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.
NASA's AIM observes early noctilucent ice clouds over Antarctica
05.12.2016 | NASA/Goddard Space Flight Center
GPM sees deadly tornadic storms moving through US Southeast
01.12.2016 | NASA/Goddard Space Flight Center
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water
In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
05.12.2016 | Power and Electrical Engineering
05.12.2016 | Information Technology
05.12.2016 | Earth Sciences