Limnological Institute, University of Konstanz, Konstanz, Germany.
Flathead Lake Biological Station, University of Montana, Polson, USA.
Nat Commun. 2021 Mar 29;12(1):1945. doi: 10.1038/s41467-021-22226-9.
Exploring the capability of organisms to cope with human-caused environmental change is crucial for assessing the risk of extinction and biodiversity loss. We study the consequences of changing nutrient pollution for the freshwater keystone grazer, Daphnia, in a large lake with a well-documented history of eutrophication and oligotrophication. Experiments using decades-old genotypes resurrected from the sediment egg bank revealed that nutrient enrichment in the middle of the 20th century, resulting in the proliferation of harmful cyanobacteria, led to the rapid evolution of grazer resistance to cyanobacteria. We show here that the subsequent reduction in nutrient input, accompanied by a decrease in cyanobacteria, resulted in the re-emergence of highly susceptible Daphnia genotypes. Expression and subsequent loss of grazer resistance occurred at high evolutionary rates, suggesting opposing selection and that maintaining resistance was costly. We provide a rare example of reversed evolution of a fitness-relevant trait in response to relaxed selection.
探索生物应对人为环境变化的能力对于评估灭绝风险和生物多样性丧失至关重要。我们研究了营养污染变化对淡水关键食草动物——水蚤的影响，该研究在一个富营养化和贫营养化历史记录良好的大型湖泊中进行。使用从沉积物卵库中复活的数十年前的基因型进行的实验表明，20 世纪中叶的营养富集会导致有害蓝藻的大量繁殖，从而导致食草动物对蓝藻的快速进化产生抗性。我们在这里表明，随后减少营养输入，伴随着蓝藻的减少，导致高度易感的水蚤基因型重新出现。食草动物的抗性表达和随后的丧失发生在高进化率下，表明存在相反的选择，并且维持抗性是有代价的。我们提供了一个罕见的例子，说明了在选择放松的情况下，与适应性相关的特征发生了反向进化。
