ABSTRACT Background Climates are changing at a rate that exceeds the adaptive capacity of species, especially endangered species. Genetic variation and phenotypic plasticity are important for population persistence, yet few studies have linked traits to seedling performance under drought in endangered species. Aims We assessed intraspecific variation and trait plasticity under drought, to understand how an endangered species would cope with increasingly severe droughts. Methods Using greenhouse experiments, we assessed drought tolerance of a critically endangered Hawaiian shrub, Schiedea obovata. Seedlings from five maternal families (three selfed and two interpopulation crosses) were subjected to daily watering or a simulated drought, and we measured growth, traits linked to drought tolerance, and days until death under terminal drought. Results Drought reduced growth but not days until death. We detected genetic variation in growth, but no trait plasticity except in carbon:nitrogen, which decreased under drought. We did not detect traits that enhanced performance under drought but identified four physiological traits whose effects on growth varied under control and drought. Conclusions Our results indicate moderate drought tolerance of an endangered shrub, and low trait plasticity. Conservation of endangered species under shifting climates will benefit from studies of stress tolerance, particularly at the vulnerable seedling stage.

中文翻译：

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一种极度濒危的地方性夏威夷灌木幼苗耐旱性和相关性状的种内变异

摘要 背景 气候变化的速度超过了物种，尤其是濒危物种的适应能力。遗传变异和表型可塑性对于种群的持久性很重要，但很少有研究将性状与濒危物种干旱条件下的幼苗表现联系起来。目标我们评估了干旱下的种内变异和性状可塑性，以了解濒危物种将如何应对日益严重的干旱。方法使用温室实验，我们评估了极度濒危的夏威夷灌木 Schiedea obovata 的耐旱性。来自五个母系（三个自交和两个种群间杂交）的幼苗每天接受浇水或模拟干旱，我们测量了生长、与耐旱性相关的性状以及在极端干旱下死亡的天数。结果 干旱减少了生长，但不会减少直至死亡的天数。我们检测到生长的遗传变异，但除碳：氮外没有其他性状可塑性，干旱条件下碳：氮下降。我们没有检测到在干旱条件下提高性能的性状，但确定了四个生理性状，它们对生长的影响在控制和干旱的情况下有所不同。结论 我们的结果表明濒危灌木具有中等耐旱性，性状可塑性低。在变化的气候下保护濒危物种将受益于抗逆性研究，特别是在脆弱的幼苗阶段。我们没有检测到在干旱条件下提高性能的性状，但确定了四个生理性状，它们对生长的影响在控制和干旱的情况下有所不同。结论 我们的结果表明濒危灌木具有中等耐旱性，性状可塑性低。在变化的气候下保护濒危物种将受益于抗逆性研究，特别是在脆弱的幼苗阶段。我们没有检测到在干旱条件下提高性能的性状，但确定了四个生理性状，它们对生长的影响在控制和干旱的情况下有所不同。结论 我们的结果表明濒危灌木具有中等耐旱性，性状可塑性低。在变化的气候下保护濒危物种将受益于抗逆性研究，特别是在脆弱的幼苗阶段。