Integrative taxonomy demonstrates the unexpected synonymy between two predatory mite species: Cydnodromus idaeus and C. picanus (Acari : Phytoseiidae)

Species of the mite family Phytoseiidae are well known as predators of mite pests all over the world. Their identification is thus of great interest for biological control. The specimens examined in this study belong to the species Cydnodromus idaeus (described from Brazil) and C. picanus (described from Chile). They were collected together on the same plant in Argentina. These species are mainly differentiated by the presence/absence of the dorsal solenostomes (gland openings) gd2. Some morphometric differences were observed between the Argentinian specimens and the type material of C. idaeus and C. picanus; however, they were not sufficient to support a species separation. Morphological and molecular analyses with two mtDNA (12S rRNA, CytB) and a nuclear DNA (ITS) marker showed no difference between Argentinian specimens with and without the solenostome gd2. Also, molecular differentiation between these latter specimens, C. picanus and C. idaeus, was very low, suggesting that all these individuals belong to the same species. Biological experiments confirm these results, as 75% of the progeny resulting from females with gd2 had gd2 present whereas all the descendants resulting from the females without gd2 had gd2 present too. The presence/absence of this solenostome seems thus to be variable within a species and cannot be used diagnostically. We conclude that all specimens from Argentina belong to C. idaeus and that C. picanus is a junior synonym of C. idaeus. The present results were unexpected as the presence/absence of solenostomes is used in Phytoseiidae identification keys and as one of a suite of diagnostic characters for discriminating between species. The consequences of these findings for the taxonomy of Phytoseiidae are discussed.