Emmonsia crescens is known as an environmental pathogen causing adiaspiromycosis in small rodents. As the generic name Emmonsia is no longer available for this species, its taxonomic position is re-evaluated. The intraspecific variation of Emmonsia crescens was analyzed using molecular, morphological, and physiological data, and the relationship between frequency of adiaspiromycosis and body temperature of host animals was explored. A North American and a pan-global lineage could be discerned, each with subclusters at low genetic distance. European strains produced the classical type of very large adiaspores, while in the North American lineage adiaspores relatively small, resembling the broad-based budding cells of Blastomyces. Members of the closely related genus Emergomyces may exhibit large, broad-based in addition to small, narrow-based budding cells. We conclude that the morphology of the pathogenic phase in these fungi differs gradationally between species and even populations, and is therefore less suitable as a diagnostic criterion for generic delimitation. Two Emmonsia species are reclassified in Emergomyces.

Emmonsia crescens被认为是导致小型啮齿动物非螺旋体病的环境病原体。由于该物种的通用名称Emmonsia不再可用，因此重新评估了其分类地位。使用分子、形态和生理数据分析了新月菊的种内变异，并探讨了非螺旋体病发生频率与宿主动物体温之间的关系。可以辨别出一个北美和一个泛全球的谱系，每个谱系都有低遗传距离的亚群。欧洲菌株产生了经典类型的非常大的水杨孢子，而在北美谱系中，水杨孢子相对较小，类似于芽生菌的广泛出芽细胞. 除了小的、窄基的出芽细胞外，密切相关的Emergomyces属的成员还可能表现出大的、宽基的。我们得出的结论是，这些真菌中致病阶段的形态在物种甚至种群之间存在分级差异，因此不太适合作为通用定界的诊断标准。两个Emmonsia物种在Emergomyces中重新分类。