Am Nat. 2019 Feb;193(2):279-295. doi: 10.1086/701124. Epub 2018 Dec 13.
Assortative mating in animals can have substantial evolutionary impact. Numerous reports also make it appear to be pervasive in occurrence. In assortative mating, defined here in behavioral terms, animals select their mates according to a particular shared trait such that mated individuals phenotypically resemble each other more than expected by chance. Body size is a widely studied assortment trait. This is especially relevant for anuran amphibians (frogs and toads), among whom reproductive advantages may accrue to large individuals of both sexes. Anurans also exhibit discrete forms of male mating behavior. Sedentary calling behavior of "sitters" allows for female choice, whereas fighting for possession of mates by "scramblers" precludes female choice. Size-assortative mating in anurans should therefore be a property of sitters, not scramblers. I used meta-analysis to assess the occurrence of true size-assortative mating in relation to mating behavior and other variables in 282 studies of 68 species of anurans. I found publication bias against reporting nonsignificant results and analytical bias resulting from pooling of samples collected at different times or places (Simpson's paradox). Pooled samples significantly inflated the apparent occurrence and strength of size-assortative mating. Controlling for such biases left little credible evidence for size-assortative mating behavior in any anurans. Instead, large-male advantage among scramblers was associated with a secondary pattern of concomitant nonrandom mating. In this disproportionate mating, neither sex behaves according to mate choice rules that could lead to consistently strong assortment. It should thus have relatively little evolutionary impact compared to true assortative mating.
动物的交配选择能产生重大的进化影响。大量报告表明，这种现象普遍存在。在这里，我们将根据行为定义将交配选择定义为：动物根据特定的共享特征选择配偶，从而使交配个体在表型上彼此之间比随机情况下更相似。体型大小是一种广泛研究的交配特征。这对于两栖动物（青蛙和蟾蜍）尤其重要，因为雄性和雌性个体的体型大小都可能具有繁殖优势。两栖动物也表现出不同形式的雄性交配行为。“静坐者”的静止性求偶行为允许雌性选择，而“争夺者”为争夺配偶而战斗则排除了雌性选择。因此，体型选择交配应该是静坐者的特征，而不是争夺者的特征。我使用荟萃分析评估了 68 种两栖动物的 282 项研究中，与交配行为和其他变量相关的真正体型选择交配的发生情况。我发现，发表的研究结果存在对非显著结果的偏见，并且由于在不同时间或地点收集的样本进行合并（辛普森悖论）而导致分析上存在偏见。合并样本显著夸大了体型选择交配的明显发生和强度。在控制了这些偏见之后，在任何两栖动物中，几乎没有可信的证据表明存在体型选择交配行为。相反，争夺者中的大雄性优势与同时发生的非随机交配的次要模式相关。在这种不成比例的交配中，两性都没有遵循可能导致一致强烈选择的配偶选择规则。因此，与真正的选择交配相比，它对进化的影响应该相对较小。
