Positive genetic covariance and limited thermal tolerance constrain tropical insect responses to global warming
Positive genetic covariance and limited thermal tolerance constrain tropical insect responses to global warming
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DOI：
10.1111/jeb.13905
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发表时间：
2021-07-23
影响因子：
2.1
通讯作者：
Baer, Christina S.
中科院分区：
文献类型：
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作者：
Garcia-Robledo, Carlos;Baer, Christina S.
热带外温动物特别容易受到全球变暖的影响，因为它们的生理被认为适应狭窄的温度范围。这项研究探讨了可能限制热带昆虫对全球变暖的热适应的三种机制：（a）不同温度下基因型性能的权衡（多面手假说），（B）性能的正遗传协方差，某些基因型在可行温度下的性能优于其他基因型（“赢家”和“输家”基因型假说），或（c）作为放松选择的潜在结果的有限遗传变异和与极端温度反应相关的基因的丧失（基因衰变假说）。我们估计的生长和存活率的变化，在多个温度下的三个热带雨林昆虫食草动物（Cephaloleia卷叶甲虫，科）。我们在一个完整的兄弟姐妹实验设计中饲养了2,746只个体，在自然界中这种甲虫所经历的温度下（即10-35摄氏度）。显着的遗传协方差是积极的16个性状，支持“赢家”和“输家”的基因型假说。只有两个性状表现出负的交叉温度性能相关。我们检测到与大小和质量相关的性状的遗传方差的显著贡献（0%-44%），但发育时间（0%-6%）或存活率（0%-4%）等可塑性性状的遗传力较低。如果目前的气温上升2到5摄氏度，低地昆虫的数量很可能会下降。令人担忧的是，当地的适应已经落后于目前的气温。维持目前全球变暖的轨迹对热带昆虫来说将是毁灭性的。然而，如果人类能够限制或减缓变暖，许多热带外温动物可能会在目前的位置持续存在，并有可能适应更高的温度。
Tropical ectotherms are particularly vulnerable to global warming because their physiologies are assumed to be adapted to narrow temperature ranges. This study explores three mechanisms potentially constraining thermal adaptation to global warming in tropical insects: (a) Trade-offs in genotypic performance at different temperatures (the jack-of-all-trades hypothesis), (b) positive genetic covariance in performance, with some genotypes performing better than others at viable temperatures (the 'winner' and 'loser' genotypes hypothesis), or (c) limited genetic variation as the potential result of relaxed selection and the loss of genes associated with responses to extreme temperatures (the gene decay hypothesis). We estimated changes in growth and survival rates at multiple temperatures for three tropical rain forest insect herbivores (Cephaloleia rolled-leaf beetles, Chrysomelidae). We reared 2,746 individuals in a full sibling experimental design, at temperatures known to be experienced by this genus of beetles in nature (i.e. 10-35 degrees C). Significant genetic covariance was positive for 16 traits, supporting the 'winner' and 'loser' genotypes hypothesis. Only two traits displayed negative cross-temperature performance correlations. We detected a substantial contribution of genetic variance in traits associated with size and mass (0%-44%), but low heritability in plastic traits such as development time (0%-6%) or survival (0%-4%). Lowland insect populations will most likely decline if current temperatures increase between 2 and 5 degrees C. It is concerning that local adaption is already lagging behind current temperatures. The consequences of maintaining the current global warming trajectory would be devastating for tropical insects. However, if humans can limit or slow warming, many tropical ectotherms might persist in their current locations and potentially adapt to warmer temperatures.