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.

杂交的结果会受到环境条件的影响，而环境条件本身也会推动类群间的生殖隔离（reproductive isolation）形成。在遗传分化种群的杂交实验中，杂交对适合度（fitness）兼具正负两方面影响，二者间的平衡可能因环境变化而发生偏移。潮间带桡足类（intertidal copepod）加州猛水蚤（Tigriopus californicus）的遗传分化种群，已被证实沿纬度梯度（latitudinal gradient）在高温下的耐热性存在差异。本研究以加州猛水蚤的多对遗传分化种群为材料开展杂交实验，并检测了这些杂种的耐热性。多数情况下，子一代杂种（first generation hybrids）的耐热性相对较高，而子二代杂种（second generation hybrids）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——既往研究常显示，这类子二代杂种在其他适合度指标上存在杂种衰退（hybrid breakdown）现象。上述结果表明，高温胁迫既可能增强杂交的正向效应，也可能削弱其负向效应，最终导致这些种群杂交组合中的杂种衰退程度降低。