Phenotypic variation and genomic variation in insect virulence traits reveal patterns of intraspecific diversity in a locust-specific fungal pathogen

Abstract

Abstract Intraspecific pathogen diversity is crucial for understanding the evolution and maintenance of adaptation in host–pathogen interactions. Traits associated with virulence are often a significant source of variation directly impacted by local selection pressures. The specialist fungal entomopathogen, Metarhizium acridum, has been widely implemented as a biological control agent of locust pests in tropical regions of the world. However, few studies have accounted for natural intraspecific phenotypic and genetic variation. Here, we examine the diversity of nine isolates of M. acridum spanning the known geographic distribution, in terms of (1) virulence towards two locust species, (2) growth rates on three diverse nutrient sources, and (3) comparative genomics to uncover genomic variability. Significant variability in patterns of virulence and growth was shown among the isolates, suggesting intraspecific ecological specialization. Different patterns of virulence were shown between the two locust species, indicative of potential host preference. Additionally, a high level of diversity among M. acridum isolates was observed, revealing increased variation in subtilisin-like proteases from the Pr1 family. These results culminate in the first in-depth analysis regarding multiple facets of natural variation in M. acridum, offering opportunities to understand critical evolutionary drivers of intraspecific diversity in pathogens. Abstract Exploring the intricate world of host–pathogen interactions, our study delves into the diverse landscape of Metarhizium acridum, a specialist fungal entomopathogen. By dissecting patterns of virulence, growth dynamics, and genomic variability across its geographic distribution, we unveil compelling evidence of intraspecific diversity. Our findings highlight varying virulence patterns among distinct locust species and a notable abundance of gene diversity, particularly in subtilisin-like proteases. These insights shed light on potential evolutionary drivers shaping natural variation within M. acridum.