Proplebeia dominicana (Wille and Chandler)

CAMARGO, JOÃO M. F., GRIMALDI, DAVID, A. & PEDRO, SILVIA R. M., 2000, The Extinct Fauna of Stingless Bees (Hymenoptera: Apidae: Meliponini) in Dominican Amber: Two New Species and Redescription of the Male of Proplebeia dominicana (Wille and Chandler), American Museum Novitates 3293, pp. 1-1 : 1-

Proplebeia dominicana (Wille and Chandler)

Figures 1–7 , 9

Trigona (Liotrigona) dominicana Wille and Chandler, 1964:187–195 (tax., description).

Trigona (Hypotrigona) dominicana ; Morris, in Zeuner and Manning, 1976: 256 (fossil review).

Trigona dominicana ; Wille, 1977: 44 (fossil review, tax. notes); 1979: 269 (tax. notes). – Michener, 1979: 322 (biogeogr., tax. notes).

? Trigona (Plebeia) black species; Wille, 1979: 269 (tax. notes).

Plebeia dominicana ; Moure and Camargo, 1978: 563–564 (tax. notes, new combination).

Trigona (Proplebeia) dominicana ; Michener, 1982: 37–45 (not published in this form but stated to be a Trigona ; tax. notes, new subgenus).

Trigona A, B, C; Michener, 1982: 41–42 (tax. notes).

Proplebeia dominicana ; Camargo et al., 1988: 153 (biogeogr. notes). – Camargo, 1989: 44 (tax. notes). – Michener, 1990: 87, 95, 105–107 (tax. notes, phylogeny). – Ayala, 1992: 60 (biogeogr. notes). – Roubik, 1992: 499, 503 (figs. tibia). – Cano et al., 1992a: 249–251 (DNA); 1992b: 619–622 (RNA). – Poinar, 1992: 466– 468 (resin collection); 1994a: 537­538 (DNA); 1994b: 73–75 (fossil review, symbiotic and parasitic associations). – Grimaldi et al., 1994: 12– 14 (electron microsc.). – Grimaldi, 1996a: 72– 73 (electron micrography); 1996b: 118 (figures, paleoecology). – Michener and Poinar, 1996: 360–361 (fossil review, tax. notes, description of male P. dominicana ). – Walden and Robertson, 1997: 1075–1077 (DNA). – Carpenter and Grimaldi, 1997: 6 (biogeogr. notes). – Stankiewicz et al., 1998: 642–645 (preservation in resin).

DIAGNOSIS: Worker. Body length ca. 3.0 mm; forewing length 2.50­2.75 mm; malar area short, ca. ½ the diameter of scape; yellow stripe on parocular areas extending above the antennal alveolus; emargination between mandibular denticles deep. Male. Integument black, smooth, and shiny; body length ca. 3.68 mm; flagellomeres ca. 1.7× longer than wide; S6 with long, wide, median projection, enlarged and bifid apically; S7 with a row of long hairs along the distal margin; gonostyli long, slender, and slightly broadened at apex.

The species was interpreted based on the original description of Wille and Chandler, which is very detailed in relation to both supraspecific and specific characters, and also on additional data provided by Michener ( 1982). Wille and Chandler presented the measurements, except length of the body and forewing, in units of the eyepiece reticle and there is no indication of the index of conversion into millimeters. In his 1979 paper (p. 269), Wille presented the conversion into millimeters of the depressed posterior rim and keirotrichiate area width of tibia III as 3: 9 units = 0.099: 0.297 mm, which is obviously wrong. If the same proportion is applied to the head width, we have 72 = 2.376 mm (!), which is only a little shorter than the length of the forewing (2.60 mm). However, in another text Wille (1964) indicated on page 123 (footnote) a conversion factor of 1 unit = 0.017 mm, which results in measurements more similar to ours and which were used for comparisons in this study ( table 1 ).

Color of integument, punctation, pubescence, and size of the specimens examined agree perfectly with the description of Wille and Chandler. The yellow stripes on the sides of the mesoscutum (0.06 mm wide) are clearly visible only in specimen DR­14­1179; on the scutellum it is not possible to distinguish a yellow stripe in any of the specimens; thin layers of air bubbles, striations, or the position of cuts in the amber piece hinder a correct judgement. Also, specimen DR­14­1173 is too deformed and discolored. The yellow maculations in the lower parocular areas, clypeus, and supraclypeal area are clearly visible (fig. 2) in all specimens exactly as described and illustrated by Wille and Chandler.

There is disagreement between our specimens and some structural characters mentioned by Michener ( 1982): the rastellum comprises seven to nine long, well differentiated, and apparently cylindrical bristles (ca. 0.09–0.10 mm), concentrated in the anterior corner of the inner side of the distal border of tibia, behind the tarsal articulation (fig. 4); the penicillum (fig. 3) is normal as in Plebeia (s.s.) and Nogueirapis , and it is not as long and parallel to the longitudinal axis of the tibia as was indicated by Michener ( 1982). In the less deformed specimens it is possible to see that the propodeum is not as vertical as it seems in the drawing presented by Michener (1990: 105, fig. 83), the slope being gentle as in Plebeia (s.s.). The width of the keirotrichiate area, measured approximately at the middle of the tibia (specimen DR­14­1175), is 0.20 mm and the bare, depressed posterior rim is 0.06 mm wide. The limit between the keirotrichiate area and the depressed posterior rim is clearly defined by a step (fig. 4). The malar area is not linear, its length being approximately equal to half the diameter of the scape.

Wille (1979: 269) referred to some black specimens as Plebeia (s. s.). Michener (1982: 41), who examined these same specimens, considered them to be Proplebeia , possibly a species distinct from P. dominicana . However, Michener and Poinar (1996: 354) referred to them only as color morphs of P. dominicana . We examined the specimens mentioned by Michener (1982, Trigona A, B, C, specimens of Kansas University, Brodzinsky coll.) and consider them conspecific with P. dominicana .

DESCRIPTION: Male. Based on specimen DR­14­1178, and details of genitalia and pregenital sterna of DR­14­954. Amber piece DR­14­1178 was cut in right angles that allowed examination in several positions. There are some bubbles, fractures, and fissures, but the bee is well preserved (figs. 1, 5), practically without deformation, which permitted virtually exact measurements to be made. The bubbles over the spiracles (fig. 5) indicate that the bee was quickly immersed by the resin. Dimensions: Approximate body length 3.68 mm, forewing length, from apex of costal sclerite to wing tip 2.75 mm (including tegula, 3.00 mm); maximum head width 1.31 mm; metasoma width 0.98 mm (figs. 1, 5). Color of integument: Black, lacking yellow markings except for one translucent spot on either side of the base of the scutellum (exactly as in worker DR­14­ 1111). Lower parocular area and distal edge of clypeus somewhat lighter, without yellow markings (specimen DR­14­954 is entirely black). Tarsi of all legs and wing veins light chestnut. Wing membrane hyaline. Pilosity: Pale yellow over entire body. Decumbent, minute hairs covering whole face; vertex with unbranched erect hairs, longest hairs 0.16 mm. Mesoscutum with sparse, slender, erect hairs, the longest ones on anterior corners ca. 0.18 mm and those on posterior edge of scutellum ca. 0.20 mm (fig. 5). Pubescence on mesepisterna a little denser than on mesoscutum, increasing in length ventrad (0.12–0.6 mm). Basal area of propodeum glabrous. Posterior edge of tibia III with unbranched hairs (ca. 0.12 mm long). T1­4 without perceptible pilosity, except some minute hairs laterally; sides of T5­7 with erect, unbranched hairs, denser and progressively longer on T6­7; the longest hairs on distal border of T7 0.14 mm. It was not possible to observe in detail the sternal pilosity in any of the specimens; only in DR­14­954 it is possible to see a row of erect unbranched hairs ca. 0.10 mm long, arranged regularly along the distal edge of S5 (figs. 6, 7). Integument: Smooth and shiny, except for some sparse piligerous punctures. Punctures of head dense, owing to the dense micropilosity, distance between punctures ca. 1 to 2× puncture diameter. Mesoscutum shiny, with large spaces among bases of hairs (3 to 4× puncture diameter). Metasomal terga smooth and shiny. Form and proportions: Head wider than long (1.31: 1.00, length measured from apex of clypeus to upper tangent of median ocellus), approximately as wide as mesosoma (1.28, measured across mesepisterna) and wider than T2 (0.98). Eyes 2.1× longer than wide (0.84: 0.40) and convergent below; upper interorbital distance 0.75, maximum distance 0.78, and lower distance 0.50. Malar area linear. Clypeus 1.4× wider than long (0.48: 0.34), slightly convex; epistomal suture almost straight on sides (fig. 1). Labrum normal, slightly convex. Clypeocellar distance 0.64. Interalveolar distance nearly equal to diameter of antennal alveolus and slightly larger than alveolorbital distance (0.13: 0.14: 0.10). Frons slightly depressed along median line. Distance between lateral ocelli ca. 2.4× diameter of median ocellus and 3.1× ocellorbital distance (0.34: 0.14: 0.11). Vertex behind ocelli rounded; preoccipital ridge slightly rounded. Scape length 4.75× its diameter (0.38: 0.08) and ca. 2 ⁄ 3 distance between antennal alveolus and lateral ocellus (0.55). Flagellum plus pedicel (1.66) ca. 4× length of scape; flagellomeres ca. 1.7× longer than wide (the second one 0.16: 0.09). Scutellum in dorsal view an equilateral arch with rounded apex, 1.8× wider than long (0.50: 0.28) (it is possible that the scutellum is a little deformed because of dehydration in the amber). Forewing 2.9× longer than wide (2.75: 0.96); pterostigma 3.6× longer than wide (0.44: 0.12); marginal cell long and narrow (0.91: 0.20), its apex open; angle between Rs and Rs + M slightly acute (approximately 85°); first abscissa of M ca. 5 ⁄ 7 length of first abscissa of Cu (0.38: 0.54), and practically as long as Rs + M + second M. First submarginal cell almost entirely open, second abscissa of Rs forming a small projection. Second submarginal cell completely absent. Hamuli, 5–6. Tibia III subtriangular, 3.1× longer than wide (0.92: 0.30) slightly biconvex, posterodistal corner rounded. Basitarsus III 4.3× longer than wide (0.52: 0.12), flattened, lateral margins subparallel, distal edge in right angle. Details of the genitalia and pregenital sterna as in figures 6, 7. S5 unmodified, except for slightly concave distal border (with a transverse row of hairs); S6 with long, wide median projection [= apical process (Michener, 1990)], enlarged and bifid apically (figs. 6, 7); visible portion of S7 strongly sclerotized. Genitalia of specimen DR­14­954 is in triggered conformation, with penis valves directed laterally (as occurs during copulation in extant Meliponini), making study of certain structures difficult; gonocoxites not entirely visible nor is an unequivocal spatha. Penis valves very long (0.67 long per 0.11 wide at base), rather arched and pointed apically; gonostylus long and slender, exposed portion 0.61 long, 0.02 wide at its slightly broadened apex (figs. 6, 7).

MATERIAL EXAMINED: Four males, AMNH­DR­14­1178 , DR­14­954 , DR­14­1174 and DR­14­812 ; eight workers, AMNH­1 DR­14­1111 , DR­14­1173 , DR­14­1175 , DR­14­ 1176 , DR­14­1179 (these selected as particularly well preserved) and three unnumbered ones from the Natural History Museum of the University of Kansas, Snow Hall (Brodzinsky coll.); all from the Dominican Republic, as described under Materials and Methods .

REMARKS: We tentatively interpreted the specimens listed above as males of P. dominicana . The males are very similar to the workers in size, conformation of the wing veins, and the yellow markings on the base of scutellum. The wings are the only structures that usually do not exhibit sexual dimorphism in Meliponini. Even for most extant species, it is only possible to associate sexes with confidence when they are collected together in the nest.

The main autapomorphies of male P. dominicana are: very long flagellomeres, ca. 1.7× longer than wide ( Michener and Poinar, 1996, mentioned 3× longer than wide, which does not correspond to their figure 8, p. 357, where the proportion is ca. 2:1), S6 with median projection very long and broad, and apically bifid, and S7 with a row of long hairs along the distal margin [superficially similar to Austroplebeia symei (Rayment, 1932) ]. Other comments are given under P. tantilla Remarks, and under Discussion below.

Figures

Figs. 1, 2. Proplebeia dominicana; 1. male, specimen AMNH­DR­14­1178; 2. worker, specimen AMNH­DR­14­1111. Scale = 1.0 mm.

Figs. 3, 4. Proplebeia dominicana, tibia III. 3. outer surface, specimen AMNH­DR­14­1179; 4. inner surface, detail of the keirotrichiate area and rastellum, specimen AMNH­DR­14­1175. Scale = 1.0 mm.

Fig. 5. Proplebeia dominicana, male, specimen AMNH­DR­14­1178. Scale = 1.0 mm.

Figs. 6, 7. Proplebeia dominicana, genitalia of male, posterior view and profile, specimen AMNH­ DR­14­954; S5–S7 = 5th–7th metasomal sterna, respectively. Scale = 1.0 mm.

Figs. 8–10. Forewing, worker; 8. Proplebeia vetusta, sp.n., holotype, specimen, AMNH­DR­14­854; 9. Proplebeia dominicana, specimen AMNH­DR­14­1175; 10. Proplebeia tantilla, sp. n., paratype, specimen AMNH­DR­14­911. Scale = 1.0 mm.

Tables

TABLE 1 Measurements (mm) of Select Specimens of Proplebeia dominicana Holotype measurements are from the original descriptions by Wille and Chandler (1964).

	Male DR­14­1178	Worker DR­14­1111	Holotype, worker
1. Head width	1.31	1.30	1.22 (72)
2. Head length	1.00	1.02	—
3. Mesosoma width	1.28	—	—
4. Tergum 2 width	0.98	—	—
5. Eye length	0.84	0.84	0.80 (47)
6. Eye width	0.40	0.36	—
7. Upper interorbital distance	0.75	0.84	0.76 (45)
8. Maximum interorbital distance	0.78	0.89	0.82 (48)
9. Lower interorbital distance	0.50	0.68	0.65 (38)
10. Clypeus length	0.34	0.23	—
11. Clypeus width	0.48	0.54	—
12. Clypeocellar distance	0.64	0.70	—
13. Malar area length	linear	0.04	0.05 (3)
14. Interalveolar distance	0.13	0.16	0.15 (9)
15. Alveolus diameter	0.14	0.14	0.12 (7)
16. Alveolorbital distance	0.10	0.16	0.17 (10)
17. Scape length	0.38	0.40	—
18. Scape width	0.08	0.08	—
19. Length of pedicel plus flagellum	1.66	—	—
20. Alveolus­lateral ocellus distance	0.55	0.58	0.65 (38)
			(lateral ocellus?)
21. 1st flagellomere length	0.16	—	—
22. 2nd flagellomere length	0.15	—	—
23. 3rd flagellomere length	0.15	0.08	—
24. 3rd flagellomere diameter	0.09	0.08	—
25. Distance between lateral ocelli	0.34	0.26	—
26. Median ocellus diameter	0.14	0.11	0.10
27. Ocellorbital distance	0.11	0.18	0.17 (10)
28. Scutellum length: width	0.28:0.50	0.26:0.44	—
29. Mesoscutum length	—	0.80	—
30. Marginal cell length	0.91	0.92	—
31. Marginal cell width	0.20	0.21	—
32. Forewing length	2.75	2.68	2.60
		(+tegula 3,12)
33. Forewing width	0.96	1.08	—
34. Tibia III length	0.92	0.96	—
35. Tibia III width	0.30	0.37	—
36. Basitarsus III length	0.52	0.42	—
37. Basitarsus III width	0.12	0.19	—
38. Hamuli	5–6	5	—
39. Pterostigma length: width	0.44:0.12	0.50:0.12	—
40. 1st abscissa of M	0.38	0.39	—
41. 1st abscissa of Cu	0.54	0.56	—
42. Rs + M + 2nd abscissa M	0.36	0.40	—
43. Total body length	3.68	3.20	2.95