Identity, Prevalence, and Pathogenicity of Entomopathogenic Fungi Infecting Invasive Polistes (Vespidae: Polistinae) Paper Wasps in New Zealand

SIMPLE SUMMARY: The Asian paper wasp Polistes chinensis is an invasive species in New Zealand and South-East Australia. This species threatens native invertebrate communities through predation and potentially competition for resources. During an ecological field study of P. chinensis in New Zealand, we discovered wasps that were infected with and were being killed by two species of pathogenic fungi. In the interest of investigating these fungi as potential biological control agents, our aim in this study was to identify the two fungal species using morphological and molecular methods, determine their natural prevalence in the studied paper wasp population, and test their infective potential to hosts in a controlled environment. We successfully identified the fungi species as Beauveria malawiensis, a generalist insect pathogen, and Ophiocordyceps humbertii, a specialist of social wasps. These are the first records of these species infecting paper wasps in New Zealand. We estimate that they produce infections in approximately 3.3% of wild P. chinensis colonies in our study site. In our infection assays, we passively exposed healthy wasp colonies to asexual fungal spores, which resulted in successful infections of B. malawiensis, and significantly increased wasp mortality rates. ABSTRACT: Two species of entomogenous fungi were discovered infecting the invasive paper wasp Polistes chinensis during an ecological study on Farewell Spit, New Zealand. We sequenced two nuclear ribosomal RDNA genes, the internal transcribed spacer (ITS) and the small ribosomal subunit 18S, and one protein-coding gene, the translation elongation factor 1-alpha (ef1 α). Combining sequence information with morphological examination, we identified these species as Beauveria malawiensis and Ophiocordyceps humbertii. We estimated that these fungi produce infection in approximately 3.3% of colonies in our study population. In bioassays, we successfully infected P. chinensis individuals from healthy colonies with B. malawiensis, with significant effects on adult mortality. This is the first record of both B. malawiensis and O. humbertii from Polistine hosts in New Zealand, and the first investigation into disease causality by these pathogens in P. chinensis. Our findings may contribute to the future development of biological control agents for paper wasps in New Zealand and elsewhere around the world.