Lindestad Olle, Aalberg Haugen Inger M, Gotthard Karl
Department of Zoology Stockholm University Stockholm Sweden.
Ecol Evol. 2021 Mar 18;11(10):5402-5412. doi: 10.1002/ece3.7433. eCollection 2021 May.
Many insects possess the plastic ability to either develop directly to adulthood, or enter diapause and postpone reproduction until the next year, depending on environmental cues (primarily photoperiod) that signal the amount of time remaining until the end of the growth season. These two alternative pathways often differ in co-adapted life-history traits, for example, with slower development and larger size in individuals headed for diapause. The developmental timing of these differences may be of adaptive importance: If traits diverge early, the potential for phenotypic differences between the pathways is greater, whereas if traits diverge late, the risk may be lower of expressing a maladaptive phenotype if the selective environment changes during development. Here, we explore the effects of changes in photoperiodic information during life on pupal diapause and associated life-history traits in the butterfly . We find that both pupal diapause and larval development rate are asymmetrically regulated: While exposure to long days late in life (regardless of earlier experiences) was sufficient to produce nondiapause development and accelerate larval development accordingly, more prolonged exposure to short days was required to induce diapause and slow down prediapause larval development. While the two developmental pathways diverged early in development, development rates could be partially reversed by altered environmental cues. Meanwhile, pathway differences in body size were more inflexible, despite emerging late in development. These results show how several traits may be shaped by the same environmental cue (photoperiod), but along subtly different ontogenies, into an integrated phenotype.
许多昆虫具有可塑性能力，既可以直接发育为成虫，也可以进入滞育状态，将繁殖推迟到下一年，这取决于环境线索（主要是光周期），这些线索表明距离生长季节结束还剩多少时间。这两种不同的发育途径在共同适应的生活史特征方面往往存在差异，例如，进入滞育的个体发育较慢且体型较大。这些差异的发育时间可能具有适应性重要性：如果特征在早期就出现分歧，那么这两种发育途径之间表型差异的潜力就更大；而如果特征在后期才出现分歧，那么在发育过程中如果选择环境发生变化，表达适应不良表型的风险可能会更低。在这里，我们探讨了生活过程中光周期信息的变化对蝴蝶蛹滞育及相关生活史特征的影响。我们发现，蛹滞育和幼虫发育速率都受到不对称调节：虽然在生命后期暴露于长日照（无论早期经历如何）足以导致非滞育发育并相应加速幼虫发育，但需要更长时间暴露于短日照才能诱导滞育并减缓滞育前幼虫的发育。虽然这两种发育途径在发育早期就出现了分歧，但发育速率可以通过改变环境线索而部分逆转。与此同时，尽管体型差异在发育后期才出现，但在体型方面的途径差异却更加不灵活。这些结果表明，几个特征可能由相同的环境线索（光周期）塑造，但沿着微妙不同的个体发育路径，形成一个综合的表型。
