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Why Do Australia and Southeast Asia Have Different Species?

Despite being relatively close to each other, Australia and Southeast Asia have wildly different animal species. Australia lacks species such as tigers, elephants, and bears that are found in Asia. In contrast, few places in Southeast Asia have marsupial species found throughout Australia. Recently, a team of researchers from The Australian National University and ETH Zurich carried out a study to investigate why this is.

The divide between animals in Australia and Southeast Asia was noted as far back as 1854. A British naturalist, Alfred Russell Wallace, noticed that there was a distinction between the species present on the islands of Bali and Lombak and another between Sulawesi and Borneo. The biological distinction was interesting when compared to the islands’ relative closeness. For example, Sulawesi was home to a few marsupials also found in Australia, while these same species were absent in Borneo. This boundary between the two biogeographical sections became known as Wallace’s Line.

The team of researchers used a variety of data to compile a comprehensive model of the region showing why Wallace’s Line exists. What they found was that, as the Australian and Eurasian Plates moved closer together, different animal species were able to spread land creatures between the two landmasses. Additionally, as new islands formed in areas of tectonic activity, species were able to move across them more easily. This meant that creatures from Asia were able to migrate toward Australia, and vice versa. However, scientists noted that more creatures spread from Asia toward Australia.

The recent findings show that this is due to the increased ability of Asian creatures to adapt to the Australian climate. These creatures evolved to flourish in tropical, humid climates. This primed them to settle in the tropical regions existing in Indonesia, New Guinea, and northern Australia. Once they arrived in new regions, these tropical species were better able to adapt quickly to their new homes.

The team’s research was published in a recent edition of Science. The information will help us understand how modern invasive species spread, and what makes them successful. Human activity has helped give rise to greater rates of invasive spread across different regions. Understanding what made species successful in establishing themselves in new regions in the past, will help us better understand current trends.

Many marsupials are endemic to Australia. One of these is the koala. Koalas have experienced rapid population loss in the past three years due to wildfires, habitat loss, and drought. Sign this petition to Help Save Koala Habitat!