Data from: Potential fitness tradeoffs for thermal tolerance in the intertidal copepod Tigriopus californicus

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.诸多物种均可对空间异质性的环境条件产生热适应，但这类温度适应所关联的适合度权衡（fitness trade-off）的本质仍有待阐明。本研究以潮间带桡足类（copepod）加州猛水蚤（Tigriopus californicus）的种群为研究对象，从局域尺度与纬度梯度两个维度开展实验，旨在探明这些种群在高温胁迫下的存活率是否已演化出差异。实验结果显示，高温胁迫耐受性随纬度降低呈显著上升趋势，这与温度适应的理论预期相符。此外，研究还发现热耐受性在更小的空间尺度上存在显著变异。本研究还在一系列更低且更温和的温度条件下，对南北加州猛水蚤种群的竞争适合度进行了检测。适合度检测结果表明：在极端高温下存活率最高的南方种群，在所测试的低温条件下其竞争适合度有所下降；而在最高温测试组中，南方种群的适合度则优于北方种群。综合上述结果，本研究表明该物种可能存在极端高温胁迫下的表现与温和温度下的适合度之间的演化权衡。