A new genus and species of Keroplatidae—Kibaleana apicospinosa gen. & sp. n.—is described from Kibale National Park in Uganda. The new genus is preliminarily placed to the tribe Orfeliini and it is characterized by a unique combination of diagnostic characters: wing vein R₄ missing, vein A₁ shortened, palpi short but five-segmented, fore tibia with apical comb of setae, absence of apical comb of setae on mid and hind tibiae, and male terminalia with relatively long and narrow gonostyli, each bearing a subapical tooth. The sequences of four fragments of mitochondrial DNA (COI, CytB, 12S, 16S) are provided along with a brief discussion about taxonomic position of the new genus.

Bibionomorpha , Sciaroidea , Orfeliini , fungus gnats, new species, taxonomy, phylogeny, Africa, mitochondrial DNA, DNA barcoding

Considerable attention has been devoted to the systematics and phylogeny of bibionomorph flies (Insecta: Diptera) during the last decade including the use of morphological as well as molecular characters (e.g. Amorim and Rindal 2007, Ševčík et al. 2016). Despite a serious discussion about composition of taxa above family level and disagreement in placing of the so-called Sciaroideaincertae sedis group (op. cit., Jaschhof 2011), the diagnosis and composition of most families, including Keroplatidae, has remained stable (e.g. Søli et al. 2000, Evenhuis 2006a, Vockeroth 2009). With four subfamilies—viz. Arachnocampinae, Macrocerinae, Keroplatinae and Sciarokeroplatinae—Keroplatidae are known to include almost one thousand species worldwide (Evenhuis 2006a). However, in spite of a profound study of Keroplatidae by the late Loïc Matile (1938–2000; Matile 1990), there is still a huge gap in a complete picture of understanding their diversity and phylogeny, especially as it concerns the tropics.

In the Afrotropical region, only one fourth of the estimated Keroplatidae diversity has so far been described (Kirk-Spriggs and Stuckenberg 2009). The rather fragmentary knowledge is reflected, inter alia, by an exceptionally high number of described monotypic keroplatid genera, viz. 33, including ten of them from the Afrotropical region. The nominal and the largest subfamily Keroplatinae, including worldwide about 70% of the described keroplatid species, is divided into two tribes: Keroplatini and Orfeliini (Evenhuis 2006a). Altogether, 136 species belonging to 24 genera of Keroplatinae are recorded from the Afrotropical region, with 15 and 121 species (8 and 16 genera) in the tribes Keroplatini and Orfeliini, respectively (Evenhuis 2006a, Ševčík et al. 2015, Blagoderov and Ševčík 2017).

Within the family limits, Keroplatinae are characterized mainly by the absence of a cerebral sclerite and the presence of a tibial comb on mid or/and hind tibia, while the number of segments of maxillary palpus and the outline of antennal segments differ between Keroplatini and Orfeliini (Matile 1990, Ševčík et al. 2015). There is no exhaustive generic key published to cover all Keroplatinae. An updated key to World Keroplatini genera has been recently published by Ševčík et al. (2015) while only regional keys are available for Orfeliini (e.g. Søli et al. 2000, Vockeroth 2009, Blagoderov and Ševčík 2017).

The current study was prompted by the discovery a series of strange looking keroplatid specimens in Malaise trap samples collected in Uganda, belonging to a single undescribed species. As it has not been possible to place it to any known genus, we decided to establish a new genus for this peculiar species.

All the material has been collected by a Malaise trap operated in Kibale NP in southern Uganda (Figs 1, 2, see also Kurina 2012). The material was collected initially into ethyl alcohol and sorted into selected groups of insects including that of fungus gnats in laboratory conditions under a stereomicroscope. The material is now stored at a temperature of -20°C, allowing appropriate study in the future. For preparing permanent slides for detailed morphological study of the new species, the wings were detached and mounted under a separate coverslip in Euparal medium. The rest of the body including terminalia was macerated in warm concentrated potassium hydroxide (KOH), thereafter washed in distilled water and dehydrated in stages of increasing concentration of ethyl alcohol. Thereafter, parts of the body were mounted separately between two coverslips in Euparal medium and attached to the same slide using stripes of adhesive tape (see also Hippa and Kurina 2012). The slide-mounting was made under a Leica S8APO stereomicroscope. The photos of general habitus, head, thorax and terminalia were combined using the software LAS V.4.1.0. from multiple gradually focused images taken by a Leica DFC 450 camera attached to a Leica 205C stereomicroscope or Leica DM 6000 B compound microscope, respectively (see also Kurina et al. 2015). Adobe Photoshop CS5 was used for editing the figures and compiling the plates. The morphological terminology follows that of Matile (1990) and Søli et al. (2000).

Figure 1. 

The sampling locality of Kibaleana apicospinosa sp. n. in southern Uganda.

Figure 2. 

Malaise trapping at Kibale National Park in southern Uganda (Photo by O. Kurina).

The material is deposited in the following collections: IZBE – Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences (formerly Institute of Zoology and Botany), Tartu, Estonia; JSL-UOC – the reference collection of the Ševčík Lab, University of Ostrava, Czech Republic.

Molecular techniques used in this study were principally described in Ševčík et al. (2016). The mitochondrial DNA sequences of COI (barcode region, 658 bp), CytB (433 bp), 12S (356 bp), and 16S (341 bp) regions are deposited in the GenBank database.

If we use the key to the genera of Keroplatidae in the Manual of Afrotropical Diptera (Blagoderov & Ševčík 2017), the new genus would run either to Macrocerinae, but it has no distinct cerebral sclerite and also its flagellomeres are not so much elongated, or to the Keroplatinae tribe Orfeliini, if we ignore the absence of apical combs on mid and hind tibia. The overall habitus of Kibaleana gen. n. suggests that it should be assigned rather to the tribe Orfeliini, at least tentatively. Most genera of Macrocerinae (except Micromacrocera Papp, 2008 and Robsonomyia Matile & Vockeroth, 1980) also have the basal part of M distinct or traceable, which is not the case of Kibaleana gen. n.

On the other hand, according to its wing venation, the new genus falls into the distinct group of genera in the tribe Keroplatini, with vein R₄ absent and A₁ reduced. This group currently includes the following mainly tropical genera: Asiokeroplatus Ševčík, Mantič & Blagoderov, 2015, Chetoneura Colless, 1962, Microkeroplatus Ševčík & Papp, 2009 and Pseudochetoneura Ševčík, 2012. However, all these four genera have reduced mouthparts and more or less shortened, flattened or otherwise modified antennae (cf. Ševčík 2012, Ševčík and Papp 2009, Ševčík et al. 2015), allowing them to be classified into the tribe Keroplatini. The number of palpal segments in Kibaleana gen. n. is five but actually only the apical three are clearly discernible (Fig. 4) while the proximal two are very small, so that they may well have been overlooked in the case of other genera. The male terminalia of Kibaleana gen. n. are quite different from both Asiokeroplatus and Pseudochetoneura, as well as from the other genera of Keroplatini, but also from most Macrocerinae.

The wing venation including absence of vein R₄, arrangement of setae on the scutum and the general facies puts the new genus close to Trigemma Hardy, 1960 – an Orfeliini genus, known by two endemic species from the Hawaiian Islands (Hardy 1960, Evenhuis 2006b). Both genera have each tibia with one apical spur: Trigemma has the spur on fore tibia small but distinct while the spurs on the mid and hind tibiae are very large (Evenhuis pers. comm.), while the spurs’ length of Kibaleana gen. n. is at least 1.4 times of the apical width of respective tibia (see Fig. 6). However, the new genus has only fore tibia with an apical comb of setae but in Trigemma, there is a small apical comb on the apex of the fore tibia and very dark and conspicuous combs on the mid and hid tibiae (Evenhuis pers. comm.). In contrast to only three clearly discernible palpal segment in Kibaleana gen. n., the species of Trigemma have four well visible segments with the apical segment very long and thin, pencil like, and length of the remaining segments about 1.5–2 times of their width (Evenhuis pers. comm.). In addition, the new genus has the anepisternum non-setose (with setae in Trigemma) and medial flagellar segments 1.5 times as long as wide (about rectangular in Trigemma). Male terminalia of both genera correspond to the simple ground plan of Keroplatidae but the gonostylus of Kibaleana gen. n. is prolonged with a subapical tooth (more wide and with a single or two pronglike projection apically in Trigemma) and tergite IX quadrangular (prolongedly ovoid in Trigemma).

The problems related to the placement of the new genus among the subfamilies and tribes within Keroplatidae represent a further confirmation of the opinion expressed by Ševčík et al. (2015), that the traditional delimitation of the tribes Keroplatini and Orfeliini, as well as of many other supraspecific keroplatid taxa, is getting more and more questionable and requires further study, especially by molecular methods.

Molecular phylogeny of the families Keroplatidae and Lygistorrhinidae based on multiple nuclear and mitochondrial markers will be presented elsewhere (Mantič et al. in prep.) and it will definitely shed more light on the phylogenetic position of not only Kibaleana gen. n. but also of many other enigmatic taxa.

The first author (OK) was funded by institutional research funding (IUT21-1) of the Estonian Ministry of Education and Research. Prof. Toomas Tammaru (Tartu, Estonia) and Dr. Freerk Molleman (Thiruvananthapuram, India) are acknowledged for organizing the collecting expedition to Uganda in February 2010. This study was partly supported by the “National Feasibility Program I”, project LO1208, of Ministry of Education, Youth and Sports of the Czech Republic and by the internal grants for specific research of the University of Ostrava (No. SGS28/PřF/2016 and SGS19/PřF/2017). We are very grateful to Dr. Neal Evenhuis (Honolulu, Hawaii) for invaluable comments on the Trigemma species and to Peter Chandler (Melksham, Great Britain) for linguistic corrections. Dr. Peter Kerr (Sacramento, USA) and Dr. Vladimir Blagoderov (London, Great Britain) are thanked for their comments and suggestions on the manuscript.