Poyarkov, Gorin, Zaw, Kretova, Gogoleva, Pawangkhanant & Che, 2019
We present a morphological and molecular assessment of the Microhyla fauna of Myanmar based on new collections from central (Magway Division) and northern (Kachin State) parts of the country. In total, six species of Microhyla are documented, including M. berdmorei, M. heymonsi, M. butleri, M. mukhlesuri and two new species described from the semi-arid savanna-like plains of the middle part of the Irrawaddy (Ayeyarwady) River Valley. We used a 2 481-bp long 12S rRNA–16S rRNA fragment of mtDNA to hypothesize genealogical relationships within Microhyla. We applied an integrative taxonomic approach combining molecular, morphological, and acoustic lines of evidence to evaluate the taxonomic status of Myanmar Microhyla. We demonstrated that the newly discovered populations of Microhyla sp. from the Magway Division represent two yet undescribed species. These two new sympatric species are assigned to the M. achatina species group, with both adapted to the seasonally dry environments of the Irrawaddy Valley. Microhyla fodiens sp. nov. is a stout-bodied species with a remarkably enlarged shovel-like outer metatarsal tubercle used for burrowing and is highly divergent from other known congeners (P-distance≥8.8%). Microhyla irrawaddy sp. nov. is a small-bodied slender frog reconstructed as a sister species to M. kodial from southern India (P-distance=5.3%); however, it clearly differs from the latter both in external morphology and advertisement call parameters. Microhyla mukhlesuri is reported from Myanmar for the first time. We further discuss the morphological diagnostics and biogeography of Microhyla species recorded in Myanmar.
Key words: Narrow-mouth frogs, Burma, Indochina, Magway, Kachin, Biodiversity, Taxonomy, mtDNA, Morphology, Acoustics, Advertisement call
Microhyla fodiens sp. nov.
Chresonymy: Microhyla rubra – (?) Parker, 1934, p. 145 (B. M. 18.104.22.168, coll. from“Moulmein, Burma”by W. Theobald).
Microhyla rubra – Wogan et al., 2008, p. 84–86; Peloso et al., 2016, p. 5, 23.
Microhyla sp. B – Mulcahy et al., 2018, p. 99, 116–117.
Diagnosis: Microhyla fodiens sp. nov. is characterized by a combination of the following morphological attributes: (1) males with medium body size, SVL 20.8 – 29.12 mm in two adult individuals, body habitus stout; (2) head flattened, triangular, much wider than long, snout rounded in dorsal and bluntly rounded in lateral views, notably protruding above lower jaw in ventral aspect; canthus rostralis rounded, indistinct; (3) skin on dorsum and flanks feebly granular with numerous small round tubercles, ventral surfaces smooth; (4) dorsolateral skinfold presents as row of large tubercles ventrally underlined with black stripe; (5) mid-vertebral skin ridge and dorsomedial stripe absent; (6) supratympanic fold almost indistinct; (7) finger I well developed, notably less than one-half length of finger II; (8) finger and toe tips lacking disks and median longitudinal grooves; (9) two large palmar tubercles (inner palmar tubercle ovoid, slightly elongated; outer palmar tubercle almost rounded); (10) two very prominent metatarsal tubercles (inner metatarsal tubercle large, beanshaped, outer metatarsal tubercle greatly enlarged, shovelshaped); (11) limbs short, tibiotarsal articulation of adpressed limb not reaching eye level; (12) toe webbing basal, reaching proximal tubercles; webbing formula: I 1–2 II 1¾–3 III 2¾–3¾ IV 4 – 2¾ V; (13) superciliary tubercles absent; (14) dorsum beige-brown with“teddy-bear-shaped”dark-brown marking running from interorbital to sacral region; two large dark-black inguinal spots continuing on dorsal surfaces of thighs; posterior surfaces of thighs and cloacal region with regular black stripes; chin and throat marbled with gray, chest and belly whitish, limbs ventrally pink. Interspecific genetic Pdistances in 16S rRNA gene fragment between new species and congeners vary from 9.1% to 12.4%.
Distribution: Microhyla fodiens sp. nov. is currently known only from the type locality in Kan Pauk, Yesagyo Township, Magway Division, Myanmar (Figure 1). The species was recorded at an elevation of 230 m a.s.l. The actual distribution of the new species is unknown, but it is likely to be found in other arid areas of the Irrawaddy River Valley in the region of the Irrawaddy and Chindwin interfluve; discovery of new localities in Magway, Sagaing, and Mandalay divisions is anticipated. The record of“Microhyla rubra”from“Moulmein, Burma”(now Mawlamyine) by Parker (1934) based on W. Theobald’s collection comes from Mon State in southern Myanmar—a region with a much milder tropical monsoon climate—might refer to a different species. The taxonomic status of this record requires clarification by further studies.
Etymology: The specific name“fodiens”is a Latin adjective in the nominative singular derived from“fodio”— Latin verb meaning“to dig”or“to burrow”referring to the distinctive enlarged shovel-shaped outer metatarsal tubercle of the new species, suggesting that it is a good burrower, which may serve as an adaptation to the dry climate of the Irrawaddy River Valley in central Myanmar. The recommended common name in English is “Burrowing narrow-mouth frog”. The recommended common name in Burmese is“Twin Aoung Thaephar”.
Microhyla irrawaddy sp. nov.
Chresonymy Microhyla sp. A – (?) Mulcahy et al., 2018, p. 99, 116–117.
Diagnosis: Microhyla irrawaddy sp. nov. is distinguished by the following combination of morphological characters: (1) small adult body size: males SVL 12.3–17.1 mm, females SVL 16.7 – 20.9 mm, body habitus very slender; (2) head small, triangular, wider than long, snout acuminate with rounded tip in dorsal view and rounded in lateral view, slightly protruding above lower jaw in ventral aspect; canthus rostralis indistinct; (3) skin on dorsum and flanks granular with irregularly scattered numerous large and small round tubercles, ventral surfaces completely smooth; (4) dorsolateral skinfold and dark lateral band absent; (5) mid-vertebral skin ridge and dorsomedial stripe absent; (6) supratympanic fold distinct; (7) finger I well developed, slightly longer than onehalf length of finger II; (8) tips of fingers II–IV and toes II–V weakly dilated, not forming conspicuous disks; peripheral grooves ventrally present on tips of fingers II–IV and toes II– IV; fingers and toes lacking dorsal median grooves or distal notches; (9) two small palmar tubercles (inner palmar tubercle rounded, prominent; outer palmar tubercle smaller and less distinct than inner, rounded, flattened); (10) two small metatarsal tubercles (inner metatarsal tubercle elongated, ovoid, flattened; outer metatarsal tubercle small, rounded, prominent); (11) limbs comparatively short, tibiotarsal articulation of adpressed limb reaching eye level; (12) toe webbing completely reduced; webbing formula: I 2–3 II 2–3 III 3 – 4½ IV 4½ – 2¾ V; (13) superciliary tubercles absent; (14) dorsum yellowish-brown with dark-brown contrasting“teddybear”- shaped marking running from interorbital to sacral region; larger tubercles on dorsum orange to red; body flanks grayish with darker mottling not clearly separated from dorsum coloration; dorsal surfaces of thighs and shanks with two to three dark crossbars; chin and throat with grayish mottling (blackish in males), body and limbs ventrally cream to whitish at belly. Interspecific genetic P-distances in the 16S rRNA gene fragment between the new species and other currently recognized species of Microhyla vary from 5.7% to 12.9%.
Distribution: Microhyla irrawaddy sp. nov. is at present known from two closely located areas in Pakokku District of Magway Division, central Myanmar: i.e., suburbs of Pakokku city on the bank of the Irrawaddy River (the type locality) and in the vicinity of Kan Pauk village, Yesagyo Township (ca. 30 km north of type locality) (Figure 1). The species was recorded from elevations of 60 to 220 m a.s.l.. A genealogically closely related population of Microhyla (herein indicated as Microhyla sp. 2, see Table 1) was recorded from the vicinity of Chatthin in Sagaing Division of northern Myanmar by Mulcahy et al. (2018). Considering the notable genetic divergence between Sagaing and Magway populations (P=2.0%), further research is needed to clarify whether Microhyla sp. 2 is conspecific with Microhyla irrawaddy sp. nov. The actual distribution of the new species is unknown and discoveries of new localities within the middle part of the Irrawaddy River Valley are anticipated.
Etymology: The new species name“irrawaddy”is given as a noun in apposition in reference to the Irrawaddy (or, officially, Ayeyarwady) River – the greatest water basin in Myanmar and western Indochina, and the cradle of Burmese civilization. The new species is known to occur in dry areas of the central part of the Irrawaddy Valley in the Magway Division, but likely has a wider distribution in the dry zone of central Myanmar. The recommended common name in English is“Irrawaddy narrow-mouth frog”. The recommended common name in Burmese is “Myanmar Thaephar”.
Nikolay A. Poyarkov, Jr., Vladislav A. Gorin, Than Zaw, Valentina D. Kretova, Svetlana S. Gogoleva, Parinya Pawangkhanant and Jing Che. 2019. On the Road to Mandalay: Contribution to the Microhyla Tschudi, 1838 (Amphibia: Anura: Microhylidae) Fauna of Myanmar with Description of Two New Species. Zoological Research. DOI: 10.24272/j.issn.2095-8137.2019.044