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For Namesake: The frog classification debate--Minervarya or Fejervarya?

  • Photo : Vidisha Kulkarni / Research Matters
    Photo : Vidisha Kulkarni / Research Matters

A new study by scientists from Technische Universität Braunschweig, Germany, University of Delhi, Delhi, India, Hiroshima University, Japan, Bangamata Sheikh Fazilatunnesa Mujib, Bangladesh, Sorbonne Universités, France, and North-West University, South Africa has modified the classification of Asian frogs of the genus Fejervarya and related genera from the family Dicroglossidae.

Frogs from the genus Fejervarya commonly known as rice frogs or cricket frogs have been the subject of intensive debates in the past few years. With new species of Fejervarya increasingly being discovered and described, like the most recent one from Goa, stability in their classification is much needed.

The team of scientists complemented previous phylogenetic studies or studies of the evolutionary relationship among the different species, with their own study based on gene analyses. The team analysed  sequences of gene fragments, from 14 nuclear loci and mitochondria. In total, 12,752 nucleotides, which are the building blocks of nucleic acids,  for 46 species representing all major lineages and relevant outgroups were analyzed. Using several molecular and statistical methods the scientists have discovered that there are two clades or groups with a common ancestor, the South Asian clade and the Southeast Asian clade. The study also reveals the Southeast Asian species as closely related to the genus Sphaerotheca.

For their study, the scientists assembled and used the largest dataset of mitochondrial and nuclear gene sequences compiled to date for the purpose of elucidating evolutionary relationships of genus Fejervarya and the related genus Sphaerotheca.

Keeping in consideration that many new species of cricket frogs are being discovered, the single-genus classification (Fejervarya) remains controversial. In this study, the team classified the frogs from the family Dicroglossidae into two genera: Southeast Asian frogs as genus Fejervarya, and South Asian frogs as genus Minervarya. They suggest that this classification resulting in two genera whose monophyly-- descendancy from a common ancestor, is strongly supported, and are unlikely to be challenged by future analyses.

Talking about the debate on the subject,the scientists say “clearly, reaching a consensus on the generic classification of Fejervarya could generate disagreement and debate, requiring a justified resolution of what could become a complex taxonomic issue; we acknowledge that any solution will necessarily remain subjective.”

Given the previous discussions and debates regarding the classification of this genus Fejervarya the scientists prefer this new arrangement, that treats South Asian and Southeast Asian taxa each as a separate genus. “This is because, despite the clear ambiguity and anticipated remaining controversy, we feel that a bio-geographically sensible, regionally circumscribed arrangement has a higher probability of stabilizing the taxonomy of these frogs.” remark the authors of the study.