Climate and competition interact to affect species' performance, such as growth and survival, and help determine species distributions and coexistence. However, it is unclear how climatic conditions modulate frequency-dependent performance - i.e. how performance changes as a species becomes locally rare or common. This is critical because declines in performance as a species becomes more common (negative frequency-dependence), is a signature of niche differences among species that stabilizes coexistence, whereas positive frequency-dependence leads to priority effects and hampers species coexistence. Here, we used dendrochronology and hierarchical models to test whether frequency-dependent growth of sugar pine (Pinus lambertiana) depends on climatic conditions. We found that growth rates were strongly dependent on annual precipitation, but no frequency-dependence was evident across all years. However, there was a strong interaction between precipitation and frequency-dependence, revealing stabilizing niche differences in dry years but positive frequency-dependence in wet years. These differences emerged due to precipitation-driven changes in the direction and strength of both con- and heterospecific competition. Overall, these results show how stabilizing and destabilizing effects can be temporally dynamic for long-lived species and interact with climate variation.

中文翻译：

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频率依赖的树木生长取决于气候

气候和竞争相互作用以影响物种的表现，例如生长和生存，并有助于确定物种分布和共存。然而，尚不清楚气候条件如何调节与频率相关的性能——即当一个物种在当地变得稀有或普遍时，性能如何变化。这是至关重要的，因为随着物种变得更加普遍（负频率依赖性），性能下降是稳定共存的物种间生态位差异的标志，而正频率依赖性导致优先效应并阻碍物种共存。在这里，我们使用树木年代学和层次模型来测试糖松（Pinus labertiana）的频率依赖性生长是否取决于气候条件。我们发现增长率强烈依赖于年降水量，但所有年份都没有明显的频率依赖性。然而，降水和频率依赖性之间存在强烈的相互作用，揭示了干旱年稳定的生态位差异，但在湿润年呈正频率依赖性。这些差异是由于降水驱动的同种特异性和异种特异性竞争的方向和强度的变化而出现的。总体而言，这些结果表明，对于长寿物种而言，稳定和破坏稳定的影响是如何在时间上动态变化的，并与气候变化相互作用。这些差异是由于降水驱动的同种特异性和异种特异性竞争的方向和强度的变化而出现的。总体而言，这些结果表明，对于长寿物种而言，稳定和破坏稳定的影响是如何在时间上动态变化的，并与气候变化相互作用。这些差异是由于降水驱动的同种特异性和异种特异性竞争的方向和强度的变化而出现的。总体而言，这些结果表明，对于长寿物种而言，稳定和破坏稳定的影响是如何在时间上动态变化的，并与气候变化相互作用。