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.

杂交结局可受环境条件影响，而环境条件本身亦可推动类群间的生殖隔离（reproductive isolation）。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，二者的权衡关系可因环境变化发生偏移。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显著差异。本研究针对T. californicus的多对遗传分化种群开展系列杂交实验，并检测了这些杂交后代的耐热性。结果显示，多数情况下第一代杂交个体的高温耐热性相对较高，而第二代杂交个体的高温耐热性总体上并未低于耐受性较弱的亲本种群。该模式与此前针对该桡足类遗传分化种群的杂交研究结果相悖，后者通常在其他适合度指标上观察到第二代杂交个体的杂种衰退（hybrid breakdown）现象。本研究结果提示，高温胁迫或可增强杂交的积极效应，或可削弱其负面影响，最终降低此类种群杂交中的杂种衰退程度。