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，即个体偏好与自身表型相似的配偶，可在存在基因流的情况下促进物种形成。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”）。若表型匹配基于受趋异自然选择（divergent natural selection）作用的性状，则物种形成过程将更为简便。在此情形下，选型交配（assortative mating）可作为该性状趋异选择的副产物快速演化而来。此前针对同域分布且存在杂交行为的三棘刺鱼（threespine stickleback，Gasterosteus aculeatus复合体）物种间选型交配的观测研究表明，表型匹配或可依托体型这一受趋异自然选择作用的性状实现。为验证该假说，我们通过实验操控个体体型的方式，排除了混淆变量的影响。实验结果显示，经体型调整的底栖型与浮游型棘刺鱼雌鱼，更偏好与自身体型更为匹配的配偶。由此可见，在面临基因流的情形下，基于表型匹配的选型交配或已促进了底栖型与浮游型三棘刺鱼的起源与存续。