An analysis of the diverse fungal communities associated with eastern larch beetles (Dendroctonus simplex LeConte) in Minnesota led to the discovery of four new fungal species in the order Ophiostomatales by UMN Blanchette Lab, MN-DNR, and USDA-ARS researchers as part of USDA Hatch project MIN22-089. The research team (led by first author Andrew Mann) also recommends re-classifying Graphium simplex fungi based on this study and prior data.
While the eastern larch beetle (Dendroctonus simplex LeConte) is a native, usually nonaggressive inhabitant of North American Tamarack trees (Larix laricina), Minnesota has been seeing an uncharacteristic, prolonged outbreak of these beetles since 2001. Past research indicates that fungi may play critical roles in bark beetles’ success in developing and reproducing within the phloem, and providing phosphorus and nitrogen to beetles (citation in original article).
To investigate and describe fungal diversity within the larch beetle communities of Minnesota, researchers isolated fungi from 56 D. simplex-infested trees in 7 sites around Minnesota, obtaining 203 fungal isolates. After lab-based culturing, DNA extraction, and PCR analyses and sequencing, the DNA sequences of the various fungal isolates were trimmed using Geneious Prime and compared to published DNA sequences using BLASTn. For full process description, please read the original paper in Mycologia.
45 different species of fungi (from four phyla, 16 orders, 26 families, and 35 genera) were identified through this study, 82% of which belonged to the phylum Ascomycota, followed by 12% Basidiomycota. Within the Ascomycota isolates, Ophiostomatales was the most common order at 59% of total isolates. Within the Ophiostomales fungi found, researchers identified four new species and named them: Ophiostoma itasca, Ophiostoma minnesotense, Ophiostoma pseudoips, and Graphilbum insulare. This investigation also led to a valuable conversation about the taxonomic classification of Graphium simplex fungus among the researchers. While research from the 1990s moved Graphium species out of Ophiostomatales and into Microascales, during this present research Mann et. al. concluded that Graphium simplex should not have been moved out of Ophiostomatales, and indicated this should be moved back and renamed Leptographium simplex comb. nov.
The findings of this study provide valuable insight into the fungal diversity associated with D. simplex, creating opportunities for future analysis into the potential roles of Ophiostomatales like G. americana as bark beetle outbreak facilitators and/or tree pathogens. Further studies could also be done over a broader geographic range in North America to determine the distribution of these new species.
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