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 <i>Euseius</i> sp. were collected. These specimens were very similar to <i>Euseius nicholsi</i> and <i>Euseius oolong</i>, 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 <i>E. nicholsi</i> and <i>E. oolong</i>. 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 <i>Euseius</i> sp., <i>E. nicholsi</i> (collected from <i>Bauhinia purpurea</i> in IZGAS and from <i>Eurya macartneyi</i> and <i>Ficus hispida</i> in Shaoguan City), and <i>E. oolong</i> (collected from <i>B. purpurea</i> in IZGAS). <i>Amblyseius swirskii</i> was used as the outgroup. Using the maximum likelihood method, the phylogenetic tree showed that these specimens of <i>Euseius</i> sp., <i>E. nicholsi</i>, and <i>E. oolong</i> clustered in a single clade. Therefore, we propose that this putative <i>Euseius</i> sp. is <i>E. nicholsi</i>, and <i>E. oolong</i> is a junior synonym of <i>E. nicholsi</i>. This study demonstrates the importance of integrative taxonomy for the proper identification of phytoseiid mites.