Lemmus lemmus chernovi Spitsyn, Bolotov & Kondakov, 2021

Spitsyn, Vitaly M., Bolotov, Ivan N., Kondakov, Alexander V., Klass, Anna L., Mizin, Ivan A., Tomilova, Alena A., Zubrii, Natalia A. & Gofarov, Mikhail Y., 2021, A new Norwegian Lemming subspecies from Novaya Zemlya, Arctic Russia, Ecologica Montenegrina 40, pp. 93-117 : 105-108

Lemmus lemmus chernovi Spitsyn, Bolotov & Kondakov ssp. nov.

Figs 6A , 7 A-C, 7G-H, 7K-L, Table 7

Common name: Novaya Zemlya Lemming

Holotype: Male RMBH Lem 005: type locality: Russia, Novaya Zemlya , Southern Island, near Malye Karmakuly Polar Station, 72.3822°N, 52.7506°E, altitude 17 m, wet saxifrage- roseroot communities, 23.vii.2015, Spitsyn leg.

Paratypes: Russia, Novaya Zemlya, Southern Island: type locality, 27.vii–01.viii.2015, 11 specimens (RMBH Lem001 – Lem004, Lem006, Lem007, Lem011, Lem019, Lem022, Lem023, Lem027), Spitsyn leg.; near Malye Karmakuly Polar Station, 72.3575°N, 52.7799°E, altitude 27 m, dry lichen- moss rocky tundra, 1.viii.2015, 1 specimen (RMBH Lem028), Spitsyn leg.; near Malye Karmakuly Polar Station, 72.3934°N, 52.7566°E, altitude 40 m, dry lichen- moss rocky tundra, 23.vii.2015, 2 specimens (RMBH Lem008, Lem009), Spitsyn leg.; near Malye Karmakuly Polar Station, 72.4058°N, 52.8285°E, altitude 60 m, dry tundra with Dryas octopetala and Astragalus alpinus , 27.vii.2015, 2 specimens (RMBH Lem020, Lem021), Spitsyn leg.; near Malye Karmakuly Polar Station, 72.3797°N, 52.7525°E, altitude 20 m, wet moss-sedge-willow tundra, 28–31.vii.2015, 4 specimens (RMBH Lem017, Lem018, Lem024, Lem025), Spitsyn leg.; near Malye Karmakuly Polar Station, 72.3739°N, 52.7167°E, altitude 28 m, stinkweed ( Artemisia tilesii ) assemblages, 5.viii.2015, 1 specimen (RMBH Lem031), Spitsyn leg.; Bezymyannaya Bay, 72.8°N, 52.5°E, 2017, 1 specimen (RMBH Lem029), local collector leg.

Molecular diagnosis: The novel subspecies differs from Lemmus lemmus lemmus by fixed nucleotide substitutions in the mitochondrial cytb (12A, 36C, 189T, 441T, 573A, 726G, 765T) and COI (198C, 200A, 302T, 542A, 602C), and the nuclear GHR (860C) and RAG1 (599T) gene fragments ( Tables 4 -5).

Differential diagnosis: The Novaya Zemlya Lemming differs from the nominate subspecies by having a cryptic coloration of dorsal surface that is dark gray with yellow and reddish hairs in adults ( Fig. 6A ) to reddish in juveniles, with an unclear longitudinal black stripe in anterior part from neck to nose (vs bright yellow coloration with black anterior part of the trunk and large black spots on head). The new subspecies is morphologically similar to Lemmus sibiricus but adult specimens from Novaya Zemlya could be distinguished from it by dorsal coloration with yellow and reddish hairs (vs brown and reddish hairs).

Description: Holotype male ( Figs 6A , 7 A-C, 7G-H, 7K-L, Table 7). Body weight 74 g; body length 130 mm, tail 13 mm. Length of hind foot 15 mm. Length of upper molar row 8.5 mm, lower molar row 8.3 mm. Color of dorsal surface grayish yellow, with an unclear longitudinal black stripe in anterior part from neck to nose. Cheeks dark gray, nose brownish gray. Ventral surface light-colored, creamy-yellow. Tail creamy. Vibrissae up to 33 mm long, black with yellow apex. Rostrum shorter than 2/3 greatest skull length; nasals do not proceed beyond the frontal edge of the incisors, rear edge rounded; gnathic process not pronounced; premaxilla rounded. Lacrimals with small ledge on the back side. Zygomatic arches parallel, jugal bone broad. Zygomatic plate broad, with slightly concave frontal margin. Zygomatic notch shallow. Nasolacrimal foramen with irregular shape, broad. Interorbital region narrow. Braincase region broad, almost square, with concavities behind the zygomatic arches. Lambdoidal ridge well developed. Postglenoid foramen elongated. Diastema long, concave; incisive foramina long and narrow. Mesopterygoid fossa broad, biconcave; parapterygoid fossa large; auditory bulla large, drop-shaped. Lower jaw large, angular process, condylar process и coronoid process large, well developed. Maxillary incisors yellowish-orange. Morphological variability. Mean body length of the type specimens (±s.e.m.) 110.9± 19.6 mm (min- max = 85-160 mm; n = 21). Color of dorsal surface grayish yellow in adults to reddish in juveniles, with an unclear longitudinal black stripe ( Fig. 6A ).

Etymology: This subspecies is named in memory of the late Academician of the Russian Academy of Sciences Yury I. Chernov (1934-2012), a prominent Russian zoologist, biogeographer, and Arctic explorer.

Distribution and habitat: This subspecies is endemic to the Southern Island of Novaya Zemlya, while its reliable records from the Northern Island of this archipelago are unknown ( Fig. 1A ). It inhabits a broad range of meadow-like ( Fig. 1B ) and tundra habitats.

Comments: The species delimitation modeling ( Fig. 2 ) suggests that Lemmus lemmus and L. sibiricus may belong to one polymorphic species, although molecular distances between these taxa correspond to an interspecific difference ( Tables 4 -5) supporting the modern concept of two young allopatric species ( Lagerholm et al. 2014, 2017; Abramson & Petrova 2018; Wilson & Reeder 2005; Wilson et al. 2017; Abramson et al. 2018).

Figures

Figure 1. Ranges and habitats of the true lemmings (Lemmus). (A) Distribution map of Lemmus taxa. Ranges were digitized based on published data and our records (Table 1). Red circles indicate sampling localities of Novaya Zemlya Lemming (L. lemmus chernovi ssp. nov.): 1 – Malye Karmakuly Polar Station (type locality), 2 – Bezymyannaya Bay (Table 1). The topographic base of the map was created with Natural Earth Free Vector and Raster Map Data (www.naturalearthdata.com). The map was created using ESRI ArcGIS 10 software (www.esri.com/arcgis). (B, C, D) Habitats of Lemmus taxa: (B) Novaya Zemlya Lemming (type locality, Novaya Zemlya), (C) Norwegian Lemming (Kola Peninsula), and (D) Siberian Lemming (Taimyr Peninsula). (Photos: Vitaly M. Spitsyn [B, C] and Natalia A. Zubrii [D])

Figure 2. Maximum likelihood (IQ-TREE) phylogeny of Lemmus taxa based on the cytb gene haplotypes. The Novaya Zemlya Lemming (Lemmus lemmus chernovi ssp. nov.) is colored red. The numbers near nodes are ultrafast bootstrap support values/Bayesian posterior probabilities. The red asterisks indicate the putative species-level clades supported by bPTP and sPTP species-delimitation models. The scale bar indicates the branch length. Outgroup taxa (Dicrostonyx torquatus, D. hudsonius, Synaptomys cooperi, and Myopus schisticolor) are not shown.

Figure 6. Dorsal view of lemming specimens: (A) Novaya Zemlya Lemming (Lemmus lemmus chernovi ssp. nov.) [holotype RMBH Lem005], and (B) Norwegian Lemming (L. lemmus lemmus) [RMBH Lem040, Kola Peninsula]. Scale bar = 10 mm. (Photos: Vitaly M. Spitsyn).

Figure 7. Comparison of crania, molar rows, and lower jaws of Novaya Zemlya (Lemmus lemmus chernovi ssp. nov.) [holotype RMBH Lem005] and Norwegian (L. l. lemmus) lemmings [specimen RMBH Lem040, Kola Peninsula]. (A, B, C) Crania of Novaya Zemlya Lemming: (A) dorsal view, (B) ventral view, and (C) lateral view. (D, E, F) Crania of Norwegian Lemming: (D) dorsal view, (E) ventral view, and (F) lateral view. Scale bar = 5 mm. (G, H) Molar rows of Novaya Zemlya Lemming: (G) maxillary, and (H) mandibular. (I, J) Molar rows of Norwegian Lemming: (I) maxillary, and (J) mandibular. Scale bar = 1 mm. (K, L) Lower jaw of Novaya Zemlya Lemming: (K) outer lateral view, and (L) inner lateral view. (M, N) Lower jaw of Norwegian Lemming: (M) outer lateral view, and (N) inner lateral view. Scale bar = 5 mm. (Photos: Vitaly M. Spitsyn).