Phylogeny, Diversity, and Distribution of Micryletta (Anura: Microhylidae) in Myanmar
The microhylid genus Micryletta, often called Paddy Frogs, is a taxonomically modest group of frogs currently comprised of eight species distributed across India, China, and Southeast Asia. None of the recent investigations into this group have explicitly focused on the diversity of these frogs in Myanmar, a critically undersampled region previously thought to contain only one species of Micryletta, M. inornata. Recent field expeditions to Myanmar conducted by the authors have resulted in the discovery of numerous populations of Micryletta in the northern and southern portions of the country in Kachin State and Tanintharyi Region, respectively. In this study, we investigate the status of these populations, their taxonomic identities, and broadly assess the diversity of this enigmatic group of frogs in Myanmar. Using comparative morphological and molecular data, we find the diversity of Micryletta in Myanmar has been poorly appreciated, which we demonstrate with the discovery of M. aishani, a species previously only known from neighboring India, and M. lineata, a species originally described from Peninsular Thailand. Our investigation into the taxonomic status of M. lineata demonstrates the validity in the recognition of this species, which is supported with evidence derived from morphology, geography, and molecular data. We additionally provide a detailed re-description of this species based on novel specimens from southern Myanmar. We also document M. inornata sensu stricto in Myanmar, sympatric with M. lineata, bringing the total to three species of Micryletta occurring in Myanmar.
(A) Map of all sampling localities for Micryletta included in this study. Countries are labeled with ISO alpha-2 codes. (B) Map of Tanintharyi Region, Myanmar—north-facing black arrowheads denote the locations of Dawei and Kawthaung, respectively. The Isthmus of Kra is located at approximately 10°N. Taxa correspond to colors in legend—circles indicate morphological and molecular data for individuals, triangles indicate morphological data strictly, and squares indicate molecular data strictly.
(A, B) Maximum likelihood phylogenies for Micryletta inferred using the 16S and COI datasets in IQ-TREE. Ultrafast Bootstrap values (UFBoot) are provided at relevant nodes. Scale bars indicate substitutions per site. (C) Illustration of M. lineata from the Dawei area, Tanintharyi Region, Myanmar, by Catalina Montalvo.
Box plots of snout–vent lengths (SVL) for Micryletta sampled in the morphological dataset—mature males (A) and females (B). (C, D, respectively males and females) Principal components analysis of males and females for 17 continuous morphological characters examined. Colors correspond in both plots, with M. aishani represented by green circles, M. cf. inornata represented by orange triangles, M. inornata sensu stricto as the blue triangle in the females plot, and M. lineata represented by the purple squares.
Micryletta lineata (USNM 587907) from Tanintharyi Region, Myanmar. Scale for each perspective given in parenthesis. (A) Ventral view (10 mm); (B) dorsal view (10 mm); (C) lateral view (1 mm); (D) volar view of right hand (1 mm); (E) plantar view of left foot (1 mm). Note that gold dots are heads of pins that were used to hold the specimen in place.
Micryletta lineata (USNM 587923) from the Tanintharyi Region, Myanmar. Dorsal views of in-life (A) and subsequent to preservation (B). Scale bar is 10 mm.
Micryletta inornata sensu stricto (USNM 587901) from Tanintharyi Region, Myanmar. Scale for each perspective given in parentheses. (A) Ventral view (10 mm); (B) dorsal view (10 mm); (C) lateral view (1 mm); (D) volar view of right hand (1 mm); (E) plantar view of left foot (1 mm). Note that gold dots are heads of pins that were used to the hold the specimen in place.
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