Data from: What was old is new again: thermal adaptation within clonal lineages during range expansion in a fungal pathogen

Range-expanding species are expected to gain an increasing importance in the context of global change. They provide a great opportunity to study contemporary evolutionary changes and to unravel the mechanisms of evolution. Cryphonectria parasitica, the causal agent of chestnut blight, originating from Asia, has been spread since the beginning of the 20th century into different continents. We took advantage of the C. parasitica recent emergence in northern France to study the changes in population genetic structure and in phenotypic traits along this colonization and climatic gradient. Four hundred twenty-seven C. parasitica isolates were sampled in 47 chestnut sites in northern France. The C. parasitica outbreak in the north was found to be due to the expansion of five dominant clonal groups from southern France and to the emergence of a few rare recombined genotypes. The evolutionary changes during C. parasitica range expansion were studied by analyzing phenotypic changes in isolates from the same clonal lineage, with or without a geographic shift. Growth rates were assessed in vitro, at four temperatures. The northern isolates grew faster at 12 and 15°C and more slowly at 28 and 32°C than the southern isolates. These results strongly suggest local adaptation to low temperatures in C. parasitica, with a trade-off of slower growth at high temperatures. They also reflect the high evolutionary potential of C. parasitica along a colonization gradient and show that clonal evolution is not a limitation for the rapid thermal adaptation of this invasive fungal species.

在全球变化的背景下，分布范围扩张物种的研究价值与日俱增。此类物种为探究当代进化过程、解析进化机制提供了宝贵契机。
栗疫病菌（Cryphonectria parasitica）是引发板栗疫病的病原菌，其原生分布区为亚洲，自20世纪初起便已扩散至多个大陆。本研究依托栗疫病菌在法国北部的新近定殖事件，针对该物种沿定殖与气候梯度的种群遗传结构及表型性状变化展开分析。
我们在法国北部的47个板栗样地中共采集了427株栗疫病菌分离株。研究发现，法国北部的栗疫病菌暴发源自法国南部5个优势克隆群的扩散，以及少量稀有重组基因型的出现。
为探究栗疫病菌分布范围扩张过程中的进化变化，我们对存在或不存在地理迁移的同一克隆谱系分离株的表型特征进行了分析。
我们在4种温度梯度下开展了体外生长速率测定。结果显示，相较于法国南部的分离株，北部分离株在12℃与15℃条件下生长速率更快，而在28℃和32℃条件下生长速率更慢。
上述结果有力证实，栗疫病菌已演化出针对低温的本地适应策略，且伴随高温下生长速率降低的进化权衡。本研究同时揭示了栗疫病菌沿定殖梯度的高进化潜能，并证明克隆进化并未限制这一入侵真菌物种的快速热适应性演化。