Bombus formosellus ( Frison, 1934 )

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 : 66-67

Bombus formosellus ( Frison, 1934)

Figs 13 , 98–102 , 192

Bremus formosellus Frison, 1934: 163 .

Bremus formosellus var. [subsp.] derivatus Frison, 1934: 166.

Bremus formosellus var. [subsp.] gradatus Frison, 1934: 167.

Bombus pyrosoma (part) – Williams 1991: 102 (non Morawitz, 1890: 349).

Bombus formosellus is known only from Taiwan ( Frison 1934; Chiu 1948; Starr 1992). Bombus pyrosoma s. lat. has been treated as a widespread Asian species by Williams (1998), to include the taxon formosellus . Here, B. formosellus is recognised as separate from the north Chinese B. pyrosoma s. str. because of their unique and strongly divergent species coalescents in the COI gene ( Fig. 10 ), corroborated by differences in morphology (see the Diagnosis). The morphological differences are subtle, but do appear to support the two as separate species within a morphologically more distinctive complex of pyrosoma s. str. + formosellus .

Our PTP analysis ( Fig. 10 ) supports relatively strongly two coalescents in the COI gene for the north Chinese B. pyrosoma s. str., and the Taiwanese B. formosellus . The two coalescent groups differ in COI barcode sequences for at least 12 diagnostic nucleotide positions (1.8% of the barcode region). These nucleotide differences are all synonymous, making no difference to the amino acid sequences at translation.

From morphology, B. formosellus has a paler colour pattern of the hair than B. pyrosoma s. str. for the females and especially for the queens. The queen of B. formosellus (below) has the hair of the thoracic dorsum with broad anterior and posterior bands strongly dominated by white, whereas for B. pyrosoma s. str. these areas are black or usually with a small minority of white hairs intermixed. The male gonostylus inner process is also not clearly divided into two teeth as it is in B. pyrosoma s. str.

Queens of this species have not previously been described. However, S. Lu located a female (ML503) in the TFRI collection that appears to be large enough (body length 20 mm) and collected early enough in the year (July 14, by I. Sung) to be a queen. This individual has lost much of its hair so the colour pattern is not clear, but females appear to show weak size-dependent dimorphism in the colour pattern of the hair: the queen has the remaining hair of T2 extensively black but with white hair narrowly anteriorly and medially and with orange hair narrowly posteriorly, especially in the lateral corners ( Fig. 98 ); whereas workers (which are smaller) either have T2 chocolate-coloured anteriorly and black posteriorly or have T2 extensively dull yellow ( Figs 99–101 ). Recently queens of this species have been reared in laboratory colonies, from which this colour pattern is confirmed (I. Sung in litt.). Males have the thoracic bands and T1–2 yellow ( Fig. 102 ).

Diagnosis

Females

Queens medium-sized body length 20 mm, workers 10–15 mm. Can be distinguished within Taiwan by the hair of the thoracic dorsum with white bands (cf. B. eximius ).

Males

Body length 13–14 mm. Can be distinguished within Taiwan by their combination of the hair of the thoracic dorsum with yellow bands, side of the thorax yellow, and T3–7 red. Genitalia ( Fig. 192 ) with the gonostylus much reduced, less than a quarter as long on its outer side as broad, with the distal edge concave and the inner distal corner with two indistinct adjacent teeth, the proximal tooth slightly shorter than the distal tooth and the two not clearly separated by an indentation (emargination) ( cf. pyrosoma s. str.); volsella with the inner distal corner produced as a narrow curved hook ( cf. rufipes -group, B. simillimus , lapidarius -group, sichelii -group, keriensis -group); eye unenlarged relative to female eye.

Material examined

Holotype

CHINA • ♂, holotype of Bremus formosellus Frison, 1934 by original designation; Taiwan , Roeichi; 15 Sep. 1924; T. Shiraki and J. Sonan leg.; INHS (examined PW).

Material sequenced (5 specimens)

CHINA – Taiwan • 1 ♀ (worker); Tayuling ; 23.9767° N, 121.5206° E; 5 Aug. 1991; C. Starr leg.; NHMUK seq: NHMPW07; PW: ML317 • 1 ♀ (worker); Tahsuehshan ; 24.3428° N, 121.1243° E; M. Kuo leg.; NHMUK seq: NHMPW09; PW: ML318 • 1 spec.; Taiwan ; 24.1806° N, 121.3101° E; GenBank seq: AF279522 ; SEHU: ML184 • 2 ♀♀ (workers); Taiwan ; 15 Jun. 2019; I. Sung leg.; TFRI seq: L11 LL12; TFRI: ML573 ML574 .

Global distribution

(Taiwanese mountain species) East Asia: CHINA: Taiwan. (INHS, NHMUK, PW, TFRI.) The species is narrowly distributed but not rare in collections.

Behaviour

Expected to be food-plant generalists. Male mate-searching behaviour is expected to resemble the patrolling of B. eurythorax .

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 64–102. 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 rufofasciatus-group. 64. Queen, China-Yunnan. 65. Queen, China-Sichuan. 66. Worker, China-Xizang. 67. Worker, China- Xizang. 68. Worker, China-Gansu. 69. Male, China-Yunnan. 70. Male, China-Xizang. 71. Queen, India- Kashmir. 72. Queen, India-Kashmir. 73. Queen, Pakistan. 74. Worker, India-Kashmir. 75. Worker, India- Kashmir. 76. Male, Pakistan. 77. Male, India-Kashmir. 78. Queen, Burma. 79. Worker, Burma. 80. Worker, China-Xizang. 81. Worker, China-Xizang. 82. Male, Burma. 83. Queen, China-Sichuan. 84. Worker, China-Sichuan. 85. Worker, China-Sichuan. 86. Worker, China-Sichuan. 87. Worker, China-Sichuan. 88. Worker, China-Xizang. 89. Male, China-Sichuan. 90. Male, China-Sichuan. 91. Queen, China-Beijing. 92. Queen, China-Beijing. 93. Worker, China-Shanxi. 94. Worker, China-Beijing. 95. Worker, China- Beijing. 96. Male, China-Beijing. 97. Male, China-Beijing. 98. Queen, China-Taiwan. 99. Worker, China- Taiwan. 100. Worker, China-Taiwan. 101. Worker, China-Taiwan. 102. Male, China-Taiwan.

Figs 190‒198. Morphology of the male genitalia for species of the subgenus Melanobombus von Dalla Torre, 1880 from the dorsal aspect, anterior at the bottom of the image, posterior at the top. 190. Bombus friseanus Skorikov, 1933, China-Yunnan. 191. B pyrosoma Morawitz, 1890, China- Beijing. 192. B. formosellus (Frison, 1934), China-Taiwan. 193. B. eriophorus Klug, 1807, Russia- North Ossetia. 194. B. lapidarius (Linnaeus, 1758), UK. 195. B. incertus Morawitz, 1881, Turkey. 196. B. semenoviaus (Skorikov, 1914), India-Kashmir. 197. B. sichelii Radoszkowski, 1859, Austria. 198. B. ladakhensis Richards, 1928, China-Sichuan. Scale bars = 1 mm.

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