Arendt J
Department of Biology, University of California at Riverside, Riverside, CA, USA.
J Evol Biol. 2015 Jan;28(1):169-78. doi: 10.1111/jeb.12554. Epub 2014 Dec 7.
Most ectotherms follow a pattern of size plasticity known as the temperature-size rule where individuals reared in cold environments are larger at maturation than those reared in warm environments. This pattern seems maladaptive because growth is slower in the cold so it takes longer to reach a large size. However, it may be adaptive if reaching a large size has a greater benefit in a cold than in a warm environment such as when size-dependent mortality or size-dependent fecundity depends on temperature. I present a theoretical model showing how a correlation between temperature and the size-fecundity relationship affects optimal size at maturation. I parameterize the model using data from a freshwater pulmonate snail from the genus Physa. Nine families were reared from hatching in one of three temperature regimes (daytime temperature of 22, 25 or 28 °C, night-time temperature of 22 °C, under a 12L:12D light cycle). Eight of the nine families followed the temperature-size rule indicating genetic variation for this plasticity. As predicted, the size-fecundity relationship depended upon temperature; fecundity increases steeply with size in the coldest treatment, less steeply in the intermediate treatment, and shows no relationship with size in the warmest treatment. Thus, following the temperature-size rule is adaptive for this species. Although rarely measured under multiple conditions, size-fecundity relationships seem to be sensitive to a number of environmental conditions in addition to temperature including local productivity, competition and predation. If this form of plasticity is as widespread as it appears to be, this model shows that such plasticity has the potential to greatly modify current life-history theory.
大多数变温动物遵循一种被称为温度-大小规则的大小可塑性模式，即在寒冷环境中饲养的个体成熟时比在温暖环境中饲养的个体更大。这种模式似乎具有 maladaptive（此处原文有误，结合语境推测可能是maladaptive，意为“适应不良的”）性，因为在寒冷中生长较慢，所以需要更长时间才能达到较大的体型。然而，如果在寒冷环境中达到较大体型比在温暖环境中具有更大的益处，比如当与大小相关的死亡率或繁殖力取决于温度时，那么它可能是适应性的。我提出了一个理论模型，展示了温度与大小-繁殖力关系之间的相关性如何影响成熟时的最佳体型。我使用来自Physa属淡水肺螺的数据对模型进行参数化。九个家系从孵化开始就在三种温度条件之一中饲养（白天温度为22、25或28°C，夜间温度为22°C，光照周期为12小时光照：12小时黑暗）。九个家系中的八个遵循温度-大小规则，表明这种可塑性存在遗传变异。正如预测的那样，大小-繁殖力关系取决于温度；在最冷的处理中，繁殖力随体型急剧增加，在中间处理中增加较缓，在最温暖的处理中与体型无关。因此，遵循温度-大小规则对该物种具有适应性。尽管很少在多种条件下进行测量，但大小-繁殖力关系似乎除了温度外，还对许多环境条件敏感，包括当地生产力、竞争和捕食。如果这种可塑性形式像看起来那样普遍，那么这个模型表明这种可塑性有可能极大地改变当前的生活史理论。
