In Bali, cockatoo is not found, but in the neighbouring island of Lombok (Indonesian), it is found.
- Australia is home to numerous marsupial species, such as the kangaroo and the koala. One can find just two representatives of these typically Australian mammals on the Indonesian island of Sulawesi, but it is not found on neighbouring Borneo.
- Australia, on the other hand, is not home to mammals that you will typically find in Asia, such as bears, tigers or rhinos.
Wallace Line
- Biodiversity researchers have long been fascinated by above abrupt change of creatures along the Wallace Line.
- The Wallace and Weber lines are imaginary dividers used to mark the difference between species found in Australia and Papua New Guinea and Southeast Asia.
Reason: tectonics
- One explanation is plate tectonics. Forty-five million years ago, the Australian Plate began to drift northwards and slid under the mighty Eurasian Plate.
- This brought two land masses closer together that had previously been far apart. It became easier for land creatures to colonise one continent from the other.
- Tectonic movements also gave rise to the creation of countless (volcanic) islands between the two continents, which animals and plants used as stepping stones to migrate westwards or eastwards.
Adaptations to the climates
- In the latest issue of Science, the researchers now show that adaptations to the climates in the areas of origin are partly responsible for the uneven distribution of Asian and Australian faunal representatives on both sides of the Wallace Line.
Environmental conditions
- In addition to plate tectonics, the environmental conditions that prevailed millions of years ago were decisive for the exchange between the two continents.
- Islands featured a tropically humid climate, which they were comfortable with and had already adapted to. The Australian wildlife was different, having evolved in a cooler climate that had become increasingly drier over time, and was therefore less successful in gaining a foothold on the tropical islands than the fauna migrating from Asia.
- The Asian climate thus favoured creatures that reached Australia via the tropical islands of the faunal region known as Wallacea, especially those that could tolerate a wide range of climates.
- Traits of species that evolved in tropical habitats include faster growth and higher competitiveness to enable them to withstand the pressure of coexistence with many other species.
- In harsher climates, such as the colder and drier regions of Australia, organisms usually have to evolve special adaptations to cope with drought and heat stress.
(Source: Science Daily)
