Data from: Evidence for lower plasticity in CTMAX at warmer developmental temperatures

Understanding the capacity for different species to reduce their susceptibility to climate change via phenotypic plasticity is essential for accurately predicting species extinction risk. The climatic variability hypothesis suggests that spatial and temporal variation in climatic variables should select for more plastic phenotypes. However, empirical support for this hypothesis is limited. Here we examine the capacity for ten Drosophila species to increase their critical thermal maxima (CTMAX) through developmental acclimation and/or adult heat hardening. Using four fluctuating developmental temperature regimes, ranging from 13‐33 °C, we find that most species can increase their CTMAX via developmental acclimation and adult hardening, but found no relationship between climatic variables and absolute measures of plasticity. However, when plasticity was dissected across developmental temperatures, a positive association between plasticity and one measure of climatic variability(temperature seasonality) was found when development took place between 26‐28 °C, while a negative relationship was found when development took place between 20‐23 °C. In addition, a decline in CTMAX and egg‐to‐adult viability, a proxy for fitness, was observed in tropical species at the warmer developmental temperatures (26‐28 ̊C); this suggests that tropical species may be at even greater risk from climate change than currently predicted. The combined effects of developmental acclimation and adult hardening on CTMAX were small, contributing to a <0.60 ̊C shift in CTMAX. Although small shifts in CTMAX may increase population persistence in the shorter‐term, the degree to which they can contribute to meaningful responses in the long term is unclear.

阐明不同物种通过表型可塑性（phenotypic plasticity）降低其对气候变化易感程度的能力，对于精准预测物种灭绝风险至关重要。气候变异性假说（climatic variability hypothesis）提出，气候变量的空间与时间变异应会筛选出可塑性更强的表型。然而，该假说的实证支持较为有限。本研究针对10种果蝇（Drosophila）展开实验，探究它们通过发育驯化（developmental acclimation）和/或成虫热硬化（adult heat hardening）提升临界热最大值（critical thermal maxima, CTMAX）的能力。本研究采用4组波动范围为13~33℃的发育温度处理，结果显示多数物种可通过发育驯化与成虫热硬化提升其CTMAX，但未发现气候变量与可塑性绝对测度之间存在关联。不过，若按发育温度梯度拆解可塑性的变化，则可观察到：当发育温度处于26~28℃区间时，可塑性与一项气候变异性测度（温度季节性，temperature seasonality）呈正相关；而当发育温度处于20~23℃区间时，二者则呈负相关。此外，在发育温度较高（26~28℃）的条件下，热带物种的CTMAX与卵到成虫存活率（适合度替代指标，proxy for fitness）均出现下降，这表明热带物种面临的气候变化风险或比当前预测更为严峻。发育驯化与成虫热硬化对CTMAX的联合效应较弱，仅能使CTMAX提升不足0.60℃。尽管CTMAX的小幅提升或可在短期内增强种群存续能力，但此类可塑性变化能否在长期内促成具有生态学意义的适应性响应，目前仍不明确。