PREMISE Environmental sex determination (ESD) is a rare sex determination system in which individuals may switch sex expression throughout their lifetimes in response to environmental factors. In sexually stable species, individuals usually bear more female flowers if the plants are larger, have greater access to limiting resources, or are in better condition. Research regarding sexually plastic species with ESD and how resources correlate with sex expression is limited. Furthermore, most research investigates resources at the population level, failing to account for resources available to individuals for growth, maintenance, or reproduction. METHODS Acer pensylvanicum is a species that is known to switch sex. Using twig samples collected during 2014-2016 in December and May, we analyzed resource status in the form of stored nonstructural carbohydrates (NSCs) and compared this with expressed sex. RESULTS We found that females had higher sugar concentrations than males. Furthermore, males changing expression to female had higher sugar concentrations during the prior winter than did males remaining male. We found that size was not a key predictor: neither male nor female-flowering individuals increased NSC concentrations with size. Dying female trees had high concentrations of NSCs throughout the dying process and only manifested reduced NSCs once dead. CONCLUSIONS This is the first study showing significant correlations between NSCs and sex expression in a plant species with ESD. These findings support the hypothesis that sex switching could be a consequence of increased resource availability and that the high female mortality of A. pensylvanicum populations is likely not a direct result of carbon starvation.

中文翻译：

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死亡、性别和糖分：性可塑性树中非结构性碳水化合物浓度的变化

前提 环境性别决定 (ESD) 是一种罕见的性别决定系统，在该系统中，个体可能会在其一生中响应环境因素而改变性别表达。在性稳定的物种中，如果植物较大，有更多机会获得有限资源或处于更好的状态，则个体通常会结出更多的雌花。关于具有 ESD 的性可塑性物种以及资源如何与性表达相关的研究是有限的。此外，大多数研究在人口层面调查资源，没有考虑到个人可用于增长、维持或繁殖的资源。方法 Acer pensylvanicum 是一种已知会转换性别的物种。使用 2014-2016 年 12 月和 5 月收集的树枝样本，我们以储存的非结构性碳水化合物 (NSC) 的形式分析了资源状况，并将其与表达的性别进行了比较。结果我们发现女性比男性有更高的糖浓度。此外，与保持雄性的雄性相比，在前一个冬天将表达改变为雌性的雄性具有更高的糖浓度。我们发现大小不是一个关键的预测因素：无论是雄性还是雌性开花个体都不会随着大小的增加而增加 NSC 浓度。垂死的雌性树在整个垂死过程中都具有高浓度的 NSC，并且只有在死后才表现出减少的 NSC。结论 这是第一项显示 NSCs 与具有 ESD 的植物物种的性别表达之间存在显着相关性的研究。