First rhyncaphytoptine mite (Eriophyoidea, Diptilomiopidae) parasitizing American hazelnut (Corylus americana): molecular identification, confocal microscopy, and phylogenetic position.

The plant genus Corylus is an economically important crop, valued especially for its nuts. Numerous pathogens and harmful phytophagous arthropods are known to damage hazelnuts. We report on a new eriophyoid mite, Rhyncaphytoptus corylivagrans n. sp., and the first record of Coptophylla lamimani both collected from leaves of American hazelnut (Corylus americana) in North Carolina, USA. Including our new data, the complex of eriophyoids from Corylus comprises 15 species from three families: Phytoptidae (2 spp.), Eriophyidae (11 spp.), and Diptilomiopidae (2 spp.). We obtained sequences of three genes (Cox1, D1-D5 28S, and ITS1-5.8S-ITS2), applied BLAST and tree-based approaches for identification of R. corylivagrans n. sp., and performed the first molecular phylogenetic analysis focused on Rhyncaphytoptinae. Among the three genes, Cox1 showed better power when used for BLAST searches. Combined molecular phylogenetic analyses inferred R. corylivagrans n. sp. as sister to R. betulae, determined several moderately supported host-specific lineages of rhyncaphytoptines, and indicated a close relationship of the new species with members of the genus Rhinotergum. In two Rhinotergum spp. from Rosaceae, confocal microscopy revealed a new structure, the needle-like anterior process of the prodorsal shield, which is absent in R. corylivagrans n. sp. Additionally, the elements of the anal secretory apparatus presumably associated with silk-production and hypothesized as a synapomorphy of Eriophyoidea, were detected in the new species, providing the first documented report of this structure in Diptilomiopidae. Our study contributes to knowledge on the biodiversity of phytoparasites associated with hazelnuts and calls for future comparative phylogenetics of Diptilomiopidae.

Molecular phylogeny of the phytoparasitic mite family Phytoptidae (Acariformes: Eriophyoidea) identified the female genitalic anatomy as a major macroevolutionary factor and revealed multiple origins of gall induction.

Phytoptidae s.str. is a lineage of eriophyoid mites associated with angiosperms. Based on representative taxon sampling and four gene markers (COI, HSP70, 18S, and 28S), we inferred the molecular phylogeny of this group and performed comparative analyses of cuticle-lined female internal genitalia. Although basal relationships were unclear, several well supported clades were recovered. These clades were supported by geography, host associations, and female genital anatomy, but contradicted the current morphology-based systematics. The monophyly of each of five conventional supraspecific groupings (Fragariocoptes, Phytoptus, Phytoptinae, Sierraphytoptinae, and Sierraphytoptini) is rejected based on a series of statistical tests. Additionally, four morphological characters (the absence of tibial solenidion φ and opisthosomal seta c1, presence of telosomal pseudotagma, and 'morphotype') were found to be homoplasies that cannot be used to confidently delimit supraspecific lineages of phytoptids. However, our molecular topology was highly congruent with female genital characters. Eight molecular clades were unambiguously supported by the shapes and topography of the spermathecal apparatus and genital apodemes. This suggests that the female genital anatomy could be an important factor affecting cladogenesis in Phytoptidae, a conclusion contrasting with the general expectation that host characteristics should be a major macroevolutionary force influencing the evolution of host-specific symbionts. Indeed, despite the high host-specificity, there were no apparent cophylogenetic patterns. Furthermore, we show that gall-inducing ability evolved multiple times in phytoptids. Because gall formation creates nearly instantaneous niche partitioning and the potential loss or reduction of gene flow, we hypothesize that it could be an important evolutionary factor affecting speciation within different host-associated clades of phytoptid mites.

Molecular phylogenetic analyses reveal a deep dichotomy in the conifer-inhabiting genus Trisetacus (Eriophyoidea: Nalepellidae), with the two lineages differing in their female genital morphology and host associations.

We analyzed the phylogenetic relationships of the genus Trisetacus using two genes [cytochrome c oxidase subunit I (COI) and D1-D2 region of 28S rDNA (D1-D2 28S)], a representive taxon sampling (nearly 40% of known diversity), and a large set of close and distant outgroups. Our analyses suggest the presence of a dichotomy between Trisetacus associated with Cupressaceae and Pinaceae. The following smaller molecular clades were found: Pin-1 (bud mites, twig sheath mites, bark gall mites, and endoparasitic mites from pinaceans), Pin-2 (needle sheath mites from pines), Pin-2a (putative Nearctic group of needle sheath mites), Pin-2b (putative Palearctic group of needle sheath mites), Cup-1 and 2 (bud, cone, seed mites and mites living under bark scales from cupressaceans). The monophyly of the recently proposed subgenus Brevithecus nested within clade Cup-2 was confirmed. Ancestral character reconstruction analyses recovered: (1) Pinaceae as the ancestral hosts of Nalepellidae and Trisetacus, (2) repetitive reductions of the spermathecal tube independently occurred in two lineages of Trisetacus from Cupressaceae, and (3) several mite habitats on host (galls, cones, twig sheaths, seeds, inside leaves, and under scales) are evolutionarily derived states, whereas living in buds or needle sheaths are ancestral states for Trisetacus clades Cup and Pin. Using confocal microscopy, we identified six basic types of the female internal genitalia of Trisetacus based on shapes of the spermatheca and spermathecal tube. These genitalic types are strongly correlated with lineages recovered by molecular phylogenetic analyses, suggesting that the female genital morphology is both evolutionarily conserved and is a factor influencing macroevolutionary patterns in this group of mites.

Comprehensive phylogeny of acariform mites (Acariformes) provides insights on the origin of the four-legged mites (Eriophyoidea), a long branch.

Eriophyoid, or four-legged mites, represent a large and ancient radiation of exclusively phytophagous organisms known from the Triassic (230 Mya). Hypothesizing phylogenetic relatedness of Eriophyoidea among mites is a major challenge due to the absence of unambiguous morphological synapomorphies, resulting in ten published hypotheses placing eriophyoids in various places in the acariform tree of life. Here we test the evolutionary relationships of eriophyoids using six genes and a representative taxonomic sampling of acariform mites. The total evidence analysis places eriophyoids as the sister group of the deep soil-dwelling, vermiform family Nematalycidae (Endeostigmata). This arrangement was supported by the rDNA and CO1 partitions. In contrast, the nuclear protein partition (genes EF1-α, SRP54, HSP70) suggests that Eriophyoidea is sister to a lineage including Tydeidae, Ereynetidae, and Eupodidae (Eupodina: Trombidiformes). On both of these alternative topologies, eriophyoids appear as a long branch, probably involving the loss of basal diversity in early evolution. We analyze this result by using phylogenetically explicit hypothesis testing, investigating the phylogenetic signal from individual genes and rDNA stem and loop regions, and removing long branches and rogue taxa. Regardless of the two alternative placements, (i) the cheliceral morphology of eriophyoids, one of the traits deemed phylogenetically important, was likely derived directly from the plesiomorphic acariform chelicerae rather than from the modified chelicerae of some trombidiform lineages with a reduced fixed digit; and (ii) two potential synapomorphies of Eriophyoidea+Raphignathina (Trombidiformes) related to the reduction of genital papillae and to the terminal position of PS segment can be dismissed as result of convergent evolution. Our analyses substantially narrow the remaining available hypotheses on eriophyoid relationships and provide insights on the early evolution of acariform mites.

A study of embryonic development in eriophyoid mites (Acariformes, Eriophyoidea) with the use of the fluorochrome DAPI and confocal microscopy.

The embryonic development of four eriophyoid mite species, Cecidophyopsis ribis, Phytoptus avellanae, Oziella liroi and Loboquintus subsquamatus, has been studied with the use of fluorochrome DAPI and confocal microscopy. The first three nuclear divisions occur on the egg periphery (the groups of 2, 4, and 6 nuclei have been recorded), while the biggest part of yolk remains undivided. After four or five nuclear divisions all nuclei are situated only in one sector of the embryo, while other sectors contain only yolk suggesting possible meroblastic cleavage. Later, the formation of superficial blastoderm takes place. A few large yolk cells are situated inside the embryo. Germ band formation initiates as funnel-like cell invagination and leads to formation of a typical stage with four paired prosomal buds (chelicerae, palps, legs I and II). Each palp contains two lobes (anterior and posterior), the adult subcapitulum is presumably a fusion product of the anterior pair of the lobes. Neither rudiments of legs III and IV, traces of opisthosomal segments nor remnants of the prelarval exuvium under the egg shell were detected. Overall, the pattern of embryonic development in eriophyoids re-emphasizes the peculiarity of this ancient group of miniaturized phytoparasitic animals, and invites researches to pursue a deeper investigation of various fundamental aspects of this aberrant group of Acari. Further studies using various fluorescent dyes and transmission electron microscopy are needed to visualize plasma membranes and clarify the pattern of early cleavage of eriophyoids.

Suboral fork: a newly discerned gnathosomal structure from the proboscis of eriophyoid mites (Acari, Eriophyoidea).

The infracapitulum of eriophyoid mites comprises a cone-like basal infracapitulum, containing a pharynx, and a distal infracapitulum, forming a proboscis ensheathing a bunch of stylets. A well-developed basal labral section was observed in all studied specimens. A newly discerned structure, the suboral fork, situated in the ventral part of the proboscis was discovered. It is larger in diptilomiopids and Nalepella and notably smaller in eriophyids and phytoptids. This structure presumably determines the site of piercing and functions in a similar way to the pressure foot of a sewing machine which controls the movements of a needle. In diptilomiopids the suboral fork might have an additional function: it is a stopper which prevents the proboscis from further penetrating into plant tissues. It is possible that the suboral fork is homologous with the labium of early derivative acariform mites. The proboscis might be a fusion product of the infracapitular lateral lips, malapophyses and the labium. The proboscis serves as a feeding structure in eriophyoids; two ways of sucking plant cell sap, depending on shapes of proboscis and labrum, are hypothesized. Further work is needed to draw conclusions on homologies and the function of all gnathosomal structures in eriophyoids.

Confocal microscopy reveals uniform male reproductive anatomy in eriophyoid mites (Acariformes, Eriophyoidea) including spermatophore pump and paired vasa deferentia.

Male internal genitalia of eriophyoid mites comprise cuticle lined (anterior genital apodeme, genital chamber and ductus ejculatorius) and soft (paired vasa deferentia and single testis) organs. Three-dimensional reconstructions based on autofluorescence show that a thin-walled genital chamber is usually situated in a transverse plane and precisely copies the shape of the spermatophore. A thin vertical longitudinal plate (homologous to female longitudinal bridge) joins the genital chamber and ventral genital cuticle. The anterior genital apodeme is a separate vertical plate situated ahead of the genital chamber and provides a rigid support for it. The brightly autofluorescent ductus ejaculatorius starts from the posterior extremity of the genital chamber and goes backward. Proximally, the ductus ejaculatorius is tube-like, whereas distally, it is expanded into a sac. Confocal laser scanning microscopy observations on males, stained with phalloidin, indicate that the proximal ductus ejaculatorius is devoid of muscles whereas the distal ductus ejaculatorius possesses well-developed musculature (the "spermatophore pump"), appearing in 3D reconstructions as a hollow sphere with three apertures: one anterior and two posterior. Two thin-walled sausage-like vasa deferentia join the distal ductus ejaculatorius with a large single testis, each junction is encircled by a strong, ring-shaped muscle (musculus sphincter testiculodeferentis). Thin muscular fibers of the wall of the testis form a net-like pattern consisting of distinct polygonal cells. The topography of the male internal genitalia and musculature suggests that, contrary to previous observations, the spermatophore head might be extruded first and then the spermatophore stalk appears. The possible role of visceral and skeletal musculature, in the process of the expulsion of a spermatophore, is discussed.

Gnathosomal interlocking apparatus and remarks on functional morphology of frontal lobes of eriophyoid mites (Acariformes, Eriophyoidea).

Comparative study of eriophyoid mite gnathosomata using different microscopic techniques shows presence of new dorsoproximal structures (here described as "interlocking apparatus"), which could consolidate mouthparts in rest (non-feeding) position and during feeding actions. Four types of the interlocking apparatus are described. Differences in the interlocking mechanisms coincide with the results of recent molecular phylogenetic studies of Eriophyoidea and provide additional support for the major clades revealed in those studies. Comparative analysis on the morphology of the frontal lobe of the prodorsal shield shows that mechanical protection of the motivator surrounding area and interlocking apparatus are possibly the primary function of the frontal lobe. Unusual shapes of the frontal lobe in selected eriophyoids (elongated, broadened, notched lobes) might result from additional functions that the frontal lobe can perform, e.g. providing additional guide for palps and stylets, or hermeticity of the space between dorsoproximal palpcoxae during feeding.

Comparative confocal microscopy of internal genitalia of phytoptine mites (Eriophyoidea, Phytoptidae): new generic diagnoses reflecting host-plant associations.

Confocal laser scanning microscopy (CLSM) methods are still rarely used by acarologists although they are very appropriate for studying minute arthropod pests, especially eriophyoid mites. In this paper, the female reproductive system of phytoptines, including the bud mite Phytoptus avellanae, the well-known pest of hazelnut, was studied using CLSM and resulted in new interpretations of the functioning anatomy of phytoptid genitalia. Comparison of cuticle-lined internal genitalia, based on novel CLSM-based 2D and 3D imaging, and multivariate analysis of morphometric measurements, show that two basic types of internal genitalia can be found within Phytoptinae: one type in phytoptines associated with monocotyledoneous hosts (especially Cyperaceae and Asparagaceae), and another one in those associated with various dicotyledoneous hosts. Phytoptines from monocots (genera Oziella and Acathrix and Phytoptus "caricis" sp. group) possess a spherical distal part of the spermathecal tube and a semitriangular transverse genital apodeme, whereas phytoptines from dicots (genus Phytoptus "avellenae" sp. group) possess an elongate distal part of the tube and a trapezoidal apodeme. These differences in the internal genitalic anatomy were used for modifying the diagnosis of phytoptine genera (Phytoptus, Oziella and Acathrix), and reorganizing the Phytoptinae, resulting in new synonymies: 11 species were transferred from genus Phytoptus "caricis" sp. group to the genus Oziella.

Distal oviduct and genital chamber of eriophyoids (Acariformes, Eriophyoidea): refined terminology and remarks on CLSM technique for studying musculature of mites.

The general morphology of cuticle-lined internal genitalia and oviduct is analyzed in intact females of the phytophagous mites, Loboquintus subsquamatus and Trisetacus cf bagdasariani (Acari: Eriophyoidea) using tetramethylrhodamine B isothiocyanate-phalloidin, three anaesthetics (magnesium sulphate, lidocaine and CO2-enriched water) and confocal laser scanning microscopy (CLSM). This is the first protocol adopted for CLSM studying musculature of mites. Revision of the previous terminology of eriophyoid internal genitalia from Nuzzaci and Alberti (Eriophyoid mites: their biology, natural enemies and control. World crop pests 6. Elsevier, Amsterdam, pp 101-150, 1996) resulted in the refinement of the terms "distal oviduct", "genital chamber" and "spermatheca". Relative position of the elements of cuticle-lined internal genitalia is discussed and a generalized 3D model and animation (available on-line as supplementary material) of eriophyoid genital apparatus are provided. The wall of eriophyoid oviduct contains strong longitudinal muscles attached to the cuticle genital chamber with folded walls. When the egg is being extruded by contraction of the oviduct muscles, it forms lobes corresponding to the internal topography of the oviduct and genital chamber; these lobes invaginate inward from the gonopore, resulting in the "flower-shaped" figures rarely observed in slide-mounted mites. Gnathosomal muscles (cheliceral muscles and extrinsic muscles of palps) and opisthosomal muscles D1 of Loboquintus mites are attached to the three posterior depressions near the rear prodorsal shield margin. Prospects of CLSM approach for studying different aspects of mite morphology are briefly discussed.

Redescription of an early-derivative mite, Pentasetacus araucariae (Eriophyoidea, Phytoptidae), and new hypotheses on the eriophyoid reproductive anatomy.

A unique set of plesiomorphic characters, and its association with an ancient gymnosperm, Araucaria araucana, have made Pentasetacus araucariae a putative relict of a lineage of gymnosperm-associated mites, itself possibly basal to all extant eriophyoids. However, the suboptimal description of this species is impeding morphological comparisons with other species, which are fundamental to eriophyoid systematics. Herein, we designate a female lectotype from syntype specimens and use additional non-type material to redescribe P. araucariae based on external and internal anatomy using different microscopic and 3D reconstruction techniques. Contrarily to statements in the literature, P. araucariae has undivided empodia in all instars, short spermathecal tubes, and large, globose spermathecae in females, as well as rudimentary genital fovea in immatures. In addition, males of P. araucariae were shown to have genitalic attributes similar to a species of Trisetacus studied in parallel, including two reservoir-like structures, which may represent parts of the genital chamber and of the ductus ejaculatorius, respectively, as well as paired testes and ducti deferentes. This is contrary to previous, limited knowledge on eriophyoids indicating that they possess a single testis. Although their short spermathecal tubes weaken the cladistic relationship between P. araucariae (Pentasetacinae) and conifer-associated Nalepellinae (e.g. Trisetacus) having long tubes, the structural similarities in male genitalia may reinforce it.

Description of a new relict eriophyoid mite, Loboquintus subsquamatus n. gen. & n. sp. (Eriophyoidea, Phytoptidae, Pentasetacini) based on confocal microscopy, SEM, COI barcoding and novel CLSM anatomy of internal genitalia.

A new pentasetacine mite Loboquintus subsquamatus n. gen. & n. sp. was found living under scale-like leaves of 2-3 years old twigs of Cupressus sempervirens in Montenegro. This mite species possesses a number of morphological features (uncommon teardrop-shaped body, traits of prosoma, atypical primitive anatomy of the genital apparatus and morphological traits of immatures) which clearly distinguish it from all other known eriophyoids. Adults of L. subsquamatus have seta vi situated on the anterior margin of a uniquely elongate lingua-like thin frontal lobe, three pits on the posterior prodorsal shield margin, a remarkable tube-like structure in the basal part of gnathosoma, a complicated three-layered epigynium, spermathecae directed antero-laterad, short spermathecal tubes and setae eu suppressed in males and possibly expressed in females. External genitalia of males and females of L. subsquamatus are fundamentally similar. Hypothesized remnants of coxisterna III or IV (forming a postgenital plate) are remarkably distinct in males. Two new morphometrical variables are proposed to supplement the CLSM protocol for description of internal genitalia of eriophyoids proposed by Chetverikov et al. (Zootaxa 3560:41-60, 2012b): (a) the length of ventral projection of the transvers genital apodeme and (b) the length of the posterior (=postspermathecal) part of the longitudinal bridge which in L. subsquamatus is remarkably long, whereas in many other eriophyoids it is reduced.

Integrative Taxonomy of the Gall Mite Nothopoda todeica n. sp. (Eriophyidae) from the Disjunct Afro-Australasian Fern Todea barbara: Morphology, Phylogeny, and Mitogenomics.

Eriophyoidea is a group of phytoparasitic mites with poorly resolved phylogeny. Previous studies inferred Eriophyidae s.l. as the largest molecular clade of Eriophyoidea, and Nothopodinae as the basal divergence of Eriophyidae s.l. We investigate the morphology and molecular phylogeny of Nothopoda todeican. sp. (Nothopodinae, Nothopodini), associated with a disjunct Afro-Australasian fern Todea barbara (Osmundaceae) from South Africa. Our analyses (1) determine new erroneous sequences (KF782375, KF782475, KF782586) wrongly assigned to Nothopodinae instead of Phyllocoptinae, (2) confirm the basal position of Nothopodinae in Eriophyoidea s.l., (3) question the monophyly of the Colopodacini and Nothopodini tribes, and (4) show the nested position of African fern-associated Nothopoda within a clade dominated by Asian nothopodines from angiosperms, which implies (a) a secondary association of nothopodines with ferns and (b) no relation between geography (continents) and the phylogenetic relationships of Nothopodinae species. Finally, we obtained a first complete mitochondrial genome for Nothopodinae and revealed a new gene order in the mitogenome of N. todeican. sp., notably deviating from those in other investigated eriophyoids. Our results contribute to resolving the phylogeny of Eriophyoidea and provide an example of an integrative study of a new taxon belonging to an economically important group of acariform mites.

Where Eriophyoidea (Acariformes) Belong in the Tree of Life.

Over the past century and a half, the taxonomic placement of Eriophyoidea has been in flux. For much of this period, this group has been treated as a subtaxon within Trombidiformes. However, the vast majority of recent phylogenetic analyses, including almost all phylogenomic analyses, place this group outside Trombidiformes. The few studies that still place Eriophyoidea within Trombidiformes are likely to be biased by incomplete taxon/gene sampling, long branch attraction, the omission of RNA secondary structure in sequence alignment, and the inclusion of hypervariable expansion-contraction rRNA regions. Based on the agreement among a number of independent analyses that use a range of different datasets (morphology; multiple genes; mitochondrial/whole genomes), Eriophyoidea are almost certain to be closely related to Nematalycidae, a family of vermiform mites within Endeostigmata, a basal acariform grade. Much of the morphological evidence in support of this relationship was apparent after the discovery of Nematalycidae in the middle of the 20th century. However, this evidence has largely been disregarded until very recently, perhaps because of overconfidence in the placement of Eriophyoidea within Trombidiformes. Here, we briefly review and identify a number of biases, both molecular- and morphology-based, that can lead to erroneous reconstructions of the position of Eriophyoidea in the tree of life.

Anatomy of the miniature four-legged mite Achaetocoptes quercifolii (Arachnida: Acariformes: Eriophyoidea).

Miniaturization is one of the important trends in the evolution of terrestrial arthropods. In order to study adaptations to microscopic sizes, the anatomy of the smallest insects was previously studied, but not the anatomy of the smallest mites. Some of the smallest mites are Eriophyidae. In this study we describe for the first time the anatomy of the mite Achaetocoptes quercifolii, which is about 115 µm long. For this purpose, we used light, scanning, and transmission electron microscopy and performed 3D reconstructions. The anatomy of A. quercifolii is compared with the anatomy of larger representatives of Eriophyoidea. Despite the small size of the studied species, there is no considerable simplification of its anatomy compared to larger four-legged mites. A. quercifolii has a number of miniaturization effects similar to those found in microinsects: a strong increase in the relative volume of the reproductive system, an increase in the relative volume of the brain, reduction in the number and size of cells of the nervous system. As in some larger four-legged mites, A. quercifolii undergoes midgut lysis at the stage of egg production. On the other hand, in A. quercifolii a greater number of opisthosomal muscles are preserved than in larger gall-forming four-legged mites.

Atypically Shaped Setae in Gall Mites (Acariformes, Eriophyoidea) and Mitogenomics of the Genus Leipothrix Keifer (Eriophyidae).

The setae in Eriophyoidea are filiform, slightly bent and thickened near the base. Confocal microscopy indicates that their proximal and distal parts differ in light reflection and autofluorescence. Approximately 50 genera have atypically shaped setae: bifurcated, angled or swollen. These modifications are known in the basal part of prosomal setae u', ft', ft″, d, v, bv, ve, sc and caudal setae h2. We assessed the distribution of atypically shaped setae in Eriophyoidea and showed that they are scattered in different phylogenetic lineages. We hypothesized that the ancestral setae of eriophyoid mites were bifurcated before later simplifying into filiform setae. We also proposed that hypo-furcating setae are a synapomorphy that unites Eriophyoidea with Nematalycidae. We analyzed four new mitochondrial genomes of Leipothrix, the largest genus with bifurcated d, and showed that it is monophyletic and has a unique mitochondrial gene order with translocated trnK. We exclude Cereusacarus juniperensisn. comb. Xue and Yin, 2020 from Leipothrix and transfer five Epitrimerus spp. to Leipothrix: L. aegopodii (Liro 1941) n. comb., L. femoralis (Liro 1941) n. comb., L. geranii (Liro 1941) n. comb., L. ranunculi (Liro 1941) n. comb., and L. triquetra (Meyer 1990) n. comb.

Molecular Aspects of Gall Formation Induced by Mites and Insects.

Recent publications on gall formation induced on the leaves of dicotyledonous flowering plants by eriophyoid mites (Eriophyoidea) and representatives of four insect orders (Diptera, Hemiptera, Hymenoptera, Lepidoptera) are analyzed. Cellular and molecular level data on the stimuli that induce and sustain the development of both mite and insect galls, the expression of host plant genes during gallogenesis, and the effects of these galling arthropods on photosynthesis are considered. A hypothesis is proposed for the relationship between the size of galls and the volume of secretions injected by a parasite. Multistep, varying patterns of plant gene expression and accompanying histo-morphological changes in the transformed gall tissues are apparent. The main obstacle to better elucidating the nature of the induction of gallogenesis is the impossibility of collecting a sufficient amount of saliva for analysis, which is especially important in the case of microscopic eriophyoids. The use of modern omics technologies at the organismal level has revealed a spectrum of genetic mechanisms of gall formation at the molecular level but has not yet answered the questions regarding the nature of gall-inducing agents and the features of events occurring in plant cells at the very beginning of gall growth.

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.

Vertical transmission and seasonal dimorphism of eriophyoid mites (Acariformes, Eriophyoidea) parasitic on the Norway maple: a case study.

Eriophyoid mites are highly host-specific, microscopic phytoparasites that primarily disperse to new hosts passively via wind. This seems paradoxical, as the likelihood of landing on an appropriate host species needed to survive appears low. Here we investigate two eriophyoids found on the Norway maple Acer platanoides: Aceria platanoidea and Shevtchenkella serrata. For 14 months, we observed mite phenotypical changes and micro-habitat distribution on host plants and their propagules. Both mite species hibernate on twigs or samaras fallen on the ground, and, in the spring, feed on buds or seedlings, respectively. This apparently novel association with plant seeds indicates that the mites can exploit the host dispersal mechanism and colonize the next generation of hosts (vertical transmission). Our seasonal and DNA sequence data also indicate that S. serrata has two distinct morphotypes that partially overlap seasonally. This work can provide new insights into the dispersal routes of eriophyoid mites and transmission patterns of plant pathogens vectored by these mites, with implications for better pest mite species control.

Phylogenetic Position of a New Trisetacus Mite Species (Nalepellidae) Destroying Seeds of North American Junipers and New Hypotheses on Basal Divergence of Eriophyoidea.

Eriophyoid mites of the genus Trisetacus Keifer are widespread parasites of conifers. A new oligophagous species, T. indelis n. sp., was discovered severely damaging seeds of North American junipers (Juniperus osteosperma, J. occidentalis, and J. californica) in the western USA. It has two codon deletions in the mitochondrial gene Cox1 rarely detected in Eriophyoidea and includes distinct morphological dimorphism of females. A phylogenetic analysis based on amino acid alignment of translated Cox1 sequences using a large set of out-groups (a) determined that two North American congeners, T. batonrougei and T. neoquadrisetus, were the closest known relatives of T. indelis n. sp., and (b) indicated that Old and New World seed-inhabiting Trisetacus from junipers do not form a distinct clade, suggesting a possible independent transition to living in seeds of junipers in America and Eurasia by Trisetacus spp. Our analysis produced a new topology consistent with a scenario assuming gradual reduction of prodorsal shield setation in Eriophyoidea and an ancient switch from gymnosperms to other hosts. Additionally, our analysis did not support monophyly of Trisetacus; recovered a new host-specific, moderately supported clade comprising Trisetacus and Nalepellinae (Nalepella + Setoptus) associated with Pinaceae; and questioned the monophyly of Trisetacus associated with Cupressaceae.