Three New Eriophyid Mite Species from China (Acari: Eriophyidae)

Simple Summary The Eriophyidae is the largest family in the Eriophyoidea, consisting of over 3790 extant species. Eriophyid mites have a patchy distribution worldwide and are concentrated in the temperate regions. In this study, we describe and illustrate three new eriophyid mites from the temperate region of China—Scolotosus ehretus sp. nov., Neotegonotus ulmchangus sp. nov., and Leipothrix ventricosis sp. nov. All three new species are vagrant on the lower leaf surface, causing no apparent symptoms to the host plant. Abstract Eriophyid mites (Eriophyidae) are strictly phytophagous and are concentrated in Europe, Eastern Asia, Southeast Asia, Western and Eastern North America, Southern India, and New Zealand. South and southwest China are hot spots for eriophyid mite species diversity and endemism. In this study, we describe two new species, Scolotosus ehretus sp. nov. on Ehretia acuminata (Boraginaceae) and Neotegonotus ulmchangus sp. nov. on Ulmus changii (Ulmaceae), from south and southwest China (the Oriental Region), and one new eriophyid mite, Leipothrix ventricosis sp. nov. on Hosta ventricosa (Asparagaceae), from northeast China (the Palearctic Region). All three new eriophyid mite species are distributed in the temperate region of China. We further provided mitochondrial gene (cox1, 12S rRNA) and nuclear gene (18S rRNA, 28S rRNA) sequences for three new species.


Introduction
Eriophyoid mites are strictly phytophagous [1]. Over 80% of eriophyoid mite species are monophagous [2,3]. Host plants supposedly played key roles in their diversification [4,5]. The Eriophyoidea include three families-Phytoptidae (ca. 160 species), Eriophyidae (ca. 3790 species), and Diptilomiopidae (ca. 450 species) [1,6]. The Eriophyidae can be differentiated from the other two families by having a gnathosoma relatively small and projecting obliquely downwards (a gnathosoma large and abruptly curved near the base in the Diptilomiopidae) and a prodorsal shield without setae vi and ve (a prodorsal shield has setae vi and ve in the Phytoptidae) [1]. Although eriophyoid mites have a worldwide distribution, the richness centers differ among the three families-the Eriophyidae are concentrated in Europe, Eastern Asia, Southeast Asia, Western and Eastern North America, Southern India, and New Zealand [4]. South and southwest China are hot spots for eriophyid mite species diversity and endemism [4].
Field surveys of eriophyoid mites have been conducted in China since 1980 [7]. To date, more than 1200 eriophyoid mites have been described in China [8]. Based on a DNA barcoding dataset, the Chinese fauna of eriophyoid mites was inferred, including over 2300 species [3]. To understand the species diversity of eriophyoid mites in China, Xiao-Feng Xue and colleagues have been conducting a long-term field survey since 2002. In this study, we describe and illustrate two new eriophyid mite species (Scolotosus ehretus sp.
Differential diagnosis. The new species is morphologically similar to Leipothrix juniperensis Xue and Yin, 2020 [16], by the presence of divided dorsal pedipalp genual setae (d), dorsal opisthosoma with three ridges, and coxal plates with granules and short lines, but can be differentiated by admedian lines absent from the prodorsal shield (admedian lines present in L. juniperensis), female genital coverflap with granules and short lines (female genital coverflap with 6 to 8 ribs in L. juniperensis).
Key to species of Neotegonotus

Discussion
In this study, we described and illustrated three new eriophyoid mite species from three genera (Leipothrix, Scolotosus, and Neotegonotus) in China. All three new species belong to the subfamily Phyllocoptinae (Eriophyidae), based on the distinct morphological characters-body shape fusiform; gnathosoma relatively small, projecting obliquely downwards; with legs having the typical segmentation; dorsal annuli broader than the ventral annuli (Amrine et al., 2003) [1]. However, the monophyly of Phyllocoptinae was rejected by molecular studies [5,28,29] as well as the non-monophyly of two genera, Leipothrix and Neotegonotus [5]. It should be noted that the phylogenetic position of L. ventricosis sp. nov. (named Leipothrix sp. H92 in Figure 2 of reference [5]) was inferred to be nested with three Paraepitrimerus species [5]. L. ventricosis sp. nov. is morphologically similar to species in the genus Paraepitrimerus [30] by exhibiting femur setae absent, an opisthosoma with three ridges, and scapular setae and tubercles ahead of the rear shield margin, but can be differentiated distinctly by dorsal pedipalp genual setae (d) divided, which is a generic character of Leipothrix [1]. Two Neotegonotus species, N. ulmchangus sp. nov. (named Neotegonotus sp. FJ27 in Figure 2 of reference [5]), and N. shangsiensis, failed to be grouped in the analysis of reference [5]. By contrast, N. ulmchangus sp. nov. was inferred to be closer to species in the genera Aculus, Abacarus, and Shevtchenkella [5]. S. ehretus sp. nov. (named Scolotosus sp. GX54 in Figure 2 of reference [5]) was nested within species from genera Tegolophus and Aculus [5]. Therefore, it is likely that their generic characteristics should be reconsidered in future studies. All three new species are distributed in the temperate region of China. The species diversity and endemism of eriophyid mites peak in temperate regions [4]. The south and southwest mountains of China are hot spots for eriophyid mite species diversity and endemism [4], reflecting potential "museums" and "cradles". Given the over 1200 eriophyoid mite species described in China [8] and suspected 2300 species for the eriophyoid mite fauna of China [3], more field surveys should be conducted, especially in the mountains of southwest China, to unveil the species diversity of eriophyoid mites.
The Leipothrix is among the most species-rich genera in the Eriophyidae, including more than 50 named species (personal data of X.-F.X.). Eighteen Leipothrix species have been reported in China. Most of them (13/18) were distributed in the temperate region, while the remaining species were distributed in the tropical region. S. ehretus sp. nov. is one of three Scolotosus species reported in the temperate region of China. The other two Scolotosus species, S. centrolobii Flechtmann and Keifer, 2010, and S. hartfordi Flechtmann and de Queiroz, 2010, were distributed in the temperate region of Brazil [17]. The genus Neotegonotus holds seven species (including N. ulmchangus sp. nov., Table 2), of which N. fastigatus and N. sycamori have a cosmopolitan distribution [18,[20][21][22][23]26,27]. All species in three genera (Leipothrix, Scolotosus, and Neotegonotus) have high (100%) host plant specificity; no alternative host plants were reported for each eriophyoid mite species.
Eriophyid mites have simplified morphological characteristics (e.g., only two pairs of legs, reduced setae on the opisthosoma and legs, ringed opisthosoma) when compared with other mite species [1]. Two fossil species dating back to the Triassic are morphologically similar to extant species [31]. It is likely that the eriophyoid mites were in morphological stasis during long-term evolution, leading to a potential species complex [3,14,32]. COI barcodes were recently explored in eriophyoid mite delimitation, enabling the discrimination of 99% of eriophyoid mite species [3]. Besides morphological characteristics, we provide a COI barcode for Scolotosus ehretus sp. nov. However, we failed to sequence the COI barcode for the other two species. We further provided mitochondrial (12S rRNA) and nuclear gene (18S rRNA, 28S rRNA) sequences for Leipothrix ventricosis sp. nov., Scolotosus ehretus sp. nov., Neotegonotus ulmchangus sp. nov. We suggested a combination of molecular sequences and morphological characters in the description of new eriophyoid mite species.