Bombus rufofasciatus Smith, 1852

Figs 13, 71–77, 188

Bombus rufo-fasciatus Smith, 1852a: 48 .

Bombus rufofasciatus var. [subsp.] championi Richards, 1928a: 107.

Bombus waterstoni Richards, 1934: 88 .

Bombus rufofasciatus s. str. is revised here as a western species separate from the eastern B. prshewalskyi because of their unique and strongly divergent species coalescents in the COI gene (Fig. 10), corroborated by differences in morphology. The morphological differences are subtle, but do appear to corroborate that the two are separate species within a morphologically more distinctive complex of rufofasciatus s. str. + prshewalskyi .

Our PTP analysis (Fig. 10) supports relatively strongly two coalescents in the COI gene for sister candidate species within a rufofasciatus -complex: the west Himalayan B. rufofasciatus s. str. and B. prshewalskyi of the eastern QTP. The two coalescent groups differ in COI barcode sequences for at least 22 diagnostic nucleotide positions (3.3% of the barcode region, although some sequences are incomplete). These differences are all synonymous, making no difference to the amino acid sequences

at translation. In contrast, examination of sequences for the slower-evolving PEPCK gene (even though it also includes faster-evolving intron regions) shows no diagnostic nucleotide changes.

From morphology, B. rufofasciatus s. str. has a slightly lighter colour pattern of the hair than B. prshewalskyi for the females (larger workers and queens), with the white bands often appearing bright white. T2 of workers (and sometimes in the far west, also of queens) is often predominantly yellow.

Current restrictions on collecting and sequencing in the areas where these two candidate species are most likely to occur in proximity (Fig. 13) make clarifying their status difficult. However, more evidence is needed to increase confidence in any interpretation of the status of these candidate species rufofasciatus s. str. and prshewalskyi and it remains possible with more sampling from the Himalaya that the two taxa could still prove to be parts of a single species B. rufofasciatus s. lat. Speciation between B. rufofasciatus s. str. and B. prshewalskyi may have arisen through vicariance between populations of the western and eastern Himalaya caused by a period of altered climate (cf. B. miniatus / B. eurythorax).

Females show size-dependent dimorphism in the colour pattern of the hair: large queens vary from having T2 black with a few yellow hairs (in the east) to having T2 predominantly yellow (in the far west in Pakistan) and T4 is white; whereas the smaller workers have T2 extensively yellow and T4 red. Males have a similar colour pattern to the workers. That the castes and sexes are conspecific has been confirmed from examining variation within one colony from Kashmir (Williams 1991).

Diagnosis

Females

Queens medium-sized body length 20–23 mm, workers 10–15 mm. Can be distinguished by their combination of the hair of T5 white and the hair on the side of the thorax white only in the dorsal half (cf. B. ladakhensis), closely similar to B. prshewalskyi but tending to have T2 with more yellow hair and the scutellum with less black hair.

Males

Body length 14–16 mm. Can be distinguished reliably at present only by their COI sequence, but tending to have T2 with more yellow hair and the scutellum with less black hair (cf. B. prshewalskyi). Genitalia (Fig. 188) 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 pronounced adjacent acute teeth, the proximal tooth often slightly shorter than the distal tooth (cf. other rufofasciatus -group species); volsella with the inner distal corner produced as a narrow curved hook ( cf. rufipes -group, B. simillimus, lapidarius -group, sichelii -group, keriensis -group); antenna short and eye enlarged relative to female eye.

Material examined

Lectotype

INDIA • ♀ (queen), lectotype of Bombus rufofasciatus Smith, 1852 by designation of Tkalců (1974a); “N.[orth]”; NHMUK (examined PW).

Material sequenced (6 specimens)

PAKISTAN • 1 ♂; upper Memosh; 34.7093° N, 76.1208° E; 5 Sep. 2017; S. Jaffar leg.; BOLD seq: 1555E08; UAP: ML256 • 1 ♂; same collection data as for preceding; BOLD seq: 1555E09; UAP: ML257 • 1 ♂; same collection data as for preceding; BOLD seq: 6877H05; UAP: ML421 .

INDIA • 1 ♀ (worker); Uttarakhand, Badrinath Valley of Flowers; 30.7291° N, 79.6193° E, 18 Aug. 1990; S. Cameron leg.; BOLD seq: 6877E07; PW: ML389 .

NEPAL • ♀ (queen); Karnali, Churta; 29.4667° N, 82.1° E; 2 Jun. 2007; F. Creutzburg leg.; BOLD seq: 1551H08; NME: ML213 • ♀ (queen); Karnali, Gothichaur; 29.1972° N, 82.3083° E; 7 Jun. 2007; F. Creutzburg leg.; BOLD seq: 1551H07; NME ML214 .

Global distribution

(West Himalayan mountain species) Himalaya: PAKISTAN, INDIA: Kashmir, Himachal Pradesh, Uttaranchal; NEPAL. (NHMUK, NME, NMS, PW, SEHU, UAP.) The species is widely distributed within its range and often abundant.

Behaviour

A colony of this species has been found underground (under large rocks) in a subalpine meadow at 3000 m a.s.l. in Kashmir (Williams 1991). Food-plant generalists and the male mate-searching behaviour is truly territorial with collisions between males in flight and replacement in perch occupancy (Williams 1991).