Leptolalax ardens, Rowley & Tran & Le & Dau & Peloso & Nguyen & Hoang & Nguyen & Ziegler, 2016

Rowley, Jodi J. L., Tran, Dao T. A., Le, Duong T. T., Dau, Vinh Q., Peloso, Pedro L. V., Nguyen, Truong Q., Hoang, Huy D., Nguyen, Tao T. & Ziegler, Thomas, 2016, Five new, microendemic Asian Leaf-litter Frogs (Leptolalax) from the southern Annamite mountains, Vietnam, Zootaxa 4085 (1), pp. 63-102 : 75-86

Leptolalax ardens sp. nov.

Figs. 7D , 9A , 10 .

Holotype. VNMN 04707/AMS R 176454, adult male, calling on clay bank 1.5 m from headwaters of 1–2m wide rocky, medium gradient, high–flow stream in evergreen forest in Kon Ka Kinh National Park, Gia Lai Province, Vietnam (14.2258º N, 108.3230º E; 1162 m elevation, Fig. 1 , Fig 9E ). Collected at 19:30 h on 21 August 2011 Jodi J. L. Rowley, Vinh Quang Dau, Huy Duc Hoang, Luong Thi Nguyen, Tan Thanh Le, Dinh Djung, and Y H'Jun.

Paratypes. AMS R 176452–176453, two adult males (both calling), and VNMN 04708/AMS R 176455– VNMN 04710/AMS R 176457, three adult males (not observed calling), collected on same date and locality as holotype. VNMN 04711 /AMS R 176458, adult female (gravid) and VNMN 04712 /AMS R 176459 adult male (calling), collected at 19:55 h on 23 August 2011 in evergreen forest in Kon Ka Kinh National Park , Gia Lai Province, Vietnam (14.2263º N, 108.3345º E; 1450 m elevation) . UNS 00530/AMS R 176460–UNS 00532/ 176462, AMS R 176463, AMS R 176464, UNS 00533/176465, UNS 00534/AMS R 176466, 176467, and NCSM 79650 , 9 adult males, collected at night on 24 August 2011 in swampy area with small rocky stream in evergreen forest in Kon Ka Kinh National Park , Gia Lai Province, Vietnam (14.2197 º N, 108.3207 º E; 1041 m elevation). All specimens were collected by Jodi J. L. Rowley, Vinh Quang Dau, Huy Duc Hoang, Luong Thi Nguyen, Tan Thanh Le, Dinh Djung, and Y H'Jun.

Etymology. The specific name “ ardens ”, meaning burning, fiery, shining, or brilliant, is used as an adjective in reference to the bold and conspicuous coloration of this species compared to other species in the group.

Diagnosis. Assigned to the genus Leptolalax on the basis of the following characters: small size, rounded finger tips, the presence of an elevated inner palmar tubercle not continuous to the thumb, presence of macroglands on body (including supra–axillary, pectoral, femoral and ventrolateral glands), the absence of vomerine teeth, the presence of tubercles on eyelids, and anterior tip of snout with pale vertical bar ( Dubois 1983; Lathrop et al. 1998; Delorme et al. 2006). Leptolalax ardens sp. nov. is distinguished from its congeners by a combination of (1) supra– axillary and ventrolateral glands present; (2) dark brownish red ventral surface with white speckling; (3) small SVL for the genus (21.6.1– 24.7 mm in 15 adult males, 24.5 mm in one female); (4) toes lacking webbing and lateral fringes; (5) tibia length 44–49% of SVL in males; (6) pectoral gland 3.5–5.6% of SVL in males, (7) mostly smooth dorsum, (8) iris dark coppery brown, (9) distinct black supratympanic line present, (10) an advertisement call with 3–10 notes with the first, introductory note encompassing one–third of each call.

Description of holotype. Head width equal to head length; snout slightly truncate in dorsal view and rounded in profile, projecting slightly beyond margin of the lower jaw; nostril closer to snout than to eye; canthus rostralis indistinct, gently rounded; lores sloping; pupil vertical; eye diameter smaller than snout length; tympanum distinct, round, diameter smaller than that of the eye; tympanic rim elevated relative to skin of temporal region; vomerine teeth absent; pineal ocellus absent; vocal sac openings slit–like, located posteriolaterally on floor of mouth; tongue wide with broad, shallow notch at posterior tip; supratympanic ridge distinct, running from eye to axillary gland. Tips of fingers rounded, very slightly swollen; relative finger lengths I <II <IV <III; nuptial pad absent; subarticular tubercles absent; a large, round inner palmar tubercle distinctly separated from small, laterally compressed outer palmar tubercle; finger webbing and dermal fringes absent. Tips of toes like fingers; relative toe length I <II <V <III <IV; subarticular tubercles absent, replaced by dermal ridges; large, oval inner metatarsal tubercle present, outer metatarsal tubercle absent; toe webbing rudimentary; lateral fringes absent. Tibia 48% of snout–vent length; tibiotarsal articulation reaching beyond tip of snout. Skin on dorsum mostly smooth with only tiny, barely raised tubercles; ventral skin smooth; pectoral gland small, oval, 0.8 mm diameter; femoral gland small, oval, approximately 0.5 mm diameter, on posteroventral surface of thigh, closer to knee than to vent; supra– axillary gland oval, raised, 0.9 mm diameter. Ventrolateral glands forming an indistinct line.

Colour of holotype in life. Dorsal surface brown with irregular, darker brown blotch down back; dark interorbital bar with pale cream edging anteriorly; two small, pale markings between axilla. Blackish brown line along canthus rostralis through eye, and continuing below supratympanic ridge, terminating above axilla, encompassing nare and most of tympanum; transverse dark brown bars on dorsal surface of thighs, tibia, tarsus, lower arms, fingers and toes; elbows and upper arms orange; large, black blotch on posterior flank and numerous, smaller black spots on sides from groin to axilla ( Fig. 10A,C ). Upper arms pale coppery orange. Dark brownish ventral surface with white speckling on entire ventral surface including throat, arms and legs; ventral margin of throat bearing broken row of slightly larger white spots. Supra-axillary gland copper; femoral glands white; pectoral glands white, ventrolateral glands white. Iris brown; minute, black reticulations throughout.

Colour of holotype in preservative. Dorsum relatively uniformly dark brown; dorsal surface of brachium, fingers and toes paler brown ( Fig. 7D ). Ventral surface of chest and thighs slightly medium brown with white speckles; throat dark brown speckled with white; and belly white speckled with brown. Macroglands creamy white.

Measurements (mm). Holotype: SVL 22.0, HDL 9.0, HDW 8.9, SNT 3.4, EYE 2.9, IOD 2.4, TMP 1.6, TEY 0.8, TIB 10.5, EN 2.0, IN 2.5, NS 1.3, ML 5.7, PL 10.8, weight in life 1.1g

Variation. Measurements of the type series are shown in Tables 2–3 and representative photographs of paratypes are shown in Figure 10 . Some specimens (VNMN 04711/AMS R 176458– VNMN 04712/1764589) have more clumped white speckling on the venter. UNS 00531/AMS R 176461 has a paler brown venter with barely distinct brown mottling. AMS R 176453, VNMN 04709/AMS R 176456, VNMN 04710/AMS R 176457, UNS 00532/AMS R 176462, AMS R 176463, UNS 00533/AMS R 176465, UNS 00534/AMS R 176466, have a distinctly pale line anterior to dark brown interorbital bar. The degree of black dorsolateral spots/flecks varies, pale edged marbling also visible on dorsum of some specimens, especially AMS R 176457, UNS 00532/AMS R 176462, UNS 00533/AMS R 176465.

Advertisement call. Call descriptions are based on the calls of seven individuals, recorded at 21.4–24.7 ºC ambient temperature. Calls were an average of 239 ms in duration and consisted of 3–10 notes (Table 4, Fig. 5D ). Calls were highly amplitude modulated, with amplitude peaking towards the end of each call. Calls contained 3–10 notes and introductory notes were present in most calls. Introductory notes were 25–41% of the call duration, contained up to 54 pulses. Non-introductory notes contained 1–3 pulses. Notes were repeated an average of 20 notes/s. The average dominant frequency was 3.3 kHz, spread more widely (~2.0–7.6 kHz) in non-introductory notes. Harmonics were weakly present at ~ 6, 9, and 12 kHz, and a fundamental frequency was not visible. To the human ear, the advertisement call of L. ardens sp. nov. is a weak squeak followed by a rasping, similar to an orthopteran.

Ecology. All specimens of Leptolalax ardens sp. nov. were found in evergreen forest between 1,041–1,450 m elevation in Kon Ka Kinh National Park. Males were heard faintly calling on the forest floor, adjacent to small streams or seeps ( Figure 9D ).

Distribution. Leptolalax ardens sp. nov. is only known from Kon Ka Kinh National Park, in Gia Lai Province, Vietnam.

Comparisons. Leptolalax ardens sp. nov. differs from all other Leptolalax species in mainland Southeast Asia on the basis of morphology, and from all congeners in the region for which comparable data is available on the basis of molecular and acoustic data.

The new species differs from L. aereus by ventral coloration, body size and the presence of a black supratympanic line, from L. bourreti by ventral coloration and body size, from L. botsfordi by male body size and relative body weight (0.41–0.47 versus 0.75–0.94 g /mm), from L. croceus by ventral coloration, presence of black supratympanic line, iris coloration and skin texture; from L. eos by ventral coloration, male body size, iris coloration and lateral fringes on toes; from L. firthi by ventral coloration, male body size, presence of black supratympanic line, iris coloration, male skin texture and lateral fringes on toes; from L. fuliginosus by ventral coloration, male body size and iris coloration; from L. heteropus by ventral coloration and male body size; from L. kecil by ventral coloration, male body size, and iris coloration; from L. melanoleucus by ventral coloration, male body size, and iris coloration; from L. minimus by ventral coloration and male body size; from L. nahangensis by ventral coloration, male body size and iris coloration; from L. nyx by ventral coloration and male body size, from L pelodytoides by ventral coloration and male body size; from L. platycephalus by ventral coloration and male body size; from L. pluvialis by ventral coloration; from L. solus by ventral coloration, male body size and iris coloration; from L. sungi by ventral coloration, male body size, presence of black supratympanic line, iris coloration and skin texture; from L. tuberosus by ventral coloration, presence of black supratympanic line, iris coloration and skin texture; from L. ventripunctatus by ventral coloration, male body size, iris coloration and skin texture; and from L. zhangyangpingi by ventral coloration, male body size, presence of black supratympanic line, and iris coloration. See Table 8 for details.

From members of the L. applebyi group, L. ardens sp. nov. differs from all species by at least one morphological character (all following morphometric differences refer to males only). The new species differs from L. applebyi by having a significantly larger body size (Wilcoxon post-hoc Z=3.7, p<0.001), larger relative tibia length (Wilcoxon post-hoc Z=2.3, p=0.020), larger relative head width (Wilcoxon post-hoc Z=2.3, p=0.023), larger relative eye diameter (Wilcoxon post-hoc Z=3.2, p=0.002) and larger pectoral gland size (Wilcoxon post-hoc Z=3.81622, p<0.001). L. ardens sp. nov. differs from L. bidoupensis by having a smaller SVL (Wilcoxon post-hoc Z= -2.0, p=0.048), larger relative tibia length (Wilcoxon post-hoc Z=3.2, p=0.001), larger relative eye diameter (Wilcoxon post-hoc Z=2.1, p=0.038) and having a relatively uniform iris coloration (versus reddish in upper and silvery gold below). L. ardens sp. nov. differs from L. melicus by having a larger SVL (Wilcoxon post-hoc Z= -3.3, p<0.001), and larger relative distance between the tympanum and eye (Wilcoxon post-hoc Z= -2.5, p=0.011). L. ardens sp. nov. differs from L. pyrrhops , by having a smaller and non-overlapping body size (Wilcoxon post-hoc Z= 3.7, p<0.001), and smaller relative tympanum diameter (Wilcoxon post-hoc Z=2.6, p=0.009), and distance between tympanum and eye (Wilcoxon post-hoc Z=2.7, p=0.006), and larger relative eye size (Wilcoxon post-hoc Z=3.6, p<0.001; although differences between the latter three measurements may be confounded by inter-observer bias). L. ardens sp. nov. differs from L. pallidus sp. nov. by having a smaller SVL (Wilcoxon post-hoc Z= -3.8, p<0.001), smaller relative tympanum diameter (Wilcoxon post-hoc Z= -2.7, p=0.007), a distinct black (versus dark brown and less distinct) supratympanic line and mostly smooth skin texture (versus distinctly tuberculate dorsum). L. ardens sp. nov. differs from L. kalonensis sp. nov. by having a non-overlapping, smaller body size (Wilcoxon post-hoc Z= 4.7, p<0.001). L. ardens sp. nov. differs from L. maculosus sp. nov. by having a smaller body size (Wilcoxon post-hoc Z=2.8, p=0.006). L. ardens sp. nov. differs from L. tadungensis sp. nov. by having a smaller body size (Wilcoxon post-hoc Z= 3.4, p<0.001) and larger relative tibia length (Wilcoxon post-hoc Z=-3.0, p=0.003). See Table 4 and Fig. 4 .

The male advertisement call of L. ardens sp. nov. differs from all members of the L. applebyi group with the exception of L. kalonensis sp. nov. From L. applebyi the call of the new species differs by having a longer introductory note and note repetition rate. From L. bidoupensis , the call of L. ardens sp. nov. differs by having an introductory note in most calls and having a higher dominant frequency. From L. melicus , the call of L. ardens sp. nov. differs by having a lower dominant frequency. From L. pyrrhops the call of L. ardens sp. nov. appears to differ by having a higher dominant frequency. From L. pallidus sp. nov. the call of L. ardens sp. nov. differs by having a shorter call duration,a higher average number of pulses in the introductory note, a higher note repetition rate and a higher dominant frequency. From L. maculosus sp. nov. the call of L. ardens sp. nov. differs by having a shorter call duration, a higher number of notes per call, a distinct introductory note, and higher dominant frequency. From L. tadungensis sp. nov. the call of L. ardens sp. nov. differs by having a relatively long introductory note. No clear differences between the call of L. ardens sp. nov. and L. kalonensis sp. nov. could be determined, perhaps in part due to the limited sample size (n=1) for L. kalonensis sp. nov. See Table 7 and Figs. 5–6 .

Leptolalax ardens sp. nov. differs from all species within the L. applebyi group by>4.5% divergence at the 16S gene fragment examined. Interspecific variation in three L. ardens sp. nov. collected from ~ 2 km apart was 0%.

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Figures

FIGURE 1. Map showing the localities where specimens in the Leptolalax applebyi group were collected in Cambodia and Vietnam. Colours of localities assigned based on molecular lineages. Paler areas are higher elevation. Dark grey lines show country boundaries, pale grey lines show watershed boundaries and blue lines show rivers.

FIGURE 4. Morphometric variation and differentiation among adult male frogs in the Leptolalax applebyi group. Boxplots of (A) SVL, (B) relative tibia length (TIB / SVL), (C) relative pectoral gland size (PEC / SVL) and (D) relative tibia length (TIB / SVL) of adult males in each molecular lineage. For all boxplots, horizontal lines within each box represent the median and boxes encompass the 75 th and 25 th quartiles.

FIGURE 5. Advertisement calls of species in the Leptolalax applebyi group minus L. pyrrhops (i) 10 s waveform of relative amplitude (Rel. amp.) over time, (ii) waveform and (iii) corresponding 2 s spectrogram of representative call expanded from first section shown in i for (A) L. applebyi holotype AMS R 171703, (B) L. bidoupensis paratype UNS 00101 / AMS R 173135, (C) L. melicus holotype MVZ 258198, and (D) L. ardens sp. nov. paratype UNS 00534 / AMS R 176466. For ambient temperatures during recordings, see Table 4.

FIGURE 7. Dorsal and ventral views of holotypes of (A) L. applebyi AMS R 171703, (B) L. bidoupensis AMS R 173133, (C) L. melicus MVZ 258198, (D) L. ardens sp. nov. VNMN 04707 / AMS R 176454.

FIGURE 9. Calling sites and representative habitats of species in the Leptolalax applebyi group. (A) L. ardens sp. nov., (B) L. kalonensis sp. nov., (C) L. maculosus sp. nov.. (D) stream in Kon Ka Kinh National Park, Gia Lai Province, where L. ardens sp. nov. males were observed 1 - 2 m from stream, calling under leaf-litter, (E) downstream from dry section of stream in Bidoup Nui Ba National Park, Lam Dong Province, where L. pallidus sp. nov. were observed calling, (F) dry stream bed in Song Luy Watershed Forest, Binh Thuan Province, where calling L. kalonensis sp. nov. were collected, and (G) dry stream bed in Ta Dung Forest, Dak Nong Province, where L. tadungensis sp. nov. were calling and collected.

FIGURE 10. Leptolalax ardens sp. nov. in life (A) male holotype VNMN 04707 / AMS R 176454, (B) male paratype AMS R 176467, (C) venter of male holotype VNMN 04707 / AMS R 176454, (D) male paratype UNS 00534 / AMS R 176466.