Microhyla nilphamariensis, Howlader & Nair & Gopalan & Merilä, 2015

Howlader, Mohammad Sajid Ali, Nair, Abhilash, Gopalan, Sujith V. & Merilä, Juha, 2015, A New Species of Microhyla (Anurα: Microhylidαe) from Nilphαmαri, Bαnglαdesh, PLoS ONE (e 0119825) 10 (3), pp. 1-18 : 5-10

publication ID	https://doi.org/ 10.1371/journal.pone.0119825
DOI	https://doi.org/10.5281/zenodo.12802446
persistent identifier	https://treatment.plazi.org/id/F94587D7-8464-1641-FDEB-FA94977EA2DD
treatment provided by	Felipe
scientific name	Microhyla nilphamariensis
status	sp. nov.

Treatment

Microhyla nilphamariensis View in CoL sp. nov. urn:lsid:zoobank.org:act:11E1D35F-7FC1–43C1–8318–747F9FC0C882

Etymology. The species name is derived from the name of the type locality Nilphamari, where the type specimens were collected.

Holotype. Adult male, MZH-2362, collected from grass-field (25° 48 0 06.12"N, 88° 53 0 59.21"E), Koya Golahut, Saidpur, Nilphamari, Bangladesh; collected by M. S. A. Howlader, June 9, 2012. GoogleMaps

Paratopotypes. MZH-2360 (adult female), MZH-2361 (adult female), MZH-2363 (adult female), MZH-2364 (adult female), MZH-2365 (adult female), and MZH-2366 (adult female) collected from the same locality as the holotype; collected by M. S. A. Howlader and Abdur Razzaque, June 9, 2012.

Diagnosis. Microhyla nilphamariensis sp. nov. is characterized by a combination of the following characters: HL 77% of HW, EN roughly six times greater than NS, IN roughly five times greater than NS, IOD two times greater than IN, MBE 15% of HL, small ovoid-shaped inner metacarpal tubercle, very small rounded outer metacarpal tubercle, toes with rudimentary webbing, absence of digital discs, inner metatarsal tubercle small and round, outer metatarsal tubercle ovoid-shaped, minute, and indistinct.

Description of taxa

Holotype (adult male). Small sized frog ( SVL 17.36 mm). Head large, triangular, wider than long, HL 77% of HW, HW 27 % of SVL, HL 21 % of SVL, MFE 67 % of HL, MBE 15 % of HL. Snout nearly rounded in lateral view, SL 46% of HL; canthus rostralis indistinct, loreal region concave. Nostrils much closer to snout tip than to eyes, NS 16 % of EN; NS 1 % of SVL, EN 7 % of SVL; nostrils rounded and very small, NS 20 % of IN, MN 92 % HL. Eye large, EL 52 % of HL, EL 11 % of SVL; interorbital distance greater than maximum width of upper eyelid greater, UEW 41 % of IOD, UEW 44 % EL, UEW 4 % SVL. Interorbital space convex, IN 49 % of IOD. Tympanum is hidden.

Arms moderately long, FAL 74% HAL, FAL 16% of SVL, HAL 22% SVL. Fingers small, free of webbing, tips are flattened. Relative length of fingers, shortest to longest: 1 <2 <4 <3; fingers lacking dermal ridge. Palm with ovoid-shaped inner metacarpal tubercle, small rounded outer metacarpal tubercle. Subarticular tubercle prominent, rounded, single tubercle per digit.

Hind limbs relatively long, TL 42% of SVL, THIGHL 86% of TL; FOL 49% SVL and TL 86% FOL, FOL 71% of TFOL. Toes long, thin, tips rounded; webbing between toes weakly developed [1(1), 2i (1.75), 2e (1), 3i (2.5), 3e (2), 4i (3), 4e (3.25), 5(1.75)]. Relative lengths of toes, shortest to longest: 1 <2 <5 <3 <4. Inner metatarsal tubercle small and round, present at base of first toe; outer metatarsal tubercle is ovoid-shaped, minute, indistinct; subarticular tubercles well-developed, nearly ovoid-shaped. Dorsal surface smooth with some tiny tubercles on the back and on the sides the body; tiny granules on upper eyelids, loreal, and cloacal region. Dorsal surface of forelimbs, thigh and tarsi glandular. Throat, chest, abdomen and ventral part of thigh and tibia smooth.

Basic dorsal coloration light brown with distinct dark brown diamond-shaped marking over the back, beginning between the eyes and extending to both the eyelids, narrowing behind the head and widening above the shoulder, then narrowing again and finally broadening out, sending a stripe to the groin and thigh ( Fig. 2 View Fig 2 ). A dark streak extends along the sides from back of the eye to shoulder. Limbs with dark cross bars. The belly is dull white; the throat and chest are brown.

Measurements (in mm). Male (holotype): SVL 17.36; HL 3.74; HW 4.82; MN 3.47; SL 1.75; MFE 2.52; MBE 0.57; IN 1.03; IOD 2.09; EN 1.25; NS 0.21; EL 1.95; UEW 0.86; HAL 3.93; FAL 2.91; LAL 1.72; THIGHL 6.41; TL 7.45; TFOL 11.96; FOL 8.61. Female (paratopotype): SVL 17.84; HL 3.85; HW 5.02; MN 3.57; SL 1.79; MFE 2.61; MBE 0.6; IN 1.06; IOD 2.16; EN 1.27; NS 0.22; EL 1.98; UEW 0.89; HAL 4; FAL 2.97; LAL 1.81; THIGHL 6.44; TL 7.51; TFOL 12.07; FOL 8.71.

Variation. Morphometric variability is described in Table 1 View Table 1 .

Distribution. Microhyla nilphamariensis sp. nov. is known only from the type locality ( Fig. 1 View Fig 1 ). However, Matsui et al. [ 18] and Hasan et al. [ 6] found individuals from Dinajpur district carrying haplotypes similar to those found from the type locality, suggesting that the distribution area might extend beyond the type locality.

Natural history. The new species was observed only at night during the rain. At the type locality, specimens were found in a grass-field near temporary pools.

Molecular phylogeny and genetic divergence of new species. The sequence divergences between Microhyla nilphamariensis sp. nov. and other congeneric species were significant, ranging from 5.7% to 13.2% for 16S rRNA ( Table 2 View Table 2 ). Intraspecific genetic divergence within the new species was estimated at 0.5%. Microhyla nilphamariensis sp. nov. formed a distinct clade in the phylogenetic analyses with high bootstrap ( ML method) and posterior probability support (Bayesian method; Fig. 3 View Fig 3 ). Microhyla nilphamariensis sp. nov. was identified as a sister taxa to M. ornata ( Fig. 3 View Fig 3 ). Molecular phylogeny suggests that M. nilphamariensis sp. nov. belongs to the Indian clade of Microhyla species group (including M. ornata and M. rubra ), rather than having closer affinity to Southeast Asian species ( Fig. 3 View Fig 3 ).

Morphological comparison. M. nilphamariensis sp. nov. is morphologically distinct from the closely related species M. ornata and M. rubra in the following qualitative characters

( Fig. 4 View Fig 4 ): inner metacarpal tubercle small and ovoid-shaped (vs. large and goblet-shaped in M. ornata ; elongated in M. rubra ), outer metacarpal tubercle very small and rounded (vs. very large, prominent and heart-shaped in M. ornata and M. rubra ), inner metatarsal tubercle small and round (vs. elongated, large and very prominent in M. ornata ; shovel-shaped in M. rubra ), outer metatarsal tubercle ovoid-shaped, minute, and indistinct (vs. compressed and large in size in M. ornata ; shovel-shaped and large in M. rubra ). Quantitative diagnostic characters include (see also: Table 1 View Table 1 , S 2 View Table 2 Fig.): head length 77% of head width (vs. roughly equal to head width in M. ornata and M. rubra ), distance from front of eyes to the nostril roughly six times greater than nostril–snout length (vs. over one and a half times greater than nostril–snout length in M. ornata ; over single time greater than nostril–snout length in M. rubra ), internarial distance five times greater than nostril–snout length (vs. nearly two times greater than nostril– snout length in M. ornata ; less than two times greater than nostril–snout length in M. rubra ), interorbital distance two times greater than internarial distance (vs. more than three times greater than internarial distance in M. ornata and M. rubra ), distance from back of mandible to back of the eye 15% of head length (vs. more than 36% of head length in M. ornata and M. rubra ). These two closely related Microhyla species are morphologically clearly distinct from the new species also according to MANOVA (F 34,18 = 334.93, P <0.001), and according to a discriminant analysis which correctly classifies all individuals to their respective species along two significant (Eigenvalues 194.51, F 36.47, P <0.001) canonical axes ( Fig. 5A View Fig 5 ). In a principal component (PC) analysis, the three species are significantly different from each other (Tukey’ s HSD; P> 0.05 in all pairwise comparisons) along the first PC-axis (Eigenvalue = 14.07; 82.8% variance explained), which correspond to variation in overall size (all traits loading positively and roughly equally on this axis), M. nilphamariensis sp. nov. being the smallest species ( Fig. 5B View Fig 5 ). The second PC-axis (Eigenvalue = 1.48; 8.7% variance explained) captures shape differences, but in this axis M. nilphamariensis sp. nov differs significantly only from M. ornata (Tukey’ s HSD, P <0.05). Nevertheless, that the M. nilphamariensis sp. nov. is clearly differentiated from M. ornata and M. rubra can also be depicted from bivariate scatterplots (S2 Fig.) showing that it’ s diagnostic ratios (see above) do not overlap with those of M. ornata and M. rubra .

Genetic divergence of M. nilphamariensis sp. nov. from all other species in the Southeast Asian clade is 10% to 13% ( Fig. 3 View Fig 3 ). Likewise, the new species is morphologically different from all known Southeast Asian species in comparison to the original descriptions [ 39 – 55]. Morphological characters of the other Southeast Asian species ( M. berdmorei , M. borneensis , M. achatina , M. butleri , M. palmipes , M. annamensis , M. annectens , M. heymonsi , M. mantheyi , M. superciliaris , M. malang , M. chakrapanii , M. marmorata , M. nanapollexa , M. pulverata , M. arboricola , M. darevskii , M. minuta , M. pineticola , M. pulchella , M. perparva , M. mixtura , M. fowleri , M. maculifera , M. petrigena , M. orientalis ) such as webbed toes with distinct digital discs, and leaf vain-type dorsal surface markings separate them from M. nilphamariensis sp. nov., which has reduced webbing, absent discs and irregular dorsal surface markings. M. sholigari also differs from M. nilphamariensis sp. nov. as it has discs on fingers ( Fig. 4 View Fig 4 ). Shovel-shaped inner metatarsal tubercle and a more rounded snout separate M. picta from M. nilphamariensis sp. nov. [ 56]. M. nilphamariensis sp. nov. lacks the minutely shagreened dorsum, mid-dorsal ridge, and deeply furrowed outer metacarpal tubercle of M. fusca [ 57]. M. nilphamariensis sp. nov. differs from M. pulchra [ 58] and M. erythropoda [ 59] in having a rounder snout, smaller body size, and rudimentary foot webbing ( M. pulchra and M. erythropoda have obtuse or obtusely pointed snouts, larger body size and half-webbed toes). M. karunaratnei [ 60] and M. zeylanica [ 61] are two species endemic to Sri Lanka, and differ from M. nilphamariensis sp. nov. by extensive digital webbing, presence of digital discs, IOD 1.6 times greater than UEW (vs. rudimentary digital webbing, absence of digital discs, IOD 2.43 times greater than UEW). Absence of digital discs differentiates M. nilphamariensis sp. nov. from M. mukhlesuri , M. fissipes and M. mymensinghensis , in which digital discs are present.