Data from: Interspecific interactions and learning variability jointly drive geographic differences in mate preferences.

Co-occurrence of closely related species can cause behavioral interference in mating and increase hybridization risk. Theoretically, this could lead to the evolution of more species-specific mate preferences and sexual signaling traits. Alternatively, females can learn to reject heterospecific males, to avoid male sexual interference from closely related species. Such learned mate discrimination could also affect conspecific mate preferences if females generalize from between species differences to prefer more species-specific mating signals. Female damselflies of the banded demoiselle (Calopteryx splendens) learn to reject heterospecific males of the beautiful demoiselle (C.virgo) through direct pre-mating interactions. These two species co-occur in a geographic mosaic of sympatric and microallopatric populations. Whereas C.virgo males have fully melanized wings, male C.splendens wings are partly melanized. We show that C.splendens females in sympatry with C.virgo prefer smaller male wing patches in conspecific males after learning to reject heterospecific males. In contrast, allopatric C.splendens females with experimentally induced experience with C.virgo males did not discriminate against larger male wing patches. Wing patch size might indicate conspecific male quality in allopatry. Co-occurrence with C.virgo therefore causes females to prefer conspecific male traits that are more species-specific, contributing to population divergence and geographic variation in female mate preferences.

近缘物种的共存可引发交配行为干扰并提升杂交风险。从理论层面来看，这可能推动演化出更强的物种特异性配偶偏好与性信号特征。另一种演化路径则是，雌性个体可通过学习排斥异种（heterospecific）雄性，以规避近缘物种带来的雄性性干扰。若雌性基于物种间差异进行泛化，进而偏好更具物种特异性的交配信号，此类习得的配偶识别偏好也可能对同种（conspecific）配偶偏好产生影响。带翅蟌（banded demoiselle，Calopteryx splendens）的雌性个体，可通过交配前的直接互动，学会排斥丽色蟌（beautiful demoiselle，C.virgo）的异种雄性。这两个物种在由同域（sympatric）种群与微异域（microallopatric）种群构成的地理镶嵌格局中共存。丽色蟌雄性的翅膀完全黑化，而带翅蟌雄性的翅膀仅部分黑化。本研究发现，与丽色蟌同域分布的带翅蟌雌性，在学会排斥异种雄性后，会更偏好同种雄性身上更小的翅斑区域。与之形成对比的是，经实验暴露于丽色蟌雄性的异域（allopatric）分布带翅蟌雌性，并未表现出对较大翅斑雄性的识别排斥。在异域种群中，翅斑大小或许能够反映同种雄性的质量。因此，与丽色蟌的同域共存会促使雌性偏好更具物种特异性的同种雄性特征，进而推动种群分化以及雌性配偶偏好的地理变异。