A decade-long study has revealed two species of birds endemic to the Western Ghats, actually belong to different genera (a genus is a taxonomic category ranking above species) and represent multiple species. This is the first time after 150 years that a bird genus endemic to India has been discovered. What were originally thought to be Western Ghats Shortwings are actually Flycatchers and those originally referred to as Laughing Thrushes are more closely related to Babblers. The nearest relatives of these bird groups are found in the Himalayas and Southeast Asia.
Although India is one of the seventeen megadiverse countries in the world, there is a consensus that instances of evolution of bird species unique to the country are few. One exception is the Western Ghats, a global biodiversity hotspot, which is home to many endemic species. Now it seems we can add a few more to this list, thanks to the efforts of an international team of field biologists, ornithologists, evolutionary biologists, phylogeneticists, and taxonomists, led by VV Robin from the National Centre for Biological Sciences (NCBS), Bangalore (present affiliation: Indian Institute of Science Education and Research, Tirupati).
“The key to making these important discoveries was genetics, which allowed us to more accurately place these birds on the evolutionary tree (genealogy or family tree of all species),” explained author Sushma Reddy from NCBS and Loyola University Chicago. “When we deciphered their genetic relationships, it was clear that these two lineages were very different from the birds with which they were previously categorised. Given their unique positions in their evolutionary trees, it made sense to give these two groups new genus names.” Now designated as Sholicola (Flycatchers) and Montecincla (Babblers), these two groups of birds are the first known instances of avifauna which have diversified from an ancestral form endemic to the Indian subcontinent. Akin to Darwin’s finches which diverged from each other across the Galapagos Islands, Sholicola and Montecincla diverged across the “sky islands” (isolated mountain tops) of the Western Ghats.
The authors assessed a wide variety of data – song, feather patterns, body measurements, DNA – to show that these populations have unique characteristics and should be treated as separate species and especially genera. It appears, the two groups evolved into new species at the same time, implying that speciation happened in response to a major climate event that was also responsible for ecological changes across the Indian subcontinent in the past.
Apart from the genetic data that led to the discovery, the study also benefitted immensely from the discovery of old specimens in the Trivandrum Natural History Museum, which were catalogued by CK Vishnudas from NCBS. “One significant advantage we had to solve this mystery was this fantastic collaboration bringing together scientists from across the world with different strengths,” said co-author Uma Ramakrishnan from NCBS. “We were also fortunate to be able to get permissions to handle the animals; we wouldn’t have been able to do this work or make these discoveries without the trust of the Forest Departments of Kerala and Tamil Nadu,” she added.
The study underlines the importance of long-term research involving both field research and museum specimens. It also highlights that there are many bird species with very narrow distribution ranges in the highly fragmented forests of the Western Ghats. The authors hope that the knowledge of their distinct evolution and ecology will draw the attention of conservationists to protect their habitats.