Climate change is rapidly altering the distribution of suitable habitats for many species as well as their pathogenic microbes. For many pathogens, including vector‐borne diseases of humans and agricultural pathogens, climate change is expected to increase transmission and lead to pathogen range expansions. However, if pathogens have a lower heat tolerance than their host, increased warming could generate so‐called thermal refugia for hosts. Predicting the outcomes of warming on disease transmission requires detailed knowledge of the thermal tolerances of both the host and the pathogen. Such thermal tolerance studies are generally lacking for fungal pathogens of wild plant populations, despite the fact that plants form the base of all terrestrial communities. Here, we quantified three aspects of the thermal tolerance (growth, infection, and propagule production) of the naturally occurring fungal pathogen Microbotryum lychnidis‐dioicae, which causes a sterilizing anther‐smut disease on the herbaceous plant Silene latifolia. We also quantified two aspects of host thermal tolerance: seedling survival and flowering rate. We found that temperatures >30°C reduced the ability of anther‐smut spores to germinate, grow, and conjugate in vitro. In addition, we found that high temperatures (30°C) during or shortly after the time of inoculation strongly reduced the likelihood of infection in seedlings. Finally, we found that high summer temperatures in the field temporarily cured infected plants, likely reducing transmission. Notably, high temperatures did not reduce survival or flowering of the host plants. Taken together, our results show that the fungus is considerably more sensitive to high temperatures than its host plant. A warming climate could therefore result in reduced disease spread or even local pathogen extirpation, leading to thermal refugia for the host.

中文翻译：

---

高温可减少天然真菌植物病原体的生长、感染和传​​播


气候变化正在迅速改变许多物种及其病原微生物的适宜栖息地的分布。对于许多病原体，包括人类媒介传播疾病和农业病原体，气候变化预计会增加传播并导致病原体范围扩大。然而，如果病原体的耐热性低于宿主，那么变暖的加剧可能会为宿主产生所谓的热避难所。预测变暖对疾病传播的影响需要详细了解宿主和病原体的耐热性。尽管植物是所有陆地群落的基础，但普遍缺乏对野生植物种群真菌病原体的耐热性研究。在这里，我们量化了天然存在的真菌病原体 Microbotryum lychnidis-dioicae 的热耐受性（生长、感染和繁殖体产生）的三个方面，这种病原体会在草本植物 Silene latifolia 上引起不育花药黑粉病。我们还量化了宿主耐热性的两个方面：幼苗存活率和开花率。我们发现温度 >30°C 会降低花药黑粉病孢子在体外萌发、生长和结合的能力。此外，我们发现接种期间或接种后不久的高温（30°C）大大降低了幼苗感染的可能性。最后，我们发现夏季田间高温暂时治愈了受感染的植物，可能减少了传播。值得注意的是，高温并没有降低宿主植物的存活或开花。综上所述，我们的结果表明，这种真菌比其寄主植物对高温更加敏感。 因此，气候变暖可能会导致疾病传播减少，甚至局部病原体被消灭，从而为宿主提供热避难所。