Valleys, gaps, climate change affect songbirds’ speciation

E.M. Manoj
KALPETTA,  
The Hindu, June 19, 2015

A new study, published in the Proceedings of the Royal Society B , by National Centre for Biological Sciences on high elevation songbirds of Western Ghats, has found that deep valleys have greater impact on speciation than shallow ones in this mountain chain.

The study was conducted by Uma Ramakrishnan and her colleagues at NCBS to investigate genetic variation of all 23 species of songbirds that inhabit the Shola forests of the sky islands of Western Ghats.

The study found that not all species are affected by the gaps. Out of the 23 species studied, 10 showed genetic divergences across the deepest, widest valley, the Palghat gap, while three others diverged across the Shenkotta gap. Only one species diverged across the shallowest valley, the Chaliyar River valley. While the Western Ghats were formed some 50 million years ago, the arrival of songbirds in the Western Ghats is only dated earliest to 34 million years ago.

Simulated studies suggested the species diverged at different times. Our study shows that it was not only the valleys and gaps in the mountain, but also the climate that affect to play an important role in these bird divergences. Going by their past response to climate changes, we can predict that future climate changes may impact the speciation of these birds, said V.V. Robin, the lead researcher of the study.

Our results reveal a richly varied, yet generalised pattern of divergence. The nested pattern of divergence across deeper versus shallower valleys also provide us clear predictability regarding where to look for the two most different individuals in a species-across the Palghat gapâ, says Ms. Ramakrishnan.

Most studies like this use museum specimens when analysing a large number of species. Knowing the topology and spending close to 400 nights out in the field really helped us sample the entire mountain community, C.K Vishnudas, a researcher said.

Pooja Gupta, another researcher, said it was an amazing experience going from the birds in the mountains to the large amount of genetic data we generated in the lab.