Previous studies have reported functional integration between dispersal and other phenotypic traits allowing individuals to alleviate dispersal costs, and such associations can affect dispersal evolution in return. In sexually reproducing species, assortative mating according to dispersal can shape the maintenance of such trait associations. Despite the potentially crucial consequences of dispersal in natural populations, assortative mating for dispersal and its underlying mechanisms remain largely unexplored. Here, we assessed assortative mating for between-patch dispersal status in a fragmented population of a small passerine bird, the collared flycatcher, and explored whether such assortative mating could result from (i) direct mate choice based on dispersal-related behavioural (aggressiveness and boldness) and morphological traits (tarsus and wing length), (ii) biased mating due to spatio-temporal heterogeneity in the distribution of dispersal phenotypes and/or (iii) post-mating adjustment of dispersal phenotype or dispersal-related traits. We found intrinsic assortative mating (i.e. positive among-pair correlation) for current dispersal status (in the year of mating) but not for natal dispersal status, even though we could not exclude it due to limited power. We also found assortative mating for boldness and age category (yearlings vs. older adults), and the probability for pair members to be assorted for current dispersal status was higher when both pair members were of similar boldness score and of the same age compared with mixed-age pairs. Mate choice based on boldness and age thus appears as a possible mechanism underlying assortative mating for dispersal status. Our analyses however remained correlative, and only an experimental manipulation of these traits could allow inferring causal links. Non-random mating for dispersal-related traits may affect the evolution of dispersal syndromes in this population. More work is nevertheless needed to fully assess the evolutionary implications of age- and behaviour-based assortative mating for dispersal.

中文翻译：

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野生鸟类种群中斑块间传播状态的分类交配：探索直接和间接潜在机制的作用。

以前的研究报告了分散和其他表型特征之间的功能整合，使个体能够减轻分散成本，而这种关联可以反过来影响分散进化。在有性繁殖的物种中，根据分布进行的分类交配可以塑造这种特征关联的维持。尽管散布在自然种群中可能产生至关重要的后果，但散布的分类交配及其潜在机制在很大程度上仍未得到探索。在这里，我们评估了一种小型雀形目鸟类（有领捕蝇器）的斑块间分散状态的分类交配，并探讨了这种分类交配是否可能来自（i）基于与分散相关的行为（攻击性和大胆）和形态特征（跗骨和翼长）的直接交配选择，（ii）由于分布中的时空异质性而导致的偏向交配散布表型和/或（iii）散布表型或散布相关性状的交配后调整。我们发现当前分散状态（在交配年份）的内在分类交配（即正对间相关性）而不是出生分散状态，尽管由于权力有限我们不能排除它。我们还发现了大胆和年龄类别（一岁鸽与老年人）的分类交配，与混合年龄的配对相比，当两个配对成员的胆量得分相似且年龄相同时，配对成员被分类为当前分散状态的概率更高。因此，基于胆量和年龄的配偶选择似乎是分散状态分类交配的一种可能机制。然而，我们的分析仍然具有相关性，只有对这些特征进行实验操作才能推断出因果关系。传播相关性状的非随机交配可能会影响该人群中传播综合征的演变。然而，需要做更多的工作来充分评估基于年龄和行为的分类交配对传播的进化影响。因此，基于胆量和年龄的配偶选择似乎是分散状态分类交配的一种可能机制。然而，我们的分析仍然具有相关性，只有对这些特征进行实验操作才能推断出因果关系。传播相关性状的非随机交配可能会影响该人群中传播综合征的演变。然而，需要做更多的工作来充分评估基于年龄和行为的分类交配对传播的进化影响。因此，基于胆量和年龄的配偶选择似乎是分散状态分类交配的一种可能机制。然而，我们的分析仍然具有相关性，只有对这些特征进行实验操作才能推断出因果关系。传播相关性状的非随机交配可能会影响该人群中传播综合征的演变。然而，需要做更多的工作来充分评估基于年龄和行为的分类交配对传播的进化影响。