Arizona Cooperative Fish and Wildlife Research Unit, School of Natural Resources and the Environment, University of Arizona, Tucson, Arizona, United States of America.
United States Geological Survey, Idaho Cooperative Fish & Wildlife Research Unit, University of Idaho, Moscow, Idaho, United States of America.
PLoS One. 2024 Jul 26;19(7):e0306660. doi: 10.1371/journal.pone.0306660. eCollection 2024.
Natal dispersal is a key demographic trait that affects population dynamics, and intraspecific variation in dispersal affects gene flow among populations and source-sink dynamics. However, relatively little is known about the selective pressures and trade-offs that animals face when departing their natal area due to the logistical difficulties associated with monitoring animals during this critical life stage. We used a randomized block design to examine the selective pressure that influence dispersal timing in juvenile burrowing owls (Athene cunicularia) by experimentally altering both food and ectoparasites at 135 nests. We also examined the effects of local food abundance, ectoparasite loads, and parental departure on natal dispersal timing. Juvenile burrowing owls varied widely in natal dispersal timing, and phenotypic plasticity in dispersal timing was evident in juvenile owls' response to our experimental treatments, local conditions, and their parents' departure from the natal area. Moreover, juveniles responded differently than their parents to experimental manipulation of food and ectoparasite loads. Juveniles typically dispersed shortly after their parents departed the natal area, but delayed dispersing more than 2 weeks after parental departure if they did not receive experimental food supplements during a low-food year. In contrast, the experimental food supplements did not affect the migratory departure decisions of adult owls in either year. Juveniles at nests treated for ectoparasites initiated dispersal at a younger age (and prior to adults in the high-food year) compared to juveniles at control nests. In contrast, parents at nests treated for ectoparasites departed later than parents at control nests. Our results suggest that unfavorable conditions (low food or high ectoparasite loads) caused juveniles to delay dispersal, but prompted adults to depart sooner. Our results highlight the extent of intraspecific variation in natal dispersal timing, and demonstrate that ecological conditions affect dispersal decisions of parents and offspring differently, which can create important trade-offs that likely affect life history strategies and responses to climatic changes.
扩散是影响种群动态的关键种群特征，种内扩散变异会影响种群间的基因流动和源-汇动态。然而，由于在这个关键的生命阶段监测动物的后勤困难，动物在离开出生地时所面临的选择压力和权衡相对知之甚少。我们使用随机区组设计，通过在 135 个巢中实验改变食物和外寄生虫，来检查影响幼穴居猫头鹰（Athene cunicularia）扩散时间的选择压力。我们还研究了局部食物丰度、外寄生虫负荷和父母离开对扩散时间的影响。幼穴居猫头鹰在扩散时间上表现出广泛的差异，而且在幼猫头鹰对我们的实验处理、当地条件和父母离开出生地的反应中，扩散时间的表型可塑性是明显的。此外，幼猫头鹰对食物和外寄生虫负荷的实验处理的反应与它们的父母不同。幼猫头鹰通常在父母离开出生地后不久就开始扩散，但如果在食物匮乏的年份没有接受实验性食物补充，它们会延迟超过 2 周的时间。相比之下，在这两年中，实验性食物补充都没有影响成年猫头鹰的迁徙离开决定。接受外寄生虫处理的巢中的幼鸟比对照巢中的幼鸟更早地开始扩散（在高食物年份比成年鸟更早）。相比之下，接受外寄生虫处理的巢中的亲鸟比对照巢中的亲鸟离开得更晚。我们的结果表明，不利的条件（低食物或高外寄生虫负荷）导致幼鸟延迟扩散，但促使成年鸟更早离开。我们的结果突出了扩散时间在种内的变异程度，并表明生态条件会以不同的方式影响父母和后代的扩散决策，这可能会产生重要的权衡，从而影响生活史策略和对气候变化的反应。
