Theloderma lacustrinum, Sivongxay, Niane, Davankham, Monekham, Phimmachak, Somphouthone, Phoumixay, Keochay & Stuart, Bryan L., 2016

Sivongxay, Niane, Davankham, Monekham, Phimmachak, Somphouthone, Phoumixay, Keochay & Stuart, Bryan L., 2016, A new small-sized Theloderma (Anura: Rhacophoridae) from Laos, Zootaxa 4147 (4), pp. 433-442 : 434-436

Theloderma lacustrinum sp. nov.

Holotype. NCSM 84682 (field tag SP 00299), adult male ( Fig. 1 ), Laos, Vientiane Province, Feuang District, Ban Naxang Village, bank of Nam Lik Reservoir , Houay Poungfan Stream , 18º48’59.5”N 102º08’06.1”E, 292 m elev., coll. 16 March 2015 by Niane Sivongxay, Monekham Davankham, Somphouthone Phimmachak, and Keochay Phoumixay.

Paratypes. NUOL 0 0 0 43 (one juvenile), NUOL 0 0 0 44 (one male), same data as holotype . NUOL 0 0 970 (one male), same data as holotype except coll. 16 December 2014 by Niane Sivongxay, Monekham Davankham, and Keochay Phoumixay . NCSM 84683, NUOL 0 0 0 45 (two males), same data as holotype except Houay Kengthang Stream, 18º51’58.2”N 102º07’20.6”E, 361 m elev., coll. 17 March 2015.

Etymology. The specific epithet taken from lacustrinus L., of lakes, in reference to Nam Lik Reservoir, a large, man-made reservoir formed by a hydropower dam that has inundated the vicinity of the type locality.

Diagnosis. Assigned to the genus Theloderma on the basis of molecular data ( Fig. 2 ). A very small-sized (second smallest known) species of Theloderma having the combination of males with SVL 17.0–20.6; pearly asperities on dorsum; no vomerine teeth; disc diameter of finger III ca. 40% of tympanum diameter; uniformly gray venter; light brown dorsum with darker brown and black markings; and a uniformly bronze iris with small black reticulations.

Description of holotype. Habitus slender. Head longer than wide. Snout slightly rounded in dorsal and lateral views; nostril oval, slightly oblique, much closer to tip of snout than to eye, internarial shorter than interorbital distance; canthus rostralis indistinct, rounded, slightly constricted behind nares; lores oblique, concave; interorbital region slightly convex, interorbital distance greater than upper eyelid width; pupil diamond-shaped, horizontal; eye diameter and snout length subequal; tympanum distinct, round, 70% of eye diameter, tympanic rim elevated relative to skin of temporal region; pineal ocellus absent; vomerine teeth absent; choanae oval, at margins of roof of mouth; tongue wide, attached anteriorly, deeply notched posteriorly; supratympanic fold from posterior margin of eye to level slightly posterior to axilla.

Forelimb slender. Finger tips with slightly expanded discs having weakly visible circummarginal grooves, finger III disc width 40% tympanum diameter; fingers slender; relative finger lengths I <II <IV <III; webbing on fingers absent; subarticular tubercles conspicuous, surfaces rounded, formula 1, 1, 2, 2; two indistinct, oval, palmar tubercles in contact, subequal in size, surfaces flat; oval, thenar tubercle, surface flat; round, indistinct supernumerary tubercles.

Hindlimb slender. Toe tips with slightly expanded discs having weakly visible circummarginal grooves, diameter of discs subequal to those of fingers; toes slender; relative toe lengths I<II<III<V<IV; rudimentary web on toe I to level of center of subarticular tubercle, continuing as fringe on preaxial side of toe II to base of tip, on postaxial side of toe II to level of distal margin of subarticular tubercle, continuing as fringe on preaxial side of toe III, on postaxial side of toe III to level midway between subarticular tubercles, on preaxial side of toe IV to level of distal margin of proximal subarticular tubercle, continuing as fringe to base of disc, postaxial side of toe IV to level of proximal margin of penultimate subarticular tubercle and continuing as a fringe to base of tip, and on toe V to level of proximal margin of subarticular tubercle; subarticular tubercles conspicuous, surfaces rounded, formula 1, 1, 2, 3, 2; inner metatarsal tubercle oval, surface flat; outer metatarsal tubercle weakly visible.

Skin smooth, with pearly asperities on side of head and dorsal surfaces of head, back, limbs, and outer margin of foot; venter coursely granular; very weak dermal fringe on outer margin of toe V from base of foot to base of tip. Velvety, ovoid nuptial pad on dorsal and posterior margin of finger I.

Color of holotype in life. Iris uniformly bronze with small black reticulations; dorsum light brown with brown hourglass-shaped marking on top of head, continuing as stripe on back to sacrum; dorsal surfaces of limbs orangebrown with irregular, black crossbands, dorsal surfaces of digits bronze (matching iris); flank gray; irregular black band from tip of snout to axilla, as narrow band below canthus and eye but as enlarged spot over nostril and tympanum; irregular, large, black spots and reticulations on flank; ventral surfaces uniformly gray.

Color of holotype in preservative. Black coloration faded to brown; brown marking on top of head and back less distinct; bronze coloration on digits faded to brown.

Variation. Paratypes closely resemble holotype. NUOL 0 0 0 43 lacks a nuptial pad and has the smallest body size in the type series (SVL 15.5), and so is deemed immature. Females, eggs, larvae, and vocalizations are unknown. Measurements are summarized in Table 1 .

Molecules. The new species was recovered in both analyses as sister to T. lateriticum Bain, Nguyen & Doan 2009 , with a Bayesian posterior probability of 1.00 ( Fig. 2 ). The holotype and sequenced paratype (NCSM 84683) differed by only a single insertion-deletion in the 16S gene fragment (and so had a p -distance of 0%). Four sequences of T. lateriticum (GenBank accession numbers LC 012848 –51) had p -distances of 0.33–4.40%. The new species and T. lateriticum (n =4) had p -distances of 10.54–10.81%. Bayesian inference of the trimmed alignment differed from that of the complete alignment only by failing to recover statistical support for the monophyly of Theloderma laeve and a sister relationship between the outgroup genera Kurixalus and Nasutixalus .

Distribution, natural history, and conservation. Theloderma lacustrinum sp. nov. is currently known only from the type and paratype localities ( Fig. 3 ), where it was collected at night (1820–2215 h) on leaves 30–80 cm above the ground near two rocky streams (292–361 m elev.) in semi-evergreen forest that flow into the Nam Lik Reservoir ( Fig. 1 ). The two known localities are approximately 5.7 air-km apart. We did not observe the new species at these localities during visits in April, July, and September 2015, suggesting that it may be seasonally active or most detectable during cooler, drier months (e.g., at lower heights in the forest canopy). The vicinity of the two known localities had not been surveyed for amphibians prior to construction of the hydroelectric dam, and thus it is not known how inundation from the reservoir may have impacted the range of the species.

Comparisons. Theloderma lacustrinum sp. nov. is most closely related to T. lateriticum ( Fig. 2 ) from Lao Cai, Bac Giang, and Son La Provinces, Vietnam ( Bain et al. 2009, Nguyen et al. 2015), but is readily distinguished from T. lateriticum by having a light brown dorsum with dark markings (nearly uniformly red in lateriticum ), by having a uniformly gray venter (distinctly spotted in lateriticum ), and by having a bronze iris (deep brick-red in lateriticum ).

Theloderma lacustrinum sp. nov. differs from all other Theloderma by having adult males with SVL <21 mm, except T. baibengense ( Jiang, Fei & Huang 2009) that has adult males with SVL 15.0–16.2, n =2 ( Jiang et al. 2009). However, T. lacustrinum sp. nov. is readily distinguished from T. baibengense by having a light brown dorsum with dark markings (dark with conspicuous white pattern in baibengense ), by having a uniformly gray venter (distinctly contrasting marbled pattern in baibengense ), and by having a bronze iris (reddish-brown in baibengense ).

Twelve additional species of Theloderma have small (sensu Rowley et al. 2011) adult body sizes, with SVL <35 mm: T. albopunctatum ( Liu & Hu 1962) , T. andersoni ( Ahl, 1927) , T. asperum ( Boulenger 1886) , T. laeve ( Smith 1924) , T. licin McLeod & Norhayati 2007 , T. nebulosum Rowley, Le, Hoang, Dau & Cao 2011 , T. palliatum Rowley, Le, Hoang, Dau & Cao 2011 , T. petilum ( Stuart & Heatwole 2004) , T. rhododiscum ( Liu & Hu 1962) , T. stellatum Taylor 1962 , T. truongsonense ( Orlov & Ho 2005) , and T. vietnamense Poyarkov, Orlov, Moiseeva, Pawangkhanant, Ruangsuwan, Vassilieva, Galoyan, Nguyen & Gogoleva, 2015 . Theloderma lacustrinum sp. nov. differs from T. laeve and T. truongsonense by having dorsal asperities (absent in laeve and truongsonense ). Theloderma lacustrinum sp. nov. differs from T. petilum by lacking vomerine teeth (present in petilum ) and by having relatively smaller finger discs, with the disc diameter of finger III ca. 40% of tympanum diameter (≥65% in petilum ). Theloderma lacustrinum sp. nov. differs from T. albopunctatum , T. asperum , T. baibengense , T. licin , and T. stellatum by having a light brown dorsum with dark markings (dorsum dark with conspicuous white pattern in albopunctatum , asperum , baibengense , and stellatum , nearly uniformly brown or white in licin ). Theloderma lacustrinum sp. nov. differs from T. albopunctatum , T. asperum , T. licin , T. nebulosum , T. palliatum , T. rhododiscum , T. stellatum , T. truongsonense , and T. vietnamense by having a uniformly gray venter (distinctly contrasting spotted, marbled or reticulated ventral pattern in albopunctatum , asperum , baibengense , chuyangsinense, lateriticum , licin , nebulosum , palliatum , rhododiscum , stellatum , truongsonense , and vietnamense ). Theloderma lacustrinum sp. nov. differs from T. andersoni by lacking two yellow spots on flank (present in andersoni ). Theloderma lacustrinum sp. nov. differs from T. laeve , T. nebulosum , T. palliatum , T. petilum , and T. truongsonense by having a uniformly colored iris (distinctly bicolored in laeve , nebulosum , palliatum , petilum , and truongsonense ).

Figures

FIGURE 1. Holotype NCSM 84682 (A) and paratype NUOL 0 0 970 (B) of Theloderma lacustrinum sp. nov. in life. Microhabitat (C) and macrohabitat (D) of type locality of T. lacustrinum sp. nov. Dorsal view (E) and ventral view (F) of holotype NCSM 84682 of T. lacustrinum sp. nov. immediately prior to preservation. Dorsal view (G) and ventral view (H) of holotype NCSM 84682 of T. lacustrinum sp. nov. in preservation. Scale bar = ca. 10 mm.

FIGURE 2. Fifty percent majority-rule consensus phylogram resulting from Bayesian analysis of 2,595 aligned sequence characters (“ complete ” alignment) of the mitochondrial 16 S gene and portions of flanking 12 S and tRNA genes from rhacophorid frogs. Black circles at nodes indicate Bayesian posterior probabilities ≥ 0.99, and open circles at nodes indicate Bayesian posterior probabilities ≥ 0.95. Numbers at terminal tips are GenBank accession numbers. An asterisk (*) indicates the species name was modified from that provided in the GenBank accession at the time of download.

FIGURE 3. Map illustrating the type locality (white star) of Theloderma lacustrinum sp. nov. in Vientiane Province, Laos, and the type locality (black star) of its closest known relative, T. lateriticum, in Lao Cai Province, Vietnam.

Tables

TABLE 1. Measurements (mm) of types of Theloderma lacustrinum sp. nov. Abbreviations defined in the text.

Measurement	Holotype male n =1	All males n =5 Range; Mean ± SD	Juvenile n =1
SVL	20.6	17.0–20.6; 18.8 ± 1.7	15.5
HDL	9.7	7.3–9.7; 8.3 ± 1.1	6.9
HDW	6.6	5.5–6.7; 6.2 ± 0.6	5.3
SNT	3.0	2.8–3.1; 3.0 ± 0.1	2.9
EYE	2.8	2.0–3.0; 2.5 ± 0.4	2.6
TMP	1.9	1.4–1.9; 1.7 ± 0.3	1.3
IOD	3.8	2.5–3.8; 3.2 ± 0.5	2.9
IND	1.8	1.6–1.8; 1.7 ± 0.1	1.6
SHK	12.0	9.7–12.0; 11.0 ± 0.9	8.5
TGH	10.9	9.3–11.1; 10.3 ± 0.7	8.2
FAL	10.2	8.4–10.2; 9.2 ± 0.8	7.3
HND	5.2	4.5–5.3; 4.9 ± 0.4	4.0
FTL	8.1	6.2–8.1; 7.1 ± 0.8	6.0