Why is a tool for SE Asian xyleborines necessary?

The Xyleborini are the largest tribe within the Scolytinae – over 1100 species of ~6100 (Hulcr et al. 2015). The tribe also includes some of the most destructive ambrosia beetle pests. In addition, this tribe includes more invasive species than any other group of Scolytinae. Interestingly, most of the species that are both pests and invasive are originally from Southeast Asia. All these features make Xyleborini the most important scolytine group in terms of biosecurity and regulation. Unfortunately, the Southeast Asian fauna is vast, and until now there was no comprehensive resource for identification of the species. The group also has a complicated taxonomic history. Nearly all species were originally described in a single genus, Xyleborus. Only in the late 19th and early 20th centuries were some genera carved out of Xyleborus (Wood 1989, Wood and Bright 1992), and it was not until recently that the genus-level classification of this group has been stabilized (Hulcr et al. 2007a, Beaver and Liu 2010, Hulcr and Cognato 2010, 2013, Beaver et al. 2014, Smith et al. 2018a,b; Cognato et al. 2020a; Sittichaya and Smith 2020; Smith et al. 2020b). The convoluted taxonomic history, the massive diversity, and the economic impact of Xyleborini necessitate a unified and current resource for their identification.

This tool is designed for identification of 35 genera and 316 species of xyleborines. Morphological identification is only for females as the males are haploid, flightless, dwarfed, rarely seen, and unknown for the majority of the species (see Xyleborini ambrosia beetles). Males can be identified using molecular diagnostics.

This Southeast Asian Xyleborini tool will be continuously developed as new knowledge of the fauna accumulates. New versions will be released when new species are discovered or reported from the region.

Geographic region covered

This tool was designed to cover the countries in mainland Southeast Asia that encompass large areas of the Oriental and Palearctic faunal regions. This area has a high volume of international trade with the United States. Countries covered include India (northeastern), Nepal, Bhutan, Bangladesh, Myanmar, Cambodia, Laos, Thailand, Vietnam, China, and Taiwan. In addition to the introductions of the species through trade, this fauna is also significant because the climate of these countries is similar to that of the United States which increases the risk of establishment of exotic xyleborine species. As of late 2019, 26 xyleborines from this region have already become established in the U.S. (Gomez et al. 2018a).

Specimen identification

Specimens from this tool were either collected by the authors or borrowed from a large number of worldwide institutions (see Acknowledgements for complete list). To ensure accurate identifications, we borrowed as many type specimens as possible and compared them to non-type material. This tool was developed in conjunction with a revision (Smith et al. 2020b) of the Southeast Asian fauna inferred from a combination of molecular and morphological characters. Over the course of this project, 76 new species, three new genera, 53 synonyms, and 42 new combinations were identified, and nine species and one genus had status restored. Many of these changes have already been published (Beaver et al. 2019; Cognato et al. 2020a; Mandelshtam et al. 2019; Sittichaya and Beaver 2018; Sittichaya et al. 2019; Smith et al. 2018a, 2018b, 2019, 2020a; Park et al. 2020; Sittichaya and Smith 2020; Wang et al. 2020), and the remaining descriptions and taxonomic changes will be published soon (Smith et al. 2020b).

Molecular data

DNA identification augments morphologically-based identification especially for immature life stages, males, damaged females, and adults of species with cryptic diagnostic characters. Thus, an additional objective to the development of this tool was to generate molecular data in order to create a foundation for DNA identification of Southeast Asian ambrosia beetles. A database of sequences for 165 of 316 species was created for the mitochondrial cytochrome oxidase I (COI) and nuclear CAD genes. All sequences have been deposited in GenBank and a nexus file of all Southeast Asian taxa is available for download here. GenBank numbers for species sequenced as part of this project are also listed on the species fact sheets.