Premise of research. Small populations on small islands are intrinsically more vulnerable to population decline and extinction. Nevertheless, small native populations that occur on multiple islands may have life-history characteristics that buffer impacts from novel disturbance regimes, and, rather than contracting, populations may be expanding. We monitored three populations of the orchid Brassavola cucullata from two Caribbean islands and asked what the likelihood of population persistence is. Methodology. Over 3–4 yr, we recorded growth, fruit production, herbivory, recruitment, and mortality for all plants in each of our populations. We assessed persistence and predicted possible population changes using both population projection models (PPMs) and integral projection models (IPMs). Our results include a mixture of traditional indexes (λ and elasticities) and more recent indexes (transient dynamics and nonlinear sensitivities). Pivotal results. Growth, reproduction, and predicted population persistence varied among years and islands. IPMs and PPMs gave similar results. The overall trend is toward a reduction in population growth rates, although population reactivity may buffer this pattern in the short term (λ>1). Populations would be extremely vulnerable to reduction if small plants dominated, yet even with an abundance of large plants, substantial reductions in population density are possible. Medium and larger plants contribute more to the persistence of the population, yet the survival and growth of small individuals might have greater effects on λ if retrogression is observed. To attain population stability, effective recruitment rates must increase dramatically. Conclusions. Populations of perennial plants on small islands can fluctuate substantially, suggesting a degree of vulnerability. While B. cucullata shows a general trajectory of decline, there are some signs of stability despite deforestation and herbivore activity. The outlook is precarious for the Saba population given the predominance of younger plants, and all three populations could decline if spasmodic recruitment fails to occur, which may happen if disturbance regimes change and the ongoing warming and drying trends persist.

中文翻译：

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小岛上的小种群：兰花有什么机会？

研究的前提。小岛上的小种群本质上更容易受到人口下降和灭绝的影响。然而，出现在多个岛屿上的小型本地种群可能具有缓冲新干扰机制影响的生活史特征，并且人口可能会扩大，而不是收缩。我们监测了来自两个加勒比岛屿的兰花 Brassavola cucullata 的三个种群，并询问种群持续存在的可能性是多少。方法。在 3-4 年的时间里，我们记录了每个种群中所有植物的生长、果实产量、食草性、补充和死亡率。我们使用人口预测模型 (PPM) 和积分预测模型 (IPM) 评估了持久性并预测了可能的人口变化。我们的结果包括传统指标（λ 和弹性）和更新的指标（瞬态动力学和非线性敏感性）的混合。关键结果。生长、繁殖和预测的人口持久性因年份和岛屿而异。IPM 和 PPM 给出了相似的结果。总体趋势是人口增长率下降，尽管人口反应性可能会在短期内缓冲这种模式（λ> 1）。如果小型植物占主导地位，种群将极易减少，但即使有大量大型植物，种群密度也有可能大幅减少。中型和大型植物对种群的持久性贡献更大，但如果观察到倒退，小个体的存活和生长可能对 λ 有更大的影响。为实现人口稳定，有效招聘率必须大幅提高。结论。小岛上多年生植物的数量可能会大幅波动，表明存在一定程度的脆弱性。虽然 B. cucullata 显示出总体下降轨迹，但尽管森林砍伐和食草动物活动，但仍有一些稳定迹象。鉴于年轻植物占主导地位，萨巴种群的前景不稳定，如果不能发生痉挛性补充，则所有三个种群都可能下降，如果干扰机制发生变化并且持续的变暖和干燥趋势持续存在，这可能会发生。尽管森林砍伐和食草动物活动，但仍有一些稳定迹象。鉴于年轻植物占主导地位，萨巴种群的前景不稳定，如果不能发生痉挛性补充，则所有三个种群都可能下降，如果干扰机制发生变化并且持续的变暖和干燥趋势持续存在，这可能会发生。尽管森林砍伐和食草动物活动，但仍有一些稳定迹象。鉴于年轻植物占主导地位，萨巴种群的前景不稳定，如果不能发生痉挛性补充，则所有三个种群都可能下降，如果干扰机制发生变化并且持续的变暖和干燥趋势持续存在，这可能会发生。