Scientists claim the morphological phenotypic plasticity found in the Kalinga cricket frog is first such in India
Indian scientists have reported a first-of-its-kind discovery of morphological phenotypic plasticity (MPP) in the Kalinga cricket frog. MPP is the ability of an organism to show drastic morphological (physical features) variations in response to natural environmental variations or stimuli.
The discovery was made by researchers Amit Hegde and Girish Kadadevaru from the Breeding Behaviour and Bioacoustics Lab, Department of Zoology, Karnatak University, Dharwad and KP Dinesh of Zoological Survey of India, Pune. The findings were published recently in the journal Zootaxa.
“The frog species was identified not long ago. Its documentation was done in 2018 and reported from the Eastern Ghats. It was thought to be endemic to the hill ranges of the Eastern Ghats,” Kadadevaru said.
In the Eastern Ghats, the species is found on the higher-elevation hill ranges of Odisha and Andhra Pradesh.
In the present research communication, Hegde and his team have reported the Kalinga cricket frog from the central Western Ghats, with the evidence of considerable ‘morphological phenotypic plasticity (MPP)’.
“The species was encountered several times during field expeditions in the Western Ghats. However, the physical characteristics vary entirely from the known Fejervaraya / Minervarya species from the Western Ghats,” Hegde said.
Humanity was still discovering new species in the 21st century and did not know a lot about them as well as how they behaved or adapted themselves to different biogeographic ranges, Hegde said.
The research paper also evoked a large number of questions on taxonomic ambiguity within the genus Fejervarya / Minervarya.
Most of the species described were known only from their locality and most old-time specimens have been lost. Hence, there is an urgent need to address or solve this problem to address taxonomic uncertainties.
“It is interesting to note that though there is a decline in the amphibian population globally, researchers in India are successfully able to explore new species and trace the geographic ranges of some rare amphibians,” Girish Kadadevaru said.
He said the recent study also indicated the frog species being endemic to the Eastern Ghats. “However, the population is seen in the Western Ghats. The biogeographic zones are very different. The frog from the Eastern Ghats is phenotypically showing certain differences when compared with the population that was observed in the Eastern Ghats,” he said.
Frogs are known to exhibit varied reproductive behaviours by adopting different modes and strategies for successful survival.
The behavioural studies of many anuran (frog or toad) species will help in generating information on the selection of breeding sites, courtship patterns and ecological adaptations, Dinesh noted.
It was only genetic analysis that helped prove that physically different-looking frogs were the same, Dinesh said.
“Only morphological character utility in the identification of the species and addressing the taxonomic uncertainties is always tricky, but the utility of genetic data and DNA barcoding tools are always handy in resolving complex taxonomic problems,” he added.
The Western Ghats and the Eastern Ghats are the two different biogeographic zones, with unique histories. While the Western Ghats are considered as a biodiversity hotspot, that is not the case with its eastern counterpart, Dinesh said.
Geologically, the Western Ghats are ancient, having Gondwanaland relict forests in the south, while the formation of the Eastern Ghats is recent, he added.
Both landscapes have unique ecosystems, with special microclimates and microhabitats that support a great number of diversities including amphibians.
Explaining the differences in morphological features, Dinesh said both populations show substantial morphological characters.
“Any classical taxonomist would consider these two populations as two different species on the basis of morphological characters alone,” he said. Explaining further, he said, colour variations across the different populations of the same species were quite common.
The Kalinga frog of the Eastern Ghats. Photo: Prudhvi Raj
“But in this case, there are contrasting morphometric differences in terms of head shape and size; the number and size of the fingers vary from two to four, which are comparatively larger. Also, the toe sizes were observed to be smaller in the frog species found in the Western Ghats,” he said.
In India, the Fejervarya / Minervarya group was complex and detailed studies on bioacoustics breeding ecology were needed to generate the information on these populations, Dinesh said.
This information will not only help to trace the distribution of these species along the peninsular region of India but could also be used to evaluate the possible links with species that were found in the North East region.
The researchers say it is the first-of-its-kind finding in amphibian research in India.
“Earlier, there were reports of morphological variations but not the combination of genetics and morphology across two different biogeographic zones. The general perception of ‘every species is everywhere’ is not the case with many Western Ghats frogs,” Dinesh said.
“If the species is widespread, its genetic divergence should be homogeneous. But in our case, there is some difference and not enough to say it is a new species,” he added.
“We speculate that the Eastern Ghats would have been a connecting land bridge for species dispersal between the Western Ghats and northeast India as the Fejervarya genus frogs are widespread,” the scientist said.
Need for a deeper understanding
The scientists said the recent findings were certainly not a habitat expansion and there was more information waiting to be found.
“We are sure this not just a habitat expansion because there is 0.2 per cent genetic divergence for the mitochondrial 16s rRNA gene. We are trying to understand the possibilities of splitting two populations of Fejervarya Kalinga due to the Deccan Trap formation (which require more nuclear gene studies and natural history studies to substantiate),” Dinesh said.
“The next questions to ask are how this little genetic divergence is leading to such contrasting morphological adaptations in these two biogeographic zones, the Western and Eastern Ghats. For example, the Kalinga frog is a semi-aquatic frog that actively breeds in the monsoon. But the Western Ghats are more influenced by the southwest monsoon, while the Eastern Ghats are influenced by the northeast monsoon,” he added.
In the era of climate change, the isolation of these two populations due to climate change should also be explored soon.
“Although a number of new species are described from India at a regular pace, the distribution range of many species is still not known with certainty. In this era of ‘mass extinction of smaller vertebrates’ and ‘rapid climate change’ scenarios, the report of ‘morphological phenotypic plasticity’ for the first time in Indian amphibian research history is phenomenal,” Hegde said.
“For conservation efforts, the less we know about the species, the more difficult it is to conserve it,” Hegde said.
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