Rank Nathan E, Dahlhoff Elizabeth P
Department of Biology, Sonoma State University, 1801 E. Cotati Avenue, Rohnert Park, California 9492, USA.
Evolution. 2002 Nov;56(11):2278-89. doi: 10.1111/j.0014-3820.2002.tb00151.x.
Rapid changes in climate may impose strong selective pressures on organisms. Evolutionary responses to climate change have been observed in natural populations, yet no example has been documented for a metabolic enzyme locus. Furthermore, few studies have linked physiological responses to stress with allozyme genotypic variation. We quantified changes in allele frequency between 1988 and 1996 at three allozyme loci (isocitrate dehydrogenase, Idh; phosphoglucose isomerase, Pgi; and phosphoglucomutase, Pgm) for the leaf beetle Chrysomela aeneicollis in the Bishop Creek region of the Sierra Nevada of California (2900-3300 m). Beetles often experience high daytime (> 32 degrees C) and extremely low nighttime (< -5 degrees C) temperatures during summer. Bishop Creek weather station data indicated that conditions were unusually dry before 1988, and that conditions were cool and wet during the years preceding the 1996 collection. We found directional changes in allele frequency at Pgi (11% increase in the Pgi-1 allele), but not at Idh or Pgm. We also found that physiological response to thermal extremes depended on Pgi genotype. Pgi 1-1 individuals induced expression of a 70-kD heat shock protein (HSP) at lower temperatures than 1-4 or 4-4 individuals, and 1-1 individuals expressed higher levels of HSP70 after laboratory exposure to temperatures routinely experienced in nature. Survival after nighttime laboratory exposure to subzero temperatures depended on gender, previous exposure to cold, and Pgi genotype. Females expressed higher levels of HSP70 than males after exposure to heat, and recovery by female Pgi 1-1 homozygotes after exposure to cold (-5 degrees C) was significantly better than 1-4 or 4-4 genotypes. These data suggest that the cooler climate of the mid-1990s may have caused an increase in frequency of the Pgi-1 allele, due to a more robust physiological response to cold by Pgi 1-1 and 1-4 genotypes.
气候的快速变化可能会对生物施加强大的选择压力。在自然种群中已观察到对气候变化的进化响应，但尚未有代谢酶基因座的相关记录实例。此外，很少有研究将应激的生理反应与等位酶基因型变异联系起来。我们对加利福尼亚内华达山脉毕晓普溪地区（海拔2900 - 3300米）的叶甲Chrysomela aeneicollis在1988年至1996年间三个等位酶基因座（异柠檬酸脱氢酶，Idh；磷酸葡萄糖异构酶，Pgi；磷酸葡萄糖变位酶，Pgm）的等位基因频率变化进行了量化。叶甲在夏季常经历白天高温（> 32摄氏度）和夜间极低温（< -5摄氏度）。毕晓普溪气象站数据表明，1988年之前气候异常干燥，而在1996年采集样本前的几年气候凉爽湿润。我们发现Pgi基因座的等位基因频率有定向变化（Pgi - 1等位基因增加了11%），但Idh和Pgm基因座没有。我们还发现，对极端温度的生理反应取决于Pgi基因型。Pgi 1 - 1个体比1 - 4或4 - 4个体在更低温度下诱导表达70-kD热休克蛋白（HSP），并且在实验室暴露于自然环境中常经历的温度后，1 - 1个体表达的HSP70水平更高。夜间实验室暴露于零下温度后的存活率取决于性别、先前的冷暴露经历以及Pgi基因型。暴露于热环境后，雌性表达的HSP70水平高于雄性，雌性Pgi 1 - 1纯合子在暴露于寒冷（-5摄氏度）后的恢复情况明显优于1 - 4或4 - 4基因型。这些数据表明，20世纪90年代中期较凉爽的气候可能导致了Pgi - 1等位基因频率的增加，这是由于Pgi 1 - 1和1 - 4基因型对寒冷有更强健的生理反应。
