Bark beetles and their associated fungi infesting native Widdringtonia species in the Western Cape province of South Africa

Abstract

Widdringtonia is a genus of native southern African Cupressaceae trees comprising two species that occur in the mountains of the Western Cape province, South Africa. Widdringtonia cedarbergensis has a localised distribution and is critically endangered, while W. nodiflora is widespread and common. Little is known regarding the biotic associations of these trees. The aim of this study was, consequently, to identify bark beetles (Curculionidae: Scolytinae) and their associated fungi on Widdringtonia species in the Western Cape. Bark beetles were collected from infested W. cedarbergensis at three different locations in the Cederberg and from W. nodiflora at one site on the Franschhoek Pass. Beetle identification was based on morphology and sequence data of the COI gene region. Fungi were isolated from beetles, their frass and the walls of their tunnels and grouped according to morphology. Morphogroups were identified by sequencing the ITS region of representative isolates. Four phylogenetically closely related bark beetle species residing in the genus Lanurgus (Micracidini) were identified, three from W. cedarbergensis stem sections, twigs and cones, respectively, and one from W. nodiflora stems. Of these, only the W. cedarbergensis twig beetle is of a previously described species and is currently known as Diplotrichus widdringtoniae. Piskurozyma sp. (Tremellomycetes) and Yamadazyma sp. (Saccharomycetes) yeasts were most closely associated with D. widdringtoniae (Lanurgus sp. 1) and Lanurgus sp. 2 beetles, whereas Geosmithia spp. (Sordariomycetes) had a strong association with Lanurgus sp. 3 and Lanurgus sp. 4. This is the first comprehensive report of bark beetles and their associated fungi infesting Widdringtonia.