Fungal pathogens are responsible for 30% of emerging infectious diseases (EIDs) in plants. The risk of a pathogen emerging on a new host is strongly tied to its host breadth; however, the determinants of host range are still poorly understood. Here, we explore the factors that shape host breadth of plant pathogens within Botryosphaeriaceae, a fungal family associated with several devastating diseases in economically important crops. While most host plants are associated with just one or a few fungal species, some hosts appear to be susceptible to infection by multiple fungi. However, the variation in the number of fungal taxa recorded across hosts is not easily explained by heritable plant traits. Nevertheless, we reveal strong evolutionary conservatism in host breadth, with most fungi infecting closely related host plants, but with some notable exceptions that seem to have escaped phylogenetic constraints on host range. Recent anthropogenic movement of plants, including widespread planting of crops, has provided new opportunities for pathogen spillover. We suggest that constraints to pathogen distributions will likely be further disrupted by climate change, and we may see future emergence events in regions where hosts are present but current climate is unfavorable.

30% 的植物新发传染病 (EID) 是由真菌病原体引起的。病原体在新宿主上出现的风险与其宿主广度密切相关。然而，人们对寄主范围的决定因素仍然知之甚少。在这里，我们探讨了影响葡萄球菌科植物病原体宿主广度的因素，葡萄球菌科是一个与经济重要作物中的几种毁灭性疾病相关的真菌家族。虽然大多数寄主植物仅与一种或几种真菌物种相关，但一些寄主似乎容易受到多种真菌的感染。然而，不同宿主记录的真菌类群数量的变化很难用遗传植物性状来解释。尽管如此，我们揭示了宿主广度的强烈进化保守性，大多数真菌感染密切相关的宿主植物，但有一些值得注意的例外，它们似乎逃脱了宿主范围的系统发育限制。最近植物的人为移动，包括农作物的广泛种植，为病原体溢出提供了新的机会。我们认为，气候变化可能会进一步破坏对病原体分布的限制，我们可能会在宿主存在但当前气候不利的地区看到未来的出现事件。