Geographic structure of a bolete-infecting cryptic species within the Hypomyces microspermus species complex in California

Abstract

Fungi in the genus Hypomyces are mycoparasites of various fungal groups. Studies within this genus have dealt primarily with taxonomic descriptions, and no studies have been published on the population biology of these fungi in natural ecosystems. In this study, genetic structure within and among six California (CA) bolete-infecting H. microspermus populations were analyzed with amplified fragment length polymorphism (AFLP). Four of the populations were collected south of the transverse mountain ranges of southern CA, whereas the other populations were from the central coast of CA (Pismo Beach) and from northern CA (Humboldt County). Thirty-nine genotypes were found among 68 isolates based on 30 AFLP markers. This was a higher degree of genotypic diversity than expected because no sexual fruiting bodies were observed in the field, suggesting that sexual reproduction occurs infrequently. These observations were also supported by multilocus disequilibrium analyses. Overall the populations were significantly differentiated (θ = 0.321, P < 0.001), and most population pairwise F_st values were also significantly different. The populations sampled also fit an isolation by distance model based on a Mantel test (P < 0.001). The overall results suggest that this pathogen has a primarily clonal population genetic structure and that spore dispersal was restricted across the sampled populations.

• AFLP
• Boletes
• cryptic species
• Hypomyces
• population genetics

Acknowledgments

We thank the University of California at Riverside CEPCEB REU program and Dr Howard Judelson for allowing our participation as well as the California State University MARC*U STAR program and the NIH for support.

Financial support of the Agricultural Experiment Station, University of California at Riverside, is also gratefully acknowledged.

Last we thank two anonymous reviewers for helpful comments.