Data from: Adaptation to climate change: trade-offs among responses to multiple stressors in an intertidal crustacean

Trade-offs may influence both physiological and evolutionary responses to co-occurring stressors, but their effects on both plastic and adaptive responses to climate change are poorly understood. To test for genetic and physiological trade-offs incurred in tolerating multiple stressors, we hybridized two populations of the intertidal copepod Tigriopus californicus that were divergent for both heat and salinity tolerance. Starting in the F2 generation, we selected for increased tolerance of heat, low salinity, and high salinity in replicate lines. After five generations of selection, heat-selected lines had greater heat tolerance but lower fecundity, indicating an energetic cost to tolerance. Lines selected for increased salinity tolerance did not show evidence of adaptation to their respective environments, however, hypo-osmotic selection lines showed substantial loss of tolerance to hyper-osmotic stress. Neither of the salinity selection regimes resulted in diminished heat tolerance at ambient salinity, however, simultaneous exposure to heat and hypoosmotic stress led to decreased heat tolerance, implying a physiological trade-off in tolerance to the two stressors. When we quantified the transcriptomic response to heat and salinity stress via RNA-sequencing, we observed little overlap in the stress responses, suggesting the observed synergistic effects of heat and salinity stress were driven by competing energetic demands, rather than shared stress response pathways.权衡效应（trade-off）可作用于共存胁迫因子引发的生理与进化响应，但目前学界对其在生物体应对气候变化时的表型可塑性与适应性响应中发挥的作用仍知之甚少。为探究生物体耐受多重胁迫时所涉及的遗传与生理权衡，本研究将对高温与盐度耐受性存在显著分化的两个潮间带桡足类种群——加州虎斑猛水蚤（Tigriopus californicus）进行杂交。自F2代起，我们在重复选育系中针对高温、低盐度及高盐度耐受性开展定向选育。经过五代选育后，高温选育系的高温耐受性显著提升，但繁殖力却出现下降，表明耐受性存在能量成本。针对盐度耐受性开展的选育系未表现出对对应环境的适应性特征；不过，低渗选育系对高渗胁迫的耐受性出现了显著丧失。不过，两种盐度选育方案均未导致受试个体在环境盐度下的高温耐受性下降；但当个体同时暴露于高温与低渗胁迫时，其高温耐受性出现降低，这表明两种胁迫的耐受性间存在生理权衡。通过RNA测序（RNA-sequencing）量化生物体对高温与盐度胁迫的转录组响应后，我们发现两类胁迫的响应通路重叠度极低，这表明观测到的高温与盐度胁迫协同效应，是由相互竞争的能量需求所驱动，而非共享的胁迫响应通路所致。