Anatrichus

Mlynarek, Julia J. & Wheeler, Terry A., 2018, Phylogeny and revised classification of the tribe Elachipterini (Diptera: Chloropidae), Zootaxa 4471 (1), pp. 1-36 : 5-11

Anatrichus Clade

The monophyly of this clade is supported (BrS = 1, Fig. 1 A ) by seven homoplasious characters: the arista more than twice as long as the height of the third antennal segment (17:1), reduced ocellar bristles (23:1), inner vertical bristles absent (25:1), mesonotum longer than wide (27:1), postpronotal bristle absent (38:1), wing with a pattern (53:2) and wing much longer than wide (55:1).

Disciphus is the basal member of the Anatrichus clade and is not closely related to Elachiptera , as previously hypothesized (Andersson, 1977; Kanmiya, 1983). It is supported (BrS = 4, Figs 1A ; 2A ) by one uniquely derived synapomorphy: one orbital bristle longer than the others (20:1), and three homoplasious characters: interfrontal bristles on the inner margin of the frontal triangle (21:2), a pair of long apical scutellar tubercles (35:2), and reduced cerci in lateral view (66:1). Disciphus subelongatus Kanmiya was nested within Elachiptera in the analysis, not with the other described species of Disciphus .

The sister clade of Disciphus is comprised of Allomedeia , Alombus , Anatrichus and Sepsidoscinis . It is supported (BrS = 3, Fig. 1A ) by a long pronotum (26:2), the postpronotum obviously longer than wide (28:1), second costal sector shorter than the third (56:2) and the abdomen at least 1.5 times longer than the thorax (58:1).

Allomedeia is supported (BrS = 1, Figs 1 A ; 2 A ) by the margin of the frons diverging dorsally (3:1), the ocellar bristles much shorter than the postvertical bristles (24:1), subapical scutellar bristles absent (47:0), femoral organ absent (48:3), wings shaded at least along the veins (53:1), reduced anal angle (54:1) ( Fig. 6 ), all bristles on cerci equal (68:1), medially fused cerci (67:1), wide surstylus (70.1), parallel-sided (71.1), with a flattened tip (75:1). The structure of the male genitalia ( Figs 8–10 ), especially the fused cerci, is a strong defining character for this group. Although medially fused male cerci is probably an apomorphy for the subfamily Chloropinae , it is an unusual character in oscinellines. Three species of Allomedeia were included in the matrix as A. prolata , A. xanthotes and A. stuckenberg . The genus and included species (all previously undescribed) were formally described by Mlynarek & Wheeler (2010b).

The remaining genera of the Anatrichus clade ( Alombus , Sepsidoscinis and Anatrichus ) form a strongly supported monophyletic clade (BrS = 8, Bootstrap = 60, Fig. 1A ) supported by 11 characters: head longer than high (1:2), postgena at least 0.5 times the length of the short axis of eye (9:2), palpus parallel-sided and ending bluntly (10:1), third antennal segment round (16:0), pronotum noticeable but short (26:1), postpronotum wider than long (28:0), scutellum triangular (30:2), no scutellar tubercles (36:0), but if present then on ventral to dorsal margin (37:1), and tergites 1+2 fully sclerotized (62:1) including one uniquely derived synapomorphy, the basally constricted abdomen (61:1, Figs 18 ; 56–57 ).

Alombus is a strongly supported monophyletic genus (BrS = 19, Figs 1 A ; 2 A ), probably partly due to several morphological changes associated with the loss of flight in this group. Ten characters: ocellar bristles as long as post-vertical bristles (24:0), scutellum dorsally convex (31:0), anterior notopleural absent (40:3), postsutural dorsocentral bristles absent (43.1), subapical scutellar bristles absent (47:0), wings absent (52:2), halters absent (57:1), tergites 1+2 more than half the length of the abdomen but not covering it completely (59:1), cerci evenly rounded (69:0), unbranched arms of the hypandrium (74:1) support its monophyly including one that is uniquely derived, the absence of an anterior notopleural bristle (40:3). Four additional character state changes in characters 53–56 were plotted by TNT as state changes in the genus, but all are inapplicable wing characters that were coded in the matrix as missing states. These have been omitted from the cladogram in Fig. 2 A .

The two remaining genera of the Anatrichus clade, Sepsidoscinis and Anatrichus , are supported as a monophyletic group (BrS = 3 Figs. 1 A , 2B ) by four characters: ocellar bristles shorter than post-vertical bristles (24:1), mesonotum as long as wind (27:0), femoral organ absent (48:3), hypandrium massive in lateral view (73:1). Although Sepsidoscinis is a monotypic genus and is the well-supported sister group to Anatrichus , we have retained it as a separate genus to maintain stability with previous nomenclature. Given the lack of research on Oriental Chloropidae , it is likely that additional species of both genera remain to be described. Sepsidoscinis is supported by 12 characters: frons dorsally diverging (3:1), frontal triangle margins straight (4:1), palpus very small and inconspicuous (12:2), interfrontal setulae on the inside margin of the the frontal triangle (21:2), ocellar bristles proclinate (22:1), scutellar tubercles more than half the length of the scutellum (35:2), four or more scutellar bristles (36:2), anterior notopleural at most half the size of the posterior notopleural (40:1), absent postsutural intraalar bristle (44:1), wings shorter than abdomen (52:1), cerci fused (67:1)with one uniquely derived synapomorphy, a bilobed surstylus (76:1, Figs 55 , 64). An additional character state change related to the shape of the surstylus (71:?) was plotted by TNT as an apomorphy for Sepsidoscinis , but that character state is inapplicable because of the highly modified surstylus in this genus and the character state change was omitted from the cladogram ( Fig. 2B ).

The limits of Anatrichus have been expanded to include the species previously assigned to Myrmecosepsis . It is supported (BrS = 3) by 16 apomorphies scutellum longer than wide at base (32:1), scutellar tubercles absent (35:0), no scutellar tubercles (36:0), many dorsal posterior notopleurals (39:3), many anterior notopleurals (40:2), thoracic spines present (41:1), scutellar spines present (42:1), many postsutural intra-alar bristles (44:2), postsutural supra-alar bristles present (45:1), wings clear (53:0), C2 costal sector longer thand C3 (56:0), one large sclerite covering the abdomen (59:2), Tergites 1+2 fused (60:1), abdomen basally rugose (63:1), abdominal sternites broken into many small pieces (65:1), surstylus with a pointed tip (75:2), of which seven are uniquely derived: many posterior and anterior notopleurals (39:3, 40:2), the modification of bristles into spines on the thorax (41:1, 44:2), the modification of the abdomen into one large sclerotized syntergite covering the entire length of the abdomen (59:2, 60:1) and the sternites divided into many pieces (65:1).

Elachiptera Clade

The monophyly of this clade is supported (BrS = 1, Fig. 1 A ) by an arista less than twice the length of the third antennal segment (17:0), the rugose surface of the scutellum (33:1) and a well sclerotized hypandrium in lateral view (73:1).

Goniaspis is the basal lineage of this group. Its monophyly is supported (BrS = 4, Fig. 3 A ) by the presence of a short to long apical hind tibial spur (51:1) and the second costal sector as long as the third (56:1). Two of the ten described species in this genus were included in the analysis as well as an additional undescribed species (new species A) that was potentially referable to Goniaspis . That species is the sister group to the rest of the genus.

The sister group to Goniaspis includes Ceratobarys, Melanochaeta and Elachiptera. Support is low (BrS = 1, Fig. 1A ) and assumes many reversals. This clade of three genera is monophyletic based on the presence of a thick arista (18:1) that is heavily pubescent (19:1) and two orbital bristles longer than the rest (20:2).

The traditional limits of Elachiptera have changed as a result of this analysis ( Figs 1A,B ), with the species previously assigned to Elachiptera divided into two monophyletic groups separated by a monophyletic Melanochaeta .

Although Wheeler & Forrest (2002) synonymized Ceratobarys with Elachiptera , we have reinstated it for the clade that is the sister group to Melanochaeta plus Elachiptera ( sensu stricto). Ceratobarys is a weakly supported genus (BrS = 1, Figs 1A ; 3A ) based on a dorsally elongated third antennal segment (15:1), although this character state is independently derived within Elachiptera . Wheeler & Forrest (2002) synonymized Ceratobarys with Elachiptera based on the observation that the type species, C. eulophus (Loew) , was closely related to a group of yellow Neotropical species of Elachiptera with a trapezoidal scutellum. While these species are congeneric, the yellow species are all part of this clade, for which Ceratobarys is the oldest available name.

Andersson (1977) considered Melanochaeta and Elachiptera closely related. This has been supported in this analysis (BrS = 1, Figs 1B , 3A ) by two characters: ocellar bristles shorter than the postvertical bristles (24:1) and a round scutellum (30:0, Figs 35 , 46 ).

Melanochaeta is a monophyletic group supported (BrS = 3, Figs 1B , 3 A ) by four characters: the frontal triangle shorter than three-quarters of the length of the frons (5:1), the reduced dorsal posterior notopleural (31:0), the dorsally convex scutellum (33:0) that is smooth in appearance (39:2).

Under our revised definition, Elachiptera is supported (BrS = 1, Fig. 1B ) by a dorsally elongated third antennal segment (15:1) and the presence of 4 or more tubercles on the scutellum (36:2). As noted above, several species previously assigned to Elachiptera have been transferred to Ceratobarys . In addition, Elachiptera now includes all of the species that were previously placed in Cyrtomomyia and Togeciphus , as well as Disciphus subelongatus . Cyrtomomyia was treated as a subgenus of Elachiptera by Sabrosky (1951) but he subsequently reinstated it to a genus (Sabrosky, 1980). The four exemplar species of Cyrtomomyia are monophyletic, but nested within Elachiptera along with Disciphus subelongatus ( Figs 1B , 3B ). Consequently, Cyrtomomyia is considered a synonym of Elachiptera , and D. subelongatus is transferred from Disciphus to Elachiptera . The type species of Togeciphus , T. katoi Nishijima , was also nested within Elachiptera ( Figs 1B , 3B ), and thus Togeciphus is synonymized with Elachiptera .

Figures

FIGURE 1A. Strict consensus tree of 288 most parsimonious trees showing relationships of Elachipterini (basal portion). Bremer support values are below the branches, bootstrap values are in bold above the branches. Species are shown in their generic assignments prior to this study; new generic limits are indicated by gray bars.

FIGURE 2A. One of 288 most parsimonious trees showing relationships of the Anatrichus clade (Disciphus, Allomedeia, Alombus). Black bars—homoplasious character states; white bars—uniquely derived character states.

FIGURE 3A. One of 288 most parsimonious trees showing relationships of the Elachiptera clade (Goniaspis, Ceratobarys, Melanochaeta). Black bars—homoplasious character states; White bars—uniquely derived character states.

FIGURES 4–10. Allomedeia xanthotes. 4. Head, lateral; 5. Antenna; 6. Wing; 7. Scutellum, dorsal; 8. Male genitalia, posterior; 9. Male genitalia, lateral; 10. Male genitalia, ventrolateral. Abbreviations: cer—cercus; epd—epandrium; hyphypandrium; sur—surstylus. Scale bars—Fig. 6 = 0.5 mm; Figs 5, 7–9 = 0.1 mm.

FIGURES 16–21. Anatrichus species. 16–18. Anatrichus pygmaeus 16. Antenna; 17. Thorax: dorsal; 18. Abdomen, dorsal; 19–21. Anatrichus taprobane 19. Male genitalia, posterior; 20. Male genitalia, lateral; 21. Wing. Abbreviations: cer—cercus; epd—epandrium; sur—surstylus. Scale bars—Figs 17, 21 = 0.5 mm; Fig. 19 = 0.1 mm.

FIGURES 56–57. 56. Alombus seminitidus: habitus; 57. Sepsidoscinis maculipennis: habitus. Scale bars = 0.5 mm.

FIGURES 50–55. Sepsidoscinis maculipennis. 50. Antenna; 51. Wing; 52. Scutellum, dorsolateral; 53. Scutellum, dorsal; 54. Male genitalia, posterior; 55. Male genitalia, lateral. Abbreviations: cer—cercus; epd—epandrium; sur—surstylus. Scale bars—Fig. 51 = 0.5 mm; Figs 54–55 = 0.1 mm.

FIGURES 33–38. Elachiptera brevipennis. 33. Head: lateral; 34. Antenna; 35. Scutellum, dorsal; 36. Male genitalia, posterior; 37. Male genitalia, lateral; 38. Male genitalia, ventral. Abbreviations: cer—cercus; epd—epandrium; hyp—hypandrium; sursurstylus. Scale bars = 0.1 mm.

FIGURES 44–49. Melanochaeta species. 44–46. Melanochaeta capreolus. 44. Head, lateral; 45. Antenna; 46. Scutellum, dorsal; 47–49. Melanochaeta atricornis. 47. Male genitalia, posterior; 48. Male genitalia, lateral; 49. Male genitalia, ventral. Abbreviations: cer—cercus; epd—epandrium; hyp—hypandrium; sur—surstylus. Scale bars = 0.1 mm.