Department of Biology, University of North Carolina-Chapel Hill, NC 27599, USA.
Evolution. 2010 Sep;64(9):2521-34. doi: 10.1111/j.1558-5646.2010.01008.x.
Thermal adaptation to spatially varying environmental conditions occurs in a wide range of species, but what is less clear is the nature of fitness trade-offs associated with this temperature adaptation. Here, populations of the intertidal copepod Tigriopus californicus are examined at both local and latitudinal scales to determine whether these populations have evolved differences in their survival under high temperature stress. A clear pattern of increasing high temperature stress tolerance is seen with decreasing latitude, consistent with temperature adaptation. Additionally, there is also evidence for significant variation in thermal tolerance on a smaller scale. The competitive fitness of pairs of northern and southern copepod populations were also examined under a series of lower, more moderate temperatures. These fitness assays show that the southern populations that have the best survival under extreme high temperatures have lowered competitive fitness at the lower temperatures tested, whereas the fitness of the southern populations exceeded that of the northern populations at the highest temperatures tested. Combined, these results suggest that there may be evolutionary trade-offs between performance at high and stressful temperatures and fitness at moderate temperatures in this species.
热适应在广泛的物种中发生在空间变化的环境条件下，但不太清楚的是与这种温度适应相关的适应度权衡的性质。在这里，检查了潮间带桡足类动物加利福尼亚桡足类的种群在本地和纬度尺度上，以确定这些种群在高温胁迫下的生存是否已经进化出差异。随着纬度的降低，高温胁迫耐受性的明显模式增加，这与温度适应一致。此外，在较小的范围内也有证据表明耐热性有显著的变化。还在一系列较低、较温和的温度下检查了成对的北部和南部桡足类种群的竞争适应力。这些适应力测定表明，在极端高温下生存最好的南部种群在较低温度下的竞争适应力降低，而在最高温度下，南部种群的适应力超过了北部种群。综合这些结果表明，在这个物种中，高温和高压力下的表现与中等温度下的适应度之间可能存在进化上的权衡。
