Saturday, July 23, 2016

[Herpetology • 2014] Hemidactylus minutus • Systematics and Biogeography of Hemidactylus homoeolepis Blanford, 1881 (Squamata: Gekkonidae), with the Description of A New Species from Arabia


Hemidactylus minutus  
Vasconcelos & Carranza, 2014

Abstract

A new species of gecko of the genus Hemidactylus (Squamata: Gekkonidae) is described from Oman and extreme eastern Yemen. Hemidactylus minutus sp. nov. is characterized morphologically by its very small size, being the smallest Hemidactylus in mainland Arabia, absence of enlarged tubercles anywhere on the body, expanded subcaudal scales beginning some way from tail base, number of preanal pores, number of lamellae under the first and fourth toes, and weakly contrasted black and white banded pattern on the ventral part of tail. It is also genetically distinct from H. homoeolepis to which it has previously been referred, and from all other closely related Hemidactylus from the arid clade in DNA sequence data for mitochondrial (12S, cyt b, ND4) and three nuclear (RAG1, MC1R, c‑mos) markers. An adult female from southern Yemen and a badly preserved juvenile from southwestern Saudi Arabia previously assigned to H. homoeolepis are morphologically differentiated from this species and from H. minutus sp. nov. and temporarily referred to as Hemidactylus sp. 12 and Hemidactylus sp. 13, respectively until more specimens are collected and analyzed.

        Up to now, H. homoeolepis was the only non-endemic native species of the Socotra Archipelago. With the description of H. minutus sp. nov., all native reptile species of Socotra are now endemic, such that this archipelago has one with the highest number of endemic reptiles in relation to its small size. In addition, as a result of our taxonomic change, the area of occupancy and extent of occurrence of H. homoeolepis have changed dramatically and thus its conservation status should be updated. Although H. minutus sp. nov. seems widely distributed and relatively abundant, its conservation status should also be re-evaluated.

Keywords: gecko, DNA, morphology, taxonomic revision, Socotra, Oman


FIGURE 5. Type localities, general dorsal views and details of Hemidactylus minutus sp. nov. from mainland Arabia. 
A) and C) type locality (Asylah, Oman) of H. minutus sp. nov.; B) dorsal view of Hemidactylus minutus sp. nov. holotype (voucher code: NHMUK2013.901; sample code: S7676); D), E), F) and G) details of the head, tail underside pattern, preanal pores, and lamellae of the 1st and 4th toes of the holotype. 

Etymology. The species epithet “minutus” is a Latin adjective that refers to the small size of this species, the smallest Hemidactylus in mainland Arabia. 

Diagnosis. A small Hemidactylus characterized by the following combination of morphological characters: (1) maximum recorded snout-vent length, SVL 34.6 mm (mean 29.2 ± 3.4 mm); (2) absence of enlarged tubercles anywhere on the body; (3) expanded subcaudal scales beginning some way from tail base; (4) head narrow and low (4.2–6.7 mm in width and 2.4–3.7 mm in height); (5) relatively short snout (2.0–2.9 mm nostril–eye); (4) 4–6 preanal pores, PAP (mean 5.8 ± 0.5); (6) four or five lamellae under the first posterior toe, LP1st (4.5 ± 0.5); (7) seven to nine, but most usually eight lamellae under the fourth posterior toe, LP4th (mean LP4th 8.0 ± 0.2); (8) weakly contrasted black and white banded pattern on the ventral part of tail.

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Distribution. Distributed along the Arabian Sea coast, from northeastern Oman to extreme eastern Yemen (Fig. 1; Appendix I, II). In Dhofar it is found more than 70 km inland, as far as Thumrait. Although the population of Hemidactylus “homoeolepis” from the Hasikaya Island in the Hallaniyat Archipelago may belong to this species, a detailed genetic and morphological analysis is needed to assess whether this population is H. minutus sp. nov., H. paucituberculatus, (also present in coastal Dhofar) or a new species. Previous reports of Hemidactylus “homoeolepis” from Masirah Island and from Jazirat Hamar an Nafur Island have been recently assigned to H. masirahensis and H. inexpectatus, respectively (Carranza & Arnold 2012; pers. observ.). Hemidactylus minutus sp. nov. can be considered nearly endemic to Oman.

 Natural history. The new species is a ground dwelling strictly nocturnal gecko, usually found in dry places with stony, gravely or even sandy substrates with rocky outcrops (Fig. 5A, C). It is abundant in many parts of its distribution range. Observations of specimens of H. minutus sp. nov. carried out by Arnold (1980) at Wadi Ayoun and Thumrait indicated that almost all the specimens (63/64) were first sighted either on the ground (38/64) or lower than 60 cm from it (25/64), and only one was found on a rock above this height. At Wadi Sayq, eighteen individuals reported also by Arnold (1980) were at heights of between 50 cm and 2 m on rock faces, but this may have been because the ground here was covered by dense vegetation following the monsoon. Hemidacytlus minutus sp. nov. is very agile, often proceeding in a series of leaps when pursued. Gravid females, each carrying a single egg, have been recorded in late September at Khawr Sawli (Arnold 1980). 


FIGURE 5. Type localities, general dorsal views and details of Hemidactylus minutus sp. nov. from mainland Arabia.
A) and C) type locality (Asylah, Oman) of H. minutus sp. nov.; B) dorsal view of Hemidactylus minutus sp. nov. holotype (voucher code: NHMUK2013.901; sample code: S7676); D), E), F) and G) details of the head, tail underside pattern, preanal pores, and lamellae of the 1st and 4th toes of the holotype.

FIGURE 5. Type localities, general dorsal views and details of Hemidactylus homoeolepis from Socotra.
  I) of an unvouchered specimen (photograph by Edoardo Razzetti); J) habitat type of H. homoeolepis, generally dry places with rocky substrate; K), M) and N) details of the head, preanal pores, and lamellae of the 1st and 4th toes of the syntype, respectively; L) detail of the pattern of underside the tail of and unvouchered specimen. 

Raquel Vasconcelos and Salvador Carranza. 2014. Systematics and Biogeography of Hemidactylus homoeolepis Blanford, 1881 (Squamata: Gekkonidae), with the Description of A New Species from Arabia. Zootaxa. 3835(4): 501–527.  DOI: 10.11646/zootaxa.3835.4.4

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