Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

The effect of climate change on the patterns of bird distribution east and west of Wallace's Line

10.04.2008
Indo-Malayan region is one of the richest bird species areas in the world. Researchers in Universiti Malaysia Sarawak found that sea level and climate changes during the last glacial period played a key role in the diversification of birds in this region where bird species gradually diversified when sea levels were low. This continues until today.

The evolutionary processes leading to the development of new species, their extinction, immigration and emigration may be influenced by both historical and contemporary mechanisms.

For instance, falling sea levels and climate during the last glacial period (about 18,000 to 10,000 years before present) had developed a savanna-like habitat in the "exposed" land area that connects the current landmasses in Sundaland (the Malay Peninsula, Sumatera, Java and Borneo). Such massive changes are predicted to have played a key role in influencing faunal composition and geographic distribution of species in the Southeast Asia region.

The current pattern of bird fauna distribution is predicted to fit the proposed landbridges or dispersal routes that appear due to the physical splitting of once continuous area by the processes of continental drift and changes in sea levels during the Last Glacial Maximum (LGM).

A study head by Asociate Professor Dr Mustafa Abdul Rahman of Universiti Malaysia Sarawak (UNIMAS), was conducted to compare the patterns of bird's species distribution in the Wallacea, Sunda and Sahul Shelf (the subregions and island of Thailand, Peninsular Malaysia, Sumatra, Borneo, Java, Bali, Lombok, Sulawesi, the Philippines and New Guinea).

Data on bird fauna in Southeast Asia, as well as New Guinea, was taken from documented field guides. A total of 88 families (with 479 genera and 1718 species) of resident breeding birds were collated (migrant species excluded). This accounts for about 17.6% of the total number of bird species in the world, making this region one of the richest bird's species regions in the world.

Analysis of species similarity among the 10 subregions/island in the study supports the model of biogeographic divergence based on historical changes in sea levels. At each of the three subgroups, the distribution of land and water birds revealed a major transition line that fitted with the glacial model.

New Guinea and the Philippines showed little species resemblance with the rest of the subregions/islands in this study. This finding agrees with the geographic position of New Guinea lying on the continental shelf of Australia and sharing much of its fauna with that island-continent.

The Philippines, on the other hand, was never joined to the Sunda Shelf's islands and mainland Asia during the last glacial period, because of the presence of deep water channels (>200m deep) that separate Philippines from the region. Even when sea level was predicted to have dropped as much as 160 m during the glacial periods, that still failed to connect the Philippines (except Palawan) archipelago with Borneo and the rest of the region.

Their findings suggest that bird's species diversification took place across a range of glacial stages, with ancient diversification between families taking place at a time of lower sea level. Diversification within families occurs at a time when Sumatra moved away from mainland Asia to form a group with Borneo. Diversification within species related closely to mainland Asia.

The pattern of distribution suggests that the descendant that crossed over from mainland Asia or remained in Sumatra during the glacial and inter-glacial period may have perished and became extinct, especially those families that have few species and shows vulnerability to environmental changes and human intervention.

While the findings support the glacial model of Southeast Asia's geographical distribution of biodiversity over space and time, it does not agree with the proposed faunal boundaries of Wallace’s line that separates the zoogeographical regions of Asia and Australasia -- the finding does not point to the major faunal transition between Bali and Lombok as well as between Borneo and Sulawesi. Instead their findings at family level agree with Mayr's line which cuts at the west of Lombok, allowing Lombok to be grouped with Java and Bali.

The bird species composition in Bali shows more resemblance to Java and Borneo while Lombok shares more of its genera and species with Sulawesi; and the bird compositions of Borneo and Sulawesi have little resemblance even at the family level even though the two islands are separated by a 50 km wide Straits of Makasar.

Resni Mona | ResearchSEA
Further information:
http://www.unimas.my/
http://www.researchsea.com

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

A Map of the Cell’s Power Station

18.08.2017 | Life Sciences

Engineering team images tiny quasicrystals as they form

18.08.2017 | Physics and Astronomy

Researchers printed graphene-like materials with inkjet

18.08.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>