Brachythemis Leucosticta", Africa's Most Familiar Dragonfly, Consists of Two Species (Odonata: Libellulidae)
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------------PhilipS. Corbet memorial issue------------ Kindred spirits: "Brachythemis leucosticta", Africa's most familiar dragonfly, consists of two species (Odonata: Libellulidae) Klaas-Douwe B. Dijkstra 1 & Nataly Matushkina2 1 National Museum of Natural History Natural is, P.O. Box 9517, 2300 RA Lei den, The Netherlands. <dijkstra©nnm.nl> 2Department of Zoology, Biological Faculty, Kiev National University, vul. Volodymirs'ka, 64, Kyiv 01033, Ukraine. <odonataly©gmail.com> Key words: Odonata, dragonfly, Anisoptera, Brachythemis, taxonomy, systematics, Africa. ABSTRACT Brachythemis leucosticta was found to include two morphotypes, which we con sider to represent separate species. Males are separable by the ventral structure of S8 and often differ in the colour of the venation and genital lobe. Females are as yet not reliably distinguishable. Examination of 1,154 males demonstrated that both species are widespread: the true B. leucosticta occupies most of tropical Africa and Mada gascar, while B. impartita (comb. nov.; corrected spelling- neotype d: Ngaoun daba Ranch, Cameroon; in RMNH) ranges north and south of the Sahara, and extends into Eurasia. The two overlap from The Gambia to Ethiopia and south at least to Lake Victoria. The presence of wing bands was scored for all examined males and 970 females. Banded females are frequent in sub-Saharan populations of B. im partita, but virtually absent in B. leucosticta and northern B. impartita. B. impartita males become banded shortly after emergence, but B. leucosticta becomes so more gradually. Larval morphology and ecology require further study, but some ecologi cal and seasonal segregation may occur in areas of overlap. Of two larval forms de scribed from Uganda, the 'mud form' may pertain to B. leucosticta, and the 'sand form' to B. impartita. INTRODUCTION Brachythemis Brauer, 1868 is a genus of stocky libellulids with conspicuously or ange or brown marked wings. The five species currently included inhabit the warm regions of Africa and Eurasia, although Deielia phaon (Selys, 1883) from E Asia probably belongs to it too (Ris 1911b; Dijkstra 2003; Pilgrim & von Dahlen 2008). B. leucosticta (Burmeister, 1839) is one of Africa's most familiar dragonflies. Mature males are easily recognised by their dark bodies and banded wings (Fig. 1). B.leuco sticta extends into southern Europe, the Near East, and Madagascar, and can be abundant around larger water bodies, especially those with exposed banks with International journal of Odonatology 12 (2) 2009:237-256 237 -------------Dijkstra & Matushkina -------------- sparse vegetation. Adults perch on or close to the ground, flying low over it, and may follow large animals- including humans -to prey on disturbed insects. Trailing big game on bare-trodden riverbanks, it may be the ultimate 'African' odonate. Indeed its abundance, behaviour, and striking appearance make it the most noted species among newcomers to the continent and the most ignored by those more 'experienced'. Philip Corbet (1999: 366) devoted two pages of his handbook and a paper with Peter Miller (Corbet & Miller 1991) to the 'accompanying behaviour' of B. leuco sticta. Miller (1988) previously investigated its reproduction, while Corbet (1957, 1959) described the larva and found it the dominant adult odonate eaten by Ugan dan Nile Crocodiles. The latter publications are from Corbet's time on Lake Victo ria in Uganda (1954-1962). Here, eager for specimens, he awarded one shilling for every dragonfly caught. However, 'only' lots of B. leucosticta were delivered and he quickly ended the scheme. Nonetheless, it now appears that what seemed endless se ries of the lake's most ubiquitous and identifiable dragonfly, probably consisted of two superficially identical taxa (see Parr 2009). Examining two syntopic Senegalese males, identified as B. leucosticta by the first author from photographs, the second author noted differences in the ventral struc ture of 58 and cerci. After ruling out lookalike Parazyxomma flavicans (Martin, 1908) (see Dijkstra 2003), a preliminary investigation showed that two types of males were distinguishable and widespread, occurring together locally. This paper de tails their characters, taxonomy, and distribution. It is dedicated to two kindred spir its, now both sadly departed, with a special relationship with Odonata, Africa, and B. leucosticta, Philip Corbet (1929-2008) and Peter Miller (1931-1996). Corbet & Miller (1991) were "indebted to the large African mammals which, by persistently moving slowly through grassland, served as targets for accompanying B. leucos ticta." As giants of odonatology they too progressed persistently, moving our sci ence forward and inspiring those who flocked around them. Indeed, over thirty odonatologists contributed to this paper. Figure 1 : Brachythemis impartita, a species that was confused with B. leucosticta for 1 70 years. This male was photographed in Burkina Faso, where both species may occur together. Photo by Olivier Esnault. 238 International Journal of Odonatology 12 (2) 2009: 237-256 ----------Two species of "Brachythemis leucosticta"---------- MATERIAL AND METHODS Distinguishing characters were determined from a series from Tanzania including both assumed taxa (61 males, 37 females, Mwanza, 1983-1986, leg. P.C. Gouds waard; in RMNH) and tested with material from elsewhere. With diagnoses estab lished, numerous collections and colleagues (see Acknowledgments) were consulted to determine extents of occurrence and variation of characters, including the pres ence of wing bands in both sexes. The collections of MRAC, MZUF, RMNH, SMNS, and ZMUH were completely revised, as was the Consiglio material from Ethiopia in MZUL (see Pinhey 1982). Altogether data of 1,154 males and 970 females were ob tained. A few records were verified from photographs. Two syntopic males from Senegal (see Table 2) were investigated more closely with light and scanning electronic microscopy. Animals were fixed and stored in 70% ethanol. External morphology was examined under a stereo-microscope to find dis tinguishing characters. Afterwards three basal and three terminal segments of the abdomen were macerated in 10% KOH, vesicae spermalis were extracted, and all cu ticular parts were examined in glycerine under a stereo-microscope. For SEM study these parts of the abdomen were washed in distilled water, dehydrated in a graded ethanol series and in acetone, critical point dried (OM CPO 7501), sputtered with gold-palladium (OM-SC7640), and examined with a Zeiss EV0-50 SEM. Repro ductive structures were compared following Miller (1982, 1988). Abbreviations for collections: ISNB - lnstitut Royal des Sciences Naturelles de Belgique, Brussels, Belgium MLUH- Wissenschaftsbereich Zoologie, Martin-Luther-Universitat, Halle, Germany MRAC - Musee Royal de l' Afrique Centrale; Tervuren, Belgium MZUF - Museo Zoologico "La Specola", Firenze, Italy MZPW - Museum of the Institute of Zoology, Polish Academy of Science, Warszawa, Poland MZUL - Museo di Zoologia dell'Universita "La Sapienza", Rome, Italy RMNH- Nationaal Natuurhistorisch Museum Naturalis, Leiden, The Netherlands SMNS - Staatliches Museum fur Naturkunde, Stuttgart, Germany ZMHB - Museum fur Naturkunde der Humboldt-Universitat, Berlin, Germany ZMUH- Zoologisches lnstitut und Zoologisches Museum der Universitat von Hamburg, Germany. TAXONOMY Males could be unambiguously assigned to two morphotypes (Table 1). Only one male type was found at most localities, with the first mainly in the northern half of Africa and adjacent Eurasia, and the second mainly in the south and Madagascar (Figs 2, 3). As no intermediates were found among 1,154 males examined across a huge geographic and environmental range, and also because the two occurred to gether at the same place and time of year (Table 2) we considered that the observed morphotypes represented two separate species. International Journal of Odonatology 12 (2) 2009: 237-256 239 -------------Dijkstra & Matushkina -------------- Table 1. Differences between the two species treated here. *similar but less prominent on 57; ** records from Angola, Central African Republic, Congo-Brazzaville, Equatorial Guinea (Bioko), Togo, and Yemen were not verified Character Brachythemis impartita Brachythemis leucosticta Male venation, Anterior and posterior borders of Borders of Pt dark, as are veins dorsal view (Fig. 7) Pt proximally pale, as are veins posterior to it and in costal and posterior to Pt; veins in costal discoidal fields, thus contrasting and discoidal fields often pale, with pale subcostal veins concolorous with subcostal veins Cells in Hw discoidal Average 89.5 (range 67-121 ), Average 76.4 (range 63-86), field (Fig. 6) 80% with 75-110 87% with 70-85 Wing bands in males: Always present Absent when teneral in females: Frequent in many populations, Very infrequent and probably but virtually absent in N of range most often absent Hamular hook (Fig. 9a) Hook longer, antero-external Hook shorter, antero-external and antero-external border of pad squarely rounded border of pad evenly rounded border of its basal pad in ventral view (Fig. 9b) Genital lobe Often largely pale, even in Always largely dark, even in darker males paler males Male ventral portion 2.4-2.8 times as long as wide 1.8-2.3 times as long as wide of tergite 58 (Fig. 8a) Male ventral carinae Straight, at most slightly kinked, Medially with a kink or lobe 58* (Fig. 8a) with few dispersed denticles marked by dense denticles Male epiproct (Fig. 8c) Usually