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Chiggers of the talmiensis group (Trombiculidae: Neotrombicula) in Russia and neighbouring territories: taxonomic analysis using computer methods

A.A. Stekolnikov

Parazitologiya, 30(5): 377-397 (1996) (In Russian, English summary).


The study of morphological variability in three similar chigger species is carried out. The variability in Neotrombicula talmiensis has been for the first time studied in geographical aspect on the main part of its range. Our collection in Western Caucasus supplied us with abundant material on N. carpathica and N. pilosa. It is the first finding of these two species in Russia and Caucasus. For all three species new localities and new hosts are recorded. Complex characters has been produced for the purpose of exact identification in the talmiensis group, by the linear discriminant analysis:

X1=93.25 – 0.42*AW – 0.41*AM – 0.87*Dm – 0.29*NDV + 0.38*PL,

X2=39.88 – 0.8*Dm – 0.6*NDV + 0.7*TaIII

Function X1 serve for separation of N. carpathica from N. talmiensis. If X1>0, the specimen measured belong to N. talmiensis, if X1<0 — to N. carpathica. X2 let to separate N. pilosa from N. carpathica. If X2>0, the specimen should be attributed to N. carpathica, if X2<0 — to N. pilosa.

The best sets of diagnostic characters, selected by discriminant analysis (AW, AM, Dm, NDV and PL for N. talmiensis and N. carpathica; Dm, NDV and TaIII for N. carpathica and N. pilosa), has been used to obtain the picture of relative distances between samples by monotonic multidimensional scaling.

Morphological differences, ecology and joint occurrence of the species are analysed. Some segregation of N. carpathica and N. talmiensis in the localities where the 2 species were found together, dissociated areal of N. carpathica (East Carpathians, Caucasus and Tuva) and stable morphological difference between the 2 forms induced us to raise N. carpathica to the specific rank. In the line N. talmiensis—N. carpathica—N. pilosa the requirements of humidity and temperature conditions appear to increase. Probably, the increase of setae number and length along the line may acquire ecological interpretation. This supposition is confirmed indirectly by the diminutive character of N. talmiensis from Kazakhstan and Crimea. The question, whether the species are only ecological forms, require more investigation.

Data bases, containing morphometric, collectional, bibliographical and taxonomic information on chiggers, created by means of DBMS FoxPro, information system ZOOINT and original computer programs were used in this study.

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