Data from: Interspecific aggression, not interspecific mating, drives character displacement in the wing colouration of male rubyspot damselflies (Hetaerina)

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.

介导种内社会互动的性状，在亲缘关系相近的同域物种（sympatric species）中可能发生重叠，进而引发代价高昂的种间互作。这类互动一直是通过生殖性状替换（reproductive character displacement, RCD）或强化作用研究生殖隔离演化的研究者的核心关注对象；而除生殖干扰外，种间性状重叠还可能引发代价高昂的种间攻击行为。此前针对红痣蟌（Hetaerina spp.）的研究表明，雄性翅色图案与竞争者识别能力在同域种群中的分化可降低种间攻击行为，这支持了争斗性状替换（agonistic character displacement, ACD）驱动性状演化的假说。然而，近期的理论模型显示，若同一雄性性状同时用于雌性的配偶识别与雄性的竞争者识别，则RCD的作用会掩盖ACD。为验证Hetaerina属物种的雌性配偶识别是否依赖雄性翅色，本研究开展了表型操控实验。与对照组雄性相比，翅部被操控为模拟同域近缘种（H. titia）的美洲红痣蟌（H. americana）雄性的交配成功率并未下降。由此可见，雌性的配偶识别并不依赖雄性翅色的物种间差异。但相较于对照组，实验组雄性的种间打斗率更高，存活率也更低。上述结果为ACD提供了更坚实的支撑，并凸显了ACD与RCD在机制层面的差异。