Integrative Morphological and Molecular Diagnostics for Euseius nicholsi and Euseius oolong (Acari: Phytoseiidae)

In a survey of Bajiaozhai National Forest Park (Guilin, China), several specimens of an Euseius sp. were collected. These specimens were very similar to Euseius nicholsi and Euseius oolong, based on morphological observations. However, some morphological characters, such as the body size, number of solenostomes on the dorsal plate, calyx shape of the spermatheca, the shape and number of metapodal platelet, teeth number on the fixed digit, length of setae j3, and macroseta Seg IV, Sti IV, and St IV were different between these specimens and E. nicholsi and E. oolong. To ascertain whether these morphological differences were interspecific or intraspecific variations, molecular analyses were conducted using mitochondrial DNA COI, 12S rRNA, and nuclear ITS markers. Based on the three molecular markers, minimal genetic distances were observed (COI 0-4%, 12S rRNA 0-2%, and ITS 0%) among the putative Euseius sp., E. nicholsi (collected from Bauhinia purpurea in IZGAS and from Eurya macartneyi and Ficus hispida in Shaoguan City), and E. oolong (collected from B. purpurea in IZGAS). Amblyseius swirskii was used as the outgroup. Using the maximum likelihood method, the phylogenetic tree showed that these specimens of Euseius sp., E. nicholsi, and E. oolong clustered in a single clade. Therefore, we propose that this putative Euseius sp. is E. nicholsi, and E. oolong is a junior synonym of E. nicholsi. This study demonstrates the importance of integrative taxonomy for the proper identification of phytoseiid mites.