Two Complete Mitochondrial Genomes of Leptobrachium (Anura: Megophryidae: Leptobrachiinae): Characteristics, Population Divergences, and Phylogenetic Implications

Abstract

The mustache toads Leptobrachium boringii and Leptobrachium liui are two attractive species in Megophryidae, in which adult males have mustache-like keratinized nuptial spines on their upper lip. However, both are under threat due to multiple factors, of which scientific studies are still very limited. In this study, two new complete mitochondrial genomes of L. boringii and L. liui were sequenced, assembled, and annotated based on next-generation sequencing. The mitogenome lengths of L. boringii and L. liui were found to be 17,100 and 17,501 bp, respectively, with both containing 13 protein coding genes, 23 tRNAs, 2 rRNAs, and 1 non-coding control region. Nucleotide diversity analyses indicate that atp8, atp6, and nad2 showed higher nucleotide diversity than cox1, cox3, and cytb. The intraspecific genetic distances among three different populations of L. boringii exceed 4%, and those between two populations of L. liui reach 7%. Phylogenetic relationships support their division into two subfamilies of Megophryidae (Leptobrachiinae and Megophryinae) as well as two species groups within Leptobrachium, corresponding to the number of keratinized nuptial spines (10–48 in the L. boringii species group vs. 2–6 in the L. liui species group). The two new mitogenomes reported in this study provide valuable data for future molecular evolutionary and conservation studies of the genus Leptobrachium and other Megophryidae toads.

Insights into phylogenetic positions and distribution patterns: Complete mitogenomes of two sympatric Asian horned toads in Boulenophrys (Anura: Megophryidae)

“…For instance, the species we previously detected in Salamandridae had a positive AT skew (Wang, Lan et al., 2022 ), whereas all the Megophryidae species in this study displayed a negative AT skew, consistent with the findings of Zhou et al. ( 2023 ). Furthermore, while the mitogenomes of species in Ranoidea exhibited gene rearrangements frequently (Igawa et al., 2008 ), no any rearrangements were identified among all the Megophryidae species examined in this study.…”

“…The phylogenetic analysis revealed that Megophryidae could be divided into two well‐supported clades, supporting the classification of the two subfamilies, Megophryinae and Leptobrachiinae. The intergeneric relationships among the two subfamilies were consistent with our previous study (Zhou et al., 2023 ), with the monophyly of each examined genus also receiving support. Based on the two most recent phylogenetic studies of Boulenophrys , the genus can be further divided into three well‐supported species groups: the B. minor group, the B. omeimontis group, and the B. boettgeri group (Lyu et al., 2023 ; Qi et al., 2021 ).…”

“…Tianping in Sangzhi County. A similar pattern was observed in mustache toads of Leptobrachium we studied before, where L. boringii and L. liui were also collected in the same region of Zhangjiajie City but occupied very different phylogenetic lineages that showed a parallel southwestern and southeastern convergence (Zhou et al., 2023 ). Notably, another species, B. caudoprocta , was also found in Mt.…”

“…The toad family Megophryidae (Bonaparte, 1850) is an Asian endemic group that primarily distributed from eastern Pakistan to western China, and southward to the Philippines and the Greater Sunda Islands (Frost, 2023). Although the taxonomic validity of Megophryidae has been challenged for a long time in the last century (Zhou et al., 2023), it is now generally recognized as a monophyletic group and includes two subfamilies, Megophryinae and Leptobrachiinae (AmphibiaWeb, 2023; Frost, 2023). According to the latest statistics, the two subfamilies comprise 134 and 187 species, respectively (Frost, 2023), making Megophryidae one of the most diverse groups of amphibians in Asia as well as in the world.…”