Department of Forest and Conservation Sciences, The University of British Columbia, Vancouver, British Columbia, Canada.
PLoS One. 2023 May 8;18(5):e0284393. doi: 10.1371/journal.pone.0284393. eCollection 2023.
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.
树皮甲虫（鞘翅目：象甲科；小蠹科）是一种蛀食树木的昆虫，它们消耗次生木质部组织和真菌。能够杀死宿主树木的物种通常与针叶树关系最为密切，因为很少有树皮甲虫物种直接侵袭和杀死硬木宿主。桤木树皮甲虫（Alniphagus aspericollis）是一种直接杀死硬木的树皮甲虫，它会在桤木（Alnus rubra）上定殖并杀死它。杀死针叶树的树皮甲虫与共生的伞菌目真菌有着众所周知的联系，这些真菌有助于它们的生活史，但桤木树皮甲虫是否有任何真菌伙伴还不得而知。本研究旨在确定桤木树皮甲虫的任何一致的丝状真菌伙伴，并描述观察到的甲虫-真菌关系的一致性。从加拿大不列颠哥伦比亚省大温哥华地区的七个地点收集了甲虫和坑道韧皮部样本。从这些样本中分离出丝状真菌，并通过 DNA 条形码技术使用内部转录间隔区（ITS）区域和其他条形码区域进行鉴定，以确定最主要的分离株的种水平分辨率。最常见的真菌伙伴是一种以前未描述的拟 Necrectria major 样真菌，Necrectria sp. nov.，它从约 67%的成虫甲虫、约 59%的韧皮部样本和约 94%的受甲虫侵袭的树木中分离出来。橡树小蠹（Ophiostoma quercus）从约 28%的成虫甲虫、约 9%的韧皮部样本和约 56%的受感染树木中分离出来，被认为是桤木树皮甲虫的偶然伙伴，而一种推测的新型橡树小蠹则从桤木树皮甲虫及其坑道中分离出来的频率较低。Cadophora spadicis 是红桤木的新记录，很少被分离出来，可能是偶然被桤木树皮甲虫携带的。总的来说，桤木树皮甲虫与伞菌目真菌的关系很松散，这表明这些真菌在甲虫与树木的相互作用中几乎没有生态意义，而拟 Necrectria sp. nov. 可能是桤木树皮甲虫的共生体，由甲虫传播。
