Data from: Male mate choice in the Trinidadian guppy is influenced by the phenotype of audience sexual rivals

In populations with male mate-choice copying, males may mitigate their risk of sexual competition by reducing their preference for a particular female in the presence of sexual rivals (audience). Because of the cost of missed mating opportunities from such an audience effect, males should reduce their mating preference to a greater extent in the presence of more sexually competitive rival compared with less competitive ones. We tested this hypothesis using the Trinidadian guppy (Poecilia reticulata). We compared a focal male’s baseline mating preference for either of two stimulus females, which differed in overall body size, in the absence of any sexual rival to his preference for the same females in the presence of a sexual rival using dichotomous-choice tests. Focal and audience males differed in body length and proportion of their body covered in orange and black pigmentation. In the presence of a larger rival, focal males exhibited a greater reduction in preference for their initially-preferred female compared to focal males in the presence of a smaller rival, irrespective of whether the latter male was more or less ornamented than the focal. The strength of the initial mating preference of focal males and the magnitude of the audience effect were significantly positively correlated when the audience male was larger than the focal male. Male guppies are thus sensitive to the phenotype of nearby males and and alter their preference for a particular mate to a greater extent in the presence of relatively larger eavesdropping males compared to smaller ones.

在存在雄性配偶选择模仿（male mate-choice copying）的种群中，雄性可通过在性竞争者（audience）在场时降低对特定雌性的偏好，来降低自身面临的性竞争风险。鉴于此类观众效应会带来错失交配机会的代价，相较于竞争程度较低的性竞争者，当面对竞争程度更高的性竞争者时，雄性应更大幅度地降低其择偶偏好。本研究以特立尼达孔雀鱼（Trinidadian guppy, Poecilia reticulata）为实验对象，对该假说进行了验证。本研究采用二分选择实验（dichotomous-choice tests），分别测定了无任何性竞争者在场时，焦点雄鱼（focal male）对两条整体体型存在差异的刺激雌鱼（stimulus female）的基础择偶偏好，并与存在性竞争者时其对相同雌鱼的偏好进行对比。焦点雄鱼与观众雄鱼（audience male）在体长以及体表橙色与黑色色素占比方面均存在差异。相较于面对体型更小的竞争者的焦点雄鱼，当面对体型更大的竞争者时，焦点雄鱼对其初始偏好雌鱼的偏好降幅更为显著，且该结果不受观众雄鱼体表装饰是否多于焦点雄鱼的影响。当观众雄鱼体型大于焦点雄鱼时，焦点雄鱼的初始择偶偏好强度与观众效应的强弱呈显著正相关。由此可见，特立尼达孔雀鱼雄鱼可感知邻近雄鱼的表型特征，相较于体型更小的窃听雄鱼（eavesdropping males），当体型更大的窃听雄鱼在场时，其会更大幅度地调整对特定配偶的偏好。