Position specificity in Chitonomyces (Ascomycota, Laboulbeniomycetes) on Laccophilus (Coleoptera, Dytiscidae): a molecular approach resolves a century-old debate

Abstract

The occurrence of Laboulbeniomycete species consistently on a precise portion of beetle integument was investigated in 13 species of Chitonomyces ectoparasitic on the aquatic diving beetle Laccophilus maculosus (Coleoptera, Dytiscidae). The phenomenon was called “position specificity” by Roland Thaxter in 1896, yet the mechanism has remained unknown. By using molecular analysis of the nucSSU rRNA gene and the 5.8S and partial ITS1 rRNA regions, 13 species of Chitonomyces reported to exhibit position specificity on Laccophilus maculosus were placed neatly into pairs of morphotypes, resulting in synonomies and recognition of six phylogenetic species (one species is a triplet). Each phylogenetic species was located at corresponding positions on male and female beetles that make contact during mating. In addition, ecological data and video footage of the mating behaviors of Laccophilus confirmed that sexual transmission is the mechanism behind this enigmatic phenomenon.

Key words:

• Ascomycetes
• Coleoptera
• fungal parasitism
• Laboulbeniales
• molecular analysis
• species delimitation
• taxonomy

Acknowledgments

We acknowledge the help of Vicki Lyle at the SUNY Upstate Medical Core DNA sequencing facility and also are thankful for the help of Bob Davies (director of Forest Properties, SUNY-ESF) for permission to collect at Heiberg Forest. We are grateful for the help of Professor Walter Rossi (Universita del'Aquila, L'Aquila, Italy) and Lisa Thompson (New York State Department of Health) for continued support and advice. This work was financially supported in full by a NSF PEET (Partnerships for Enhancing Expertise in Taxonomy) grant (0529722 to A. Weir). We thank the graduate students, Jessica Gibson and Dawn Higginson, and undergraduate students, Amy Reilly, Luke Sarantino, Kim Quell, Zac Still and Daren Card, who worked with us in the field and laboratory supported by Research Experience for Undergraduates (REU) financial support through NSF.