Phrynocephalus mystaceus khorasanus, Solovyeva, Evgeniya N., Dunayev, Evgeniy N., Nazarov, Roman A., Mehdi Radjabizadeh,, Poyarkov, Nikolay A. & Jr.,, 2018

Solovyeva, Evgeniya N., Dunayev, Evgeniy N., Nazarov, Roman A., Mehdi Radjabizadeh,, Poyarkov, Nikolay A. & Jr.,, 2018, Molecular and morphological differentiation of Secret Toad-headed agama, Phrynocephalusmystaceus, with the description of a new subspecies from Iran (Reptilia, Agamidae), ZooKeys 748, pp. 97-129 : 99-105

Phrynocephalus mystaceus khorasanus ssp. n. Figs 6A, B; 7; 8; Table 4

Holotype.

ZMMU R-11913 (adult female; field number NR-1191).

Type locality.

Iran, Khorasan historical area, Khorasan Razavi Province (ostan), environs of Gonabad, the right bank of the Kale-Shur River; sand dunes (see Fig. 9); N34°39', E58°43'; elevation 850 m a. s. l. Collected by Roman A. Nazarov and Mehdi Radjabizadeh on April 25, 2005.

Paratypes.

ZMMU R-13009 (one adult male with everted hemipenial structures, field number RAN 1723; and one adult female, field number RAN 1724) was collected in Iran, Khorasan historical area, Khorasan Razavi Province, 20 km east of the town of Boshrouyeh (N33°54', E57°30'; elevation 864 m a. s. l.) by Dmitriy A. Bondarenko, Roman A. Nazarov, and Mehdi Radjabizadeh on May 05, 2009. The rest of paratypes were collected in the area close to the type locality. ZMMU R-13011 (one adult male with hemipenial structures, field number RAN 1947; and one subadult female, field number RAN 1948) was collected in Iran, Khorasan Razavi Province, 60 km north of the town of Gonabad, stabilized or semi-stabilized sands (N34°36', E58°14'; elevation 867 m a. s. l.) by Roman A. Nazarov, Rustam K. Berdiev, Vlad G. Starkov, and Mehdi Radjabizadeh on June 02, 2009. ZMMU R-13169 (subadult female) was collected in Iran, Khorasan Razavi Province, 30 km north of the town of Gonabad, on sandy massif on the right bank of the Kale-Shur river (N34°35', E58°43'; elevation 888 m a. s. l.) by Roman A. Nazarov, Dmitriy A. Bondarenko, and Mehdi Radjabizadeh on May 10, 2010. ZMMU R-12202 (juvenile female with slightly orange lower surface of the tail, field number N-093) was collected in Iran, Khorasan Razavi Province, 60 km north of the town of Gonabad, on sands (N34°36', E58°44'; elevation 881 m a.s.l.) by Dmitriy A. Bondarenko on April 20, 2006.

Diagnosis.

A member of Ph. mystaceus species complex based on the following combination of morphological attributes: (1) a large-sized Phrynocephalus species with SVL up to 97.5 mm, tail shorter than SVL; (2) pair of cutaneous flaps present at mouth corners with numerous spiny scales along flap edges; (3) distinctly flattened body and tail; (4) toes with fringes formed by triangular scales; subdigital lamellae on toes III and IV with ridges. Phrynocephalus mystaceus khorasanus ssp. n. can be distinguished from the nominative subspecies of Ph. mystaceus by the following combination of two diagnostic morphological characteristics: (1) 24-27 lamellae on toe IV; (2) few supralabial scales (less than 14). In life, the new subspecies can be further distinguished from the nominative subspecies by the orange color of the lower surface of tail in young specimens (lemon to yellowish in Ph. m. mystaceus except the populations from Eastern Kazakhstan and western China, formerly described as Ph. m. aurantiacocaudatus ). MtDNA sequences of Phrynocephalus mystaceus khorasanus ssp. n. are markedly distinct from those in all other populations of Ph. mystaceus with sequence divergence in the range of 6.84-7.28% between them. The new subspecies is notably smaller than the representatives of southern populations of Ph. m. mystaceus from Uzbekistan and Turkmenistan, formerly described as Ph. m. galli , which can reach SVL up to 122.7 mm ( Anderson 1999), whereas for Iranian population Anderson (1999) reported the largest specimen of Ph. mystaceus to have SVL up to 77.7 mm. SVL in the largest specimen in our sampling reached 86.0 mm, while Molavi et al. (2014) recorded a specimen with SVL of 97.5 from Semnan Province.

Etymology.

The name of the new subspecies khorasanus is a Latinized toponymic adjective, derived from Khorasan, the name of the historic area and a Khorasan Razavi Province in the northeast Iran, where the new subspecies was found. We suggest the "Khorasan Secret Toad-headed Agama" as a common name in English.

Description of holotype.

Medium-sized agamid lizard, adult female, specimen in good state of preservation; body dissected on ventral side along the midline of belly (dissection ca. 20 cm in length). Measurements and counts of the holotype are presented in Table 4.

Head large, rounded, distinctly wider than neck region (see Fig. 7A); body and tail notably flattened. Snout abruptly blunt, head almost vertical in profile view (see Fig. 7E), nostrils invisible dorsally (see Fig. 7C). Nasals separated from each other by single scale (see Fig. 7D). Dorsal surface of head with distinct pileus consisting of small slightly keeled scales; ca. 30 scales across the pileus. Pineal scale separated from nasals by 13 smaller scales; scales covering orbital area somewhat smaller than those on frontal surface of head; occipital scales not enlarged. Five scales contacting subnasal ventrally (see Fig. 7D). Subnasal scale not in contact with inner (medial) side of supranasal. Supralabials separated from subnasal scale by 6 rows of small granular scales (see Fig. 7D). Pair of skin-folds form characteristic ear-shaped flaps in mouth corners, edges of each flap with enlarged conical scales, two groups of similarly enlarged conical scales on each side of head posterior to the mouth angle at tympanal area (see Fig. 7E). Supralabial scales anterior to cutaneous fold at mouth angle 11/12 (hereafter data for symmetrical characteristics is given in Right/Left order); 9/9 of anterior supralabials notably flattened, 2/3 posterior supralabials conical-shaped; supralabials separated from small granular scales of lower eyelid by 3/4 rows of scales, ventral row of these scales almost the same size as supralabials (see Fig. 7E). Single small scale between the posteriormost supralabial and insertion of cutaneous fold at mouth angle. Infralabial scales anterior to cutaneous fold - 6/6, 3/3 of anterior infralabials notably flattened, posterior infralabials cone-shaped. Posterior corner of eye and insertion of cutaneous fold at mouth angle separated by row of three enlarged flat scales (see Fig. 7E). Vertebral scales not enlarged. Scales at middle of dorsum slightly bigger than scales on dorsolateral and lateral surfaces of body. Dorsal scales with weak keels, becoming cone-shaped laterally, forming almost triangular spines on the flanks. Notably enlarged spiny scale (about four times the size of adjacent scales) on each side of thorax behind maxilla, two groups of enlarged spiny scales on each lateral surface of neck region (see Fig. 7E). Tail notably flattened along its whole length. Scales on dorsal surface of tail and on ventral surface of tail posterior half notably keeled; scales on lateral sides of tail with well-pronounced spines. Limbs comparatively long: hindlimb length greater than distance from cloaca to gular fold. Toe IV bearing a single row of subdigital lamellae, each with a well-pronounced ridge on its volar surface; lateral sides of toe IV with two rows of enlarged triangular scales that form distinct serrated fringe (see Fig. 7F). Similar crests present on lateral surfaces of toe III, triangular scales on toe III notably smaller compared to those on toe IV (see Fig. 7F). Number of lamellae on toe IV 24/24, on toe III 16/16; number of enlarged triangular scales on toe IV 20/20, on toe III 9/9.

Color of holotype in life.

In life dorsum sandy-beige; with numerous small black and white dots and reticulations; row of three pairs of irregular-shaped larger dark blotches on each side of vertebral line; ventral surfaces of body, limbs and proximal part of tail white; ventral surface of tail tip black, chin and throat with gray reticulations, chest with blackish longitudinal blotch. Ten brownish transverse bars (wider than interspaces) on dorsal surface of tail, faint at tail basis, get more distinct towards tail tip. Internal surfaces of mouth angle cutaneous flaps in life are pinkish, and may become red when animal displays a threatening posture.

Color of holotype in preservative.

In preservative, numerous dark spots and mottling are distinct on dull sandy-gray background color of dorsum. They form vermiculate patterns ca. 1-2 scales wide. On lateral parts of dorsum these lines form 6-7 indistinct dark transverse bands. Ten dark transverse bars on dorsal side of tail are well-distinct (Fig. 7A). Three posterior dark bars have a distinct light-beige longitudinal line between them along midline of tail. Tail ventral surface light yellowish-white. Ventral surface of head with distinctive dark greyish marbling (Fig. 7A). Distinct triangular longitudinal black spot in the middle of chest area resembling a “necktie”, ca. 8.8 mm in length. Black coloration of distal part of ventral surface of tail 24 mm in length.

Paratype variation.

Variations of morphological characteristics in the type series are shown in Table 4 and in Fig. 8. In general, morphology of paratypes corresponds well to morphology of the holotype. SVL of new subspecies varies in range of 85.0-86.0 mm in two males, and in range of 54.0-70.0 in five females; tail length 76.0 mm in males, 51.0-67.0 mm in females; tail comparatively shorter in male specimens (SVL/TL ratio 1.12-1.13) than in females (SVL/TL ratio 1.00-1.06); however, the sample size is too small to detect significant differences. Length of dark distal part of ventral surface of tail varies from 20 to 27 mm. Number of subdigital lamellae on toe III varies from 17 to 20, from 25 to 28 on toe IV. Number of enlarged triangular scales of lateral fringes on toe III from 7 to 11, on toe IV from 18 to 21. Number of flattened anterior supralabials 6-11, total number of supralabials (to insertion of cutaneous fold at mouth angle) varies from 10 to 15. Number of small scales ventrally in contact with subnasal scale 3-6. Subnasal scale in all paratypes (except one specimen ZMMU R-13009) touches supranasal along medial edge of latter. In nearly all paratypes supralabials are separated from subnasal by five rows of small scales (only in ZMMU R-13009 by 4/5 rows of small scales). In most specimens, there is one small scale between last supralabial and insertion of cutaneous fold at mouth angle (specimen ZMMU R-13011 has two scales, ZMMU R-13169 lacks such scales). Number of flat anterior infralabials varies from 2 to 4, total number of infralabials to insertion of cutaneous fold at mouth angle varies from 5 to 7 (only ZMMU R-13009 has 3/3 infralabials). Number of black irregularly shaped spots on dorsum also may vary: from 4 to 6 pairs of black spots on each side of vertebral line (see Fig. 8A).

We were unable to detect sexual dimorphism in morphometric and meristic characteristics of Ph. mystaceus khorasanus ssp. n., however our sample size (N = 7) was too small. Molavi et al. (2014), who also examined seven specimens of both sexes from Semnan Province, was also unable to detect sexual dimorphism in morphological features in their sample.

Distribution.

To date, the new subspecies is known from two major localities in southwestern part of Khorasan Razavi Province (environs of the towns of Gonabad and Boshrouyeh, this study) and from a single locality in the easternmost part of Semnan Province of Iran (Ahmad Abad village, Molavi 2014). The record from the environs of the town of Boshrouyeh appears to be the southernmost known locality for Ph. mystaceus complex known to date. The three records of Ph. mystaceus by Anderson (1999) from the northern part of Khorasan Razavi Province, North Khorasan and Golestan provinces are all located along the border with Turkmenistan. These populations most likely correspond to Ph. m. mystaceus rather than to Ph. mystaceus khorasanus ssp. n. as they are close to the range of the nominative form and there are no biogeographic barriers that separate these populations. On the contrary, localities in Khorasan Razavi and Semnan provinces are situated on different elevations and sand massifs are isolated from the range of Ph. m. mystaceus by at least 200 km of habitats unsuitable for Ph. mystaceus . We anticipate new records of the new subspecies in sandy areas of Khorasan Razavi, Semnan and, possibly, northern part of Yazd and South Khorasan provinces.

Habitat.

Ph. mystaceus khorasanus ssp. n. inhabits sandy areas with sparse vegetation in northeast Iran at comparatively higher altitudes, than other Ph. mystaceus subspecies. The usual habitat is represented by dunes of loose sands and semi-stabilized dunes with rare grass, occasional bushes of Haloxylon sp. and Tamarix sp. and large open sandy areas (Fig. 9). The areas inhabited by the new subspecies receive almost no rainfall during the year. In the town of Gonabad the average annual temperature is 17.3 °C, the average temperature in July reaches 29.2 °C, the average temperature in January is 4.8 °C; In Boshrouyeh the average annual temperature is 19.7 °C, the average temperature in July is 31.9 °C, the average temperature in January is 6.6 °C. (http://www.climate-data.org).

Lizards burrow in sand, digging short tunnels and chambers; they can quickly dig into sand by rapid lateral movements of the body (Anderson, 1999).

Comparisons with other subspecies.

Comparisons of the new subspecies from Khorasan Razavi and Semnan provinces of Iran with the nominative subspecies Ph. m. mystaceus sensu lato from Middle Asia, Caspian basin, and westernmost Xinjiang (China) are summarized below. In preservative, the new subspecies can be differentiated from specimens of Ph. m. mystaceus by the following combination of morphological attributes: lower number of subdigital lamellae on the IVth toe (SLIV 25.7 (24-27; N = 7) in vs. 30.2 (25-35; N = 70) in Ph. m. mystaceus sensu lato); comparatively lower number of supralabials (SL 12.1 (10-14; N = 7) vs. 14.9 (10-19; N = 70) in Ph. m. mystaceus sensu lato) and by the comparatively shorter black distal part on the tail ventral surface (TL-black/TL 0.38 (0.36-0.40; N = 7) vs. 0.42 (0.32-0.48; N = 70) in Ph. m. mystaceus sensu lato). In life, juvenile and young specimens of the new subspecies can be further distinguished from Middle Asian / Caspian Basin populations of Ph. mystaceus by is rusty orange color of the proximal part of tail ventral surface (vs. lemon-yellow in Ph. m. mystaceus sensu stricto), but is similar to orange tail coloration in juveniles of East Kazakhstan - western China populations described as Ph. m. aurantiacocaudatus .

We do not recognize Ph. m. galli as a separate subspecies due to the absence of stable genetic and morphological differences of this subspecies from Ph. m. mystaceus (see above). The Phrynocephalus mystaceus dagestanica form from Daghestan ( Ananjeva “1986” 1987) is very close to the populations from the Volga River basin and was considered a synonym of Ph. m. mystaceus by several authors ( Semenov and Shenbrot 1990; Barabanov and Ananjeva 2007). Our molecular and morphometric data do not support monophyly or significant differentiation of Ph. m. aurantiacocaudatus from Eastern Kazakhstan and western China. The only stable difference between this population and Ph. m. mystaceus sensu stricto is the tail coloration in juveniles. We consider that additional genetic and morphological data is needed to clarify taxonomic status of East Kazakhstan Ph. mystaceus populations.

Discussion.

Our study indicates deep genetic divergence between Iranian populations of Ph. m. khorasanus ssp. n. and the rest of the populations within the range of the species. However, morphological differentiation within Ph. mystaceus complex is less clear with only a few morphological characteristics that reliably separate these two lineages. Differentiation pattern for the mtDNA COI gene within the Middle Asian and Caspian populations of Ph. mystaceus complex suggests that East Kazakhstan was populated by Ph. mystaceus earlier than the rest of Middle Asia. After that, a dispersal process from the east to the west likely took place. Morphologically different populations of Ph. mystaceus across Middle Asia present considerable amount of variation both in body size and in such morphological features as the relative size of cutaneous flaps in the mouth angles, relative tail length, etc. This high morphological plasticity may be connected with psam mophilous biology of this species, as it was suggested by previous researchers ( Vel’dre 1964a, 1964b; Semenov and Shenbrot 1990; Golubev and Sattorov 1992).

The data of phylogenetic analyses in the present paper clearly indicates that the whole territory of Middle Asia, including westernmost China and Caspian region, is inhabited by a single poorly differentiated mtDNA lineage. Golubev and Sattorov (1992) argued that coloration of the ventral tail surface in juveniles of Ph. mystaceus is also subject to high variation, and “orange-” and “yellow-tailed” specimens can be occasionally recorded within the same population, thus suggesting that subspecies within Ph. mystaceus should not be recognized. Our mtDNA genealogy indicates that both Ph. m. " galli " and Ph. m. " aurantiacocaudatus " do not form a respective monophyletic units and are genetically indistinguishable or very close the nominative subspecies P. m. mystaceus sensu stricto (p-distance 1.65-1.87% in case of East Kazakhstan populations).

On the contrary, the Khorasan population described herein as Ph. m. khorasanus shows very deep genetic divergence in mtDNA which is comparable to the species-level divergence in Phrynocephalus , but is only moderately differentiated morphologically. Indeed, previous research on four mtDNA genes also showed significant differentiation between Ph. mystaceus from Khorasan and Ph. m. mystaceus (p-distances: COI - 7.18%; ND4 - 6.6%; ND2 - 8.0%; and cyt b - 6.6%) (see Solovyeva et al. 2014). According to our unpublished data on molecular dating of 4 mtDNA genes these two forms diverged during Pliocene about 3.7 Ma (Solovyeva et al., 2018). Further studies are required to verify the taxonomic status of Ph. m. khorasanus ssp. n., including morphological examination of larger samples and molecular analysis of the nuclear DNA markers in order to check the presence of possible isolation between the Iranian and Middle Asian forms of Ph. mystaceus . The new subspecies inhabits sand dunes in the northeastern Iran; this desert area is separated from the range of Ph. m. mystaceus by Kopet-Dagh Mountain Ridge making the possibility of gene flow between these populations quite low. However, the taxonomic status of Ph. mystaceus populations reported by Anderson (1999) from northern Iran (northern parts of Golestan, North Khorasan and Khorasan Razavi provinces) is unclear and require verification. Additional fieldwork in northern Iran, western Afghanistan, and southern Middle Asia is required to recover new populations of Ph. mystaceus complex. Further progress in understanding of the phylogenetic relationships within Ph. mystaceus complex might lead to reconsideration of the taxonomic status of the Khorasan population as a full species.