Andersson Björn, Berglund Olof, Filipsson Helena L, Kourtchenko Olga, Godhe Anna, Johannesson Kerstin, Töpel Mats, Pinder Matthew I M, Hoepfner Lara, Rengefors Karin
Department of Marine Sciences, University of Gothenburg, Göteborg, Sweden.
Department of Biology, Lund University, Lund, Sweden.
Mol Ecol. 2024 Oct;33(20):e17116. doi: 10.1111/mec.17116. Epub 2023 Sep 11.
Phytoplankton have short generation times, flexible reproduction strategies, large population sizes and high standing genetic diversity, traits that should facilitate rapid evolution under directional selection. We quantified local adaptation of copper tolerance in a population of the diatom Skeletonema marinoi from a mining-exposed inlet in the Baltic Sea and in a non-exposed population 100 km away. We hypothesized that mining pollution has driven evolution of elevated copper tolerance in the impacted population of S. marinoi. Assays of 58 strains originating from sediment resting stages revealed no difference in the average tolerance to copper between the two populations. However, variation within populations was greater at the mining site, with three strains displaying hyper-tolerant phenotypes. In an artificial evolution experiment, we used a novel intraspecific metabarcoding locus to track selection and quantify fitness of all 58 strains during co-cultivation in one control and one toxic copper treatment. As expected, the hyper-tolerant strains enabled rapid evolution of copper tolerance in the mining-exposed population through selection on available strain diversity. Within 42 days, in each experimental replicate a single strain dominated (30%-99% abundance) but different strains dominated the different treatments. The reference population developed tolerance beyond expectations primarily due to slowly developing plastic response in one strain, suggesting that different modes of copper tolerance are present in the two populations. Our findings provide novel empirical evidence that standing genetic diversity of phytoplankton resting stage allows populations to evolve rapidly (20-50 generations) and flexibly on timescales relevant for seasonal bloom progressions.
浮游植物具有较短的世代时间、灵活的繁殖策略、庞大的种群规模和高度的遗传多样性，这些特性应有助于在定向选择下快速进化。我们对波罗的海一个受采矿影响的入海口的硅藻中肋骨条藻种群以及100公里外一个未受影响的种群的铜耐受性局部适应性进行了量化。我们假设采矿污染推动了中肋骨条藻受影响种群中铜耐受性的进化。对来自沉积物休眠阶段的58个菌株的分析表明，两个种群对铜的平均耐受性没有差异。然而，采矿地点的种群内变异更大，有三个菌株表现出超耐受表型。在一项人工进化实验中，我们使用了一个新的种内代谢条形码位点来跟踪选择，并量化所有58个菌株在一个对照和一个有毒铜处理的共培养过程中的适应性。正如预期的那样，超耐受菌株通过对可用菌株多样性的选择，使受采矿影响的种群迅速进化出铜耐受性。在42天内，在每个实验重复中，一个单一菌株占主导地位（丰度为30%-99%），但不同的菌株在不同的处理中占主导地位。参考种群的耐受性超出预期，主要是由于一个菌株中缓慢发展的可塑性反应，这表明两个种群中存在不同的铜耐受模式。我们的研究结果提供了新的经验证据，表明浮游植物休眠阶段的遗传多样性使种群能够在与季节性水华进程相关的时间尺度上快速（20-50代）且灵活地进化。
