Samba (Samba) turkana Packer

Packer, Laurence & Martins, Dino J., 2015, A new species of Samba s. str. (Hymenoptera: Melittidae) from the Turkana Basin, Kenya with observations on the function of the metatibial spur in females, Zootaxa 3918 (2), pp. 261-272 : 262-267

Samba (Samba) turkana Packer , new species

( Figs. 1–3 )

Diagnosis. Easily identified as a member of the subgenus Samba by the enormous and strongly curved single metatibial spur ( Fig. 1G ). The new species is easily separated from the others in the subgenus by lacking dark markings on the metasomal terga ( Fig. 1A ) and in having the metapleural pits widely separated ( Fig. 1E ). It differs from S. calcarata in having the mesobasitarsus more than twice as long as wide ( Fig. 1F ). Although the female of S. ascheri Michez & Patiny is unknown, the wings of the latter species are stated to be brown, whereas those of the new species are mostly clear ( Fig. 1A ) and the mesoscutum of S. ascheri is densely punctate with i<d ( Michez et al., 2010), whereas that of the new species is sparsely punctate with i=2–8d on the disc ( Fig. 1D ).

Description. Female: Dimensions: Head width 2.7mm, forewing length 5.9mm, body length 8.0mm.

Colouration: Black with orange and brown markings. Following parts orange: scape, pedicel, F1–F4 (rest of flagellum reddish–brown), pronotum (suffused with dark brown adjacent to pronotal foramen below and weakly on the pronotal collar between pronotal lobes), large patch on mesoscutum anterolaterally, scutellum (suffused with dark brown anteriorly), metanotum, vertical portion of mesopleuron, metapleuron, metapostnotum medially (remainder red–brown), lateral surface of propodeum (posterior surface reddish–brown); metasoma (except pygidial plate red–brown anteriorly darkening to black towards apex and S6 mostly orange–brown), metasomal terga immediately anterior to apical impressed areas yellow–orange. Legs mostly dark orange–brown. Tegula amber. Costal vein blackish, remaining venation including prestigma and stigma brown. Wing membrane translucent, weakly suffused with orange–brown on apex of radial cell and anterior 2/3 of marginal cell, darker beyond wing veins and on apex of marginal cell.

Pubescence: White, woolly, somewhat appressed and largely obscuring underlying integument on face between epistomal suture and midway between antennal socket and lateral ocellus, genal area, dorsal angle of pronotum, pronotal lobe, posterior margin of mesoscutum, metanotum anteriorly, mesopleuron anteriorly, lateral and most of posterior surface of propodeum, posterior surface of profemur and protibia, dorsal surface of mesotibia and mesobasitarsus, apex of metafemur and metatibia. Such hairs mostly <1.5MOD except anteriorly on mesopleuron ~2.2MOD. Long, fine white hairs on hypostomal area, coxae, trochanters, mesopleuron posteriorly and metasternum. Long fine yellow–orange hairs on mesal surface of procoxa, mesothoracic venter and metasternum. Protarsus with dense, simple, orange hairs <3MOD dorsally. Protibia and mesobasitarsus with sparse, long pale orange hairs ventrally, <3MOD. Metatibial scopa sparse, hairs simple, robust, <3.5MOD. T1–T5 with sparse, suberect, white hairs towards sides, <2,5MOD; prepygidial fimbria orange–brown; T6 with golden hairs except white laterally. Metasomal sterna with pale yellow to white hairs, longest on S1 and S5 ~2MOD.

Sculpture. Shiny, lacking microsculpture except metasomal sterna weakly imbricate. Clypeal punctures dense medially, i<d, irregularly spaced towards sides, i=0.3–1.5d, sparsely punctate apically. Supraclypeal area with finer, dense punctures, i~0.5d. Lower paraocular area more finely and regularly punctate, i<0.5d. Area between lateral ocellus and compound eye coarsely, unevenly, punctate, i=0.3–4d. Hypostomal area shallowly and somewhat densely punctate, i<d, except medially and anteriorly where punctures larger, and irregularly spaced, i=0.5–6d. Mesoscutum more evenly and densely punctate anterolaterally, i~d than on disc, i=2–8d, punctures on disc variable in size. Scutellum distinctly punctate, i=0.5–4d. Hypoepimeral area punctures coarse, i=0.5–1d; mesepisternal punctures shallower, i=0.5–2d. Lateral surface of propodeum with small, obscure punctures. Metapostnotum weakly striolate anterolaterally and mesad, otherwise lacking surface sculpture. T1–T2 with numerous minute punctures and sparser large ones, smaller punctures less numerous than large ones on T3, almost absent on T4–T6 except where giving rise to hairs of prepygidial fimbria; larger punctures increasing in size and density from T1–T5, somewhat smaller but dense on T6. Metasomal sterna distinctly and irregularly punctate, i=1–6d except more evenly spaced on S6, i=2–3d.

Structure. Head: Broader than greatest width of mesosoma, 69:65, 1.75X as wide as long, 40. Labrum four times broader than medial length, 4:1, with broad weak transverse ridge that forms an upside–down U–shaped weak tubercle medially, lacking tooth either side of concavity of tubercle. Clypeus weakly concave apicomedially, margin of concavity beveled, with median raised line indistinct above, absent below. Supraclypeal area somewhat protuberant, convex. Malar space linear. IAD:AOD 9:15. IOC:OOC 10:15. Compound eyes weakly convergent below, UOD;LOD 47:44. Frontal line depressed, shallow and narrow above, wide and deep below. Vertex concave in frontal view. Genal area subequal to width of eye in lateral view. Scape longer than F1–F5 combined, narrow, L:W 19:4; pedicel quadrate, F1 longer than wide, F2 short, F3–F9 each shorter than wide, F10 with width and length subequal, F11 longer than wide.

Mesosoma: Pronotum lacking horizontal surface posteromedially. Mesoscutum much broader than long: 45:33; admedian and parapsidal lines weakly raised. Scutellum longer than metanotum and anterior less strongly declivitous surface of metapostnotum combined, the three parts in the ratio of 12:5:2.5 respectively. Protibial spur with malus less than half as long as spur, 5:12; mesotibial spur robust, strongly curved at apex; mesobasitarsus laterally compressed, broad, L:B 24:9; metatibial spur strongly curved, enormous, chord length almost as long as metabasitarsus 25:27; metabasitarsus flattened, broad, L:B 27:11, apex truncate, weakly overhanging base of second metatarsomere. Forewing basal vein and cu–v interstitial on M+Cu; first submarginal cell longer than second, lengths on posterior margins 23:17; distance between first recurrent vein and first submarginal crossvein equal to that between second recurrent vein and second submarginal crossvein; stigma more than 3X longer than prestigma, 17:5; marginal cell 5X longer than greatest width 35:7; jugal lobe less than 0.5X as long as vannal lobe, 23:53.

Metasoma: Apical impressed areas of terga broader medially than at sides, on T2 9:5. Pygidial plate narrow, acutely pointed, lateral margins weakly concave.

Additional features described from the darkest paratype. Mouthparts ( Figs. 2C–E ): Cardo short and broad, L:B 32:6; cardinal lever elongate, strongly curved, apically subparallel to main axis of cardo; inner cardinal process enormous, concave ventrally. Stipes short, L:D 43:19, dorsal margin weakly biconvex, ventral margin strongly convex basally, weakly concave apically, outer surface longitudinally carinulate apically and ventrally. Postpalpal galea less than half entire length of galea, 15:35 and shorter than its greatest breadth, 17; galeal comb with 8 teeth, longest mesad; apex of galeal blade with approximately 5 robust setae oriented ventrad. Maxillary palpus with 6 palpomeres, first longest and broadest, 2nd–5th decreasing in length and width, 6th narrowest of all but subequal in length to 2nd. Lacinia long, narrow, obliquely oriented, pointed at both ends, with 3 robust bristles apicad and a few finer ones basad. Lorum short, transverse, acutely pointed at sides, somewhat broader mesad with deep and narrow anterior concavity and paired posterior processes surrounding base of mentum. Mentum weakly sclerotized towards sides, gradually increasing in breadth to membranous apex. Prementum considerably modified, fragmentum at base elongate, vertically oriented, 4 times longer than width at midlength; lateral walls of prementum membranous except towards base and around labial palpus, ligular arm scrolled and well sclerotized basad, briefly deflected mesad then extending apically as obliquely flattened rod ending in a bifurcation; ventral surface convex for basal 2/5, concave for following 3/10 and then convex for apical 3/10; subligular process gradually narrowing then expanded towards apex, apex bent dorsad; labial palpus with palpomeres 1–3 gradually decreasing in length and breadth, 4th palpomere narrowest, almost as long as first; paraglossa absent.

S6 and sting apparatus: S6 apodeme with length and width subequal, transapodemal ridge weak but complete on right hand side, absent on left; marginal ridge extending slightly mesad along anterior edge; anterior margin evenly concave; apex produced medially, apex of process weakly concave. T7 hemitergite (= spiracular plate) with medial portion of marginal ridge straight, anterior and lateral portions of apodemal ridge forming a continuous curve, apodemal region extending anteromedially as a triangular process; lateral lamella extending from close to anterior margin of apodemal ridge, gradually widening anterolaterally and then subparallel to lateral portion of ridge; lamina spiracularis extending beyond apex of lateral portion of marginal ridge but not beyond apex of medial portion of ridge, spiracle at apex of lamina spiracularis at midwidth. T8 hemitergite (= oblong plate) with anterior margin of apodeme concave, posterior margin convex, broadly rounded mesad. Gonoplac (=gonostylus or sting sheath) digitiform, setae towards apex slightly longer than diameter. Furcula with ventral arms longer than dorsal arm, dorsal arm almost as deep as long. Valve of first gonapophysis (= sting shaft) curved dorsad.

Variation. the darkest paratype differs from the holotype in having a weak medial longitudinal ridge on the clypeus, albeit perhaps formed mostly as a result of the punctures immediately adjacent being arranged almost in longitudinal lines ( Fig 2A ) and in having a darker mesosoma ( Fig. 2B ) as follows: pale colouration on pronotum restricted to orange–brown ventrally and on pronotal lobe, on mesopleuron orange restricted to posterior margin below scrobal groove, on metepisternum restricted to posterodorsal marking, legs more extensively dark brown, metapostnotum entirely black, propodeum with orange restricted to vertical lateral surface; hairs on mesopleuron posteroventrally and metasternum pale orange, prepygidial fimbria black medially, white laterally. The darkest paratype is also somewhat larger, head width 2.8mm, forewing length 6.1mm, body length 8.3mm.

Most of the remaining paratypes are similar in coloration to the holotype, but two are notably paler as follows: mesosoma entirely orange except for red–brown suffusion across mesoscutum and mesepisternum pale brown ventrally ( Fig. 3 ).

Material Studied: Holotype female: KENYA; Turkana , South Turkwel, Turkana Basin Institute, N03 08.458' E035 51.956', 455 m, 17.ix.2014, P. Lomosingo and D. Martins. Seven paratypes, same locality and, except for two, the same date: the darkest specimen was caught on 12.iv.2012 and bears a the code number TBI-BEE-00114 and a green DNA barcode reference label CCDB 09808 B08 and another was collected Ex. Tribulus terrestris L. ( Zygophyllaceae ), on 9.v.2012 with the code number TBI-BEE-00112 and barcode reference label CCDB 09808 C04. The holotype and two paratypes are to be housed at TBIK the remainder are at PCYU.

Etymology: The species is named after the type locality and the name is to be considered a noun in apposition.

Phylogeny: The character states for S. turkana are as follows preceded by the character number and state as in Michez et al., (2010) (their characters 13–21 were scored from males and thus were not available for the new species): 1–1 paraglossa absent; 2–0 maxillary palpus nearly hairless; 3–1 stipital flange present; 4–1 labrum with a transverse ridge; 5–1 vertex concave in anterior view; 6–0 metapleural pits well separated; 7–1 propodeum slanting (albeit anterior portion briefly less vertically oriented than the rest of the structure, nonetheless it was scored as 1); 8–1 propodeal triangle smooth; 9–0 2nd abscissa of forewing Rs oblique; 10–1 jugal lobe approximately half as long as vannal lobe; 11–1 forewing basal vein interstitial with cu–v; 12–1 mesotibial spur coarsely ciliate; 22–1 inner orbits of compound eye subparallel; 23–2 head less than 0.75X as long as wide; 24—medial longitudinal clypeal ridge, this character was scored as polymorphic as the holotype lacks it, but a paratype has a weak ridge; 25–0 upper paraocular area not differently sculptured from adjacent frontal area; 26–1 meso– and metathoracic legs with red (or orange) markings; 27–1 mesotrochanter and mesofemur with yellow bristles on ventral surface; 28–1 mesotibial spur robust; 29–1 mesotibial spur strongly curved at apex; 30–1 metabasitarsus less than 3X as long as wide; 31–1 metabasitarsus apically projecting above insertion of second tarsomere (albeit weakly); 32–1 T1–T2 with red markings (or entirely red); 33–1 T2–T4 lacking apical hair bands, albeit weakly present laterally; 34–1 pygidial plate raised medially (albeit weakly).

Character 35 is new: 35–0 metatibia with two apical spurs, neither of which is remarkably elongate and strongly curved, 35–1 metatibia with one apical spur which is remarkably elongate and strongly curved. All taxa included in Michez et al., (2010) score 0 for this character except S. calcarata and S. turkana which have state 1 and S. ascheri which is unknown.

The resulting phylogeny is 60 steps long, with a CI of 65 and RI of 83 and its topology (Fig, 4) is identical to that obtained by Michez et al. (2010) but with the three Samba species forming a polytomy. Monophyly of Samba s.str. is well supported ( Fig. 4 ). Successive approximations character weighting stabilized after a single round and yielded a tree identical to that shown in figure 4 except that S. ascheri was sister to the remaining two species of the subgenus Samba . Given that S. ascheri and S. turkana are known only from the male and female respectively, little confidence can be placed in these alternative resolutions.

DNA Barcodes. Full length barcode sequences of 658bp were obtained from two paratypes specimens and the sequences were identical despite the morphological differences noted above. Barcode voucher code labels for the included taxa are provided in the appendix. They cluster with other species of the genus Samba . The phylogeny based upon DNA barcodes included only 4 species of Samba and among the outgroups included previously, Eremephanta Popov was unavailable. The resulting tree was 417 steps, with a CI of 75 and RI of 78. Figure 5 shows the topology with branch lengths proportional to the number of evolutionary changes. The combined data matrix resulted in a tree that was entirely unresolved for species of Samba (not shown).

Figures

FIGURE 3. Samba turkana: oblique lateral view of mesosoma of the palest paratype.

FIGURE 4. Phylogeny for species of Samba and select related genera. Small numbers above the internodes indicate the character numbers from Michez etal. (2010) (see also “ Phylogeny ” section above), small numbers below internodes indicate the state that the character changes to along that internode. Large numbers above and below the internodes show support for the monophyletic groups subtended by that internode: GC values and traditional bootstrap frequencies respectively. Filled in circles indicate unique apomorphies, open circles indicate homoplasious apomorphies. See text for details. The character state vector for the new species is: 101110110111 --------- 12 * 01111111111.

FIGURE 5. Phylogeny of Samba based upon DNA barcode sequences. Branch lengths are proportional to the number of base changes. The black bar represents 2 % sequence divergence.

FIGURES 1 A – G. Samba turkana: Figs. 1 A & B holotype, remainder from a paratype. Fig. 1 A. Lateral habitus. Fig. 1 B. Head, frontal view. Figs. 1 C-G a paratype. Fig. 1 C. Clypeus, oblique view to show lack of medial carina or ridge (arrow). Fig. 1 D. Dorsum of mesosoma to show sparse punctation. Fig. 1 E. Metapleuron to show relative position of metapleural pits (arrows). Fig. 1 F. Mesobasitarsus to show length to width. Fig. 1 G. Metatibia and metatarsus to show enormously developed metatibial spur.

FIGURES 2 A – E. Samba turkana: darkest paratype female. Fig. 2 A. Clypeus, oblique view to show weakly developed median longitudinal ridge (label line). Fig. 2 B. Lateral view of mesosoma to show darker colouration than in holotype (compare to Figs. 1 A and 1 E). Fig. 2 C. Cardo, mentum and prementum to show, as labelled: a) enormous inner cardinal process, b) sclerotized sides to mentum (broken and somewhat displaced at basal 1 / 3, and c) elongate fragmentum. Fig. 2 D. Lorum to show posterior concavity (label line). Fig. 2 E. Prementum, slightly oblique dorsal view to show, as labelled: a) form of ligular arm, b) membranous lateral wall; c) concave apex of ligular arm.