How the Wallace line explains the difference in species across continents Premium
The Hindu
Discover the Wallace Line, a biogeographical boundary between Asia and Australia, through the eyes of naturalist Alfred Russel Wallace.
Kangaroos and cockatoos are synonymous with Australia and tigers and orangutans with Asia. Both these continents boast rich biodiversity that is also very unique. A simple yet popular way to understand these ‘separate greatnesses’ has taken the shape of the Wallace line.
In the late 19th century, the English naturalist Alfred Russel Wallace noticed a dramatic shift in the composition of organisms as he moved from Asia to Australia, New Guinea, and other islands nearby. He posited an invisible barrier in the ocean, later called the Wallace line, running between the islands of Bali and Lombok, striking north between Borneo and Sulawesi before curving south of Mindanao. To him this line was like a fence between the different kinds of animals on the two sides.
Wallace and others conducted eight years of fieldwork to carefully plot the line across many kilometres, in the process laying the foundations of modern biogeography: the study of how species are distributed and how they got there.
Over the years, the line has attracted considerable research interest. “The Wallace line … ties partly into the theory of evolution. Nowhere else on the earth do you see such a dramatic shift over such a narrow distance. Organisms are not just scattered randomly,” Jason R. Ali, honorary associate researcher at the Senckenberg Society for Nature Research, Germany, said.
At their closest, the islands of Borneo and Sulawesi are just over 20 km apart yet they support very distinct plants, mammals, and birds. Wallace was more baffled by Sulawesi. It’s one of the largest islands in the archipelago and home to species found nowhere else on the planet, including tarsiers (family Tarsiidae), the lowland anoa (Bubalus depressicornis), and the mountain anoa (Bubalus quarlesi), which are both of Asian origin. Yet Sulawesi is also home to Australian marsupials like the dwarf cuscus (Strigocuscus celebensis).
The island frustrated Wallace, who repeatedly redrew his line because he was unsure whether it belonged to Asia or Australia. He wrote in 1876 that the animals here showed “affinities” to Africa, India, Java, the Maluku Islands, New Guinea, and the Philippines.
Why do Sulawesi have species from both sides of the line while most others didn’t? Wallace had deduced the essential answer all those years ago but it has accrued greater depth with more research over time.
Explore the necessity, types, challenges, and potential of bioremediation in India for environmental restoration and public health.
Researchers in India uncover genetic factors linked to early oral cancer onset in tobacco chewers, enhancing cancer prediction and prevention.
Mahindra’s XEV 9S is a modern, family-focused electric SUV with premium design, a spacious tech-rich cabin, refined performance and advanced safety features. Discover variants, pricing and real-world impressions in our detailed review.
Samantha interview: On pickleball, her battles with a rare autoimmune condition and learnings
Experience the thrilling Akkulam Glass Bridge in Thiruvananthapuram, offering stunning views and adventure activities for all ages.
Climate scientists and advocates long held an optimistic belief that once impacts became undeniable, people and governments would act. This overestimated our collective response capacity while underestimating our psychological tendency to normalise, says Rachit Dubey, assistant professor at the department of communication, University of California.
Indian astronaut Shubhanshu Shukla predicts a transformative decade for India’s space exploration and international collaboration.