Many organisms experience seasonal windows of opportunity for growth and reproduction. These windows represent intervals in time when organisms experience improved prospects for advancing their life history objectives, constrained by the combined effects of seasonally variable biotic and abiotic conditions acting independently or in combination. While seasonal windows of opportunity are likely to be widespread in nature, relatively few studies have conducted the repeated observations necessary to identify them or suggest the factors that structure them in time. Here, we present the results of three experimental studies conducted at different field sites in three different years in which we manipulated the phenology of monarch caterpillars (Danaus plexippus) throughout the growing season. The primary aims of these experiments were to a) identify seasonal windows of opportunity for successful larval development on milkweed (Asclepias spp.), and b) to suggest which factors are most likely to constrain these windows of opportunity in time. We found strong seasonal windows of opportunity in the developmental success of monarchs, with distinct periods of higher developmental prospects during each study year. We evaluated the role of seasonal variation in abiotic thermal stress, host plant density, host plant defensive traits, and natural enemy risk as potential factors that may limit seasonal windows of opportunity. By comparing the seasonal patterns of larval success and potential explanatory factors across all three years, we find patterns that are consistent with seasonally variable abiotic conditions, host plant availability, host plant traits, and natural enemy risk factors. These results suggest the potential for seasonal variation in the factors that limit monarch larval development and population growth. More generally, this study also highlights the value of temporally explicit experimental studies that can identify and examine seasonal patterns in species interactions. This article is protected by copyright. All rights reserved.

中文翻译：

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马利筋-君主相互作用的季节性机会窗口

许多生物体经历了生长和繁殖机会的季节性窗口。这些窗口代表生物体在推进其生活史目标方面经历改善前景的时间间隔，受到季节性变化的生物和非生物条件独立或组合作用的综合影响的限制。虽然季节性机会窗口在自然界中可能很普遍，但相对较少的研究进行了必要的重复观察以识别它们或提出及时构建它们的因素。在这里，我们展示了在三个不同年份在不同现场进行的三项实验研究的结果，其中我们在整个生长季节操纵了帝王毛虫 (Danaus plexippus) 的物候。这些实验的主要目的是 a) 确定马利筋 (Asclepias spp.) 幼虫成功发育的季节性机会窗口，以及 b) 建议哪些因素最有可能及时限制这些机会窗口。我们在帝王蝶的发育成功中发现了很强的季节性机会窗口，在每个研究年度都有明显的更高发展前景的时期。我们评估了季节性变化在非生物热应激、寄主植物密度、寄主植物防御性状和天敌风险中的作用，作为可能限制季节性机会窗口的潜在因素。通过比较所有三年中幼虫成功的季节性模式和潜在的解释因素，我们发现了与季节性可变的非生物条件、寄主植物可用性、寄主植物性状和天敌风险因素。这些结果表明，限制帝王蝶幼虫发育和种群增长的因素可能存在季节性变化。更一般地说，这项研究还强调了时间明确的实验研究的价值，这些研究可以识别和检查物种相互作用中的季节性模式。本文受版权保护。版权所有。