Hemidactylus nicolauensis Vasconcelos & Köhler & Geniez & Crochet 2020, sp. nov.
Creators: name: Vasconcelos, Raquel
name: Köhler, Gunther
name: Geniez, Philippe
name: Crochet, Pierre-André
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Reptilia
Squamata
Gekkonidae
Hemidactylus
Hemidactylus nicolauensis

description: Hemidactylus nicolauensis sp. nov.
(Figs. 1–7, Tables 1–3)
urn:lsid:zoobank.org:act: 9C484E9A-5A72-4186-9C6F-1C89ECC6721B
Holotype. SMF 86992 (Morphobank M 585325–M585346), adult male, from Ribeira Funda around 250 m. a.s.l., São Nicolau Island, Cabo Verde (16.66°N, 24.34°W; WGS 84), collected 01 April 2007 by Gunther Köhler, GK.
Paratypes. UCV2018/004 (previously SMF 86991; Morphobank M 585298–M585321) adult female from Ribeira Funda, collected by GK; SMF 90057 (Morphobank M 585736–M585746) and SMF 90058 (Morphobank M 585747–M585754), juveniles and same data as holotype.
Other specimens examined. In addition to the holotype and paratypes, we have examined four specimens housed in London: NHMUK 2005.1637 – 40 collected 1 km past Cachaço in direction to Tarrafal de São Nicolau (16.6189°N, 24.3335°W) on 4 August 1997 by J. A. Mateo and P. Geniez. As reported by Arnold et al. (2008), these were in a too poor condition to be used in morphological analyses, but three of them have been included in the genetic analyses. Also, the animals corresponding to the tissue number BEV. T5652, DNA sample code H07, Morphobank M 675961– M675962), adult female and tissue number BEV. T5651 (DNA sample code H06, Morphobank M 673362–M673366), adult female, both from 200 m NE of Cachaço church, São Nicolau, Cabo Verde (16.6242°N, 24.3301°W), found 01 March 2012 by PAC were also examined. As far as we know these ten specimens constitute all the known material and records of the species. Five specimens were included in the genetic analyses, and eight voucher specimens were included in the morphological analyses (Table 1), including the holotype and paratypes.
Etymology. The species epithet refers to the island of São Nicolau, the only island of Cabo Verde where the new species is currently known to occur.
Diagnosis. A small Hemidactylus that shares all the morphological features common to the Cabo Verde endemic species (see Arnold et al. 2008), but characterized by the following combination of characters: no enlarged tubercles on dorsum or upper tail, two precloacal pores (one on each side) in males, two fully divided toe lamellae at the tip of the longest fingers and toes.
Hemidactylus nicolauensis sp. nov. is morphologically most similar to its sister taxon H. bouvieri, as both species have enlarged scales and toe lamellae (scansors) under toes and fingers, with minute hair-like structure under the toe lamellae. It is differentiated from H. bouvieri by the following characters: in H. nicolauensis sp. nov. the maximum size is larger (SVL 41 mm vs. 36 mm in H. bouvieri; Table 2), the toe lamellae tend to be more divided, with usually two fully divided toe lamellae (sometimes three) under the longest toes and fingers, whereas in H. bouvieri, the toe lamellae are entire (with a narrowing at the middle for the largest ones) or there is one or (rarely) two entirely divided toe lamellae near the tip of the fingers or toes (see Table 3). The difference is best appreciated under the third finger where it is diagnostic: there are at least two divided toe lamellae in H. nicolauensis sp. nov., whereas in H. bouvieri there is at most one divided toe lamellae under third finger.
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Head colouration seems diagnostically different in the live specimens we have examined (colour photos of live specimens: six H. nicolauensis sp. nov. and five H. bouvieri; Fig. 7): the dark band that runs along the snout side in front of the eye is thinner and better defined in H. bouvieri (less well marked and/or thicker in H. nicolauensis sp. nov.) whereas the top of the head has many more dark elements in H. nicolauensis sp. nov., resulting in a less clean and contrasted head pattern in all age classes (see Figs. 3, 7; Morphobank M585300 versus M676174). In addition, the dorsal colouration of H. nicolauensis sp. nov. is usually less contrasting and the dark bands across the dorsum do not reach as far down on the flanks as in H. bouvieri (Morphobank M585300 versus M676180; Fig. 7). In H. bouvieri, most individuals have a distinct pale yellowish background colouration with contrasting dark band on dorsum joining with a continuous dark band along the flanks. In H. nicolauensis sp. nov., the colouration is never as contrasting as in most H. bouvieri, and most animals have shorter dark bands across dorsum, no continuous dark bands along flank, and a generally darker and less contrasting body and head colouration, although there is an overlap in body colouration between the two species (Morphobank M585300 versus M676180; Fig. 7).
Finally, head shape in most individuals differs between the two species, with H. bouvieri having a longer and more pointed snout than H. nicolauensis sp. nov.. Again, there is variation in this feature, as some H. bouvieri have a snout shape that is not clearly different from H. nicolauensis sp. nov. (see Figs. 3, 7 and Morphobank M676174 versus M585304).
Hemidactylus nicolauensis sp. nov. differs morphologically from H. boavistensis by its smaller size (the latter reaching up to 50 mm SVL), coarser and less numerous ventral scales (26 or 27 versus 35–38 across mid-belly in H. boavistensis), lower number of enlarged scales and digital lamellae under fourth hind toe (5–8 versus 7–9), and its narrower head. The two species have also a clearly different colouration (e.g.: Morphobank M585300 versus M678224; Fig. 7). Finally, H. nicolauensis sp. nov. differs morphologically from H. lopezjuradoi by its lower number of precloacal pores in males (one on each side versus three on each side in H. lopezjuradoi) and by the absence of the enlarged small tubercles on the back that are typical of H. lopezjuradoi.
Description of the holotype and variation. The holotype is an adult male, 40.5 mm from tip of snout to cloaca, regenerated tail length 30 mm, eight supralabials on each side, seven (left side) and eight (right side) infralabials, two precloacal pores (one on each side) separated by a single scale, five enlarged scales and lamellae under second toe, six under third toe, seven under fourth hind toe and seven under fifth toe (Morphobank M585325–M585346).
Due to the poor state of conservation of the NHMUK specimens, the following description is mainly based on the four SMF and two BEV specimens. A small species, SVL varying between 33 and 41 mm in apparently adult specimens (including a female carrying eggs and a male with well-developed precloacal pores). Tail long and thick, 70 to 80 % of the body length in the two specimens with complete tail, even thicker when regenerated. Long forelimbs and hind limbs with five fingers and toes.
First finger and toe much smaller than other digits and without well-developed claw. Second and fifth fingers approximately same size, third finger longer, fourth finger the longest, all with a narrow tip carrying a claw projecting out of an enlarged middle part of the fingers. Hind foot and toes of same structure, but with fifth toe longer than second and toes with more developed tips and claws than fingers. Starting from the tip, the underside of each finger and toe has one large and elongated, but entire lamella, followed by 2–3 transversally elongated lamellae that are divided or centrally constricted, and 1–3 enlarged scales that are clearly larger than the other scales under hand and foot. The lamellae harbour tiny hair-like structures typical of many geckos. There are 3–5, 5, 5–6, 6 and 5–6 enlarged scales and lamellae under first to fifth finger and 3–4, 5, 5–6, 5–8 and 5–7 enlarged scales and lamellae under first to fifth toes.
Head elongated, snout long with straight or convex upper snout, hardly protruding small nostrils, large eyes with diameters larger than distance from eye to tip of snout. Distance from eye to snout equals distance from eye to ear opening. Ear opening very small (smaller than average supralabials), roundish. Supralabials and infralabials 7–8. Rostral large, reaching nostril and depressed in the middle as if it was semidivided. Three scales border the nostril in addition to the rostral. Mental scale triangular with rounded outer edge, approximately as broad as long, bordered by two postmental scales with a long suture. Three to four rows of enlarged scales border the postmental posteriorly. Rest of head, limbs and body scalation rather uniform, covered by small, round, flat scales, smaller on head and neck and even smaller in temporal area and on side of neck, 23–29 scales across top of head between the eyes (excluding superciliaries). No collar or gular fold. Ventrals gradually larger, triangular, broader than long, in 26 or 27 in longitudinal rows. Unregenerated tail (present in the two SMF juveniles) covered dorsally and laterally with larger flat rectangular scales, arranged in nearly regular tail rings; under the tail a single row of much larger scales, each tail covering most of the undertail width. Regenerated tail covered with larger scales arranged less regularly; undertail variable, covered of slightly larger scales with irregular disposition (hence without the single row of much larger scales of original tails). Both sexes have a few short blunt tubercles on each side of tail basis.
Colouration of live specimens available for one (adult female) SMF specimen, the two adult female BEV specimens and three of the NHMUK specimens. Body pale grey to brown, with five dark crossbands on back, the first one between forelimbs and the last one between hind limbs, larger than the intervening pale areas, often with irregular edges and/or invaded by pale elements; head same colour as body, with a dark patch on top of back of head, and various amount of dark elements on top of head, with a dark band running from the snout to the insertion of forelimbs, where it sometimes joins an irregular dark band running along flanks to tail basis, but this dark band along flanks is often missing. Limbs and digits dark, about same colour as dark crossband on dorsum, often with scattered pale scales. Tail yellow to pale red, with dark irregular narrow crossbands when intact, and an even more irregular dark pattern when regenerated. Underparts pale, whitish to greyish, except undertail that is uniformly yellow to pale red. Lamellae and some enlarged scales under toes and fingers contrastingly paler.
Sexual dimorphism weakly developed, males have two well-developed precloacal pores (one on each side) situated in front of the cloaca and separated by a single scale.
Distribution. São Nicolau Island, Cabo Verde Archipelago. So far only known from three localities in two areas (central mountains around Cachaço and Ribeira Funda on the north coast, see Fig. 1 and Table 1), but doubtlessly far more widespread. Further research needed to establish its distribution range on São Nicolau.
Natural history. The rarity of these geckos makes their precise ecological requirements uncertain. Specimens have been found in the more humid areas of the island. Around Cachaço, the two localities where they have been found are situated at the foot of rocky outcrops, and, in one of them, the two animals were found in the most humid microhabitat, next to a spring with water dropping from the rock surface. In Ribeira Funda, the species has been collected in a narrow valley between cliffs and steep rocky slopes. These animals are supposed to be mainly nocturnal, and all specimens have been found inactive by day under stones or in rock crevices. In one spot, two females were found together (the two BEV specimens). One female from Ribeira Funda collected on 1 April 2007 (UCV2018/004 or former SMF 86991) carried a single, large, well visible egg.
Conservation status. Not Evaluated. All native reptiles in Cabo Verde are endemic to these islands, although this is not widely-recognized among the public and policy makers. In addition, geckos are generally feared due to traditional beliefs, and there may be occasional persecution (Vasconcelos et al. 2013). Education is therefore needed to raise awareness of these species and of their conservation requirements and stressing that these animals are inoffensive to humans. The existing conservation regulations should also be updated to reflect changes in both taxonomy and conservation status (Vasconcelos 2013b). There is very little information on the population status and ecology of H. nicolauensis sp. nov., so the precise impacts of identified and potential threats require further research. For H. bouvieri, H. nicolauensis sp. nov., and H. lopezjuradoi, the paucity of records both historically and recently, in spite of active research on all the islands, indicates low population densities or severe fragmentation of the occupied range (rather than an extraordinary low detectability) and suggests a marked population decline since human colonization of the islands (Arnold et al. 2008).
description: Published as part of Vasconcelos, Raquel, Köhler, Gunther, Geniez, Philippe & Crochet, Pierre-André, 2020, A new endemic species of Hemidactylus (Squamata: Gekkonidae) from São Nicolau Island, Cabo Verde, pp. 501-522 in Zootaxa 4878 (3) on pages 506-517, DOI: 10.11646/zootaxa.4878.3.4, http://zenodo.org/record/4425319