Discocerinini Cresson

Costa, Daniel N. R., Mathis, Wayne N. & Marinoni, Luciane, 2016, A revision of the shore-fly genus Lamproclasiopa Hendel (Diptera, Ephydridae), ZooKeys 631, pp. 1-99 : 4-6

Taxon classification Animalia Diptera Ephydridae

Tribe Discocerinini Cresson

Discocerinini Cresson 1925a: 228 [as Discocerini]. Type genus: Discocerina Macquart 1835. Cresson 1942: 104 [correct spelling, as a "new tribe" in key]. Mathis and Zuyin 1989: 435 [diagnosis, monophyly]. Mathis and Zatwarnicki 1995: 163-186 [world catalog]. Zatwarnicki and Mathis 2001: 5-51 [tribal revision]. Zatwarnicki et al. 2016: 1-34 [phylogenetic review of tribe].

Diagnosis.

A tribe of Gymnomyzinae that is distinguished from other tribes of the subfamily by the following combination of characters:

Head: Frontal vitta (or ocellar triangle) mostly bare of setulae, not conspicuously setulose; ocellar setae well developed, inserted anterolaterad of anterior ocellus; reclinate fronto-orbital seta inserted anteromediad of proclinate fronto-orbital (if 2 proclinate fronto-orbital setae, reclinate seta inserted anteromediad of larger, posterior, proclinate seta); pseudopostocellar setae well developed, proclinate, slightly divergent, usually at least half length of ocellar setae. Pedicel bearing a large seta anterodorsally; arista bearing 4-6 dorsal rays, inserted along length of arista; conical process of basal flagellomere in lateral view finger-like. Face generally shallowly arched, frequently more prominent at level of dorsal facial setae, not conspicuously pitted, rugose, tuberculate, or carinate. Gena generally short (secondarily high in some species), bearing setulae (including midportion) and 1 large seta, its posterior (postgenal) margin rounded, not sharp. Oral opening and clypeus narrow; mouthparts generally dark colored; proboscis with number of pseudotracheae quite variable; lacinia Y-shaped with narrow posteromedial arm, dorsal arm spatulate; 2 different kinds of cibarium: (1) primitive type with dispersed medial sensillae arranged sparsely in a horizontal line; (2) advanced type with medial sensillae arranged densely in a sinuous line.

Thorax: Mesonotum generally microtomentose, frequently densely so, although variable; mesonotal setae weakly developed, only posteriormost pair of dorsocentral and acrostichal conspicuous; postsutural supra-alar seta usually evident although sometimes reduced or absent; prescutellar acrostichal setae inserted approximate and posterior of alignment of posteriormost dorsocentral setae; scutellar disc usually densely setulose; scutellum bearing 2 large, marginal setae: notopleural setae 2, inserted at same level near ventral margin, in some genera notopleuron bears setulae in addition to the two large notopleural setae (Figs 2, 9); anepisternum with 2 subequal setae in serted along posterior margin. Wing with vein R2+3 moderately long. Foreleg normally developed, not raptorial with greatly enlarged femur.

Abdomen: Five tergites visible, usually not densely covered with microtomentum. Male terminalia: Epandrium as inverted U, encircling cerci, anterior margin rounded, in lateral view with setae mainly on dorsum and along anteroventral margin; cerci paired, hemispherical, setose; presurstylus lacking or fused indistinguishably with ventral margin of epandrium; anterolateral arms of epandrium attached with ventral apex of gonites, middle of posterior margin a base for phallapodeme; phallapodeme situated under aedeagus, associated with hypandrium and with ventral part of base of aedeagus, ventral margin with lobate appendix providing attachment for genital muscles that move aedeagus; gonite paired, connecting sides of base of aedeagus and laterodorsal margin of epandrium, bearing 1 or some setulae; aedeagus tubular, tapered anteriorly; ejaculatory apodeme usually lacking, if present as a spatula ( Zatwarnicki et al. 2016, Figs 99-100).

Discussion.

Several of the characters noted in the diagnosis are synapomorphies and establish the tribe’s monophyly ( Zatwarnicki et al. 2016). These are as follows: (1) ocellar setae inserted slightly in front of alignment of anterior ocellus; (2) reclinate fronto-orbital seta inserted in front of proclinate fronto-orbital seta; (3) conical process of basal flagellomere in lateral view finger-like; (4) prescutellar acrostichal setae small and inserted close together and behind the transverse alignment of the posteriormost dorsocentral setae (secondarily lacking in some species); and (5) presurstylus of the male terminalia either lacking or fused indistinguishably with the ventral margin of the epandrium. Larvae are microphagous and in other aspects are similar to those of Hyadinini ( Ilytheinae).

As currently characterized, the tribe Discocerinini is one of the richest tribes within the family Ephydridae (225 species), and numerous additional species, especially from tropical zones, remain to be described. Many of the undescribed species are already in collections, and undoubtedly numerous others await collection. With the recent phylogenetic review of the tribe ( Zatwarnicki et al. 2016) and description of additional genera and subgenera, there are now 13 genera and two subgenera. Two genera are monotypic and have relatively localized distributions: Galaterina in the Solomon and Andaman Islands and Pectinifer limited to the Neotropics ( Mathis et al. 2016). Other genera are more speciose and widespread. Aquachasma (24 species), Facitrichophora (4 species), Hydrochasma (10 species), and Polytrichophora (nominate subgenus) (22 species) are found in the New World. The distributions of Lamproclasiopa (24 species) and Orasiopa (15 species) extend from the New World into the Australasian and Oriental Regions. Diclasiopa (4 species), Gymnoclasiopa (25 species), Hecamedoides (26 species) and Ditrichophora (39 species) have been recorded from all Regions except the Neotropics. Two genera, Discocerina (20 species) and Polytrichophora (subgenus Sklodowskopa ) (10 species), are essentially cosmopolitan.

Phylogenetic considerations.

Zatwarnicki et al. (2016) proposed division of Discocerinini into four groups of genera (their proposed synapomorphies are provided in parentheses):

The Gymnoclasiopa group with Gymnoclasiopa (aedeagus with lateromedial appendices and facial setae arranged close to eye margin);

The Diclasiopa group with Diclasiopa , Ditrichophora , Hecamedoides and Pectinifer (gonite elongated, that is tapered apically);

The Lamproclasiopa group with Galaterina , Lamproclasiopa , and Orasiopa (subgenera Orasiopa and Reymontopa ) (palpal setae with papilla-like bases); and

The Discocerina group with Aquachasma , Discocerina , Facitrichophora , Hydrochasma and Polytrichophora (nominate subgenus and subgenus Sklodowskopa ) (reduced number of pseudotracheae, modified cibarium and the ventral receptacle bearing anterodorsal projection).

Zatwarnicki et al. (2016) acknowledged that groups three and four together ( Aquachasma , Discocerina , Galaterina , Hydrochasma , Lamproclasiopa , Orasiopa , and Polytrichophora ) form a clade that is the best supported lineage within the tribe, being based on (1) notopleuron setulose and (2) gonites elongated and bar-like without an anterior projection or the gonite is fused with the hypandrium (character 32.1-2). As such, we prefer the continued recognition of these seven genera as a single group, the Discocerina group, and use subgroups for further division of this group (the Lamproclasiopa and the Discocerina groups of Zatwarnicki et al. 2016).

In the classification that Zatwarnicki et al. (2016) proposed (their character numbers are in parentheses), the Lamproclasiopa -subgroup has palpal setae with papilla-like bases (character 13). Within the Lamproclasiopa subgroup, the monophyly of the genus Lamproclasiopa is established by two characters (autapomorphies): (1) postsutural supra-alar (character 11 in Zatwarnicki et al. 2016) and (2) prescutellar acrostichal setae greatly reduced or lacking (character 22 in Zatwarnicki et al. 2016). The monophyly of its sister group, the combined Galaterina + Orasiopa , is confirmed by an increased number of pseudotracheae (convergent with Pectinifer ). Thus, in the most recent classification, Lamproclasiopa is the sister-group of the combined lineage of Galaterina + Orasiopa , and these three genera together form an assemblage that is now the Lamproclasiopa subgroup.

Key to genera of Discocerinini