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

Phylogenomics resolves the higher-level phylogeny of herbivorous eriophyoid mites (Acariformes: Eriophyoidea)

BACKGROUND

Eriophyoid mites (Eriophyoidea) are among the largest groups in the Acariformes; they are strictly phytophagous. The higher-level phylogeny of eriophyoid mites, however, remains unresolved due to the limited number of available morphological characters-some of them are homoplastic. Nevertheless, the eriophyoid mites sequenced to date showed highly variable mitochondrial (mt) gene orders, which could potentially be useful for resolving the higher-level phylogenetic relationships.

RESULTS

Here, we sequenced and compared the complete mt genomes of 153 eriophyoid mite species, which showed 54 patterns of rearranged mt gene orders relative to that of the hypothetical ancestor of arthropods. The shared derived mt gene clusters support the monophyly of eriophyoid mites (Eriophyoidea) as a whole and the monophylies of six clades within Eriophyoidea. These monophyletic groups and their relationships were largely supported in the phylogenetic trees inferred from mt genome sequences as well. Our molecular dating results showed that Eriophyoidea originated in the Triassic and diversified in the Cretaceous, coinciding with the diversification of angiosperms.

CONCLUSIONS

This study reveals multiple molecular synapomorphies (i.e. shared derived mt gene clusters) at different levels (i.e. family, subfamily or tribe level) from the complete mt genomes of 153 eriophyoid mite species. We demonstrated the use of derived mt gene clusters in unveiling the higher-level phylogeny of eriophyoid mites, and underlines the origin of these mites and their co-diversification with angiosperms.

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.

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.

Endoparasitic Gall Mites: Two New Novophytoptus Species (Eriophyoidea, Phytoptidae) from Southern African Sedges (Cyperaceae, Carex) and New Hypotheses on the Phylogeny of Novophytoptines

Eriophyoid mites (Acariformes, Eriophyoidea) are microscopic chelicerates morphologically greatly preadapted to endoparasitism on plants. Members of at least six phylogenetically distant eriophyoid genera from two families homoplastically transitioned to endoparasitism and acquired the ability to penetrate under the plant epidermis and feed on parenchymatous cells, usually causing necrosis. Theoretically, endoparasites are expected to show patterns of codivergence with hosts more than ectoparasites. Novophytoptus Roivainen 1947 is the only eriophyoid genus comprising exclusively endoparasitic species living in subepidermal tissues of herbaceous monocots of three families of the order Poales: Cyperaceae, Juncaceae, and Poaceae. Here, we described two new endoparasitic species, N. limpopoensis n. sp. and N. zuluensis n. sp., from southern African sedges Carex spicatopaniculata Boeckeler ex C.B.Clarke and C. zuluensis C.B.Clarke, respectively, and investigated the Cox1 phylogeny of Novophytoptus. Contrary to expectations, molecular phylogenetics did not recover host-specific mite clades associated with Cyperaceae and Juncaceae, but revealed geographical groups of Novophytoptus species from Africa and Eurasia. Our results provide a substantial basis for future coevolutionary studies on novophytoptines, which will be possible when more species and sequences of Novophytoptus from geographically remote regions and from diverse hosts representing all major clades of Poales become available for analyses.

Macroevolutionary analyses point to a key role of hosts in diversification of the highly speciose eriophyoid mite superfamily

The superfamily Eriophyoidea includes >5000 named species of very small phytophagous mites. As for many groups of phytophagous invertebrates, factors responsible for diversification of eriophyoid mites are unclear. Here, we used an inferred phylogeny of 566 putative species of eriophyoid mites based on fragments of two mitochondrial genes and two nuclear genes to examine factors associated with their massive evolutionary diversification through time. Our dated phylogeny indicates a Carboniferous origin for gymnosperm-associated Eriophyoidea with subsequent diversification involving multiple host shifts to angiosperms-first to dicots, and then to monocots or shifts back to gymnosperms-beginning in the Cretaceous period when angiosperms diverged. Speciation rates increased more rapidly in the Eriophyidae + Diptilomiopidae (mostly infesting angiosperms) than in the Phytoptidae (mostly infesting gymnosperms). Phylogenetic signal, speciation rates, dispersal and vicariance results combined with inferred topologies show that hosts played a key role in the evolution of eriophyoid mites. Speciation constrained by hosts was probably the main driver behind eriophyoid mite diversification worldwide. We demonstrate monophyly of the Eriophyoidea, whereas all three families, most subfamilies, tribes, and most genera are not monophyletic. Our time-calibrated tree provides a framework for further evolutionary studies of eriophyoid mites and their interactions with host plants as well as taxonomic revisions above the species level.

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.

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.

Symbiotic bacteria of the gall-inducing mite Fragariocoptes setiger (Eriophyoidea) and phylogenomic resolution of the eriophyoid position among Acari

Eriophyoid mites represent a hyperdiverse, phytophagous lineage with an unclear phylogenetic position. These mites have succeeded in colonizing nearly every seed plant species, and this evolutionary success was in part due to the mites' ability to induce galls in plants. A gall is a unique niche that provides the inducer of this modification with vital resources. The exact mechanism of gall formation is still not understood, even as to whether it is endogenic (mites directly cause galls) or exogenic (symbiotic microorganisms are involved). Here we (i) investigate the phylogenetic affinities of eriophyoids and (ii) use comparative metagenomics to test the hypothesis that the endosymbionts of eriophyoid mites are involved in gall formation. Our phylogenomic analysis robustly inferred eriophyoids as closely related to Nematalycidae, a group of deep-soil mites belonging to Endeostigmata. Our comparative metagenomics, fluorescence in situ hybridization, and electron microscopy experiments identified two candidate endosymbiotic bacteria shared across samples, however, it is unlikely that they are gall inducers (morphotype1: novel Wolbachia, morphotype2: possibly Agrobacterium tumefaciens). We also detected an array of plant pathogens associated with galls that may be vectored by the mites, and we determined a mite pathogenic virus (Betabaculovirus) that could be tested for using in biocontrol of agricultural pest mites.

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

Simple Summary

Eriophyoid mites are microscopic herbivores associated with higher plants. Some of them are serious pests due to their ability to vector viruses and cause other damage to host plants. Mites of the genus Trisetacus are widespread parasites of conifers. They usually live in buds, cones, and rarely within needles of Pinaceae (pine family) and Cupressaceae (cypress family). We discovered a new species, Trisetacus indelisn. sp., severely damaging seeds of three North American junipers in the western USA. This species possesses two morphologically different forms of females and has two deletion mutations in the gene cytochrome oxidase subunit I (Cox1). Such mutations are rare in eriophyoids and were previously detected only in two pestiferous species from palms and hazelnut. Our molecular-phylogenetic analyses determine the closest known relatives of the new species and suggest that Old and New World Trisetacus independently transitioned to living in seeds of junipers. Additionally we show that reconstruction of the phylogeny of Eriophyoidea based on one gene, Cox1, produces a poorly-resolved but biologically consistent tree topology to hypothesize the evolution of Eriophyoidea. Overall, our study improves our understanding of the diversity of conifer-inhabiting mites and indicates further needs in investigating the phylogeny of Eriophyoidea.

Abstract

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.