Data from: Climate, demography, and lek stability in an Amazonian bird

Lekking is a rare, but iconic mating system where polygynous males aggregate and perform group displays to attract females. Existing theory postulates that demographic and environmental stability are required for lekking to be an evolutionarily viable reproductive strategy. However, we lack empirical tests for the hypotheses that lek stability is facilitated by age-specific variation in demographic rates, and by predictable, abundant resources. To address this knowledge gap, we use multistate models to examine how two demographic elements of lek stability—male survival and recruitment—vary with age, social status and phase of the El Niño Southern Oscillation (ENSO) in a Neotropical frugivorous bird, the wire-tailed manakin (Pipra filicauda). Our results show that demographic and environmental conditions were related to lek stability in the Ecuadorean Amazon. Apparent annual survival probability of territorial males was higher than that of non-territorial floaters, and recruitment probability increased as males progressed in an age-graded queue. Moreover, annual survival of territorial males and body condition of both floaters and territory holders were higher following years with El Niño conditions, associated with reduced rainfall and probably higher fruit production in the northern Neotropics, and lower after years with wet, La Niña conditions that predominated our study. Recruitment probabilities varied annually, independent of ENSO phase, and increased over our study period, but the annual mean number of territorial males per lek declined. Our results provide empirical support for hypothesized demographic and environmental drivers of lek dynamics. This study also suggests that climate-mediated changes in resource availability can affect demography and subsequent lek stability in a relatively buffered, lowland rainforest.

求偶场（lekking）是一种罕见却极具标志性的交配系统，在此系统中实行一雌多雄制的雄性会聚集在一起，通过群体展示行为吸引雌性。现有理论推测，种群动态与环境稳定性是求偶场行为成为进化上可行繁殖策略的必要条件。然而，目前尚缺乏针对以下假说的实证检验：求偶场的稳定性可通过种群统计率的年龄特异性变异，以及可预测的充足资源来维持。为填补这一认知空白，我们采用多状态模型，以新热带食果鸟类线尾娇鹟（Pipra filicauda）为研究对象，探究求偶场稳定性的两个种群统计要素——雄性存活率与补充率——如何随年龄、社会地位以及厄尔尼诺南方涛动（ENSO）相位发生变化。我们的研究结果显示，种群统计与环境条件与厄瓜多尔亚马逊地区的求偶场稳定性相关。领域雄性的年度表观存活率高于无领域漂浮个体，且补充概率随雄性所处年龄等级队列的推进而升高。此外，在经历厄尔尼诺条件的年份后，领域雄性的年度存活率，以及漂浮个体与领域占有者的身体状况均有所提升——这类厄尔尼诺年份通常伴随降雨量减少，且可能与新热带北部地区的果实产量增加相关；而在研究期间占主导的湿润拉尼娜年份后，上述指标则有所下降。补充概率每年均存在波动，且不受ENSO相位影响，并在研究期间整体呈上升趋势，但每个求偶场的领域雄性年均数量却出现下降。我们的研究结果为求偶场动态的种群统计与环境驱动假说提供了实证支持。本研究同时表明，由气候介导的资源可利用性变化，即便在相对受保护的低地热带雨林中，也能对种群统计特征以及后续的求偶场稳定性产生影响。