Inbreeding is generally thought to have negative consequences for organismal health. However, despite the potential fitness effects, it remains surprisingly common among wild populations. In many cases, the complex factors that underlie mating dynamics make predicting whether individuals should or do avoid inbreeding quite challenging. One reason inbreeding may persist among species is that the likelihood of encountering relatives can be rare. Thus, even if inbreeding has severe consequences, selection to avoid mating with kin will be weak in species that are highly dispersed. Here we investigated if migratory monarch butterflies (Danaus plexippus), which are famous for their dispersal ability, actively avoid inbreeding. We found that neither female nor male monarchs choose mates based on relatedness. These results support the hypothesis that movement ecology can mask the deleterious effects of inbreeding and relax selection for active inbreeding avoidance behaviors. Overall, our data add to the growing list of studies showing that inbreeding avoidance is not the behavioral “default” for most species. We also highlight the implications that inbreeding may have on the declining populations of this iconic butterfly.

人们普遍认为近亲繁殖会对机体健康产生负面影响。然而，尽管有潜在的健康影响，它在野生种群中仍然令人惊讶地普遍。在许多情况下，交配动态背后的复杂因素使得预测个体是否应该或确实避免近亲繁殖相当具有挑战性。近亲繁殖在物种之间持续存在的原因之一是遇到亲戚的可能性很小。因此，即使近亲繁殖会产生严重后果，在高度分散的物种中，避免与亲属交配的选择也会很弱。在这里，我们调查了以分散能力着称的迁徙帝王蝶（Danaus plexippus ）是否主动避免近亲繁殖。我们发现雌性和雄性君主都不会根据亲缘关系来选择配偶。这些结果支持这样的假设：运动生态学可以掩盖近交的有害影响，并放松对主动近交回避行为的选择。总体而言，我们的数据添加到越来越多的研究列表中，表明避免近亲繁殖并不是大多数物种的行为“默认”。我们还强调了近亲繁殖可能对这种标志性蝴蝶数量下降的影响。