Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, 92093.
Evolution. 2014 Jan;68(1):204-15. doi: 10.1111/evo.12254. Epub 2013 Sep 12.
Early generations of hybrids can express both genetic incompatibilities and phenotypic novelty. Insights into whether these conflicting interactions between intrinsic and extrinsic selection persist after a few generations of recombination require experimental studies. To address this question, we use interpopulation crosses and recombinant inbred lines (RILs) of the copepod Tigriopus californicus, and focus on two traits that are relevant for the diversification of this species: survivorship during development and tolerance to thermal stress. Experimental crosses between two population pairs show that most RILs between two heat-tolerant populations show enhanced tolerance to temperatures that are lethal to the respective parentals, whereas RILs between a heat-tolerant and a heat-sensitive population are intermediate. Although interpopulation crosses are affected by intrinsic selection at early generational hybrids, most of the sampled F9 RILs have recovered fitness to the level of their parentals. Together, these results suggest that a few generations of recombination allows for an independent segregation of the genes underlying thermal tolerance and cytonuclear incompatibilities, permitting certain recombinant lineages to survive in niches previously unused by parental taxa (i.e., warmer thermal environments) without incurring intrinsic selection.
早期的杂交种可以表达遗传不兼容性和表型新颖性。了解内在选择和外在选择之间的这些冲突相互作用在几代重组后是否仍然存在，需要进行实验研究。为了解决这个问题，我们使用了加利福尼亚桡足类动物 Tigriopus californicus 的种群间杂交和重组自交系 (RIL)，并关注了与该物种多样化相关的两个特征：发育过程中的存活率和对热应激的耐受性。两个耐热种群之间的实验杂交表明，大多数耐热种群之间的 RIL 对父母本致死的温度表现出增强的耐受性，而耐热种群和热敏种群之间的 RIL 则处于中间水平。尽管种群间杂交受到早期世代杂种的内在选择的影响，但大多数采样的 F9 RIL 已经恢复到与其亲本相同的适应度水平。总之，这些结果表明，几代的重组可以使热耐受性和细胞质核不兼容性的基因独立分离，从而允许某些重组谱系在以前未被亲本分类群利用的小生境（即较温暖的热环境）中生存，而不会受到内在选择的影响。
