School of Environment, University of Auckland, Auckland 1010, New Zealand.
Department of Ecology and Evolutionary Biology, University of California, Santa Cruz 95060, CA, USA.
Proc Biol Sci. 2020 Jun 10;287(1928):20200608. doi: 10.1098/rspb.2020.0608. Epub 2020 Jun 3.
Body size is a key functional trait that is predicted to decline under warming. Warming is known to cause size declines via phenotypic plasticity, but evolutionary responses of body size to warming are poorly understood. To test for warming-induced evolutionary responses of body size and growth rates, we used populations of mosquitofish () recently established (less than 100 years) from a common source across a strong thermal gradient (19-33°C) created by geothermal springs. Each spring is remarkably stable in temperature and is virtually closed to gene flow from other thermal environments. Field surveys show that with increasing site temperature, body size distributions become smaller and the reproductive advantage of larger body size decreases. After common rearing to reveal recently evolved trait differences, warmer-source populations expressed slowed juvenile growth rates and increased reproductive effort at small sizes. These results are consistent with an adaptive basis of the plastic temperature-size rule, and they suggest that temperature itself can drive the evolution of countergradient variation in growth rates. The rapid evolution of reduced juvenile growth rates and greater reproduction at a small size should contribute to substantial body downsizing in populations, with implications for population dynamics and for ecosystems in a warming world.
体型是一个关键的功能特征，预计在变暖的情况下会下降。众所周知，变暖会通过表型可塑性导致体型缩小，但对体型对变暖的进化反应知之甚少。为了测试体型和生长率因变暖而产生的进化反应，我们使用了最近（不到 100 年）由温泉形成的强烈热梯度（19-33°C）的共同来源建立的食蚊鱼（）种群。每个温泉的温度都非常稳定，几乎与来自其他热环境的基因流隔绝。实地调查显示，随着地点温度的升高，体型分布变得更小，较大体型的繁殖优势降低。在共同饲养以揭示最近进化的特征差异后，温暖来源的种群表现出幼体生长速度减慢和在较小体型时增加生殖力的特征。这些结果与可塑温度-体型规律的适应性基础一致，并表明温度本身可以驱动生长率反梯度变异的进化。在小体型时，幼体生长速度降低和繁殖增加的快速进化，应该会导致种群的体型大幅缩小，这对种群动态和变暖世界中的生态系统都有影响。
