Data from: A rapidly evolved shift in life history timing during ecological speciation is driven by the transition between developmental phases

For insect species in temperate environments, seasonal timing is often governed by the regulation of diapause, a complex developmental program that allows insects to weather unfavorable conditions and synchronize their lifecycles with available resources. Diapause development consists of a series of distinct phases including initiation, maintenance, termination, and post-diapause development. The evolution of insect seasonal timing depends in part on how these phases of diapause development and post-diapause development interact to affect variation in phenology. Here, we dissect the physiological basis of a recently evolved phenological shift in Rhagoletis pomonella (Diptera: Tephritidae), a model system for ecological divergence. A recently derived population of R. pomonella shifted from specializing on native hawthorn fruit to earlier fruiting introduced apples, resulting in a 3-4 week shift in adult emergence timing. We tracked metabolic rates of individual flies across post-winter development to test which phases of development may act either independently or in combination to contribute to this recently evolved divergence in timing. Apple and hawthorn flies differed in a number of facets of their post-winter developmental trajectories. However, divergent adaptation in adult emergence phenology in these flies was due almost entirely to the end of the pupal diapause maintenance phase, with post-diapause development having a very small effect. The relatively simple underpinnings of variation in adult emergence phenology suggest that further adaptation to seasonal change in these flies for this trait might be largely due to the timing of diapause termination unhindered by strong covariance among different components of post-diapause development.

对于温带环境中的昆虫物种而言，季节性时间节律通常由滞育（diapause）的调控所决定——滞育是一套复杂的发育程序，可帮助昆虫耐受不利环境条件，并使其生命周期与可获取的资源同步。滞育发育包含一系列明确的阶段，包括启动、维持、终止以及滞育后发育（post-diapause development）。昆虫季节性时间节律的演化，在一定程度上取决于滞育发育与滞育后发育的这些阶段如何相互作用，进而影响物候（phenology）的变异。

本研究解析了新近演化出的物候转变的生理基础，该转变发生在苹果绕实蝇（Rhagoletis pomonella，双翅目：实蝇科）——生态分化研究的模式系统——身上。一个新近分化的苹果绕实蝇种群，原本专性寄生于本土山楂果实，如今转向了结果更早的外来苹果，这使其成虫羽化时间提前了3至4周。我们追踪了越冬后发育过程中单个果蝇的代谢速率，以检验哪些发育阶段能够独立或协同作用，促成这一近期演化出的时序分化。

苹果寄主种群与山楂寄主种群的果蝇，在越冬后发育轨迹的多个维度均存在差异。然而，这些果蝇成虫羽化物候的适应性分化，几乎完全源于蛹期滞育维持阶段的结束，滞育后发育的影响极小。成虫羽化物候变异的相对简单的调控基础表明，这些果蝇针对该性状对季节变化的进一步适应，或许主要取决于滞育终止的时序，且不会受到滞育后发育各组分间强协变关系的干扰。