Deuterogyny and the Association of Two Vagrant Eriophyoid Mites (Acariformes, Eriophyoidea) with the Host-plant Generative Organs of Two Broad-leaved Trees in North-West Russia.

Phytoparasitic mites of the superfamily Eriophyoidea Nalepa live and feed on mature leaf surfaces, between leaf bud scales, and (though less commonly) on flowers or fruits. In this study, we focused on the seasonal associations of two eriophyoid species, Shevtchenkella serrata (Nalepa 1892) with the Norway maple tree (Acer platanoides L.), and Brevulacus reticulatus Manson 1984 with the common oak (Quercus robur L.). These species have complex life cycles with two morphologically different, seasonal female forms, the protogyne and deutogyne. In B. reticulatus, both forms retain all the major generic characteristics but in S. serrata only the protogynes conform to the diagnosis of Shevtchenkella, whereas the deutogynes have the typical traits of Anthocoptes. We confirmed the conspecificity of the protogynes and deutogynes of both eriophyoid species by sequencing a barcode fragment of the Cox1 gene from which we obtained four pairwise identical sequences: ON920305/ON920306 (S. serrata) and ON920307/ON920308 (B. reticulatus). In addition, taxonomical studies on Shevtchenkella and Brevulacus resulted in new synonymies and combinations: (1) Oxypleurites obtusus Roivainen 1947 is considered a deutogyne of S. serrata and treated as a junior synonym of S. serrata; (2) two rhyncaphytoptine species from North America are transferred from the genus Rhyncaphytoptus to Brevulacus: B. albus (Keifer 1959) comb. nov. and B. atlanticus (Keifer 1959) comb. nov.; and (3) one species, B. salicinus Soika et al. 2017, is excluded from Brevulacus and transferred to Rhyncaphytoptus: Rhyncaphytoptus salicinus (Soika et al. 2017) comb. nov. Apart from distinct morphological deuterogyny in S. serrata and B. reticulatus, we observed the persistent association of S. serrata with the generative organs of the maple tree, A. platanoides, leading to transmission to the next host generation via the seed-containing winged fruits (samaras) and subsequent colonization of seedlings. In B. reticulatus, similar synchronization with host-plant dispersal was not detected; however, in mid-summer, temporary colonization of immature acorns and feeding was observed. Additional studies conducted in various ecosystems and including different ecological groups of plants, especially anemochorous plants, are needed to estimate the frequency of the association of eriophyoids with plant generative organs, seeds and seedlings to better understand what role in mite ecology such associations may play.