Proc. VII Intern. Symp. on Zygaenidae, Innsbruck 2000, in print

 

Variation of Zygaena brizae (ESPER, 1800) in Georgia (Zygaenidae, Zygaeninae)

Günter Buntebarth, Ampferweg 10, D-38678 Clausthal-Zellerfeld/Germany

Abstract

Two subspecies ofZygaena brizae can be distinguished in Georgia, i.e. s subsp. tbilisicaand subsp. araratensis. They are separated not only geographically but also in their flight period and habitus, however, in another way than reported in the literature. The male genitals also demonstrate constant differences in their structure. A zone of overlapping seems to exist: on the southern slopes of the Caucasus a site was found where both subspecies might be sympatric. Because the phenotypes vary so much in their coloration, individual populations could well be described as new subspecies.
According to the recent revision of the Zygaeninae (Hofmann & Tremewan, 1996), two subspecies of Zygaena brizae are recognized in Georgia, viz., subsp. araratensis (REISS, 1935) in western Georgia and subsp. tbilisica (REISS & REISS, 1973) in the vicinity of the capital Tbilisi. The author has collected several dozen of specimens at eight sites: on the southern slopes of the Caucasus, in the Adshara Mts, southwest of Achalziche, in the Gombori Mts and within a radius of 50km of Tbilisi, at elevations of 500-2000m (Fig. 1). The eastern specimens were collected during 5 seasons in 1991 to 1999, the Caucasian specimens in 1991 and 1993 and the specimens in the western part of Georgia in 1999 and 2000. The original descriptions of the above-mentioned subspecies do not agree well with this material. For example, they cannot be distinguished by features such as length and breadth of the forewing streaks and the breadth of the black hindwing border, because they exhibit extensive variation and individual specimens may differ from the statistical mean habitus. Therefore, the definition of subspecies cannot be varified. 

Fig. 1: Map of Georgia which indicates the locations at which Zygaena brizae has been found

 
 



 
 

Fig. 2: Zygaena brizae - 3 columns left: subsp. araratensis, - 3 columns right: subsp. tbilisica 


 

The eastern region of Georgia is exposed to continental climate. In the Tbilisi region, the summer is hot, long and dry, but in the Gombori Mts, east of Tbilisi, the climate is a high mountainous one with a long and cold winter and a short summer. Even the local climate is different, the populations which were found at both sites are, without exception, normally thinly scaled. In spite of the different local climate, the variation of its feature with the altitude may be small. No objective difference can be realized. This subspecies occurs from May to June and it is most abundant at the beginning of June as Fig.3b demonstrates. As usually, the males fly somewhat earlier than the females. The size varies from 27 to 30mm (Fig. 3a) and only a few specimens are smaller. No preference exists within this interval. 

The second subspecies Z. brizae araratensis appears to be confined to the higher regions of western Georgia. The sites are located in the Raja region which is on the southern slopes of the Caucasus, in the Adshara Mts at elevations of 1700-2000m and southeast of Achalziche at an altitude of 1500m.

The region of Achalziche is located in the transition zone between maritime and continental climate. The winter is long and cold and the summer is short, especially at the high altitudes. 

Whereas the eastern specimens are thinly scaled and appear pale, are the western ones intensively coloured. The wings are densely scaled, without exception. Near Achalziche, only a few specimens have been found. They coincide with those which were collected near Kars/Turkey. They fly in July and they are a little smaller than the animals at Abbastumani in the Adshara Mts. Abbastumani is approximately 30km distant, but the local climate is different and the altitude is 300m higher at Abbastumani. Between both areas is a wide geological depression which separates the sites. Abbastumani is a mountainous area which is relatively wet compared to Achalziche which his very dry. At both sites, subsp. araratensis flies in July and is most abundant middle of July (Fig. 4b). It is known from the literature that they fly from end of June until beginning of August (Holik & Sheljuzhko, 1955). In comparison to the subsp. tbilisica, the main occurrence is 6 weeks later which cannot be understood as a local influence. The histogramme of the size of subsp. araratensis (Fig. 4a) also differs from that one of subsp. tbilisica. Many subsp. araratensis are small whereas many subsp. tbilisica are large, esp. the females.
 
 



 
 

Fig. 3:Zygaena  brizae tbilisica - a) distribution of the size - upper part of the column: females, lower part of the column: males, - b) flight period of females (upper part of the column) and males (lower part of the column).


 
 

Whereas the size of subsp. tbilisica equally varies from 27 to 30mm, exhibits the subsp. araratensis a typical Gaussian distribution curve with a maximum at 28mm which coincides with the most common size of the males. Its scale varies from 24 to 31mm. However, most of the females are smaller, i.e. 26mm. 

On the southern slopes of the Caucasus, Z. brizae was rare at the investigated site. Only one male was found on 17/18th June which can be considered as a dark specimen of subsp. tbilisica or as a light one of subsp. araratensis and another one was caught on 7th-10th July which is more pale.



 
 

Fig. 4:Zygaena brizae araratensis - a) distribution of the size, upper part of the column: females, lower part of the column: males, - b) flight period of females (upper part of the column) and males (lower part of the column).


 
 

A further subdivision is acceptable among the specimens of the subsp. araratensis (Fig. 2). Approximately 25% of the specimens of Abbastumani have a concentration of red pigment around the disco-cellular neuration of the forewings while in the hind wings it appears as intensive red spots on the red background. Because of the bright coloration and the densely scaled wings, it could well be described as a new subspecies. However, the recent efforts are supported to reduce the number of unnecessary subspecies. 

It is somewhat suspicious that one kind flies throughout the summer, i.e. from end of May until the beginning of August. Even both subspecies exhibit constant differences in their phenotypes and flight season, they are considered as one kind. 

Besides the feature, differences may also be realized in the structure of genitals. An inspection of the uncus and lamina dorsalis may help to contribute to a solution of this problem (Fig. 5). The central European brizae as well as the subsp. tbilisica are identical according to 7 males of the subsp. tbilisica. The base of the cornuti which is connected to the tegumen is more or less smooth at the brizae specimens and the tip of the cornuti is like a needle. 



 

Fig. 5: Uncus ofZygaena brizae - left column: subsp. tbilisica

central column: subsp. araratensis; right column: lamina dorsalis of subsp. tbilisica

(upper three figure) and of subsp. araratensis (lower figure)


 

On the other hand, the same base of subsp. araratensis has a distinct morphology as 4 males exhibit. The same difference is recognized at the 2 specimens which are collected in the Caucasus in June, resp. in July. The lamina dorsalis is small at both groups and at the few figures, no distinctive difference can be realized.

In summarizing the analysis, it can be stated that a process of separation is going on which is strongly supported by the specimens which are collected at the same site in the southern Caucasus and which represent both subspecies in their phenotype, flight time and genitals. A further indication of the evolutionary process of the subsp. araratensis is given in the literature, where several additional species and subspecies of this group are described (Holik & Sheljuzhko, 1955) and additionally, a new attribute is described in this text.

References

Hofmann, A. & Tremewan, W.G. 1996. A systematic Catalogue of the Zygaeninae (Lepidoptera: Zygaenidae) 251pp. Colchester.

Holik, O. & SheljuzhkoL. 1955. Über die Zygaenen-Fauna Osteuropas, Kleinasiens, Irans, Zentralasiens und Sibiriens, Mitt. Münch. Ent. Ges. 44/45, 82-95.

Reiss, H. 1935. Neues über asiatische Zygaenen, im besonderen die Zygaenen-Fauna von Ak-Schehir in Kleinasien. Int. Ent. Z.29 : 121-124, 139-142, 149-151, 159-161, 186-192, 207-209, 221-223, 229-232, pl., figs.

Reiss, H. & Reiss, G. 1973. On Zygaena (Mesembrynus) adsharica Reiss (Lep., Zygaenidae): description of two new races. Entomologist?s Rec. J. Var. 85: 89-92, pl.6, figs.1-8.