Data from: Hybrid breakdown weakens under thermal stress in population crosses of the copepod Tigriopus californicus.

The outcome of hybridization can be impacted by environment conditions, which themselves can contribute to reproductive isolation between taxa. In crosses of genetically divergent populations, hybridization can have both negative and positive impacts on fitness, the balance between which might be tipped by changes in the environment. Genetically divergent populations of the intertidal copepod Tigriopus californicus have been shown to differ in thermal tolerance at high temperatures along a latitudinal gradient. In this study a series of crosses were made between pairs of genetically divergent populations of T. californicus and the thermal tolerance of these hybrids was tested. In most cases the first generation hybrids had relatively high thermal tolerance and second generation hybrids were not generally reduced below the less-tolerant parental population for high temperature tolerance. This pattern contrasts with previous studies from crosses of genetically divergent populations of this copepod which often show hybrid breakdown in these second generation hybrids for other measures of fitness. These results suggest that high temperature stress could either increase the positive impacts of hybridization or decrease the negative impacts of hybridization resulting in lowered hybrid breakdown in these population crosses.

杂交的结果可受环境条件影响，而环境条件本身也可促成类群间的生殖隔离。在遗传分化种群的杂交组合中，杂交对个体适合度兼具正负两方面的影响，二者的平衡可因环境变化而发生偏移。研究显示，潮间带桡足类（intertidal copepod）加州虎斑猛水蚤（Tigriopus californicus）的遗传分化种群，沿纬度梯度在高温下的耐热性存在差异。本研究以多对加州虎斑猛水蚤的遗传分化种群开展杂交实验，并检测了各类杂交后代的高温耐热性。多数实验组合中，第一代杂交后代的高温耐热性相对较高，而第二代杂交后代的高温耐热性通常未低于耐受性更弱的亲本种群。该模式与此前针对该桡足类遗传分化种群杂交的研究结果相悖，后者的第二代杂交后代往往在其他适合度指标上表现出杂种衰退（hybrid breakdown）现象。上述结果表明，高温胁迫既可增强杂交的正向效应，亦可削弱其负向效应，最终降低此类种群杂交中的杂种衰退程度。