A study in the Tree Protection Co-operative Programme (TPCP) at FABI confirms the identity of seven novel fungal species associated with Dendroctonus valens, the red turpentine beetle. The study follows on surveys on the fungal associates of the beetle in China and North America. Results from this work appear in Persoonia.
Work by researchers in the Tree Protection Co-operative Programme at the University of Pretoria confirms the identify of seven new Ophiostomatalean fungi associated with Dendroctonus valens, also known as the red turpentine beetle (RTB). Many Ophiostomatalean fungi, according to the authors, are “ecologically adapted for dispersal by scolytine bark beetles such as the red turpentine beetle.”
Native to Central and North America, the beetle is a secondary pest in its native range. It has however killed indigenous pine trees in China, primarily Pinus tabuliformis, following an outbreak in the 1990s. The aim of this study, led by Dr Seonju Marincowitz, was to confirm the identity of unnamed taxa collected from surveys in China in 2004 and 2005 and in North America in 2008 and 2009. Thirty species were identified in these surveys, though seven remained unnamed. The study involved the sequencing of gene regions based on available reference sequences for the species complexes to which they belong. Detailed morphological descriptions were made for those taxa that were found to represent novel species.
The researchers confirm the novel nature of these species but also highlight that some of these taxa presented as distinct species by Taerum et al. (2013), were however, known species. “Leptographium sp. 1 and Leptographium sp. 2 of Taerum et al. represent L. terebrantis and Ophiostoma sp. 2 is O. ips,” wrote the authors.
Six of the seven novel species identified in the study reside in the Grosmannia galeiformis-species complex, the Leptographium olivaceum-species complex and the Ophiostoma ips-species complex. “One novel species did not belong to any of the previously defined complexes, but clearly resided in Ophiostoma,” observed the researchers.
The four novel species in the G. galeiformis-species complex were named Leptographium doddsii, L. gordonii, L. owenii and L. seifertii. In the L. olivaceum-species complex, the researchers identified Leptographium raffai and Ophiostoma gilletteae and O. shanziensis in the O. ips-species complex.
Because the beetles do not have specialised structures in which they carry the fungi, the authors suggest “[s]ome fungi are likely to have closer relationships with the beetles than others.” They suggest that phoretic mites could also play an important role in vectoring these fungi.
This study highlights the danger that pests pose when introduced to new environments. A minor pest in its native habitat, RTB became a tree-killing pest in a new environment, China. The researchers warn that the diversity of the fungal species associated with RTB present a “biosecurity risk” when accidently introduced and they encounter naïve hosts or form new vector-symbiont associations.
“Resolving the identity of the fungal taxa associated with the RTB enhances our ability to better understand new invasions and potential risks of range expansions by this beetle,” conclude the authors.