![]() The findings are important for the researchers: "They make it clear that we can only understand today's distribution patterns of biodiversity if we include the geological development and climatic conditions of prehistoric times in our considerations," says Pellissier. ![]() "Something that is rare in tropical frogs." "Many Australian frogs bury themselves in the ground and remain dormant for long periods for this reason," Skeels points out. These include behavioural adaptations such as nocturnal activity and physiological adaptations to minimise water loss. 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. 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. "The historical context is crucial for understanding the biodiversity distribution patterns observed today and was the missing piece of the puzzle explaining the enigma of Wallace's line," says first author Alexander Skeels, a postdoctoral researcher in Pellissier's group.Ĭompetitive advantages for tropical species This made it easier for them to settle on the new continent. 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. 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. These islands featured a tropically humid climate, which they were comfortable with and had already adapted to. Based on simulations, the researchers found that animals originating from Asia were more likely to "hop" across the Indonesian islands to reach New Guinea and northern Australia. In addition to plate tectonics, the environmental conditions that prevailed millions of years ago were decisive for the exchange between the two continents. 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. It combines reconstructions of the climate, plate displacements between 30 million years ago and the present day and a comprehensive data set for around 20,000 birds, mammals, reptiles and amphibians that are recorded in the region today. In order to better understand this asymmetrical vertebrate distribution along the Wallace Line, researchers led by Loïc Pellissier, Professor of Ecosystems and Landscape Evolution at ETH Zurich, have created a new model. More Asian animals in Australia than vice versaīut why more species found their way from Asia to Australia - countless poisonous snakes, thorny lizards ( Moloch horridus), hopping mice ( Notomys sp.) or flying foxes bear witness to this - than the other way round has been a mystery until now. 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. ![]() It became easier for land creatures to colonise one continent from the other. This brought two land masses closer together that had previously been far apart. Forty-five million years ago, the Australian Plate began to drift northwards and slid under the mighty Eurasian Plate. How these distribution patterns came about, however, has not yet been clarified in detail. He described an (invisible) biogeographical line running between Bali and Lombok and Borneo and Sulawesi that marked the westernmost distribution of Australian fauna.īiodiversity researchers have long been fascinated by this abrupt change of creatures along the Wallace Line. This abrupt change in the composition of the animal world already caught the eye of the British naturalist and co-discoverer of evolutionary theory Alfred Russell Wallace, who travelled through the Indo-Australian Archipelago from 1854 to 1862 to collect animals and plants.
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