Exploring 120 years of invasion history of Sirex noctilio and Amylostereum areolatum in Australasia.

Eshetu, F. B.*¹, Barnes, I.¹, Nahrung, H. F.², Fitza, K. N. E.¹, Slippers, B.¹

¹ Department of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute, University of Pretoria, Pretoria, South Africa
² Forest Research Institute, University of the Sunshine Coast, Queensland, Australia

The woodwasp Sirex noctilio and its symbiotic fungus, Amylostereum areolatum, are important invasive pests of Pinus spp. in Australasia and many other parts of the world. Sirex noctilio was first reported outside its native distribution in New Zealand in 1900, and then in Tasmania in 1952 and mainland Australia in 1961. In this study, we consider the invasion history of these organisms across Australasia through population genetic analysis using mitochondrial sequence data and microsatellite markers and compare it with a previously published dataset from global collections. The study included contemporary (n=461) and historical (n=41) samples of S. noctilio dating back to 1952 and fungal samples from across the range. No population structure was found in Australian and New Zealand populations of S. noctilio or the fungal symbiont A. areolatum. The S. noctilio populations in these countries were lower in genetic diversity than other populations sampled around the world. The results also suggest multiple introductions and a shared introduction history between these two countries. Amylostereum areolatum populations from Australia and New Zealand clustered separately from all other countries and were highly clonal. The results of this study likely reflect an efficient quarantine system in recent decades, which isolated these populations and reduced their complexity compared to other parts of the world and informs the management of S. noctilio.

Keywords: genetic diversity; historical samples; insect-fungus co-invasion; population structure; Sirex management