Integrative taxonomy demonstrates synonymy between Euseius amissibilis Meshkov and Euseius gallicus Kreiter & Tixier (Acari: Phytoseiidae)

Abstract

Taxonomy of the predatory mite family Phytoseiidae (Acari: Mesostigmata) is essentially based on morphological observations, and only a few studies use integrative approaches that include mainly morphological and molecular analysis. Species of the genus Euseius Wainstein (Acari: Phytoseiidae) are pollen feeding generalist predators belonging to “Type IV” group. There are more than 200 species of the genus that are considered to be valid. However, there could be a series of synonyms among these valid species. Euseius gallicus Kreiter & Tixier is one of the recently described species and its natural populations have been reported from a total of 10 countries. There are some molecular studies showing that E. gallicus represents a different lineage and separated adequately from the other well-known and common species, E. stipulatus in the Western Palearctic region. However, it shows great morphological similarities with E. amissibilis Meshkov, a species previously described from Tajikistan. According to its original description, these two species can be separated based on a few differences in their setal lengths, but doubts remain regarding the similarities between them. Therefore, we examined the type material of E. amissibilis, and newly collected materials from various localities including the type locality. We conducted molecular analyses, using two gene markers (ITS and Cox1) to determine whether these two species are conspecific. Results show that all morphological characters and measurements of the type and the newly collected materials of E. amissibilis fall within the range indicated in the original description of E. gallicus. Moreover, zero and low levels (≤6% previously considered as variation for phytoseiid mites) of genetic distances were detected among the specimens of these two species from different populations based on ITS and Cox1 gene markers, respectively. As conclusion, this study confirms that E. gallicus is a junior synonym of E. amissibilis. In addition, based on our best knowledge, a ventral pore-like structure located on ambulacral stalk of the first leg is observed for the first time in a species of the family Phytoseiidae, probably even in the order Mesostigmata.