Description

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Context

Wallace Line represents critical biogeographical boundary between Asia & Australia shaping species distribution & influencing unique biodiversity of regions like Sulawesi however ongoing threats of habitat destruction as well as climate change now pose significant risks to these ecosystems necessitating urgent conservation action.

Key Highlights

Wallace Line Definition:

Proposed by naturalist Alfred Russel Wallace in 19th century.

Marks boundary between the species of Asia & Australia passing through Indo-Malay Archipelago.

Runs between Bali and Lombok then between Borneo & Sulawesi curving south of Mindanao.

Species found to west of the line such as those in Java, Bali, Borneo share common traits with those from the Asian mainland while species to east of line in Sulawesi & New Guinea resemble Australian fauna. For example:

Asian species: Tigers, elephants, rhinoceroses.

Australian species: Marsupials like kangaroos, koalas, platypuses

Wallace fieldwork over eight years helped lay foundations for modern biogeography study of species distribution.

Wallace noticed dramatic difference in species on either side of the line which led to his theory of an invisible barrier between Asia & Australia.

Sulawesi’s Unique Biodiversity:

Sulawesi is home to both Asian-origin species (e.g. tarsiers, anoa) & Australian marsupials (e.g. dwarf cuscus).

Wallace was puzzled by Sulawesi unique species mix leading him to redraw his line multiple times.

The island showed “affinities” to various regions including Africa, India, Java, New Guinea, Philippines.

Geological and Evolutionary Insights:

Sulawesi species distribution can be explained by past tectonic movements that caused island separation and isolated species allowing for independent evolution.

Australia drift from Antarctica & movement towards Asia millions of years ago caused volcanic islands in Indonesia which later spurred evolutionary divergence of species.

Climatic Influence on Species Migration:

Tropical islands of Malay stayed warmer & wetter compared to Australia facilitating migration of Asian species to Australia.

Australian species faced more challenges migrating to Asia due to harsher climatic conditions & late emergence of migration routes.

Modern Research & Technological Advancements:

Recent studies analyzed 20,000 species of birds, mammals, reptiles, amphibians to understand relationship between species across Wallace Line.

Advanced evolutionary modelling & computer simulations are now used to better understand species adaptations & migration patterns.

Relevance to Current Conservation:

Indo Malay Archipelago is facing significant habitat destruction exacerbated by climate change.

Future Focus on Conservation:

Instead of redrawing biogeographical lines focus should be on understanding how species will respond to habitat loss & climate change.

Research suggests technological advancements & multidisciplinary insights will be crucial for conservation efforts moving forward.

Weber Line

Located between Borneo and Sulawesi Weber Line defines another boundary between Asian & Australian species though it is less well known than Wallace Line.

It reinforces geographic distinction between these two ecozones further highlighting divergence of species in this region.

Asia-Australia Divide

During periods of geological upheaval such as separation of Australian continent from Southeast Asian landmass millions of years ago species on either side of divide evolved in isolation. The isolation led to significant evolutionary differences:

Asian species: Typically placental mammals including tigers, rhinoceroses, elephants.

Australian species: Notable for marsupials (kangaroos, koalas) & monotremes (platypus, echidna).

Sulawesi

Sulawesi located on boundary of the Wallace & Weber lines presents an intriguing case in biogeography.

The island exhibits a mixture of species from both Asia as well as Australia making it unique example of evolutionary intersection. Examples of species found here include:

Tarsiers: Primates that are typically found in Southeast Asia.

Marsupials: Species like dwarf cuscus which are more aligned with Australian fauna.

Species Adaptation

Wallace Line & Weber Line have played major role in shaping evolutionary paths of species in this region. Some key examples of species adaptation across divide include:

Marsupials: These mammals such as kangaroos & koalas evolved on the Australian side of line & are prevalent in the islands to the east.

Monotremes: Species like the platypus & echidna which lay eggs are native to Australian continent & nearby islands.

Asian Placental Mammals: Species like tigers, rhinoceroses, elephants evolved in Asia & spread westward to islands near the Wallace Line.

The separation of species by Wallace and Weber lines allowed these animals to evolve independently adapting to their environments. This evolutionary divergence is key feature of biogeography in the region.

Indo-Malay Archipelago and key islands in relation to the Wallace Line

Region/Archipelago	Key Islands	Geographical Location	Notable Features
Indo-Malay Archipelago	Sumatra	Located west of the Wallace Line	Home to unique species, like tigers, orangutans.
	Java	Located west of the Wallace Line	Rich biodiversity, heavily influenced by both Asian and Australian fauna.
	Bali	Just west of the Wallace Line	Tropical island with a mix of Asian species.
Borneo	Borneo	Straddles the Wallace Line (north)	Shared fauna from both Asia and Australia.
Sulawesi	Sulawesi	Straddles the Wallace Line	Distinct species from both Asia and Australia, including marsupials and tarsiers.
Lombok	Lombok	Just east of the Wallace Line	Marks the boundary for species between Asia and Australia.
Philippines	Mindanao	Near the Wallace Line	Rich, diverse fauna with species unique to the region.
New Guinea	New Guinea	East of the Wallace Line	A diverse mix of both Australian and Asian species, heavily influenced by the surrounding seas.
Timor	Timor	East of the Wallace Line	Known for species from both regions but more influence from Australia.

Notable Archipelagos of the world

Region	Archipelago	Location	Key Features
Southeast Asia	Indo-Malay Archipelago	Southeast Asia (Indonesia, Philippines)	Includes islands like Sumatra, Borneo, Java, and the Philippines, home to diverse species and tropical climates.
	Philippine Archipelago	Philippines	Over 7,000 islands with rich biodiversity, home to unique flora and fauna.
	Maluku Islands	Between Sulawesi and Papua New Guinea	Known for tropical biodiversity and being part of the Wallace Line.
Pacific Ocean	Polynesian Archipelago	Central Pacific	Includes islands like Fiji, Tonga, and Samoa; known for cultural diversity and tropical landscapes.
	Melanesian Archipelago	Southwestern Pacific (including Papua New Guinea)	Contains thousands of islands, characterized by cultural diversity and volcanic activity.
	Micronesian Archipelago	Western Pacific	Includes tiny islands like Palau and the Marshall Islands.
Caribbean Sea	Greater Antilles	Caribbean (Cuba, Jamaica, Hispaniola)	Home to large islands with tropical climates and rich history.
	Lesser Antilles	Caribbean (smaller islands from Puerto Rico to Trinidad)	Tropical islands with coral reefs and volcanic origin.
Indian Ocean	Maldives	South of India, off the coast of Sri Lanka	Composed of 26 atolls, known for its white sandy beaches and coral reefs.
	Comoros Islands	Between Madagascar and Mozambique	Known for volcanic activity and rich marine biodiversity.
Arctic Ocean	Svalbard Archipelago	Arctic Ocean (Norway)	Polar archipelago known for ice fields, polar bears, and tundra ecosystems.
	Canadian Arctic Archipelago	Northern Canada	Composed of many islands, with glaciers, wildlife, and arctic environments.
North America	Alaska Archipelago	Alaska (USA)	Includes islands like the Aleutian Islands, known for wildlife and volcanic activity.
South America	Chilean Archipelago	Chile	Includes the Juan Fernández Islands and Chiloé, with temperate climates and biodiversity.
Europe	British Isles	United Kingdom	Composed of Great Britain and Ireland, home to temperate climates and rich history.
	Greek Archipelago	Greece (Eastern Mediterranean)	Known for its historical significance, beaches, and islands like Crete and Rhodes.
Africa	Canary Islands	Off the coast of North Africa	Spanish territory, known for volcanic origin and unique flora and fauna.
	Cape Verde Islands	Off the coast of West Africa	Volcanic islands with a tropical climate and rich culture.
Oceania	Australian Archipelago	Off the coast of Australia	Includes Tasmania and other surrounding islands, with unique ecosystems.
Antarctic Ocean	South Shetland Islands	Antarctica	Antarctic region known for ice-covered islands and cold climate.

Notable Biogeographical Lines in the world

Biogeographical Line	Location	Significance	Key Characteristics
Wallace Line	Between Borneo/Sulawesi & Bali/Lombok	Separates species of Asian and Australian origin.	Divides Southeast Asia's flora and fauna into distinctly different regions; notable for differences in species between islands like Borneo and Sulawesi.
Weber Line	Between Bali and Lombok, Indonesia	Similar to Wallace Line but slightly further west; also marks a biogeographical boundary between Asian and Australian species.	Marks a division between Australasian and Southeast Asian species.
Lydekker’s Line	Between Bali and Lombok (and parts of the western Indonesian islands)	Named after Richard Lydekker, it marks the northern boundary of Australian species in Southeast Asia.	Divides Australian and Asian species further to the east of Wallace's line.
Huxley Line	Between the Indonesian archipelago and Asia	Represents a zone of transition between the fauna of Southeast Asia and the Australasian region.	Often associated with the gradual blending of species between Wallace and Lydekker's lines.
Zanetti’s Line	Along the eastern coast of Madagascar	A biogeographical boundary that separates the fauna of Madagascar from mainland Africa.	Influences the differentiation of species in Madagascar, which evolved separately due to geographic isolation.
Gulfs of Suez and Aqaba Line	Between the Red Sea and the Mediterranean	Defines different marine species found in the Red Sea compared to the Mediterranean.	It separates different aquatic species found in the Red Sea from those in the Mediterranean.
Murray-Darling Line	Across Australia (roughly central)	Divides species of Australian fauna, specifically between the western and eastern sides of Australia.	Divides two different ecosystems in Australia, notably in relation to river systems and freshwater species.
Tethys Line	Across the Mediterranean Sea	Reflects the ancient separation between Tethys Ocean species and those of the Atlantic Ocean.	A historic line related to the splitting of continents and evolution of species that existed during the break-up of the supercontinent Pangea.
Bering Strait	Between Russia and Alaska	Separates the ecosystems of North America and Eurasia.	A historical land bridge that connected the Old World and New World, facilitating species migration during glacial periods.
Equator	Across the globe	Divides the Earth into the Northern and Southern Hemispheres.	Defines the tropical regions of the Earth with high biodiversity, particularly near the equator in the Amazon, Congo, and Southeast Asia.
Tropic of Cancer/Capricorn	Around the Earth (north and south)	Divides the world into temperate and tropical regions.	Marks the extent of the tropical zone and divides ecosystems into tropical, subtropical, and temperate climates.
Himalayan Line	Across the Himalayas in Asia	Separates species and ecosystems between the Indian subcontinent and East Asia.	Influences the unique biodiversity of the Himalayan mountain range, affecting plant and animal life in both the northern and southern parts.
Alps Line	Across the Alps (Europe)	Separates species of flora and fauna in the Alps from those of the rest of Europe.	Divides the high-altitude alpine ecosystem from the lower elevation regions of Europe.

Sources:

THE HINDU

PRACTICE QUESTION

Q. What does the Wallace Line separate in the Indo-Malay Archipelago?

a) The climate zones of Southeast Asia and Australia
b) The landmasses of India and Indonesia
c) The animal species of Asia and Australia
d) The cultural traditions of different islands

Correct answer: c)

Explanation:

The Wallace Line is an imaginary boundary that separates Asian animal species (like tigers and elephants) from Australian species (like kangaroos and marsupials). It highlights the difference in wildlife between these regions.