Leptotrombidium, , Vercammen-Grandjean, 1960

STEKOLNIKOV, ALEXANDR A., 2013, <strong> <em> Leptotrombidium </ em> (Acari: Trombiculidae) of the World </ strong>, Zootaxa 3728 (1), pp. 1-173 : 9-27

Classification of Leptotrombidium s.s.

Given that the publication of Vercammen-Grandjean and Langston (1976) is hardly accessible, here I reproduce the system of Leptotrombidium s.s. from that work to facilitate future references (see Supplement 2). Names of taxa in this list are given verbatim, without changes in their taxonomic status which were made later (see below). In my own system, I retained only the groups of clearly related species (see below) ignoring some phylogenetic hypotheses proposed by the above authors without any supporting evidence. One should not exclude, however, that the classification of the authors, although not explicitly justified but based on their examination of the majority of Leptotrombidium species known at that time, may be supported by further evidence and become more realistic than I can confirm now.

The only attempt to classify the whole genus Leptotrombidium after Vercammen-Grandjean and Langston (1976) was made by Wang (1981) who proposed a series of artificial species groups based on the formula of palpal setation (fPp). Later this system was used by Wang and Yu (1992) who provided a list of 82 Chinese species and a key for identification of 79 species. I consider this classification to be meaningless, because there is no evidence of the phylogenetic significance for this single character and the system based on it is solely a repetition of the sequence of species in the identification key.

I classify here the genus Leptotrombidium into 52 “natural” and 19 “artificial” species groups. Each “natural” group includes at least two species, which are closely related to each other judging from their similarity in all available features: standard morphological traits, measurements, and shapes (e. g., the shape of the posterior scutal margin, barbs on the scutal and idiosomal setae). For larger groups, the primary diagnostic characteristics were the shape of the scutum, shape of barbs on scutal and idiosomal setae, and some rare character states, such as six setae in the first dorsal row for the species group tarsale , or palpal claw with two prongs for the species group langati . Therefore, the set of “natural” groups reflects all cases of an evident close affiliation among species. The remaining species, which I cannot include in any “natural” group, are assigned into artificial groups according to the characters used at the highest levels in the key proposed in the present work (mostly fD and fPp). “Natural” groups have their names derived from species names, while artificial groups are designated by their numbers and brief diagnoses. Within the groups, the sequence of species corresponds to the numbers of the couplets in the key, where the respective species appear. The sequence of groups corresponds to the means calculated from the numbers of these couplets within each group.

This nonhierarchical classification should be regarded only as a first step toward building a global system of Leptotrombidium , and it is intended primarily for an easier recognition of possible relatives for new species.

I treat all previously described subspecies as species, if they are distinct from nominative subspecies; such changes in the rank are not mentioned further. Subspecies that cannot be distinguished from nominative subspecies on the base of their descriptions are considered to be synonyms. Seven taxa were described by Vercammen- Grandjean and Langston (1976) as varieties ( Leptotrombidium bodense var. kinabalui , L. bodense var. megabodense , L. bodense var. tenompaki , L. langati var. megalangati , L. langati var. minului , L. langati var. ului , and L. miculum arvinum var. saigoni ). According to ICZN Code (Art. 45.6.3.), their names are deemed to be infrasubspecific and thus unavailable. In the present work, I apply them to species with the descriptions given by Vercammen-Grandjean and Langston (1976) for the above varieties. Therefore, according to ICZN Code (Arts 23.3.4 and 45.5.1.), I become the author of these taxa.

Some emendations of chigger species names are made here to bring them in correspondence with the grammatical neutral gender of the name Leptotrombidium ; these emendations are not mentioned specifically.

Species groups composition tarsale group: L. pipellae , L. aenigmami , L. tarsale .

Group 1 (fD=2H-8-6-6-4-2, N/N/NNN): L. biluoxueshanense .

Group 2 (fD=2H-8-6-6-4-2, fPp=B/N/BNN): L. insigne .

Group 3 (fD=2H-8-6-6-4-2, fPp=B/N/BBB): L. dichotogalium .

Group 4 (fD=2H-8-6-6(8)-…N/N/BNN, PL/SB): L. lanceolatum , L. abramovi , L. madiense , L. zhongdianense , L. bambicola , L. hiemale , L. wulingshanense , L. dabashanense , L. linji , L. discum , L. dongluoense , L. yui , L. wugongense , L. linhuaikongense , L. kitasatoi , L. eothenomydis , L. rattistae , L. qiui , L. nyctali , L. jianshanense , L. andrei , L. spicanisetum , L. ushi , L. cangjiangense , L. longchuanense .

longisetum group: L. longisetum , L. bawangense .

gongshanense group: L. gongshanense , L. longimedium .

taishanicum group: L. taishanicum , L. cricethrionis . burmense group: L. elisbergi , L. burmense . langati group: L. megalangati , L. megabodense , L. bodense , L. kinabalui , L. langati , L. ului , L. afrobodense , L.

minului, L. tenompaki , L. clarum . longimedian group: L. oculascutum , L. longimedian . furcagaleala group: L. furcagaleala , L. waltoni . russicum group: L. subrussicum , L. russicum . scanloni group: L. scanloni , L. monstrosum , L. hanseni . Group 5 (fD=2H-8-6-6(8)-4(6)-…, N/N/BNN, SB/PL or SB-PL): L. vivericola , L. tikhonovi , L. labuani , L. yulini ,

L. cuonae , L. xiaguanense , L. zhongjingi , L. tenuipalpe , L. tardum , L. lianghense , L. harrisoni , L. fulmentum ,

L. filasensillum , L. peniscutum , L. deplanoscutum , L. yuebeiense , L. romaniense , L. bunaense , L.

densipunctatum, L. laxoscutum , L. kulkarnii , L. kawamurai , L. guzhangense , L. shenzhense , L. koreanum , L.

hupeicum, L. nanchangense , L. chuanxi , L. rubellum , L. subangulare , L. shuqui , L. tupikovae , L. bochkovi . silvaticum group: L. jianense , L. urogale , L. xiayui , L. silvaticum , L. hyongsunahi , L. oreophilum , L. album . arenicola group: L. arenicola , L. umbricola , L. miculum . deliense group: L. subangi , L. sialkotense , L. spicapilum , L. paulum , L. pentafurcatum , L. deliense . akamushi group: L. delimushi , L. akamushi , L. isosetosum , L. imphalum , L. philippinense . brinchangense group: L. brinchangense , L. insolitum , L. periosum , L. sylvestre , L. phangi , L. rowanae , L.

pilosum, L. gentryi , L. kundini . arvinum group: L. arvinum , L. saigoni . tenjini group: L. wenense , L. fujii , L. kuroshioi , L. tenjini , L. tanakaryoi , L. miyairii . vanderghinstei group: L. vanderghinstei , L. australe . fulleri group: L. youyi , L. fulleri . dumitrescui group: L. orghidani , L. myoticulum , L. siligorense , L. dumitrescui . allosetum group: L. allosetum , L. shanghaense . Group 6 (fD=2H-8-6-6-4(6)-…, N/N/BNB): L. hsui , L. kunxi , L. quadrifurcatum , L. xiaowei , L. shaowuense , L.

sheshui, L. kitaokai , L. serum , L. trapezoidum , L. hazatoi , L. postfoliatum , L. pseudofulmentum , L.

kunmingense. flureli group: L. flureli , L. zhangmuense . rapmundi group: L. miyajimai , L. rapmundi , L. dendrium . Group 7 (fD=2H-8-6-6-6-2, fPp=B/B/BNN): L. muridium . Group 8 (fD=2H-8-8-6-5-4-2, N/N/BNB, AM>PL>AL): L. hengdun . orientale group: L. gracipalpe , L. intermutatum , L. zeta , L. subintermedium , L. intermedium , L. orientale , L.

dahai, L. shimokitaense , L. tosai , L. palaple , L. murotoense , L. pallidum , L. burnsi , L. teramurai , L.

subpalpale, L. himizui , L. palpale . Group 9 (fD=2H-8(9)-8-8(6)-6(8)-..., N/N/BNN): L. sinicum , L. mirum , L. apodemi , L. yentanshanense , L.

qujingense, L. rectanguloscutum , L. sinotupaium , L. tsushimaense , L. kiangsuense , L. lushanense , L.

obscurum, L. cosmetornisi . alopeciatum group: L. alopeciatum , L. spicatum , L. horridum , L. tupaianum , L. baluense . Group 10 (fD=2H-10-6-6-4-2, fPp=N/N/BNB): L. angolaense . xishani group: L. xishani , L. neotebraci . apodevrieri group: L. orestes , L. apodevrieri . Group 11 (fD=2H-10-8-6-4-2): L. laoense , L. sandfordi , L. ralli , L. bhimtalense , L. peromysci . fletcheri group: L. luzonense , L. fletcheri . linjeromae group: L. javani , L. linjeromae . fujianense group: L. fujianense , L. tungum . Group 12 (fD=2H-10-8-8-8-…, fPp=N/N/BNN): L. alpinum , L. lawrencei . myotis group: L. myotis , L. californicum , L. avonense , L. vespertilum , L. miniopteri . Group 13 (fD=2H-10-8-8-4-4, fPp=N/N/BNB): L. yasuokai . Group 14 (fD=2H-10-8-8-(2–4)-2(0), fPp=N/N/BBB): L. megaloti . Group 15 (fD=2H-12-8-2-13-2-14-8-4-2, fPp=N/B/BBB): L. solitarium . Group 16 (fD=2H-10-11-9-6-4-2, fPp=N/N/BNN): L. mugidi . pavlovskyi group: L. fukuokai , L. tectum , L. pavlovskyi , L. rupestre . shuyui group: L. shujingi , L. shuyui , L. yunshui , L. yongshengense . binbium group: L. mitchelli , L. binbium , L. peniculatum , L. macacum . apertum group: L. derlatkoi , L. liaoji , L. smirnovi , L. auritum , L. apertum . asetulum group: L. huangdi , L. yigongense , L. insulare , L. asetulum . europaeum group: L. ningpocalli , L. europaeum , L. alanicum , L. schlugerae . irregulare group: L. rufocanum , L. hubeiense , L. noxium , L. multiplex , L. solum , L. keruleniense , L. heiense , L.

xinjiangense, L. bicoxalis , L. taiyuanense , L. irregulare , L. bayanense , L. wolandi . dux group: L. typhlomyis , L. bashuense , L. dunqingi , L. halidasys , L. kalrai , L. dux , L. toshiokai , L. megatoshiokai ,

L. paradux . Group 17 (fD=2H-10(12)-10-10(8)-6(8)-…, fPp=N/N/BNN): L. wangi , L. narayanshahi , L. pilaltum , L.

macacaphilum, L. bengbuense . miyazakii group: L. owuense , L. miyazakii . yunlingense group: L. ejingshanense , L. jinmai , L. yunlingense . magnum group: L. submagnum , L. kunshui , L. biji , L. keukenschrijveri , L. globosum , L. dooleyi , L. baoshui , L.

sixinum, L. magnum, L. huangchuanense , L. shuiqui , L. caudatum , L. shuminense , L. arctonycis , L.

xianglinense. mordax group: L. mordax , L. yunnanense . sexsetum group: L. sexsetum , L. jianzhaense . sinhgarhense group: L. subobscurum , L. discrepans , L. cebephium , L. turdicola , L. tenipilum , L. besali , L.

sinhgarhense, L. malayanum . scutellare group: L. yidun , L. dianchi , L. basoglabrose , L. scutellare . pentagonum group: L. wulanense , L. pentagonum , L. laojunshanense . abidi group: L. raropinne , L. nainae , L. mongolicum , L. dehradunense , L. baltalense , L. latum , L. dihumerale , L.

kunitzkyi, L. oblongatum , L. hirsutum , L. alaicum . angkamii group: L. zhongi , L. angkamii , L. bishanense , L. robustisetum . multisetosum group: L. multisetosum , L. subsexsetum , L. spilletti . Group 18 (fD=2H-(9–12)-8(10)-10-8-…, fPp=N/N/BNB): L. radfordi , L. minense , L. jinense , L. gemiticulum . lagone group: L. tamanta , L. lagone . parapalpale group: L. tithwalense , L. parapalpale . Group 19 (fD=4H-(10–12)-(10–12)-(10–12)-…): L. saltuosum , L. puta .

Morphometric analysis

The main objective of this analysis is to evaluate the a priori created species groups. The large number of Leptotrombidium species and the lack of qualitative diagnostic traits for most of them make a formal morphometric analysis especially important here. For example, 111 species of the genus have fPp = N/N/BNN, Pc = 3, Gn = 2, fCx = 1.1.1, fSt = 2.2, and fD = 2H-8-6-6-…, i.e., they are identical in all standard nonmetric characters and differ from each other mainly by measurements. It should be taken into account that such traits as fSc and PL/SB are really indices based on morphometrics and that details of setal shape, shape of posterior scutal margin, and other subtle distinctions have not been uniformly described across different works and, therefore, have a limited utility in the classification of the whole genus.

A bootstrapping cluster analysis shows, however, that reliable hierarchical classification of Leptotrombidium s.s. based on morphometrics is impossible. The resulted dendrogram ( Fig. 3 , Table 1) consists of a series of isolated clusters with AU p-values ≥ 0.95, but associations of these clusters are not statistically supported. Such result is not unexpected, as the set of morphometric variables included in the analysis was too small for such a large taxon. Moreover, some variables are highly correlated with each other (for example, length of legs or of the different types of idiosomal setae) and therefore are nearly redundant. Separation of some aberrant species is also evident from the dendrogram, but cannot serve for classification purposes. Thus, L. multisetosum differs from other Leptotrombidium species in the extremely numerous idiosomal setae (NDV = 276 vs. 43–210; L. kalrai with NDV = 260 was excluded from the analysis as its description has a missing value); L. insolitum , L. periosum , L. sylvestre , L. pipellae , and L. wulingshanense are characterized by very long setae and legs, but their idiosomal setae are not numerous; and L. typhlomyis , L. toshiokai , L. megatoshiokai , L. bashuense , L. dux , L. dunqingi , and L. halidasys have numerous idiosomal setae (NDV = 98–210) and wide scutum (PW = 101–114).

Thus, it is necessary to concentrate our attention on statistically supported clusters or clusters with p-values close to the threshold ( Figs. 4–6 ). For 37 clusters, the AU p-values were ≥ 0.95. Thirteen “natural” species-groups represented in the analysis by more than one species were found included completely each in one cluster although included some additional species (Table 2). Among these groups, the largest is the species-group deliense with 9 species, including synonyms ( Fig. 5 , A). Only the group longisetum , which is consisted of two species, forms its own cluster #280 ( Fig. 3 ). Seven of nine species belonging to the group akamushi ( L. delimushi , L. akamushi , L. delimushi syn. delimushi kumaoense, L. isosetosum , L. imphalum , L. imphalum syn. imphalum sabahense, and L. imphalum syn. imphalum ceylonicum) are included in one cluster with AU p-value close to the threshold ( Fig. 5 , D). The group abidi (13 species) is divided almost completely in two clusters: its five “small” species

( L. raropinne , L. nainae , L. mongolicum , L. latum , and L. raropinne syn. abidi ) are included in the cluster #212 ( Fig. 4 , G), while seven “large” species ( L. hirsutum , L. oblongatum , L. kunitzkyi , L. alaicum , L. dihumerale , L. baltalense , and L. dihumerale syn. dihumerale khurdangense) were classified to the cluster #320 ( Fig. 4 , D). More than a half of the group irregulare were placed in the cluster #239, and five of them ( L. irregulare , L. bayanense , L. bicoxalis , L. multiplex , and L. wolandi ) constitute a separate cluster with a high statistical support ( Fig. 6 , D). It is noteworthy, that the whole group dumitrescui (4 species parasitizing bats: L. orghidani , L. siligorense , L. dumitrescui , and L. myoticulum ) is included in the same cluster as two species ( L. miniopteri and L. avonense ) from the other group of bat chiggers, myotis ( Fig. 4 , F). If we include these two species into the group dumitrescui , the system can get some geographical correlation: the group dumitrescui will be composed of five European (including three Romanian) and one Indian species, while two American and one Chinese bat chiggers will remain in the group myotis .

Several other cases when two or more species from the same a priori species group belong to the same cluster can be easily obtained from the Table 2. One can conclude that at least some of the intuitively created Leptotrombidium species groups have a statistical support. The remarkable fact is the clear separation of the groups deliense and akamushi corresponding to the “Triad” of Vercammen-Grandjean and Langston (1976), which was assumed by the authors as a basis of their system. I may expect that the most obvious relations among species established in the above dendrogram will be confirmed by more detailed further investigations. On the other hand, a considerable separation of undoubtedly intraspecific forms can also be seen on the dendrogram. Thus, L. alanicum from Armenia and the sample of L. europaeum from Avlan Lake in Turkey were found included in the cluster #158, while L. europaeum from type locality belongs to the cluster #114 and all remaining samples of these two species are members of the cluster #239. The former cluster is moreover very distant from the latter ones. This fact clearly demonstrates a limitation of morphometric analysis as applied to such a large and generally monomorphic taxon as Leptotrombidium .

Species descriptions

Species group tarsale

Diagnosis. fPp = N/N/BNN; Pc = 3(2); Gn = 2; fSc: PL ≥ AM> AL; SB-PL; fCx = 1.1.1; fSt = 2.2; fD = 2H-6-6- 6-4-2 or 2H-6-2-2; DS = 11–26; VS = 20–33; NDV = 41–46; Ip = 670–1031; AW 58–81, PW 66–95, SB 26–33, ASB 24–39, PSB 11–18, SD 38–54, AP 22–38, AM 43–89, AL 35–65, PL 43–132, S 58–113, H 44–89, D min 37– 83, D max 47–99, V min 20–47, V max 42–83, pa 227–360, pm 208–310, pp 235–369. Malaysia, Laos.

Figures

FIGURE 3. Cluster analysis. Clusters with AU p-values ≥ 0.95 are shadowed, their numbers are given on the right side. AU (above) and BP (below) p-values are given (as percentages) only for the clusters not presented in figures 4–6. Species names are given selectively (see Table 1 for all names).

FIGURE 4. Fragments of the dendrogram from Fig. 1, in the top-down direction. AU p-values are given above and BP pvalues below each cluster; numbers are given for the largest clusters with AU p-values ≥ 0.95 only.

FIGURE 5. Fragments of the dendrogram from Fig. 1, in the top-down direction. See explanation to Fig. 4.

FIGURE 6. Fragments of the dendrogram from Fig. 1, in the top-down direction. See explanation to Fig. 4.