Abstract:
Changes in symbiont assemblages can affect the success and impact of invasive species, and may provide
knowledge regarding the invasion histories of their vectors. Bark beetle symbioses are ideal systems to study
changes in symbiont assemblages resulting from invasions. The red turpentine beetle (Dendroctonus valens) is a
bark beetle species that recently invaded China from its native range in North America. It is associated with
ophiostomatalean fungi in both locations, although the fungi have previously been well-surveyed only in China. We
surveyed the ophiostomatalean fungi associated with D. valens in eastern and western North America, and identified
the fungal species using multi-gene phylogenies. From the 307 collected isolates (147 in eastern North America and
160 in western North America), we identified 20 species: 11 in eastern North America and 13 in western North
America. Four species were shared between eastern North America and western North America, one species
(Ophiostoma floccosum) was shared between western North America and China, and three species (Grosmannia
koreana, Leptographium procerum, and Ophiostoma abietinum) were shared between eastern North America and
China. Ophiostoma floccosum and O. abietinum have worldwide distributions, and were rarely isolated from D.
valens. However, G. koreana and L. procerum are primarily limited to Asia and North America respectively.
Leptographium procerum, which is thought to be native to North America, represented >45% of the symbionts of D.
valens in eastern North America and China, suggesting D. valens may have been introduced to China from eastern
North America. These results are surprising, as previous population genetics studies on D. valens based on the
cytochrome oxidase I gene have suggested that the insect was introduced into China from western North America.
