Morphometric analyses reveal synonymy of two monotypic genera, Huangiella and Tumoris (Acari, Eriophyoidea, Eriophyidae)

Abstract Morphological variation of Huangiella lanyuensis (Huang, 2001) and Tumoris sanasaii Huang, 2001 from Taiwan was analyzed using multivariate statistical methods. We show that these species are the same and propose to use the name Tumoris sanasaii. No significant differences between populations from Lanyu and Green Island (type localities for Huangiella lanyuensis and Tumoris sanasaii, respectively) were found; however, mites from Yangmingshan (northern Taiwan) differed substantially from these two groups. Synonymy resulted from our study is as follows: Huangiella Kammerer, 2006 is a junior synonym of Tumoris Huang, 2001; Absentia lanyuensis Huang, 2001 is a junior synonym of Tumoris sanasaii Huang, 2001. We also study the sexual variation of populations from Green Island. The result showed the females significantly larger than the males at 17 variables.


Introduction
Eriophyid mites, also known as gall, blister, erineum, bud and rust mites, have more than 200 genera and about 3700 described species worldwide (De Lillo and Amrine 2003). They differ from the other mites by having only two pairs of legs and by their entirely herbivorous habits. The body is minute in size (80-250 µm) with most of the body structures reduced. These characteristics make them a difficult taxon to study and the actual diversity may be several folds higher than currently known (Amirne 1996). Huang (2001a, b) established two monotypic eriophyid genera Absentia and Tumoris based on A. lanyuensis Huang and T. sanasaii Huang, respectively. The former species was reported from Symplocos cochinchinensis philippinensis (originally misidentified as S. c. cochinchinensis) in Lanyu (Orchid Island) (Huang 2001a), whereas the latter was collected from Green Island (Ludao) from the same plant subspecies (Huang 2001b). No subsequent species has been added to these two genera since then. The name Absentia was later found preoccupied and a replacement name, Huangiella, was proposed by Kammerer (2006).
Here we add another mite population from S. c. cochinchinensis in northern Taiwan and made several morphometric analyses to determine if these groups are distinct. Sexual variation in the Green Island population was also analyed by multivariate analysis to reveal the morphological difference between sexes.
Through microscopic examination, 136 out of the 246 slides prepared from the mite samples collected from S. c. philippinensis on Lanyu and Green Island were found to be the species in question. Eighty-five individuals allowing measurements of all morphometric variables, including 32 females from Lanyu (LF), 22 males and 31 females from Green Island (GM and GF, respectively), were chosen for morphometric measurement and analysis. We also prepared mite specimens collected from Symplocos c. cochinchinensis in Yangmingshan (north Taiwan). Out of 24 individuals, 16 females (YF) were chosen for measurements.

Variable Selection and Measurement
Thirty-three variables for morphometric analyses were selected and measured ( Table 1). The variables includes ones based on the the homologous landmarks or length of setae commonly used in taxonomic descriptions. The distance between setal tubercles was measured by truss method (Strauss and Bookstein 1982;Huang et al. 1996) (Fig. 1), and was doubly measured in opposite orientations then averaged. All morphometric data in this study were shown in micrometers (µm).

Analysis
We evaluated geographic and sexual variations in morphology with multivariate analysis of variance (MANOVA). Morphometric data obtained from 101 mites from three localities was analyzed. Females of Yangmingshan, females of Lanyu, and females of Green Island (YF+LF+GF) were used to test if they are the same species, whereas the individuals from Green Island (GM and GF) were used to detect the sexual variation. Morphometric measurements (including distance between setal bases and the lengths of setae) were standardized by subtracted the mean. Principal components analysis (PCA) was then applied to reduce multicollinearity. Variation among populations in derived orthogonal principal components was firstly identified with MANOVA. Once a significant result was detected, pair-wise MANOVA tests after Bonferroni adjustment (α-level: 0.05 divided by n comparisons) were followed to identify the pair(s) leading to the difference. We also created a canonical centroid plot, which provides a convenient way for simultaneously inspect differences among populations (the canonical centroid plot depicted the 95% confidence interval for centroid of each population and an overlap of boundary represents no difference in response variables). We then applied analysis of variance (ANOVA) to determine which response variable (i.e. PC1, PC2, etc.) accounted for the variation. Lastly, differences in those morphometric measurements with high absolute loadings in selected principal components (those that significantly differed among populations) were tested with ANOVA or t-test. For the MANOVA test, normality of response variables (PC values for morphometric measurements) was confirmed with Shapiro-Wilk test, and multivariate outliers were identified with jackknifed Mahalanobis distance. All the procedures were implemented in JMP 8.0 (SAS Institute Inc., Cary, N.C.).
Sexual variation was observed in all these 17 variables (t-test), with the females significantly larger than the males (Table 3).

Identity of the geographical groups
The analyses on geographical groups revealed no significant differences between the Lanyu and Green Island populations, indicating that H. lanyuensis and T. sanasaii are actually the same. On the other hand, the group from Yangmingshan, previously identified by KWH as Tumoris sanasaii, is distinct. Though sharing similar diagnostic characters with T. sanasaii, the Yangmingshan group differs significantly from the true T. sanasaii by morphometry. The former group feeds on a different subspecies of host plant in the temperate northern Taiwan, in contrast to true T. sanasaii living on subtropical or tropical Green Island and Lanyu. At present it is difficult to determine whether it is intra-or inter-specific difference. We would suggest their differentiation being above subspecies level because eriophyid mites have more rapid evolution rate than their host plants. A further study using multidisciplinary approaches would be required to solve the problem.
Owing to the reduced morphological structures and minute size of eriophyids, descriptive diagnosis is usually unsatisfactory in differentiating closely related species.  Molecular identification is also difficult owing to the hardness to isolate a single individual of an identified species from a mite community without making a slide. Morphometric analyses thus provide a reasonable option with balance in effectiveness and efficiency. The present and many previous studies have proved morphometrics a useful tool in eriophyoid classification (Huang et al. 1996;Magud et al. 2007;Skoracka et al. 2002;Navia et al. 2006Navia et al. , 2009Skoracka 2009a, b).   Redefinition of the genus. Body spindle-shape, narrowing abruptly posteriorly; shield pentagonal, lobe present, with bulge between scapular tubercles, scapular tubercles set ahead of rear shield margin, seta directed upward; leg segments normal, coxae with 3 pairs of tubercles and seta, hind genual seta absent; empodium simple; opisthosoma differentiated into broader dorsal annuli and narrower ventral annuli, first dorsal annulus broad, fused forming a broad plate joined to prodorsal shield, dorsum with 3 ridges, median ridge ending before submedian ridges, the second ventral tubercle and setae (e) absent; coverflap with short ridges at base. Differential diagnosis. This genus is close to Proneotegonotus Mohanasundaram 1983, but differs from the latter by the absence of the second ventral tubercle and setae (e), presence of the first ventral tubercles and setae (d), and a bulge between the dorsal tubercles in prodorsal shield.
Classification. In Huang (2001b) Tumoris was assigned to Tegonotini by the presence of lateral lobes in opisthosoma. After examining more specimens from several localities, we found the lateral lobes previously recognized were actually the submedian ridges on the dorsal opisthosoma (Pl. 1, b). According to the scapular tubercles located ahead of the rear shield, we re-assign this genus to Phyllocoptini.