Rhampholeon plumptrei sp. nov. Hughes, Behangana, Tilbury, Menegon, Kusamba, and Greenbaum

Plumptre’s pygmy chameleon

urn:lsid:zoobank.org:act: 1A0EBA3F-A6DF-4A11-ABFB-8EF2880D47C8

Synonymy.

Rhampholeon boulengeri — de Witte 1965 (partim), Drewes & Vindum 1998, Nečas & Schmidt 2004 (partim), Matthee et al. 2004 (partim), Tolley et al. 2013 (partim), Stipala 2014, Glaw 2015 (partim), Tilbury & Tolley 2015 (partim), Spawls et al. 2018 (partim), Tilbury 2018 (partim)

Rhampholeon sp. 1 — Hughes et al. 2018

Etymology. The specific epithet honors Andrew J. Plumptre for his efforts in promoting the conservation of Albertine Rift biodiversity and whose leadership with the Wildlife Conservation Society has inspired scientists in Africa and around the world.

Holotype. UTEP 22668 (field no. DFH 291), adult female, UGANDA, Western Region, Kigezi sub-region, Kabale District, Bwindi Impenetrable National Park, Habinyanja Swamp, 00.98896° S, 29.63013° E, 1830 m elevation, 14 June 2015, collected by D.F. Hughes and M. Behangana at night from forest vegetation about 1 m above the ground (Fig. 9A).

Paratype (topotype). Same collection details as holotype, one adult female, UTEP 22669 (field no. DFH 292).

Paratypes. One sub-adult male, UTEP 22667 (field no. DFH 257), UGANDA, Western Region, Kigezi sub-region, Kabale District, Bwindi Impenetrable National Park, Buhoma, 00.98918° S, 29.62944° E, 1846 m elevation, 14 June 2015, collected by E. Greenbaum and W. Rivera at night from forest vegetation. One small juvenile, UTEP 22666 (field no. DFH 252), UGANDA, Western Region, Kigezi sub-region, Kabale District, Bwindi Impenetrable National Park, Buhoma, 00.99045° S, 29.61884° E, 1523 m elevation, 13 June 2015, collected by D.F. Hughes, M. Behangana, E. Greenbaum, and W. Rivera at night from forest vegetation (Fig. 9B). Three juvenile males and one adult female, UTEP 21685, 21386 (field nos. ELI 2764, 2816), UTEP 22757 – 22758 (field nos. ELI 2815, ELI 2817), UGANDA, Western Region, Kigezi sub-region, Kabale District, Bwindi Impenetrable National Park, Ihihizo River, 00.99045° S, 29.61884° E, 1563 m elevation, 29 May 2014, collected by D.F. Hughes, K.A. Tolley, S. Davies, A.A. Turner, and J. Kielgast at night from forest vegetation about 1–2 m above the ground (Figs. 9C, 9F).

Referred specimens. CAS 17682, 176864–176865, 176868, 176873, 176875–176876 (field nos. CAS-RCD 11445, 11474, 11476–11477; J. Vindum 0814, 0941, 0956; 01.00975° S, 29.62069° E, 1585 m elevation), 201681– 201682, 201687, 201689–201691 (field nos. J. V. V. 4146–4147, 4184, 4186–4187, 4334; 00.97833° S, 29.69500° E, 1615 m elevation), UGANDA, Western Region, Bwindi Impenetrable National Park (13 specimens). PEM-R 16517 (field no. CT 355), UGANDA, Western Region, Kalinzu Central Forest Reserve (00.38583° S, 30.10638° E, 1468 m elevation) (1 specimen). UTEP 21686–21688, 22683 (field nos. CFS 1013 w, 1025–1026w, 1050w), DRC, North Kivu Province, Bunyantenge (00.26315° S, 28.94348° E, 1692 m elevation; Mount Vibende, 00.46247° S, 28.91721° E, 1892 m elevation; Kaunzo, 00.45250° S, 28.91518° E, 1675 m elevation; Kaluta River, 00.43317° S, 28.90392° E, 1629 m elevation) (4 specimens). UTEP 21689–21690 (field nos. MUSE 10193, 10226), UTEP 22748–22752 (field nos. MUSE 10248–10252) (Mulwa; 02.37620° S, 28.32768° E, 1497 m elevation), UTEP 22753–22756 (field nos. MUSE 10259–10262) (Nyala; 02.34809° S, 28.28111° E, 1289 m elevation), MTSN 6898–6899 (Madiriri; 02.30926° S, 28.64935° E, 2036 m elevation), DRC, South Kivu Province, Kahuzi-Biega National Park (13 specimens).

Diagnosis. Rhampholeon plumptrei sp. nov. is in the subgenus Rhinodigitum because of its distinctly bicuspid claws, prominent rostral process, smooth plantar surfaces, and phylogenetic placement, thus easily distinguishing it from the six species in the other two subgenera (i.e., Rhampholeon and Bicuspis): R. gorongosae Broadley, 1971, R. marshalli Boulenger, 1906, R. spectrum (Buchholz, 1874), R. spinosus (Matschie, 1892) R. temporalis (Matschie, 1892), and R. viridis Mariaux & Tilbury, 2006. Rhampholeon plumptrei sp. nov. can be distinguished from all other Rhampholeon species by the following combination of traits: (1) lack of prominent mite pockets in the inguinal region distinguishes it from R. beraduccii Mariaux & Tilbury, 2006, R. platyceps Günther, 1893, R. chapmanorum Tilbury, 1992, R. maspictus Branch, Bayliss & Tolley, 2014, R. tilburyi Branch, Bayliss & Tolley, 2014, R. bruessoworum Branch, Bayliss & Tolley, 2014, and R. nebulauctor Branch, Bayliss & Tolley, 2014; (2) presence of prominent mite pockets in the axillary region distinguishes it from R. nchisiensis (Loveridge, 1953) and R. acuminatus Mariaux & Tilbury, 2006; (3) distinct supra-orbital and canthal crests distinguishes it from R. hattinghi Tilbury & Tolley, 2015; (4) geographic restriction in the Albertine Rift, central Uganda, and eastern Kenya distinguishes it from R. uluguruensis Tilbury & Emmrich, 1996, R. moyeri Menegon, Salvidio & Tilbury, 2002, R. colemani Menegon et al., 2022, R. sabini Menegon et al., 2022, R. rubeho Menegon et al., 2022, R. nicolai Menegon et al., 2022, R. waynelotteri Menegon et al., 2022, and R. princeeai Menegon et al., 2022; (5) slightly shorter tails and shorter cranial crest gaps in males distinguishes it from R. boulengeri; (6) slightly longer inter-limb lengths in males, larger eye diameters and longer inter-limb length in females, and longer snout lengths in both sexes distinguishes it from R. monteslunae sp. nov.; (7) slightly shorter head, snout, and mouth lengths in females, and longer inter-limb length in females distinguishes it from R. nalubaale sp. nov.; (8) genetic divergence and non-overlapping elevational range at sites of co-occurrence distinguishes it from R. bombayi sp. nov.; and (9) genetic divergence and allopatric distribution distinguishes it from R. msitugrabensis sp. nov.

Genetic differentiation and variation. A summary of pairwise sequence divergence for three DNA markers (16S, ND2, and RAG-1) among individuals of R. plumptrei sp. nov. and other Rhampholeon species is presented in Supplementary Material 1.

Description of holotype (UTEP 22668). Adult female, SVL 49.2 mm and TL 12.5 mm. Body shape leaf-like. Casque flattened, with short head. Neck indistinct from head. Supra-orbital crests distinct with cluster of tubercles connected by a ridge with 16 tubercles across casque and 22 tubercles from peak-to-peak of crests. Rostral process 1.63 mm, composed of elongated tubercles. Temporal crest discrete with several enlarged tubercles extending posteriorly from mid-eye. Nares open in a posterior orientation. Canthal ridge consists of raised tubercles, one raised higher than others near snout. Ninety-eight upper and 90 lower labial tubercles are present along tip of snout to rictus of mouth. Body covered in nearly homogenous, flattened tubercles. Several larger conical tubercles present on dorsal flanks around midbody. Crenulated dorsal crest, more prominent from mid-body to nape. Many enlarged conical tubercles present on limbs. Claws markedly bicuspid.

Coloration of holotype (in life). A photograph of the holotype (in life) is presented in Figure 9A. Background color is orangish brown with more white coloration towards ventral area. Head is similar in color to body. Gular region is white, and this color extends onto ventral region. Two diagonal dark brown lines extend from near dorsal crest posteriorly to lateral flanks, resembling veins of a leaf. Tail is similar color as body with obvious white coloration underneath. Several small greenish to yellow patches present on upper limbs and near nape. Larger body tubercles are darker brown.

Variation. A summary of descriptive morphometrics for R. plumptrei sp. nov. is presented in Table 3, comparative boxplots in Figure 4, and measurements of the type specimens in Table 5. Photographs displaying color variation in life are presented in Figure 9. Morphological proportions are generally consistent with those of the holotype. Males have smaller body sizes (males [M]: mean 42.5 mm, range 27.7–53.3 mm, n = 18; females [F]: mean 50.8 mm, range 30.3–60.2 mm, n = 18) and longer tails than females (M: mean 12.3 mm, range 9.0– 15.7 mm, n = 18; F: mean 11.9 mm, range 8.3–13.9 mm, n = 18). Body coloration is consistently brown, gray, or tan, occasionally with reddish or white hues. Often exhibits one, sometimes two, dark brown lines on the lateral flanks extending diagonally from the dorsal crest toward the hind limbs, resembling veins of a leaf. In juveniles, the top of the head and legs can be black. Usually, the largest conical tubercle near the nape is much darker than the body. Legs and tail can be a darker brown than the body.

Reproduction. Five females were gravid (UTEP 21689, UTEP 22748, UTEP 22750, UTEP 22755, and UTEP 21686). Gravid females had a mean SVL of 55.4 mm (49.2–60.2 mm) and a mean TL of 12.4 mm (10.9–13.9 mm). These females were collected in April (n = 1), July (n = 1), and November (n = 3). The smallest specimen examined (UTEP 22666) was collected on 13 June 2015 with SVL 22.2 and TL 5.8 from Bwindi Impenetrable National Park, Uganda.

Distribution, natural history, and conservation. Rhampholeon plumptrei sp. nov. is found in montane and sub-montane forests at an elevation range from 1203–2269 m. This species has a very large geographic distribution from eastern DRC (Kahuzi-Biega National Park) to western Kenya (Kakamega Forest National Reserve), including its occurrence in several protected areas (e.g., Bwindi Impenetrable National Park, Uganda) (Hughes et al. 2018). We note there is also a documented population in Mabira Central Forest Reserve, Uganda, found at the Rainforest Lodge (00.38202° N, 33.01702° E, 1325 m), which represents an intermediate site between the Albertine Rift and the easternmost populations in Kenya (MB, pers. obs). At the type locality, Drewes & Vindum (1998) indicated that this species was found at elevations up to 2100 m where it was seen perched from 100 to 500 mm above the ground on ferns along trails and near streams. Furthermore, Drewes & Vindum (1998) stated that this species was the most common lizard that they encountered during their night surveys and that females had a maximum clutch size of four eggs. In contrast, extensive mark-recapture chameleon surveys across five nights in November 2018 by one of us (DFH) in Bwindi Impenetrable National Park along the Hamufa Trail (near Ruhija) detected only a single female R. plumptrei sp. nov. at an elevation of 2269 m, which was sleeping on a shrub at a perch height of 305 mm and a perch diameter of 1.14 mm. During five nights with three surveyors, this chameleon species was actually the least frequently encountered compared with Trioceros johnstoni (> 70 captures) and Kinyongia tolleyae (> 20 captures). The surveys of Drewes & Vindum (1998) found only a single specimen at 2100 m elevation (Ntengere River) with nearly all of their collections coming from mid-elevation sites around Buhoma, which occurs at about 1500 m elevation. In this study, only two specimens that we examined were found above 2000 m elevation, and just four specimens were from 1700 to 2000 m elevation. Taken together, it seems that R. plumptrei sp. nov. is most common at mid-elevations (1200–1700 m), uncommon at higher elevations (1700–2000 m), and rare above 2000 m. For a detailed list of lizard species present at the type locality see Drewes & Vindum (1998), and for Kakamega Forest, Kenya, see Wagner & Böhme (2007) and Lötters et al. (2007).