Ctenophorus modestus ( Ahl, 1926 )

Dong, Caroline M., Johnston, Greg R., Stuart-Fox, Devi, Moussalli, Adnan, Rankin, Katrina J. & McLean, Claire A., 2021, Elevation of Divergent Color Polymorphic and Monomorphic Lizard Lineages (Squamata: Agamidae) to Species Level, Ichthyology & Herpetology 109 (1), pp. 43-54 : 48-50

Ctenophorus modestus ( Ahl, 1926)

Swift Rock Dragon

Figures 1D–H , 4C–D , 5B

Amphibolurus modestus ( Ahl, 1926: 187–188) .

Amphibolurus decresii ‘northern race’ ( Houston, 1974: 52).

Ctenophorus decresii ‘northern lineage’ ( McLean et al., 2013: 52 ).

Types.— The original description was based on two syntypes, both from ‘Australien’ and registered as ZMB30092 ( Ahl, 1926). We designate the subadult male as lectotype (now registered as ZMB 54516; Fig. 5B ) and the adult female as paralectotype (ZMB 30092; Fig. S3 ; see Data Accessibility) because only the male exhibits the diagnostic coloration. No exact locality is available for these specimens.

Diagnosis.— Ctenophorus modestus is a member of the C. decresii species group ( Houston, 1974; Houston and Hutchinson, 1998). Within the C. decresii species group, C. modestus is distinguishable by the following combination of characters: snout scales smooth to longitudinally keeled; vertebral scales flat; a smooth-edged dark lateral stripe, sometimes interrupted to form a separate blotch posterior to the tympanum; and in males, throat coloration is polymorphic (orange, yellow, orange-yellow, or gray) with or without an overlay of gray reticulations and a small central black patch. Description.— A moderately sized lizard reaching a maximum SVL of approximately 85 mm and total length of 255 mm. Head and body depressed. Tail long and tapered to a fine tip. Forelimbs moderately long, almost reaching groin when adpressed. Hindlimbs long and reaching or almost reaching snout when adpressed. Finger lengths: 4. 3. 5. 2. 1; toe lengths: 4. 3. 5. 2. 1. Characteristic of the genus, a distinct row of enlarged keeled scales extending from the nostril, below the eye to above the tympanum ( Houston and Hutchinson, 1998). Ear membranes exposed and scale-free. Scales on snout are smooth to longitudinally keeled. 13–18 supralabial scales; 13–18 infralabial scales; 4–6 scales between rostral and nasal; 4–6 scales between supralabial and nasal; 9– 13 internasal scales; 19–27 subdigital lamellae on the fourth toe ( McLean et al., 2013). Small clustered pale yellow to orange spines anterior to tympanum. Dorsal crest is small, no more than a series of keeled scales, becoming smaller posteriorly and not reaching base of tail. Nuchal crest low or absent. Scales on the dorsal surfaces of the limbs and tail are keeled. The gular fold is strongly developed and extends across the shoulders. 34–45 femoral and precloacal pores are arranged in a straight line along the thighs. Pores are present but smaller in females.

Adult male base color varies from gray-blue to brown, with pale blue flanks ( Figs. 1H , 4C ). The dorsolateral surface of the head is brown, with orange around the eyes, nostrils, and along the upper jaw, and beneath the tympanum terminating at the neck. The extent of this coloration varies among individuals and depends on location. A broad black lateral stripe begins posterior to the eye, becoming thicker posterior to the tympanum and terminating at the groin. A thin cream, yellow, or orange stripe begins at the tympanum and terminates just posterior to the shoulder ( Figs. 1H , 4C ). On the ventral surface, males are cream with orange flushes on the belly, hindlimbs, and the length of the tail during the breeding season. A dark chest patch tapers to a point midbody and sometimes extends along the undersides of the forelimbs. This dark patch may vary in intensity, from black to gray. Male throat coloration varies among individuals with distinct gray, orange, yellow, and orange-yellow morphs ( Teasdale et al., 2013; Fig. 1D–G ). Base throat color sometimes overlain with gray reticulations or with a distinct black mark in the center of the throat.

Adult females are cryptically colored, predominantly graybrown to orange-brown, densely patterned with darker and lighter speckling ( Fig. 4D ) and sometimes a thin, pale vertebral line. Similar to males, a black lateral stripe runs along the flanks, but sometimes less prominently than in males. White to cream on the ventral surface, with varying degrees of gray reticulations on the throat. Orange to yellow flushes on the belly and gular region during the breeding season. Juveniles resemble adult females in coloration and pattern. Color patterning remains visible in fresh spirit-preserved specimens but fades with time.

Measurements (mm) and meristic characters of lectotype.— (Bilateral meristics as left [L] and right [R]) SVL, 52.9; TL, 95.6; AGL, 24.3; HL, 18.1; HW, 14.0; HD, 7.8; EYE, 3.8; SL, 6.6; JL, 8.3; NW, 5.3; HUML, 7.7; RADL, 8.5; HANL, 11.7; FINL, 5.6; FEML, 14.5; TIBL, 17.4; FOOT, 21.3; TOE, 11.5; SUPRA, 15L/16R; INFRA, 18L/19R; ROSNAS, 4–5L,5R; SUPRANAS, 4L/3–4R; INTERNAS, 12; SDL, 25L/25R; FP, 22L/20R.

Distribution and natural history.— Ctenophorus modestus inhabits rocky areas and outcrops, sheltering in rock crevices, similar to other members of the C. decresii group ( Gibbons, 1979). The species occurs throughout the Flinders and Olary Ranges in South Australia, Australia ( Figs. 2C , 3A , 6 ). These lizards occupy habitats ranging from well-watered to semi-arid, with sparse vegetation and are active in hot weather ( Houston, 1974; Gibbons, 1979). Adults occur almost exclusively on rocks, but juveniles may be found among surrounding vegetation up to 100 meters away ( Houston, 1974; Gibbons and Lillywhite, 1981). Adults perch conspicuously on elevated sites to bask and/or perform territorial and courtship displays ( Gibbons, 1979). If disturbed, they will run into a crevice or beneath a rock slab. Predators are predominantly birds but likely also include elapid snakes ( Gibbons and Lillywhite, 1981; Stuart-Fox et al., 2004).

Figures

FIG. 1. (A) The blue mainland male throat of C. decresii sensu stricto and (B) the blue reticulated with yellow throat found on Kangaroo Island. The four male throat morphs of Ctenophorus modestus: (D) orange, (E) yellow, (F) orange-yellow (yellow with an orange central patch), and (G) gray. Male dorsolateral patterning and coloration differ where (C) C. decresii sensu stricto has a more ‘‘pinched’’ or broken lateral stripe with a greater extent of bordering orange or yellow coloration, and (H) C. modestus has a relatively straight edged lateral stripe with cream and orange coloration terminating at the shoulder.

FIG. 4. Males (A, C) and females (B, D) of Ctenophorus decresii (A, B) from Palmer and Mengler’s Hill Lookout, respectively, and C. modestus (C, D) from Telowie Gorge, all from South Australia, Australia (photos: copyright Adam Elliott).

FIG. 5. (A) Dorsal (left) and ventral (right) photographs of the lectotype of Ctenophorus decresii (Duméril and Bibron, 1837; MNHN 6545). This specimen is an adult male collected from Kangaroo Island, South Australia, in January 1803 (photos: Nicolas Vidal, Muséum national d’Histoire naturelle Paris). (B) Dorsal (left) and ventral (right) photographs of the lectotype of Ctenophorus modestus (Ahl, 1926; ZMB 54516). This specimen is a subadult male from ‘‘Australien’’ without an exact locality or reference to a collector or donor (photos: Frank Tillack, Museum für Naturkunde Berlin).

FIG. 3. (A) Map showing localities of examined museum specimens: Ctenophorus modestus (squares); C. decresii sensu stricto (circles); C. fionni (triangles); and C. vadnappa (plus [þ]). Specimens without GPS coordinates are excluded. (B–C) Linear discriminant analyses of (A) males and (B) females based on 23 variables: Ctenophorus modestus (squares); C. decresii (circles); C. fionni (triangles); and C. vadnappa (plus [þ]). 95% confidence ellipses are shown. The lectotypes (males) and paralectotypes (females) of C. modestus and C. decresii are indicated with arrows.

FIG. 2. Genetic divergence between Ctenophorus modestus (northern Flinders Ranges [NFR], southern Flinders Ranges [SFR], Olary Ranges [OR]) and C. decresii (mainland south [MS] which encompasses the Mount Lofty Ranges and Fleurieu Peninsula, and Kangaroo Island [KI]) and specimens examined for morphological analyses. (A) Results of a Bayesian analysis of ancestry in the program STRUCTURE (K ¼ 2). Each vertical bar represents an individual and individuals are ordered by population and latitude (from north to south). The proportion of white and gray represents the proportion of C. modestus and C. decresii ancestry in each individual, respectively. (B) Two-dimensional principal coordinate plot (PCoA) showing pairwise genetic distances between individuals: Ctenophorus modestus (squares), C. decresii (circles). 95% confidence ellipses of each population are shown. Both A and B were constructed from a genomic SNP dataset of 1333 SNPs (n ¼ 148). (C) Map showing geographic locations of samples of C. modestus and C. decresii shown in A and B.

FIG. 6. Geographic distribution of Ctenophorus modestus (squares) and C. decresii (circles) based on specimens in Australian Museums from the Atlas of Living Australia (data: https://doi.org/10.26197/ 5d91626857226); coordinates which were likely inaccurate (e.g., unsuitable habitat) were removed. Protected areas described in the Collaborative Australian Protected Areas Database (CAPAD, 2018) are shown as gray areas. The extent of occurrence is shown for C. modestus (49,102 km2; orange lines) and C. decresii (6,604 km2 total [mainland: 5,772 km2; Kangaroo Island: 832 km2], blue lines).