are interacting (Sinervo and Lively 1996; Yewers et al, 2016; Scali et al, 2021). Because more aggression in lizards is associated with greater access to resources and greater reproductive success (Herrel et al, 2009), differential morph aggression could play important roles in the evolution and maintenance of color polymorphism (Sinervo and Lively, 1996; Dijkstra et al, 2008; Horton et al, 2012; Yewers et al, 2016; Tinghitella et al, 2018; Scali et al, 2021).…”

“…Some lizard color morphs with alternative behavioral strategies exhibit different levels of aggression (Bastiaans et al, 2013; Abalos et al, 2016; Yewers et al, 2016; Brock et al, 2022a), and certain color morphs even exhibit morph aggression bias where they adjust their aggressive behaviors depending on the morph with which they are interacting (Sinervo and Lively 1996; Yewers et al, 2016; Scali et al, 2021). Because more aggression in lizards is associated with greater access to resources and greater reproductive success (Herrel et al, 2009), differential morph aggression could play important roles in the evolution and maintenance of color polymorphism (Sinervo and Lively, 1996; Dijkstra et al, 2008; Horton et al, 2012; Yewers et al, 2016; Tinghitella et al, 2018; Scali et al, 2021). Using aggressive behaviors to win contests over limited resources such as space and mating opportunities can increase morph relative fitness and reproductive success and, in turn, affect morph allele frequencies (Sinervo and Lively, 1996; Tinghitella et al, 2018).…”

“…If morphs of the same color compete more often or exhibit like-morph aggression bias then the color morph at the lowest frequency in the population would experience less aggression than more common morphs (Seehausen and Schluter, 2004), thereby creating social conditions that may allow the least common morph to increase in frequency in the population, a type of Allee effect (Kingston et al, 2003; Qvarnström et al, 2012; Dhiman and Poria, 2018). Thus, morph aggressive interactions can play a role in balancing selection via negative frequency-dependent selection that maintains morph diversity over long timescales (Sinervo and Lively, 1996; Seehausen and Schluter, 2004; Scali et al, 2021).…”