A break in the Western Ghats

Variation: There are biogeographic distinctions in species north and south of the Palghat Gap.
| Photo Credit: File Photo

Often referred to as as a major discontinuity in the Western Ghats, the Palghat Gap is about 40 km huge, with the steep Nilgiris and Anamalai hills, each rising above 2,000 msl, on both aspect.

The Palghat Gap has traditionally been necessary as a major gateway into the State of Kerala. It is a hall for each roads and railways that connects Coimbatore with Palakkad. The Bharathappuzha river flows by means of it. In distinction to the tropical rainforests of the Western Ghats, the vegetation in the Palghat Gap is assessed as dry evergreen forest. It additionally marks a divide in the natural world of the area. For instance, a number of species of frogs are discovered solely on one aspect of the Gap. 

Geological upheaval

The Gap is a geological shear zone that runs from east to west. Shear zones are weak areas in the earth’s crust — that is the cause why tremors are typically felt in the area Coimbatore.

The origin of the Palghat Gap additionally stems from the drift of continental cabinets after Australia and Africa broke off from the Gondwana landmass. 

India and Madagascar remained as one landmass till large-scale volcanic exercise break up the two, the break up occurring the place the Palghat Gap is situated — that is mirrored in the Ranotsara Gap on the jap face of Madagascar. How way back did the Gap originate? The landmass break up about 100 million years in the past, and the Gap had fashioned earlier than this; though how lengthy earlier than is debated.

It has been speculated that one cause for the biogeographic distinctions in species in north and south of the Gap might be resulting from an historic river or an incursion of the sea in the distant previous. 

Elephant populations on the Nilgiris aspect differ in their mitochondrial DNA from elephants in the Anamalai and the Periyar sanctuaries. 

One research from IISc Bangalore has analysed DNA sequence divergence information in populations of the White-bellied Shortwing, an endemic and threatened hen. Birds discovered round Ooty and Baba Budan are referred to as the Nilgiri blue robin; the Anamalai group differs barely in look, and is named the White-bellied blue robin.

South of the Gap

The biodiversity of a area is expressed in two methods: species richness, which pertains to what number of species are discovered in an ecosystem, and phylogenetic variety, the place you add up the evolutionary age of all the species you discover.

Both these traits are ample in the Western Ghats south of the Palghat Gap, as reported in a latest research by teams from the CCMB at Hyderabad and different establishments ( Proceedings of the Royal Society B, April 2023). There are over 450 species of bushes right here, together with some resembling  Magnolia champaca (Champa; Tamil: Sambagan) which have been round for over 130 million years.

Warm climate resulting from proximity to the equator, and moist air brings loads of rain to the southern Western Ghats. Therefore, this area has been an island refuge for all types of life, whilst cycles of ice ages and droughts have lowered biodiversity in surrounding areas. The Western Ghats in north of the Palghat Gap obtain extra rain yearly, however the south will get rain extra evenly all through the 12 months. 

( The article was written in collaboration with Sushil Chandani, who works in molecular modelling. sushilchandani@gmail.com)