Why in News? 

In the 19th century, Alfred Wallace noticed a sharp difference in species composition between Asia and Australia, leading to the identification of the Wallace Line. 

What is the Wallace Line? 

• Definition: An imaginary boundary separating the distinct Asian and Australian ecosystems. 
• Location: Runs through the Makassar Strait (between Borneo and Sulawesi) and between Bali and Lombok, dividing the Sunda and Sahul continental shelves. 
• Species Distribution 
  • West of the Wallace Line (Bali, Borneo, Java): Asian species like monkeys, rhinos, tigers, and hornbills. 
  • East of the Wallace Line (Lombok, Sulawesi, Timor, Australia): Australian species like tree kangaroos, cockatoos, and honeyeaters. 

Wallacea Region 

• The area between the Wallace Line and the Weber Line. 
• Includes Sulawesi, Flores, Lombok, Timor, with unique species like the Komodo dragon, babirusa, and giant bees. 

Formation of the Wallace Line 

• Continental Drift: 85 million years ago, Australia separated from Antarctica, isolating species and driving independent evolution. 
• Deep Ocean Barriers: Makassar Strait remained submerged, preventing species migration. 
• Climate Adaptation: Asian and Australian species evolved separately, adapting to distinct environments.