International Journal ofOdonatology 4 (1): 35-40,2001 © 2001 Backhuys Publishers. 35 The Orthetrum coerulescens complex in Bulgaria (Odonata: Libellulidae) Milen Marinov P.O. Box 134, BG-1000 Sofia, Bulgaria. <[email protected]> Received 17 February 1999; revised 12 September 2000; accepted 20 February 2001. Key words: Odonata, dragonfly, Orthetrum, hybridisation, taxonomy, biogeography, Bulgaria. Abstract Although there are many records of Orthetrum coerulescens in Bulgaria, the presence of the nominotypical subspecies is doubtful. A critical analysis of all specimens available revealed that they belong either to 0. c. anceps or to intermediate forms, but not to 0. c. coerulescens. The latter taxon is therefore omitted from the Bulgarian species list, bringing the number of recorded species to 66. Introduction In the dragonfly fauna of Bulgaria (Beshovski 1994) Orthetrum coerulescens (Fabricius) as well as 0. anceps (Schneider) are listed. 0. coerulescens has been reported from Bulgaria as an imago (Beshovski 1964a; 1965) and as a larva (Beshovski, 1964b; 1968). Further records of this species are given by Klapalek (1894), Petkov (1921), Nedelkov (1923), and Donath (1987), but without stating whether they referred to larvae or adults. 0. anceps has been recorded from Bulgaria by Mauersberger (1985, 1990, 1994) and Beutler (1987). In the light of new taxonomic considerations 0. coerulescens and 0. anceps are considered to be closely related taxa within the so-called coerulescens complex. Mauersberger (1994) has published a thorough revision of both taxa. He shows that coerulescens and anceps are conspecific, but well differentiated at the subspecies level. He also demonstrates on basis of the morphology of the lamina anterior that there is a broad transition zone with intermediate forms where the ranges of coerulescens and anceps overlap. Klingenberg & Martens (1995) have also treated the taxonomic relationship within the 0. coerulescens complex. They describe an intermediate form recorded in southern Spain. The Balkans are known as the eastern zone where the ranges of both taxa overlap (Bartenef 1930). It can therefore be expected that intermediate forms will be found in Bulgaria too. If we accept the phenotype 4, as defined by Mauersberger (1994) and reported by him from Bulgaria, as intermediate between coerulescens and anceps, this is indeed the first published confirmation of the presence of intermediate forms in this country. 36 Many other adult specimens were recently analysed by me, and the results are given here. The present paper summarizes the information about the occurrence of the 0. coerulescens complex in Bulgaria. Material and methods A total of 61 male specimens of the Orthetrum coerulescens complex available at the Institute of Zoology; National Museum of Natural History; Biological Department of the Sofia University and Forestry University, Sofia, and in the author's collection were checked. The material of Klapalek (1894), Nedelkov (1923), Beshovski (1964a, 1965) and Donath (1987) was not available for re-examination. As currently no reliable feature for larval determination is available (Gerken & Sternberg 1999 vs Butler 1992, 1993), Beshovski's (1964b; 1968) larval material is not included in this study either. The material is deposited in the author's collection (no. 1-17), in the Institute of Zoology (no. 18-34), in the Forestry Institute (no. 35), in the Biological Department of Sofia University (no. 36-58), and in the National Museum of Natural History (no. 59-61). I reviewed the literature concerning species distribution within the current Bulgarian borders and compared it with available material and with the description of the five phenological types given by Mauersberger (1994). For differentiation between both taxa, I used the shape of the lamina anterior in the male as the key feature (Mauersberger 1994; Klingenberg & Martens 1995). Each specimen examined is shown here as an individual drawing of its lamina anterior. An UTM-grid map was used to represent the distribution of the different phenotypes in Bulgaria. Results All specimens listed by Petkov (1921) as Orthetrum coerulescens turned out to be 0. brunneum (Fonscolombe), and were eliminated from the analysis. In the others, the structure of the lamina anterior showed a tendency towards an upright projection in its upper part. Its apex was never swollen, but pointed and turned upwards (sometime slightly backwards), i.e. it invariably showed the triangular form typical of 0. anceps to at least a certain degree. A separation between typical anceps and intermediate forms was necessarily somewhat arbitrary because the shape of the lamina varied significantly among the individuals checked. Those individuals with a wide lamina anterior, slightly rounded in its very apical part (Fig. 1), were identified as intermediate form. I found 22 such specimens. The phenotype 1 of nominotypical 0. c. coerulescens (as described by Mauersberger 1994), was never confirmed. Intermediate forms occur throughout the country (Table 1, Fig. 2). 37 (\(\(\(\f\(\(\1\f\f\ 2 3 4 5 6 1 a 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 (\(\1\f\(\(\\\(\.,~~ 31 32 33 34 35 36 37 31 39 40 (\ (( (\(\ (\J\ \\ t\ (\ ~ ~ 51 52 53 54 55 56 57 58 59 60 61 Figure I. Shape of the lamina anterior in 61 Bulgarian males of the Orthetrum coerulescens complex, lateral view. Discussion Much material collected in and published from Bulgaria before the 1980s was identified as 0. coerulescens or 0. brunneum instead of 0. anceps. This is understandable, knowing that even one of the syntypes of Libellula anceps Schneider, 1845, is in fact 0. brunneum (Schneider 1985). 38 -r-- Figure 2. Distribution map of the Orthetrum coerulescens complex in Bulgaria. t - typical anceps form; t -intermediate form; e -both forms together. My results are in line with Seidenbusch's (1997) suggestion about an "overlapping of 0. coerulescens along the northern Mediterranean coast and the Black Sea coast ..." . They also conform with the distribution scheme of Dumont (1977) and Mauersberger (1994) for 0. anceps. There appears to be no occurrence of typical 0. c. coerulescens in Bulgaria: only typical 0. c. anceps and intermediate forms occur in many different sites across the country (Fig. 2). The more abundant records of the latter from the Black Sea coast simply reflect the fact that more material was available from that area. The whole of Bulgaria is therefore part of the hybrid zone. This is not surprising, taking into account the geographical situation of the country in a faunal transition area. This hybrid zone is possibly maintained by immigration of the two typical forms (phenotypes 1 and 5), which occupy its western and eastern border areas (Mauersberger 1994). In view of this massive hybridisation, and the fact that subspecies by definition replace each other in space, I agree with the assumption that a subspecific rank is more appropriate for the taxon anceps than a full species rank. Undoubtedly 0. c. anceps is well established in Bulgaria. This leads to the conclusion that 0. coerulescens sensu stricto should be eliminated from the Bulgarian Odonata species check-list. Thus a total of 66 species has been reported so far for the country. 39 Table I. Collection data, sample sites and phenotype of Bulgarian males of the Orthetrum coerulescens complex. Each individual number refers to the numbers in Fig. I. no. date sample site phenotype 1-3 18.07.1994 Varna Botanical garden intermediate 4 anceps 5 21.05.1994 Kardjali intermediate 6-9 28.07.1997 Rupite anceps 10 04.08.1997 2 km W of Elchovo anceps 11 31.08.1994 Srebarna intermediate 12-13 17.06.1995 Pomorie lake - canal intermediate 14-15 17.06.1995 Pomorie lake - canal anceps 16 17.08.1997 Shabla - tuzlata anceps 17 15.07.1996 Vaya fish farms anceps 18-20 27.07.1973 Kulata anceps 21 27.07.1973 Kulata intermediate 22 12.06.1985 Rupite anceps 23 18.06.1975 Breznitza anceps 24 11.07.1986 Kneja anceps 25-28 06.07.1988 Sandanski - Liljanovo anceps 29 07.07.1988 Sandanski - Liljanovo intermediate 30 08.08.1986 Bregovo intermediate 31-32 01.07.1987 Passarel anceps 33 12.08.1987 Varna intermediate 34 09.07.1987 Zlataritza intermediate 35 05.08.1997 NW vulcanic hill Kojuch intermediate 36-49 15.-25.07.1998 Varna Botanical garden anceps 50-58 15.-25.07.1998 Varna Botanical garden intermediate 59 05.08.1918 Koprivstitza anceps 60 12.06.1938 Sandanski anceps 61 19.05.1917 Sandanski anceps Acknowledgements I thankS. Beshkov, Prof. V. Beshovski, N. Simov and N. Kodjabashev who cooperated and gave me free access to the material studied. 40 References Bartenef, A., 1930. Sind Orthetrum anceps Schn. und Orthetrum coerulescens Fabr. (Odonata, Libellulidae) selbstandige Arten? Zoologischer Anzeiger 91: 61-71. Beshovski, V., 1964a. Odonata from the Bulgarian Black Sea coast. In Bulgarian; English title and summary. Bulletin de l'Institut de Zoologie et Musee 15: 115-129. Beshovski, V., 1964b. Odonata from the South Bulgaria. In Bulgarian; English title and summary. Bulletin de l'Institut de Zoologie et Musee 17: 109-124. Beshovski, V., 1965. Odonata from the Bulgarian riverside of the Danube and from certain water reservoirs in Northern Bulgaria. In Bulgarian; English title and summary. Bulletin de l'Institut de Zoologie et Musee 18: 159-168. Beshovski, V., 1968. Odonata-Larven der stehenden Gewasser in Bulgarien. In Bulgarian; German title and summary. Bulletin de l'Institut de Zoologie et Musee 26: 5-27. Beutler, H., 1987. Libellen aus dem Einzugsgebiet der Struma in Bulgarisch-Mazedonien (Odonata). Opuscula Zoologica Fluminensia 16: 1-8. Butler, S.G., 1992. The larva of Orthetrum anceps (Schneider, 1845) (Odonata: Libellulidae). Opuscula Zoologica Fluminensia 100: 1-6. Butler, S.G., 1993. Key to the larvae of European Orthetrum Newman (Anisoptera: Libellulidae). Odonatologica 22: 191-196. Donath, H., 1987. Odonaten von der siidbulgarischen Schwarzmeerkiiste. Notulae Odonatologicae 2: 157-159. Dumont, H., 1977. A review of the dragonfly fauna of Turkey and adjacent Mediterranean islands (Insecta: Odonata). Bulletin et Annales de Ia Societe Royale Entomologique de Belgique 113: 119-171. Gerken, B. & K. Sternberg, 1999. Die Exuvien europaischer Libellen - The exuviae of European dragonflies. Arnika & Eisvogel, Hoxter & Jena. Klapalek, F., 1894. (Studies on neuropteran and orthopteran insects in Bulgaria]. In Bulgarian. Sbornik Narodni Umotvoreniya, Nauka i Knijnina 11: 451-471. Klingenberg, K. & A. Martens, 1995. Records of an intermediate form between Orthetrum coerulescens (Fabricius) and 0. anceps (Schneider) in southern Spain (Anisoptera: Libellulidae). Advances in Odonatology, Supplement 1: 117-121. Mauersberger, R., 1985. Libellen (Odonata) von der nordbulgarischen Schwarzmeerkiiste. Entomologische Nachrichten und Berichte 29: 119-207. Mauersberger, R., 1990. Libellenbeobachtungen aus dem bulgarischen Balkan-Gebirge (Stara Planina). Libellula 9: 43-59. Mauersberger, R., 1994. Zur wirklichen Verbreitung von Orthetrum coerulescens (Fabricius) und 0. anceps (Selys) = 0. anceps (Schneider) in Europa und die Konsequenzen fiir deren taxonomischen Rang (Odonata, Libellulidae). Deutsche Entomologische Zeitschrift, Neue Folge 41: 235-256. Nedelkov, N., 1923. [VIIJ'h contribution to the studies on the Bulgarian entomological fauna.( In Bulgarian. Spisanie na Balgaskata Akademiya na Naukite 25: 45-52. 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