The genus Dettopsomyia Lamb, 1914 (Diptera, Drosophilidae) from southern China

Abstract The genus Dettopsomyia was established by Lamb in 1914 for a single species, De.formosa described therein. It contains 13 known species recorded from the Old World (the Oriental, Australasian, Palearctic and Afrotropical regions). In the present paper, five new species discovered from southern China are described as members of Dettopsomyia: De.acutipenis Wang & Gao, sp. nov., De.serripenis Wang & Gao, sp. nov., De.discontinua Wang & Gao, sp. nov., De.camelonota Wang, Li & Gao, sp. nov. and De.paranigrovittata Wang, Li & Gao, sp. nov. The new species were delimitated, based on not only morphological characters but also molecular data.


Introduction
The genus Dettopsomyia was established by Lamb (1914) for De. formosa described therein as the type species. Since then, a number of species have been added as new members to this genus or transferred from other genera by some authors, bringing the total number of known species in Dettopsomyia to 13. Duda (1926) described two Indonesian species, Dettopsomyia jacobsoni and De. acrostichalis, and transferred Drosophila pictipes de Meijere,

Specimens
Taxon sampling for morphological examination and DNA barcoding is shown in Table 2. The specimens were mostly captured by net sweeping above herbs in open forest, or at forest edge. Specimens were preserved in 70% (for morphological examination) or 100% ethanol (for DNA sequencing).
The examined specimens are deposited in the following institutes:

KIZ
Kunming Natural History Museum of Zoology, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, China; SEHU Systematic Entomology, the Hokkaido University Museum, Hokkaido University, Sapporo, Japan.

Species delimitation and description
As pointed out by Okada (1982) and Bock (1982), it is difficult to definitely determine the generic assignment of the studied specimens to Dettopsomyia Lamb, 1914or Styloptera Duda, 1924, based on morphological characters, for the present. As we address this issue in Discussion, it needs a systematic revision for these genera based on a full-scale molecular phylogenetic analysis of the subfamily Drosophilinae and ancestral state reconstruction of the morphology by character-mapping on the inferred tree. In the present study, therefore, we provisionally classify all studied specimens into Dettopsomyia according to the principle of priority (ICZN), since there is a possibility that the two genera are synonymized in future systematic studies. Then, they were classified into morpho-species referring to Okada's (1982) 13 characters (Table 1): the character states (referred to as CS-code in descriptions of species) for all the known and putatively new species of Dettopsomyia are summarized in Table 3. The morpho-species were further examined for other external morphology and detailed structures of dissected phallic and periphallic organs by the same methods as in Li et al. (2014). For each morphospecies, at least one representative specimen was selected for mitochondrial COI DNA sequencing. We followed Li et al. (2014) and Yang et al. (2017) for extraction of DNA, PCR and sequencing, using Folmer et al. (1994) primer pair LCO1490 (5'-GGT-CAACAAATCATAAAGATATTGG -3') and HCO2198 (5'-TAAACTTCAGGGT-GACCAAAAAATCA -3'). The sequences were edited in the SeqMan module of the DNAStar package (DNAStar Inc. 1996), and aligned in MEGA7 (Kumar et al. 2016). We performed tree-and distance-based DNA barcoding, with a neighbor-joining (NJ) tree constructed in MEGA7 with K2P distances (i.e., the Kimura 2-parameter distances) and comparison of the maximum intraspecific and the minimum interspecific pdistances. The morpho-species were then reconsidered by integrating information from the morphology and DNA barcode data. McAlpine (1981) was followed for the morphological terminology, and Zhang and Toda (1992) for the definitions of measurements and indices.

Species delimitation
The specimens were assigned into six morpho-species (one known and five new) of the genus Dettopsomyia. The alignment of the 38 barcodes spans (658 nucleotide sites in length) included 169 variable sites, among which 156 were parsimony informative. Fig. 1 shows the NJ tree built with the barcodes (GenBank accession numbers: MZ645104-MZ645141). The tree lends strong supports to the monophyly of each of the morpho-species with BP (bootstrap percentage) = 100, except De. serripenis sp. nov. for which only one barcode was determined. The minimum and maximum K2P distances between and within the morphospecies are shown in Table 4. All the minimum interspecific K2P distances (≥ 0.0924), except for that between De. serripenis sp. nov. and De. discontinua sp. nov. (0.0132), were substantially larger than the maximum intraspecific distances (≤0.0391). Dettopsomyia serripenis sp. nov. formed a highly supported clade (BP = 100) with a compact cluster (K2P ≤ 0.0048, BP = 100) of 12 barcodes of De. discontinua sp. nov. (Fig. 1, Table 4). However, the former is readily distinguished from the latter in the morphology of both male and female (see the morphological diagnosis defined below for De. discontinua sp. nov.). On the other hand, the largest intraspecific distance (0.0391) was observed within the morpho-species De. nigrovittata (Table 4). Although the 18 barcode sequences of this species formed a monophyletic cluster (BP = 100), they were split into two subclusters with BPs = 58 and 96 (Fig. 1). However, no significant differentiation attributable to this subdivision was detected in either morphology (see Taxonomic account), habitat or geographical distribution (Table 2) between the two subclusters. We therefore regarded all these 18 specimens as of the same species (i.e., De. nigrovittata).
Similarly, we identified two specimens of which K2P distance (0.0152) slightly exceeded the least interspecific distance (0.0132) (

Key to Oriental species of Dettopsomyia
In this key, some figures published by Lamb (1914), Duda (1924Duda ( , 1926, Okada (1956Okada ( , 1982, Hardy (1965), and Takada (1976)  Scutum and scutellum blackish brown to black (Fig. 8B) Okada, 1982), which is, however, distinguished from the new species by the number of dark, longitudinal stripes on scutum: six in the new species, but ten in De. fruhstorferi.
Male terminalia (Fig. 5F-I): Epandrium with three setae per side laterally; ventral lobe short, narrow, apically round and sclerotized like peg, with two small setae subapically. Surstylus with prensisetae arranged in V-shape (approximately seven on caudal margin and 6-8 in oblique row on outer surface; one or two dorsalmost on outer surface somewhat separated from others), several upward-curved setae on ventral to subventral portion of inner surface and one or two trichoid setae on outer surface near base of epandrial ventral lobe. Cercus broadly fused to epandrium, pubescent anteriorly, with approximately 28 setae; several setae along caudoventral margin shorter. Hypandrium somewhat trapezoid; apodeme anteriorly truncate, twice as wide as long. Paramere fused to hypandrium, not pubescent but with a single setula. Aedeagus distally membranous, subapically dilated and serrated on lateral margins around gonopore, apically sharply pointed; apodeme as long as aedeagus.  Diagnosis. This species is closely related to De. serripenis sp. nov., forming a highly supported (BP = 100) clade with it (Fig. 1). These two species are indistin-guishable in CS-code from each other: De. discontinua sp. nov. (AbCD?FGHiJKLM) and De. serripenis sp. nov. (AbCD??GHiJK?M). However, they can be easily distinguished from each other by the following characters: 1) cercus caudoventrally strongly sclerotized and protruded ventrad like finger (Fig. 6F) in De. discontinua sp. nov. (abbreviated Dd here), but only pointed at caudoventral corner (Fig. 5F) in De. serripenis sp. nov. (abbreviated Ds); 2) surstylus with approximately 11 prensisetae on distal margin and nine or ten ones on medial portion of outer surface, arranged together nearly in circle (Fig. 6F, G) in Dd, but with 14 or 15 prensisetae arranged in V-shape (Fig. 5F, G) in Ds; and 3) marginal peg-like ovisensilla in row interrupted around subterminal, long, trichoid seta (Fig. 6J, K) in Dd, but in continuous row (Fig. 5J, K) in Ds.
Description. (♂, ♀; not repeating characters common to De. acutipenis sp. nov.). Head (Fig. 7A, B): Ocellar setae located just inside triangle made by ocelli. Frons with blackish brown stripes. Face grayish yellow to blackish brown; carina broad, dorsally strongly swollen and blackish brown, medially yellowish brown, ventrally nearly flat, black and with broad, pale yellow, traverse band. Clypeus blackish yellow. Gena pale yellow, ventrally black. Palpus gray, paddle-shaped in ventral view, with one prominent apical seta and several ventral ones. Antennal pedicel long triangular, black, laterally with yellowish patch; 1 st flagellomere long, somewhat triangular, black, with pale patch on inner, dorsal margin; arista with brown dorsal and ventral branches nearly as long as whitish trunk.
Thorax (Fig. 7A, B): Scutum, scutellum, and thoracic pleura grayish yellow. Scutum with blackish brown to black, longitudinal stripes interweaved with each other. Scutellum medially with blackish brown to black patch merged with lateral black spots covering bases of ipsilateral scutellar setae. Acrostichal setulae in two vestigial rows. Dorsocentral setae three pairs; anteriormost pair distinctly shorter and thinner, located slightly anterior to transverse suture and more widely separated from each other. Basal scutellar setae divergent.
Female terminalia ( Diagnosis. This species closely resembles De. nigrovittata in the external morphology and male terminalia, but can be distinguished from it by the surstylus chaetotaxy: in De. paranigrovittata sp. nov., approximately 23 subequal, peg-like prensisetae arranged roughly in five sets on medial to distal portion of outer surface and two upward-curved, trichoid setae on subventral portion of inner surface (Fig. 8F, G); but in De. nigrovittata, approximately 25 more or less heteromorphic setae arranged in three rows on upper half of outer surface and two larger setae at lower tip (Okada 1956: fig. 31C, as De. argentifrons).

Discussion
Since the early days of taxonomy for Dettopsomyia and Styloptera, these two genera have been ambiguous in their systematic positions. Until now, only few phylogenetic studies have been conducted to clarify the relationships between them. Grimaldi (1990) classified these two genera with Jeannelopsis Seguy, Tambourella Wheeler, Mulgravea Bock, Sphaerogastrella Duda, Hypselothyrea de Meijere, and Liodrosophila Duda in the Styloptera genus group, based on a cladistic analysis using 217 characters of 120 species. However, each genus was represented by a single species in his analysis. In Yassin's (2013) Bayesian phylogenetic tree based on DNA sequences of 70 genera of the Drosophilidae, Styloptera (represented by S. formosae only) was coupled with the subgenus Dorsilopha Sturtevant (represented by Drosophila busckii Coquillett, 1901), and Dettopsomyia (represented by De. nigrovittata) was placed into a clade containing the genera Jeannelopsis, Dichaetophora Duda, Hirtodrosophila Duda, Zygothrica Wiedemann, and Mycodrosophila Oldenberg. To completely solve this ambiguity in the systematics of the subfamily Drosophilidae a full-scale molecular phylogenetic analysis should be conducted with extensive taxon sampling from Dettopsomyia, Styloptera and putatively related genera and subgenera. The species diversity of Dettopsomyia and Styloptera has also been less explored: only 13 and ten species were known, respectively, before the present study. Our finding of five new Dettopsomyia species from southwestern China ( Fig. 3) suggests that more unknown species remain to be discovered from the Oriental region. To precisely delimit the boundaries of these genera, as many species as possible need to be incorporated into the systematic study. The natural history of Dettopsomyia flies is still less explored. However, our collection records suggest their florivorous nature. Adult flies of De. acutipenis sp. nov. and De. serripenis sp. nov. were collected from flowers of Zingerberaceae, De. serripenis sp. nov. also from inflorescences of Alocasia odora (Araceae), and De. paranigrovittata from an inflorescence of Rhaphidophora decursiva (Araceae). Additionally, offspring adults of De. paranigrovittata sp. nov., De. discontinua sp. nov., and De. nigrovittata emerged from infructescences with decayed spathe of R. decursiva in laboratory rearings, and Carson and Okada (1980) reported rearing De. repletoides (under the name of Styloptera repletoides) from infructescences of Colocasia esculenta (Araceae). Wheeler (1951) observed dipteran larvae and puparia in a rotting, bleeding part of banana plant, and adults emerged from them and were identified as De. nigrovittata. Thus, some species of Dettopsomyia use decayed plant materials as a breeding substrate.