Data from: Experimental confirmation that body size determines mate preference via phenotype matching in a stickleback species pair

Mate choice by phenotype matching, whereby individuals prefer a mate whose phenotype is similar to their own, should facilitate speciation with gene flow. This is because the genes that control mate signal (the phenotype being matched) also determine the preferred mate signal (‘mate preference’). Speciation is made even easier if phenotype matching is based on a trait under divergent natural selection. In this case, assortative mating should readily evolve as a by-product of divergent selection on the trait. Previous observational studies of assortative mating between sympatric, hybridizing threespine stickleback species (Gasterosteus aculeatus complex) suggested that phenotype matching might occur by body size, a trait under divergent natural selection. To test this we used experimental manipulation of body size to rule out the effects of confounding variables. We found that size-manipulated benthic and limnetic stickleback females prefer mates whose body size more closely matches their own. It is thus likely that assortative mating by phenotype matching has facilitated the origin and persistence of benthic and limnetic threespine sticklebacks in the face of gene flow.

基于表型匹配（phenotype matching）的配偶选择——即个体偏好选择表型与自身相似的配偶——本应促进存在基因流的物种形成。这是因为控制配偶信号（即被匹配的表型）的基因，同时也决定了个体所偏好的配偶信号（即‘配偶偏好’）。若表型匹配基于受到趋异自然选择（divergent natural selection）的性状，则物种形成过程会更为简易：此时选型交配（assortative mating）可作为该性状趋异选择的副产物快速演化。此前针对同域分布（sympatric）且存在杂交行为的三棘刺鱼（Gasterosteus aculeatus复合体）间选型交配的观察研究表明，表型匹配可能通过体尺寸这一受趋异自然选择的性状实现。为验证该假说，我们通过实验操控个体体尺寸以排除混淆变量的影响。实验结果显示，经体尺寸操控的底栖型与浮游型三棘刺鱼雌性，更偏好体尺寸与自身更为匹配的雄性配偶。综上，基于表型匹配的选型交配，或在基因流存在的前提下，推动了底栖型与浮游型三棘刺鱼的起源与存续。