Filamentous fungal associates of the alder bark beetle, Alniphagus aspericollis, including an undescribed species of Neonectria

Abstract

Bark beetles (Coleoptera: Curculionidae; Scolytinae) are tree-infesting insects that consume subcortical tissues and fungi. Species capable of killing their host trees are most commonly associated with conifers, as very few bark beetle species infest and kill hardwood hosts directly. The alder bark beetle, Alniphagus aspericollis, is a hardwood-killing bark beetle that colonizes and kills red alder, Alnus rubra. Conifer-killing bark beetles have well-known associations with symbiotic ophiostomatoid fungi that facilitate their life histories, but it is unknown whether A. aspericollis has any fungal associates. This study was conducted to identify any consistent filamentous fungal associates of A. aspericollis and characterize the consistency of observed beetle–fungus relationships. Beetles and gallery phloem samples were collected from seven sites throughout the Greater Vancouver region in British Columbia, Canada. Filamentous fungi were isolated from these samples and identified by DNA barcoding using the internal transcribed spacer (ITS) region and other barcode regions for resolution to the species-level for the most dominant isolates. The most common fungal associate was a previously undescribed Neonectria major-like fungus, Neonectria sp. nov., which was isolated from ~67% of adult beetles, ~59% of phloem samples, and ~94% of the beetle-infested trees. Ophiostoma quercus was isolated from ~28% of adult beetles, ~9% of phloem samples, and ~56% of infested trees and deemed a casual associate of A. aspericollis, while a putatively novel species of Ophiostoma was more infrequently isolated from A. aspericollis and its galleries. Cadophora spadicis, a new record for red alder, was rarely isolated and is probably coincidentally carried by A. aspericollis. Overall, A. aspericollis was only loosely associated with ophiostomatoid fungi, suggesting that these fungi have little ecological significance in the beetle–tree interaction, while Neonectria sp. nov. may be a symbiote of A. aspericollis that is vectored by the beetle.

Valsalnicola oxystoma (Rehm) D.M. Walker & Rossman - primary biotic agent responsible for the dieback and high mortality of green alder in Călimani and Rodnei Mountains (North-Eastern Romania)

“…Species distribution includes Japan (Kobayashi 2007), Europe where it was reported from Italy (Pisetta et al 2012), Switzerland, Austria (Urban 1960), Belgium, Sweden (Vleugel 1911), United Kingdom (Cannon et al 1995), Hungary (Szabo 2009), Czech Republic, in Tatra Mountains (Urban 1960), Slovenia (Anonymous 2022b) as well as Canada (British Columbia) (Lee et al 2023) and USA (Alaska) (Winton 2013). The presence of V. oxystoma is mentioned for the third time in Romania, the first identification being made by Urban (1960) in the Făgăraș Mountains, on A. alnobetula in 1956.…”

Cladosporium—Insect Relationships

“…The ambrosia beetles (Coleoptera, Curculionidae, Scolytinae) are known to spread fungi that develop in the galleries they dig in the host trees [221]. Although experimental evidence leans for selected fungi, such as species of Fusarium, Geosmithia, Penicillium and Raffaelea, to be more systematically involved in these mutualistic relationships [36,52,222,223], Cladosporium is often isolated both from the insects and their galleries [52,94,133,134]. Particularly, isolation and identification based on biomolecular methods demonstrated the association of C. perangustum with Xylosandrus compactus after female beetles were found carrying the fungus on their body [77]; previously, Cladosporium had been regarded as the principal food source of this species [224].…”