Swiss Federal Research Institute WSL, Birmensdorf, Switzerland.
Department of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, Switzerland.
Glob Chang Biol. 2021 Mar;27(6):1181-1195. doi: 10.1111/gcb.15469. Epub 2020 Dec 20.
The ongoing increase in global temperature affects biodiversity, especially in mountain regions where climate change is exacerbated. As sessile, long-lived organisms, trees are especially challenged in terms of adapting to rapid climate change. Here, we show that low rates of allele frequency shifts in Swiss stone pine (Pinus cembra) occurring near the treeline result in high genomic vulnerability to future climate warming, presumably due to the species' long generation time. Using exome sequencing data from adult and juvenile cohorts in the Swiss Alps, we found an average rate of allele frequency shift of 1.23 × 10 /generation (i.e. 40 years) at presumably neutral loci, with similar rates for putatively adaptive loci associated with temperature (0.96 × 10 /generation) and precipitation (0.91 × 10 /generation). These recent shifts were corroborated by forward-in-time simulations at neutral and adaptive loci. Additionally, in juvenile trees at the colonisation front we detected alleles putatively beneficial under a future warmer and drier climate. Notably, the observed past rate of allele frequency shift in temperature-associated loci was decidedly lower than the estimated average rate of 6.29 × 10 /generation needed to match a moderate future climate scenario (RCP4.5). Our findings suggest that species with long generation times may have difficulty keeping up with the rapid climate change occurring in high mountain areas and thus are prone to local extinction in their current main elevation range.
全球气温持续升高影响着生物多样性，特别是在气候变化加剧的山区。树木作为固着、长寿命的生物，在适应快速气候变化方面尤其面临挑战。在这里，我们表明，瑞士石松（Pinus cembra）在林线附近的等位基因频率变化率较低，导致其基因组对未来气候变暖的高度脆弱，这可能是由于该物种的长世代时间所致。利用瑞士阿尔卑斯山成年和幼年群体的外显子组测序数据，我们在假定的中性基因座上发现等位基因频率变化的平均速率为 1.23×10 /世代（即 40 年），与与温度（0.96×10 /世代）和降水（0.91×10 /世代）相关的假定适应性基因座的相似速率。这些最近的变化在中性和适应性基因座的向前时间模拟中得到了证实。此外，在处于定居前沿的幼年树木中，我们检测到了在未来更温暖和干燥气候下可能有益的等位基因。值得注意的是，在与温度相关的基因座中观察到的过去等位基因频率变化率明显低于估计的平均速率 6.29×10 /世代，这是为了匹配中度未来气候情景（RCP4.5）所需的。我们的研究结果表明，具有长世代时间的物种可能难以跟上高山区快速发生的气候变化，因此它们很容易在当前的主要海拔范围内灭绝。
