The species included in the genus Epiophlebia Calvert, 1903 represent an exception within Recent lineages – they do not belong to either dragonflies (Anisoptera) nor damselflies (Zygoptera). Nowadays, the genus is solely known from the Asian continent. Due to their stenoecious lifestyle, representatives of Epiophlebia are found in often very small relict populations in Nepal, Bhutan, India, Vietnam, China, North Korea, and Japan. We here present a taxonomic re-evaluation on the species status of Epiophlebia diana Carle, 2012, known from the Sichuan province in China, supplemented with a morphological character mapping on a genetic tree to highlight synapomorphies of E. diana and E. laidlawi Tillyard, 1921. We conclude that E. diana is a junior synonym of E. laidlawi. Furthermore, we discuss the Recent distribution of the group, allowing for predictions of new habitats of representatives of this group.

Anisozygoptera, Epiophlebia laidlawi, E. sinensis, E. superstes, genetic sequences, relict dragonfly, synonymy

Odonata Fabricius, 1793 are classified into the suborders Anisoptera Sélys, 1854 (dragonflies), Zygoptera Sélys, 1854 (damselflies), and the enigmatic taxon, Epiophlebia Calvert, 1903. Presently, the genus Epiophlebia is considered to be the sister-group of the Anisoptera [Anisoptera + Epiophlebia = Epiprocta Lohmann, 1996], with several extinct lineages nested in between (cf. Bechly 1996; Lohmann 1996; Rehn 2003; Fleck et al. 2003; Grimaldi and Engel 2005); the validity of Epiprocta is supported by numerous phylogenetic studies (cf. Hovmöller et al. 2002; Fleck et al. 2008; Bybee et al. 2008, 2021; Blanke et al. 2012, 2013; Misof et al. 2014; Letsch et al. 2016; Büsse et al. 2018; Kohli et al. 2021; Suarov et al. 2021). These taxa were considered to form a suborder, called ‘‘Anisozygoptera’’, which comprise mainly Jurassic fossils (Nel 1993) and the recent species of the genus Epiophlebia, until it was shown that ‘‘Anisozygoptera’’ are polyphyletic (Nel 1993; Lohmann 1996; Rehn 2003). Because the species of the genus Epiophlebia show some distinct characters of Zygoptera as well as Anisoptera (Asahina 1954; Büsse 2016), they are often considered as relict species (Asahina 1954; Davies 1992; Mahato 1993). From a morphological point of view, the genus Epiophlebia seems to represent the most ancestral character distribution of Recent Odonata (Blanke et al. 2012, 2015; Büsse et al. 2015; Büsse 2016).

Adult Epiophlebia are very conspicuous (Fig. 1), and in the field they can easily be identified by the black-yellow striped coloration (Asahina 1954) and their characteristic slow and rather uncoordinated appearing undulating flight (Rüppell and Hilfert 1993). Morphologically, the anisopterous body shape, the zygopterous shape of the wings, and the convex frons are some of the main distinguishing characteristics (Asahina 1954; Büsse 2016). The larvae of Epiophlebia also resemble dragonflies, as they use a rectal chamber for respiration, but jet propulsion, which is typical for Anisoptera (Corbet 1999), has never been observed (Tabaru 1984). Their morphological distinction is rather subtle, so they are easily mixed up with, for example, gomphids or petalurids (Asahina 1954) – as happened to Epiophlebia diana Carle, 2012. The type specimens of E. diana were collected by “Dr. David C. Graham in the mountainous regions of western Szechuan” (Needham 1930). Needham however, misidentified the larvae of Epiophlebia as Gomphidae (Carle 2012).

Figure 1. 

Epiophlebia superstes from Japan, lateral view A adult B larva.

While the ancestors of present Epiophlebia species were at their peak in the Mesozoic era and were possibly distributed over large areas on the pre-Asian continent (Carpenter 1992; Nel et al.1993), recent species have restricted ranges, often confined to small areas in Asia: Epiophlebia superstes Selys, 1889 in Japan; Epiophlebia laidlawi Tillyard, 1921 in Nepal, India, Bhutan, and Vietnam; Epiophlebia sinensis Li & Nel, 2012 in North Korea and China, and Epiophlebia diana also in China (Asahina 1954; 1963; Tani and Miyatake 1979; Büsse et al. 2012; Carle 2012; Li et al. 2012; Fleck et al. 2013; Büsse 2016) showing a characteristic disjunct distribution (Büsse et al. 2012).

Since the habitat requirements of the genus Epiophlebia seem to be very specific, the range of Recent habitats is extremely restricted. Epiophlebia species prefer cold mountain streams with temperatures of about 4 to 5 °C in winter and about 16–17 °C in summer (data published for E. superstes by Tabaru (1984)) and altitudes between 1,300 to approximately 3,000 m (data published for E. laidlawi by Brockhaus and Hartmann (2009)). This stenoecious lifestyle has restricted the genus Epiophlebia to cold habitats, like glacial refuges (De Lattin 1967; Büsse et al. 2012).

For recently diverged species, or for taxa that are described under the assumption of incipient speciation, it can be challenging to develop a morphological character set that reveals the true pattern of evolutionary history for a taxon. Further complicating matters is that there are often separate, not cross-referenced, descriptions of adults and larvae for Odonata. In the case of the genus Epiophlebia, adults and larvae are described for E. superstes and E. laidlawi, while for E. sinensis only the adults and for E. diana only the larva is known. The species status of E. diana has already been critically discussed and is doubtful (cf. Dijkstra et al. 2013; Büsse 2016). We, therefore, present a taxonomic re-evaluation of the species status of E. diana. Unfortunately, the type specimen is untraceable and seems lost (F.L. Carle, author of E. diana as well as J.J. Dombroskie of the Cornell University Insect Collection, New York, USA: personal communication, see Büsse 2016). However, a combination of morphology, phylogeny, and biogeography, described here, lays a solid basis for the designation of E. diana as junior synonym of E. laidlawi.

Here, we examined morphological data from Büsse (2016) and several other publications (i.e., Asahina 1954, 1961; Büsse et al. 2012; Carle 2012; Li et al. 2012; Dorji 2015). A matrix composed of all characters used in the past to evaluate Epiophlebia larval and adult characters is shown in Table 1; briefly this includes larval traits and adult characters related to size and colouration, features of the head, abdomen, genitalia, and appendages. The phylogeny that was used here was based on Büsse et al. (2012; fig. 2). The main justification for using Büsse’s and colleagues (2012) phylogeny is that presently there are few overlapping sequence fragments across the species of Epiophlebia. Here, we examined all available mitochondrial and nuclear gene fragments for the genus Epiophlebia from GenBank to evaluate what available data was present for the genus (Table 2). Unfortunately, to date E. superstes is the only species for which sequence data are available for a broad sampling of genes. No genetic data is available for E. diana, presumably because the describing author has misplaced the existing specimens (F.L. Carle personal communication). With such a dataset, we decided to use the phylogeny provided by Büsse et al. (2012) which is the most comprehensively sampled phylogeny for the genus currently available. In terms of character mapping, briefly, characters were traced in Mesquite (Maddison and Maddison 2016) using both the ancestral state reconstruction parsimony and likelihood functions. Consistency index values for a matrix including all traits in Table 1 were evaluated in Mesquite against a tree assuming (E. sinensis (E. superstes (E. diana, E. laidlawi))) and found to be 1.0.

Figure 2. 

Character mapping on a strict consensus tree based on Büsse et al. (2012). Synapomorphies are shown as black boxes, numbers indicate which of the characters shown in Table 1 serves as the synapomorphy.

For photography, we used specimens of E. superstes (because of availability) to depict the general habitus of the very similar Epiophlebia species. For stacked photography, a custom-made 3D-printed illumination dome system (Bäumler et al. 2020) and an Olympus OMD 10mkII digital camera (Olympus K.K., Tokyo, Japan), equipped with a Leica 45 mm macro lens (Leica Camera AG, Wetzlar, Germany) was used. All images were subsequently processed in Affinity Photo and Affinity Designer (Serif Ltd, Nottingham, United Kingdom).

We are grateful to SM Bybee and D Paulson for pushing us to write this manuscript. SB is grateful for the constant support of SN Gorb and was directly supported through the DFG grants BU3169/1-1 and 1–2. Furthermore, SB wants to thank H Lohmann for many elucidating discussions on the biogeography of Epiophlebia species. JLW is grateful for many thoughtful discussions about odonate morphology with ML May.