Interspecific aggression and character displacement of competitor recognition in
            Hetaerina
            damselflies

Traits that mediate intraspecific social interactions may overlap in closely related sympatric species, resulting in costly between-species interactions. Such interactions have principally interested investigators studying the evolution of reproductive isolation via reproductive character displacement (RCD) or reinforcement, yet in addition to reproductive interference, interspecific trait overlap can lead to costly between-species aggression. Previous research on rubyspot damselflies ( Hetaerina spp.) demonstrated that sympatric shifts in male wing colour patterns and competitor recognition reduce interspecific aggression, supporting the hypothesis that agonistic character displacement (ACD) drove trait shifts. However, a recent theoretical model shows that RCD overshadows ACD if the same male trait is used for both female mate recognition and male competitor recognition. To determine whether female mate recognition is based on male wing coloration in Hetaerina , we conducted a phenotype manipulation experiment. Compared to control males, male H. americana with wings manipulated to resemble a sympatric congener ( H. titia ) suffered no reduction in mating success. Thus, female mate recognition is not based on species differences in male wing coloration. Experimental males did, however, experience higher interspecific fighting rates and reduced survival compared to controls. These results greatly strengthen the case for ACD and highlight the mechanistic distinction between ACD and RCD.

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Asymmetric interspecific competition drives shifts in signalling traits in fan-throated lizards

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2020.2141 ◽

2020 ◽

Vol 287 (1940) ◽

pp. 20202141

Author(s):

Amod M. Zambre ◽

Akshay Khandekar ◽

Rajesh Sanap ◽

Clairissa O'Brien ◽

Emilie C. Snell-Rood ◽

...

Keyword(s):

Interspecific Competition ◽

Species Recognition ◽

Character Displacement ◽

Social Signals ◽

Lizard Species ◽

Male Aggression ◽

Species Overlap ◽

Asymmetric Pattern ◽

Competitor Recognition

Interspecific competition can occur when species are unable to distinguish between conspecific and heterospecific mates or competitors when they occur in sympatry. Selection in response to interspecific competition can lead to shifts in signalling traits—a process called agonistic character displacement. In two fan-throated lizard species— Sitana laticeps and Sarada darwini —females are morphologically indistinguishable and male agonistic signalling behaviour is similar. Consequently, in areas where these species overlap, males engage in interspecific aggressive interactions. To test whether interspecific male aggression between Si. laticeps and Sa. darwini results in agonistic character displacement, we quantified species recognition and signalling behaviour using staged encounter assays with both conspecifics and heterospecifics across sympatric and allopatric populations of both species. We found an asymmetric pattern, wherein males of Si. laticeps but not Sa. darwini showed differences in competitor recognition and agonistic signalling traits (morphology and behaviour) in sympatry compared with allopatry. This asymmetric shift in traits is probably due to differences in competitive abilities between species and can minimize competitive interactions in zones of sympatry. Overall, our results support agonistic character displacement, and highlight the role of asymmetric interspecific competition in driving shifts in social signals.

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Reproductive interference explains persistence of aggression between species

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2014.2256 ◽

2015 ◽

Vol 282 (1804) ◽

pp. 20142256 ◽

Cited By ~ 35

Author(s):

Jonathan P. Drury ◽

Kenichi W. Okamoto ◽

Christopher N. Anderson ◽

Gregory F. Grether

Keyword(s):

Species Differences ◽

Sympatric Species ◽

Reproductive Interference ◽

Interspecific Aggression ◽

Interspecific Territoriality ◽

Interspecific Divergence ◽

Species Pairs ◽

Taxonomic Groups ◽

Competitor Recognition ◽

Female Coloration

Interspecific territoriality occurs when individuals of different species fight over space, and may arise spontaneously when populations of closely related territorial species first come into contact. But defence of space is costly, and unless the benefits of excluding heterospecifics exceed the costs, natural selection should favour divergence in competitor recognition until the species no longer interact aggressively. Ordinarily males of different species do not compete for mates, but when males cannot distinguish females of sympatric species, females may effectively become a shared resource. We model how reproductive interference caused by undiscriminating males can prevent interspecific divergence, or even cause convergence, in traits used to recognize competitors. We then test the model in a genus of visually orienting insects and show that, as predicted by the model, differences between species pairs in the level of reproductive interference, which is causally related to species differences in female coloration, are strongly predictive of the current level of interspecific aggression. Interspecific reproductive interference is very common and we discuss how it may account for the persistence of interspecific aggression in many taxonomic groups.

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Agonistic character displacement of genetically based male colour patterns across darters

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2018.1248 ◽

2018 ◽

Vol 285 (1884) ◽

pp. 20181248 ◽

Cited By ~ 4

Author(s):

Rachel L. Moran ◽

Rebecca C. Fuller

Keyword(s):

Common Garden ◽

Character Displacement ◽

Colour Pattern ◽

Signal Evolution ◽

Interspecific Aggression ◽

Mating Preferences ◽

Aggressive Interactions ◽

Allopatric Populations ◽

Colour Patterns ◽

Female Mating Preferences

Agonistic character displacement (ACD) occurs when selection to avoid maladaptive interspecific aggression leads to the evolution of agonistic signals and/or associated behavioural biases in sympatry. Here, we test for a pattern consistent with ACD in male colour pattern in darters (Percidae: Etheostoma ). Male colour pattern has been shown to function in male–male competition rather than female mating preferences in several darter species. Additionally, males bias their aggression towards conspecific over heterospecific males in sympatry but not in allopatry, consistent with divergent ACD in male behavioural biases. We use a common garden approach to show that differences in male colour pattern among four closely related darter species are genetically based. Additionally, we demonstrate that some aspects of male colour pattern exhibit enhanced differences in sympatric compared to allopatric populations of two darter species, consistent with ACD. However, other male colour traits are more similar between species in sympatry compared with allopatry, indicating that not all signal components are under strong divergent selection in sympatry. This study provides evidence that interspecific male–male aggressive interactions alone can promote elaborate male signal evolution both between and within species. We discuss the implications this has for male-driven ACD and cascade ACD.

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