Skelly David K
School of Forestry and Environmental Studies and Department of Ecology and Evolutionary Biology, Yale University, 370 Prospect Street, New Haven, Connecticut 06511, USA.
Evolution. 2004 Jan;58(1):160-5. doi: 10.1111/j.0014-3820.2004.tb01582.x.
Prior studies have shown that macrogeographic gradients in temperature associated with latitude and altitude can lead to countergradient patterns of variation in a number of taxa: individuals from colder environments are known to grow or develop faster than their conspecifics from warmer environments when placed in a common setting. In this study, I hypothesized that countergradient variation also is important at microgeographic scales. The wood frog, Rana sylvatica, breeds in open-canopied, temporary wetlands as well as those heavily shaded by vegetation. Shading leads to cooler thermal environments that are associated with embryonic development rates as much as 50% slower than those in unshaded wetlands. Wetlands with contrasting canopy environments are often found within tens or hundreds of meters of each other. In a common garden experiment, embryos from nearby natural wetlands displayed countergradient variation: individuals collected from shaded wetlands developed up to 12% faster than those collected from relatively unshaded wetlands. The results of this study suggest that the concept of countergradient variation may be extended to small scales of space. In addition, the rate and scale of vegetation dynamics (the agent of wetland shading) imply that divergence in development among residents of nearby wetlands may be relatively rapid, on the order of decades.
先前的研究表明，与纬度和海拔相关的温度宏观地理梯度可导致许多分类群出现反梯度变异模式：当置于共同环境中时，来自较寒冷环境的个体已知比来自较温暖环境的同种个体生长或发育得更快。在本研究中，我假设反梯度变异在微观地理尺度上也很重要。林蛙（Rana sylvatica）在树冠开阔的临时湿地以及植被严重遮荫的湿地中繁殖。遮荫导致较凉爽的热环境，与胚胎发育速率相关，比无遮荫湿地中的胚胎发育速率慢多达50%。具有对比性树冠环境的湿地通常彼此相距数十米或数百米。在一项共同花园实验中，来自附近天然湿地的胚胎表现出反梯度变异：从遮荫湿地收集的个体发育速度比从相对无遮荫湿地收集的个体快多达12%。本研究结果表明，反梯度变异的概念可能扩展到小空间尺度。此外，植被动态（湿地遮荫的因素）的速率和尺度意味着附近湿地居民之间发育的差异可能相对较快，大约在几十年的时间尺度上。
