Tamiops mcclellandii ( Horsfield, 1839 )

Hinckley, Arlo, Maldonado, Jesús E., Tamura, Noriko, Leonard, Jennifer A. & Hawkins, Melissa T. R., 2024, Lost in synonymy: Integrative species delimitation reveals two unrecognized species of Southern Asian tree squirrels (Rodentia: Sciuridae: Callosciurinae), Vertebrate Zoology 74, pp. 683-707 : 683-707

Tamiops mcclellandii ( Horsfield, 1839)

Sciurus mcclellandi Horsfield, 1839 , Proceedings of the Zoological Society of London 1839: 152.

Sciurus pembertoni Blyth, 1842 , Journal of the Asiatic Society of Bengal 11: 887.

Sciurus macclellandi manipurensis Bonhote, 1900 , Annals and Magazine of Natural History (Series 7) 5: 51.

Holotype.

Holotype not specified in description. Two examined specimens are labeled as cotypes: NHMUK 79.11. 21.372, skin and skull, an adult male, also marked as “ lectotype ”, and NHMUK 79.11. 21.373, skin and skull, a young adult marked as “ lectoparatype ”.

Type locality.

“ Assam ” [= Assam, India].

Emended diagnosis.

A small-sized Tamiops (average HB = 116.5 mm, W = 56.7 g, GLS = 32.7 mm; Table S 8; Moore and Tate 1965; Liu et al. 2022) that can be distinguished from all other relatives by the combination of the following characters: relatively weakly striped summer pelage, with outer dark stripes paler than inner dark stripe; narrow (maximum width: 3–5 mm) outer pair of light stripes which are connected to a distinct pale facial stripe; outer light stripes are paler than inner light stripes and have a different width; no traces of rust / orange suffusion in venter (except very rarely in the chest), crown, or nape; absence of a yellow / orange hue in ear tufts; venter hairs have a great extent of gray at their base, which is not entirely covered by the tip lighter coloration, giving the venter an overall dull yellow-buff mixed with gray / brown coloration; golden / yellow tipped tail hairs; relatively large baculum with shaft and blade, shaft lacks a small concavity where the blade is attached, blade lacks ridges, blade attachment orientation is tangent to shaft orientation (Figs 8 A, D and 9 A, B ).

Comparisons.

It can be externally distinguished from its allopatric relatives Tamiops maritimus and T. mishanica , as well as the allopatric / elevational parapatric T. swinhoei , based on its smaller size and outer pair of light stripes which are connected to a light facial stripe in T. mcclellandii , but just extend to the shoulder in the other species (except in T. swinhoei in which it can be rarely connected with a faint line). Its pelage is also generally harsher, thinner, and shorter vs softer, denser and longer in T. swinhoei (although these features are affected by latitude, elevation and seasonality), and it lacks a yellow / orange hue in its ear tufts and reddish suffusion in crown while these features are frequently present in T. swinhoei . Its facial stripe is distinctive vs diffuse in T. minshanica , and its venter is buff or gray colored, lacking any red hue vs rust colored in T. minshanica ( Liu et al. 2022) . It can be differentiated from allopatric Tamiops rodolphii based on the following external features: outer light lines are thinner but more distinctive, contrasted and lighter than inner light lines which are less conspicuous vs outer and inner light lines are of equal width and similar brightness, distinctiveness, and contrast with the dorsum in T. rodolphii ; outer dark line coloration is homogeneous along the anterior-posterior axis vs outer dark lines grade posterior-anteriorly from black / dark brown to brown / reddish-brown in T. rodolphii ; absence of a thin pale brown line across the black mid-dorsal line vs presence of a thin pale brown line across the black mid-dorsal line in T. rodolphii (except in SE Thailand populations); generally duller, venter coloration which goes from buff to yellow (without any trace of red, except in the chest of three Mishmi Hill female specimens) vs generally brighter, orange-yellow to salmon-ochraceous in T. rodolphii . A comparison with Tamiops barbei has been included in the following account, after this species has been formally revalidated.

Distribution, habitat and natural history.

Distributed across the Eastern Himalayas including Nepal, Sikkim ( NE India), Bhutan, Assam and Arunachal Pradesh ( NE India), Kachin ( Myanmar), and Yingjiang County, north of the Daying River ( SW China; Figs 2 , S 5). It extends southward across the Arakan Range including the Garo, Khasi, Lushai, Mishmi, Naga and Chin Hills (Table S 1; iNaturalist; Li et al. 2005; Thapa et al. 2016). Its distribution is possibly limited to the southeast by the Irrawaddy River basin and to the east by the Taping / Daying, Shweli / Longjiang, or Nu Jiang / Salween Rivers since the allopatric T. barbei has been recorded at Maymyo (Mandalay) and Zhenkang (Yunnan), to the west of these rivers (Table S 1; iNaturalist; Li et al. 2005). It has been recorded from ca. 170 to 2743 m a. s. l. in tropical and subtropical forest. This species seems to be replaced, perhaps outcompeted, at higher elevations by Tamiops swinhoei in northern Myanmar (Table S 1; Ronald Kaulback field notes, NHMUK specimen tags; Moore and Tate 1965). Tamiops mcclellandii rarely comes to the ground, often observed “ high up in tall trees, moving in short rushes and then staying motionless, sometimes head downward, often some minutes at a time … never seen one in low bushes ” (Lord Cranbrook letter, described in Moore and Tate 1965). Similarly, in Arunachal Pradesh, T. mcclellandii was not recorded on the ground and was shown to mainly forage on bark along tree trunks below 10 m, particularly on bark of the species Kydia calycina , Pterospermum acerifolium , and Amoora wallichii ( Datta and Goyal 2008) . In northern Myanmar, it was collected at 12 meters up in dead pine tree in dense pine tree and rhododendron forest at 2743 m a. s. l., but also in a yam field surrounded by “ light ” (possibly secondary) forest at 914 m a. s. l. (Ronald Kaulback field notes, NHMUK specimen tags). Recorded in pairs or small groups often sharing the same tree with Dremomys lokriah ( Moore and Tate 1965) , and feeding on the bark of Dipterocarpus macrocarpus (iNaturalist). Mating recorded in April in Bhutan (https://www.inaturalist.org/observations/210973847).

Conservation.

Recorded in Neora Valley, Royal Manas, Namdapha, Jigme Singye Wangchuck, Phrumsengla, and Nat Ma Taung National Parks, Buxa and Pakke Tiger Reserves, Eaglenest and Pangolakha Wildlife Sanctuaries, and Cherrapunji-Mawsynram Reserve Forest (Table S 1; iNaturalist; Datta and Goyal 2008). Also recorded very close to Khangchendzonga and Phawngpui National Parks (Table S 1). This species was recorded in logged forest, but it was significantly less abundant than in nearby unlogged primary forest ( Datta and Goyal 2008).

Comments.

Cyt b pairwise uncorrected genetic distances between populations from Sikkim and the Arakan Range are relatively high (ca. 5–6 %) but there is little nuclear differentiation ( Hinckley et al. 2023 a).

Figures

Figure 2. Map of tropical East Asia indicating the localities of museum specimens examined in this study for Tamiops mcclellandii. Different subspecies are labeled with different symbols, while different colors illustrate the potential distribution of the two major genetic lineages described by Hinckley et al. (2023 a), inferred from pelage variation. Darker background shades correspond to higher elevations.

Figure 8. Dorsal and ventral views of the skins of (A) Tamiops mcclellandii (NHMUK 79.11. 21.372, lectotype), (B) T. barbei barbei (NHMUK 1914.7. 8.36, topotype), and (C) T. barbei inconstans (NHMUK 12.7.25.31, holotype); live images of (D) T. mcclellandii taken by Lee Alloway in Kumarkata, Assam, India, and (E) T. barbei taken by Andaman Kaosung in Kaeng Krachan District, Thailand.

Figure 9. Baculum comparison between Tamiops barbei and T. mcclellandii. A Lateral (left) view of T. mcclellandii (USNM 564453); B ventrolateral view of T. mcclellandii (USNM 564453); C lateral (left) view of T. barbei (USNM 297043); D ventrolateral view of T. barbei (USNM 297043).