There is considerable debate about the occurrence of assortative mating between phenotypic traits measured within natural populations. Meta-analyses have implied that assortative mating occurs generally in natural populations, but recent work indicates these conclusions largely result from biased data. Specifically, estimates of phenotypic correlations between mating partners do not solely result from nonrandom associations between individual-level traits of partners but also from other biological processes (joint phenotypic plasticity, indirect genetic effects), methodological practices (observer bias) and other unexplained residual correlations (e.g. correlated measurement error). This paper puts this critique to test. First, we estimated the overall phenotypic correlation between phenotypic traits of mating partners for a wild population of great tits. Second, we estimated various key variance components to reveal the extent to which phenotypic correlations between partners resulted from assortative mating, reversible plasticity, social partner effects and methodological practices. We performed our analyses for a range of phenotypic traits (body mass, breathing rate, exploration behaviour, wing and tarsus length) to derive general conclusions not hinging on the specifics of the traits involved. Our analyses support the conclusion that patterns of assortative mating exist at first glance but occur because of the biasing effects of correlated residuals likely caused by a combination of phenotypic responses to unknown environmental factors or measurement error-not because of intrinsic patterns of assortative mating.

中文翻译：

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交配伙伴之间强烈的表型性状相关性不是由野生大山雀（Parus major）的组合交配引起的。

关于在自然种群中测量的表型性状之间是否发生分类交配存在相当大的争论。荟萃分析表明，分类交配通常发生在自然种群中，但最近的工作表明这些结论主要来自有偏见的数据。具体来说，交配伴侣之间表型相关性的估计不仅来自伴侣个体水平特征之间的非随机关联，还来自其他生物学过程（联合表型可塑性、间接遗传效应）、方法实践（观察者偏差）和其他无法解释的残差相关性（例如相关的测量误差）。本文对这一批评进行了测试。第一的，我们估计了野生大山雀种群的交配伙伴表型特征之间的整体表型相关性。其次，我们估计了各种关键方差分量，以揭示伴侣之间的表型相关性在多大程度上是由组合交配、可逆可塑性、社会伴侣效应和方法实践引起的。我们对一系列表型特征（体重、呼吸频率、探索行为、机翼和跗骨长度）进行了分析，以得出不依赖于所涉及特征的具体情况的一般结论。