Bombus tanguticus Morawitz, 1887

Williams, Paul H., Altanchimeg, Dorjsuren, Byvaltsev, Alexandr, Jonghe, Roland De, Jaffar, Saleem, Japoshvili, George, Kahono, Sih, Liang, Huan, Mei, Maurizio, Monfared, Alireza, Nidup, Tshering, Raina, Rifat, Ren, Zongxin, Thanoosing, Chawatat, Zhao, Yanhui & Orr, Michael C., 2020, Widespread polytypic species or complexes of local species? Revising bumblebees of the subgenus Melanobombus world-wide (Hymenoptera, Apidae, Bombus), European Journal of Taxonomy 719, pp. 1-120 : 67-69

Bombus tanguticus Morawitz, 1887

Figs 13 , 103–107 , 206

Bombus tanguticus Morawitz, 1887: 200 .

Our PTP analysis ( Fig. 10 ) of coalescents in the COI gene supports a single species B. tanguticus within the tanguticus- group as identified in the four gene species tree ( Figs 21–22 ), corroborated by differences in morphology.

Bombus tanguticus has a distinctive morphology and has been placed in a separate subgenus, Tanguticobombus ( Pittioni 1939b), although this was synonymised with the subgenus Melanobombus by Richards (1968). A close relationship with other species of the subgenus Melanobombus is supported by an analysis of COI barcodes by Williams (2018), which like the tree for the COI gene here ( Fig. 10 ), placed this species in the lapidarius -group. In contrast, when the species tree was estimated from four gene trees that include slower-evolving nuclear genes that can provide more reliable support for older relationships, B. tanguticus is placed in its own tanguticus -group next to the lapidarius -group ( Fig. 21 ). Female morphology is inconclusive, because the labrum has a very narrow median groove and the posterior ocello-ocular areas are relatively unpunctured, which support grouping B. tanguticus with B. lapidarius . In contrast, the more densely hairy hind corbiculum and elongate hind basitarsus (as well as large queen body size) support a closer relationship of B. tanguticus with B. simillimus . Resolving this question might be possible with information from other genes, but it is very likely that the morphology of the male genitalia, once the male is described, will be diagnostic among the two species groups. This is one of the few bumblebee species world-wide for which the male still remains unknown ( Williams 2018).

The typical colour pattern of this species is yellow banded, but a worker from Qinghai (ML219) has a white-banded colour pattern, as confirmed from their identical COI barcode sequences (Fig. 9).

Diagnosis

Females

Queens very large body length 22–28 mm, workers 12–13 mm. Can be distinguished in the QTP by their combination of labral lateral tubercles medially narrowing and projecting as small pointed pyramids, the median longitudinal furrow between them deep and unusually narrow, 0.2× as broad as the labrum, forming a triangular notch (broader for co-occurring B. tibeticus , B. (Sibiricobombus) semenovi Morawitz, 1887 , B. (Sibiricobombus) asiaticus Morawitz, 1875 s. lat.); mandible lacking a distinct sulcus obliquus, the posterior notch (incisura) anterior to the posterior tooth very weak or absent; clypeus with many large punctures especially in the dorsal half, the apical impressions unusually deep; antennal segment 3 (A3) short, nearly equal in length to A5, and only 1.5 × as long as A4 (substantially longer for co-occurring B. tibeticus , B. semenovi , B. asiaticus s. lat.); the mid basitarsus with the posterior distal corner acute; hind tibia with the outer (corbicular) surface weakly reticulate and shining, for the queens uniformly covered (even in the centre) with dense short black fine branched hairs (these can become abraded for older queens and are few or absent in workers); hind basitarsus long and narrow, nearly 4× as long as its greatest breadth, the posterior edge almost straight in its distal 4⁄5, the posterior distal corner acutely produced (basitarsus shorter and broader for co-occurring B. tibeticus , B. semenovi , B. asiaticus s. lat.), the outer surface with the short hair black with only short side branches so that some of the shining outer surface is visible between them (cf. dense overlapping pale hair for B. tibeticus ); T6 posteriorly with a subapical rounded (nearly circular) boss, the apex for workers truncated or for queens deeply and narrowly divided medially (T6 undivided for queens of co-occurring B. tibeticus , B. semenovi , B. asiaticus s. lat.).

Males

Unknown.

Material examined

Lectotype

CHINA • ♀ (queen), lectotype of Bombus tanguticus Morawitz, 1887 by designation of Williams (2018); Qinghai, “Bassin des gelb.[en] Flusses” (= source area of the Huang He, probably near Zhaling Hu: Williams 2018); [1884]; [N. Przhevalsky leg.]; ZIN (examined PW).

Material sequenced (3 specimens)

CHINA – Qinghai Province • 1 ♀ (worker); Xiangpishan ; 36.7589° N, 99.6041° E; 30 Aug. 2010; P. Williams leg.; BOLD seq: 6875A06; PW: ML9 • 1 ♀ (worker); Kunlun Pass ; 35.7258° N, 94.1626° E; 13 Aug. 2013; P. Williams leg.; NHMUK seq: NHMRC2; PW: ML219 . – Xizang Province • 1 ♀ (queen); Kamba county (Z715 80 km); 28.2193° N, 88.7942° E; 10 Jul. 2018; Q.-T. Wu leg.; IOZ seq: BB11; IOZ: ML566 .

Global distribution

(Qinghai-Tibetan-Plateau species) East Asia: CHINA: Xizang, Qinghai. – Himalaya: INDIA: Kashmir, Sikkim. (IAR, IOZ, NHMUK, PW, ZIN.) This is one of the highest recorded bumblebees in

the world, from an elevation of ca 5640 m a.s.l. ( Williams 2018: along with B. tibeticus ). The species is widely distributed but generally very rare ( Fig. 206 ). There are data available for only 12 queens and 2 workers, including the two recent queens from Kamba county, Xizang, collected in 2018 (IOZ, examined PW).

Behaviour

Expected to be food-plant generalists but very few records known ( Williams 2018). Males of B. tanguticus are expected to be flying during mid to late August, either visiting flowers or searching for mates in semi-arid habitats at elevations above 4500 m a.s.l. ( Williams 2018). Males of the mountain species B. keriensis have been found patrolling near high ridges towards the upper end of the species’ elevational range (above 4000 m a.s.l.) in Kashmir ( Williams 1991). Similar ‘hill-topping’ near high mountain ridges towards the upper end of its elevational range in the QTP is likely for B. tanguticus .

Figures

Figs 12‒13. Maps of sequenced samples. 12. The rufipes-group and festivus-group. 13. The rufofasciatus- group as recognised as species from the UHF-PTP analysis in Fig. 10. Keys to the coloured symbols are shown on the left (in some cases symbols on the map for one species may overlie symbols for another). Maps projected onto a sphere in ArcGIS using World_Shaded_Relief basemap © 2014 ESRI and showing boundaries between countries as recognised by the UN.

Figs 103–138. Simplified diagrams for the colour patterns of the hair on the dorsum for the species from the integrative analysis. The dorsum is divided into regions, each of which shows only the predominant or most apparent colour for that region using a simplified colour palette, with olive indicating a mixture of black and yellow hair, and grey indicating a mixture of black and white hair. The tanguticus-group. 103. Worker, China-Qinghai. 104. Worker, China-Qinghai. 105. Queen, China-Qinghai. 106. Queen, China-Xizang. 107. Queen, India-Kashmir. The lapidarius-group. 108. Queen, Russia-North Ossetia. 109. Worker, Azerbaijan. 110. Queen, Georgia. 111. Male, Russia-North Ossetia. 112. Male, Russia-North Ossetia. 113. Male, Russia-North Ossetia. 114. Male, Turkey. 115. Queen, Morocco. 116. Queen, Spain. 117. Queen, Spain. 118. Queen, UK. 119. Male, Spain. 120. Male, Spain. 121. Male, UK. 122. Male, UK. The sichelii-group. 123. Queen, Iran. 124. Male, Iran. 125. Queen, India-Kashmir. 126. Queen, India- Kashmir. 127. Male, India-Kashmir. 128. Male, India-Kashmir. 129. Queen, Iran. 130. Queen, Russia- Sakha. 131. Queen, China-Sichuan. 132. Worker, China-Sichuan. 133. Queen, Mongolia. 134. Worker, Mongolia. 135. Queen, Spain. 136. Worker, Austria. 137. Male, Turkey. 138. Male, Mongolia.

Figs 205–206. Maps of all available global records with all of the specimens examined and confirmed here. 205. Bombus richardsiellus (Tkalců, 1968). 206. B. tanguticus Morawitz, 1887. Relief map with hill shading for the region centred on Tibet with (grey lines) borders to national administration as in UN maps. Image created in ArcGIS using World_Shaded_Relief basemap © 2014 Esri.

Fig. 10. October 2019 (Fig. 8) Bayesian PTP analysis of MrBayes tree of unique COI barcodes (UHF- PTP). Symbols as in Fig. 9.

Fig. 21. A sample of 10 000 species trees from among 100 million trees for species of the subgenus Melanobombus von Dalla Torre, 1880 reconstructed with *BEAST from gene trees for the COI, 16S, opsin and PEPCK genes, displayed in green using Densitree, with the summary ‘root canal’ superimposed as a thick blue line. The outgroup B. nobilis Friese, 1905 is shown.

Fig. 22. Most likely dated phylogenetic (ultrametric) tree for the species of the subgenus Melanobombus reconstructed von Dalla Torre, 1880 with *BEAST from trees for four genes (COI, 16S, PEPCK, opsin) with B. nobilis Friese, 1905 as the outgroup (not shown), estimated as the maximum-clade-credibility tree among a sample of 10 000 species trees with a 1% burn-in out of 100 million MCMC trees. Values above the nodes are Bayesian posterior probabilities showing support for groups. Values below the nodes are estimated dates of divergence in Ma (millions of years before the present) calibrated from a molecular estimate for the date of crown divergence within the subgenus Melanobombus. Grey bars show the 95% confidence limits on the estimated dates of divergence. Species groups discussed in the text are labelled in circles: rp = rufipes-group; fs = festivus-group; rf = rufofasciatus-group; tg = tanguticus-group; la = lapidarius-group; si = sichelii-group; and ke = keriensis-group.