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DISPLAYING POSTS TAGGED: biogeography (5)

Exploration of Sulawesi, Indonesia

Author
by Bonnie & Rashika
Publish date
11 November 2013
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Bonnie Gambhir is a Computer Science student with interests in scientific exploration. Rashika Premchandralal is pursuing a Master’s Degree in Biotechnology. Both are studying at the University of Melbourne.

This is the second post of an MV Blog mini-series celebrating the past, present and future of exploration on planet Earth and commemorating the adventures of Alfred Russel Wallace who died 100 years ago.

Wallace's exploration of the islands of Indonesia contributed to the theory of evolution by natural selection, as well as the field biogeography–the study of the distribution of species over space and time. Wallace famously divided the world’s animals into zoogeographic regions, with his travels through modern day Indonesia providing important clues about the transitions of more Asian-like species to those of Australian origin.

"The island of Sulawesi is a place where many Asian lineages get their easternmost distribution and many Australian lineages get their westernmost distribution, and Sulawesi represents a mixture of the flora and fauna of these two great continents," says Dr Kevin Rowe.

Skull of Babirusa MV specimen R8050: skull of Babirusa, Babyrousa celebensis, an ancient lineage of pigs on Sulawesi. Pigs are not native to the Australian continent and Sulawesi represents their easternmost distribution.
Image: Karen Rowe
Source: Museum Victoria
 

mount of Bear Cuscus MV specimen C27221: mount of Bear Cuscus, Ailurops ursinus. An ancient relative of the Ringtail Possum, the Bear Cuscus is endemic to Sulawesi and represents the westernmost distribution of Australian marsupials that never reached the Asian continent.
Image: Karen Rowe
Source: Museum Victoria
  

Since Wallace’s time, further scientific exploration in Wallacea has contributed immensely to our understanding of the distribution and evolution of species.

Researchers at Museum Victoria are continuing this exploration on the island of Sulawesi; Dr Kevin Rowe and Dr Karen Rowe have made several expeditions in recent years, leading to the description of new mammal species and new knowledge of the evolutionary relationships between Indonesian and Australian birds.

When Wallace visited Sulawesi, he recorded only five species of rodents. Today, we recognise almost fifty. Described in 2012 by Kevin and colleagues, one recently- discovered species from Sulawesi challenges the definition of rodent. The unique rat, Paucidentomys vermidax, (meaning “few-toothed worm-devouring mouse”) is the only rodent, among more than 2,200 species, with pointed upper incisors and no molars.

Dr Kevin Rowe with Paucidentomys vermidax Dr Kevin Rowe with Paucidentomys vermidax, a nearly toothless rodent, on the day of its discovery in the rainforests of Sulawesi.
Image: Kevin Rowe
Source: Museum Victoria
 

The honeyeater family Meliphagidae is one of the most diverse groups of Australian birds. Most of the nearly 170 species are found in Australia, New Guinea and adjacent Pacific Islands. A few species are native to Wallacea where the family reaches the westernmost limits of its distribution. Through her fieldwork on Sulawesi, Karen is studying the endemic genus Myza and their relationship to all other honeyeaters.

Lesser Sulawesi Honeyeater Lesser Sulawesi Honeyeater, Myza celebensis, found in the forests of Mount Dako, Sulawesi in 2013.
Image: Karen Rowe
Source: Mustum Victoria
 

Expeditions to Sulawesi by MV researchers and their Indonesian and US colleagues have produced several new records of species that have not been recorded since the 1970s. Many of these species were previously known from a single locality and are listed as 'data deficient' by the IUCN Red List of Threatened Species. Hence the recent exploration of Sulawesi is helping to improve understanding of the habitat requirements and distributions of these little-known species.

Local knowledge and assistance is as much a part of modern exploration as it was in Wallace’s time. Our final post in this series will explore how international cooperation has contributed to the success of Museum Victoria’s research in the region.

Links:

MV Blog posts about Sulawesi field research

Wonderful Wallacea

Author
by Kevin Rowe
Publish date
12 January 2012
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Kevin is the Senior Curator of Mammals at Museum Victoria. He reports on his recent expedition to the mountains of Sulawesi, Indonesia in this series of blog posts.

Last Sunday was the birthday of Alfred Russel Wallace who, along with Darwin, co-founded the theory of natural selection. As Ursula reported, Wallace's expedition through the Malay Archipelago (modern-day Indonesia) also prompted him to develop the field of biogeography and to define the zoogeographical regions of our planet; that is, where groups of animals are found and why.

World map showing the zoogeographical regions. Wallace's world map showing the zoogeographical regions in different colours.
Image: A.R. Wallace
Source: Copyright expired. Sourced from Wikimedia Commons.
 

Biogeography proposes that the species native to a particular region are determined by geographic processes such as vicariance (isolation) and dispersal (colonisation). Natural selection then drives species to evolve traits suited to survival and reproduction in their environments available in their geographic context. Biogeography and natural selection combined often result in species from different regions converging on similar morphological solutions to similar selective pressures.

Consider the mammals of Australia, which are the product of millions of years of natural selection acting on a set of species determined by biogeography. Australia, along with New Guinea, comprises the continental shelf of Sahul that today, as well as in Wallace's time, is separated by the Indonesian archipelago from the Asian continental shelf, Sunda. During low sea levels of the Pleistocene (the last 2 million years), Australia, New Guinea, and adjacent islands were one continuous landmass as were Malaysia, Sumatra, Java, and Borneo on the Asian side. Between them was Sulawesi, the Moluccan islands and the Lesser Sunda islands (Nusa Tenggara) all separated by deep ocean channels. This region at the interchange between Asia and Australia is referred to as Wallacea.

Map of Sunda and Sahul Map of Sunda and Sahul and the Wallace Line, the Lydekker Line and the Weber Line.
Image: Maximilian Dörrbecker
Source: Used under CC BY-SA 3.0 from Wikimedia Commons.
 

85 million years ago Australia was connected to Antarctica and via Antarctica to South America. When a meteorite crashed into the Yucatan peninsula of North America 65 million years ago annihilating the dinosaurs (except a few feathered and crocodilian ones), Australia was already starting to drift away from Antarctica. For 40 million years Australia drifted in isolation and only about 10 million years ago began to collide with Asia. The mammals that made this journey survive today as the marsupials and monotremes that are unique to Australia and New Guinea. The marsupials have evolved to fill many ecological roles with adaptations similar to placental mammals on other continents, a process driven by natural selection leading to convergent evolution.

Convergent evolution between the Thylacine and the Red Wolf. An example of convergent evolution. The Thylacine (left) and the Red Wolf (right) occupy similar roles in the ecosystem and have similar dog-like characteristics, even though they belong to entirely different groups of animals.
Image: Left: Heath Warwick | Right: ucumari
Source: Left: Museum Victoria | Right: Used under CC BY-NC-ND 2.0 from ucumari.
 

The native terrestrial mammals of Australia, however, are not just the result of isolation but are also descended from a select group of intrepid colonisers from Asia. These are the native bats and rats that account for nearly half of the mammal species of Australia. The rats are remarkable because they are the only non-flying, terrestrial mammals to colonize Australia before humans and they did it twice; once 5 million years ago (Rowe et al, 2008) and again 1 million years ago (Rowe et al, 2011). Both colonisers clearly came from Asian sources but the details of how they crossed multiple ocean channels and archipelagos are still unclear. In part this is hindered by our limited understanding of rat diversity from Wallacea, a condition that I and my colleagues endeavour to correct with our recent expeditions to Sulawesi.

Links:

More on convergent evolution of marsupial and placental mammmals

Happy birthday A.R. Wallace

Author
by Ursula
Publish date
8 January 2012
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Ursula Smith works in the natural sciences collections at Museum Victoria. Though a palaeontologist by training she finds all the collections fascinating and swings between excitement at all the cool stuff in them and despair at the lack of time to look at it all.

Today is the birthday of Alfred Russel Wallace, who was born on 8 January, 1823. While he isn't terribly well known today, at the end of the 19th century he was one of England's best-known naturalists – which is saying something considering that he was a contemporary of people such as Charles Darwin and Joseph Hooker. In fact, Wallace’s famous letter to Darwin prompted the latter to write On the Origin of Species after a joint presentation of their work to the Linnean Society. This post, however, is about another of Wallace’s important contributions to biology.

Photograph of Alfred Russel Wallace, taken in Singapore, 1862. Photograph of Alfred Russel Wallace, taken in Singapore, 1862.
Source: In the public domain, sourced from Wikimedia Commons.
 

After trying his hands at a few trades, Wallace became a field collector – a career that combined his desire to travel with his passion for natural history. After four years collecting along the Amazon River (and an eventful return voyage to England in which he spent 26 days in a lifeboat after his ship caught fire and sank!), Wallace set off for the Malay Archipelago – what is now Malaysia and Indonesia – and spent nearly eight years collecting shells, insects, reptiles mammals and birds for sale in England. The book he published about this trip, The Malay Archipelago, the land of the orang-utan and the bird of paradise; a narrative of travel, with studies of man and nature, was one of the best selling travel books of the nineteenth century.

Museum Victoria has around 200 bird specimens collected by Wallace on this trip that were sold to John Gould and then donated to the museum. Birds are very important in Wallace's story - not only was he looking specifically for the highly sought after birds of paradise on his trip so he could sell them to collectors in England, but his observations about the distribution of birds amongst the islands he visited were highly important in allowing him to develop the theory we today call biogeography – the science of where animals live and why.

Shelf of bird mounts A shelf of bird mounts collected by AR Wallace in the Museum Victoria collection.
Image: Ursula Smith
Source: Museum Victoria
 

In June of 1859 Wallace made an unscheduled trip between the islands of Bali and Lombok when he couldn't find a direct boat from Singapore to Makassar (at the south end of the island of Sulawesi, then called Celebes). He noticed that even though the islands are within sight of each other and very similar in size, elevation and climate, the bird species on Lombok were very different from those he'd seen on Bali. Wallace came to the conclusion that the two islands belonged to distinct Zoological provinces. He wrote in The Malay Archipelago:

I may mention that during a few days' stay in the island of Bali I found birds of the genera Copsychus, Megalaima, Tiga, Plocus, and Sturnopastor, all characteristic of the Indian region and abundant in Malacca, Java, and Borneo; while on crossing over to Lombock, during three months collecting there, not one of them was ever seen; neither have they occurred in Celebes nor any of the more eastern islands I have visited. Taking this in connexion with the fact of Cacatua, Tropidorhynchus, and Megepodius having their western limit in Lombock, we may consider it established that the Strait of Lombock (only 15 miles wide) marks the limits and abruptly separates two of the great Zoological regions of the globe.

In a paper about the distribution of birds in 1868 T.H. Huxley labelled this boundary that Wallace had described between the Asian and Australian biological regions as 'Wallace's Line', the name by which we still know it today. Since then we've discovered that there are other boundaries passing through the archipelago that are relevant to groups other than birds, but Wallace's Line remains the best known and the area is still an important location for research today.

Bird collected by Wallace Bird specimen, an adult female Eclectus Parrot, in the MV collection that was collected by AR Wallace.
Image: Ursula Smith
Source: Museum Victoria
 

Links:

Meet Me at the Museum: Birds of Paradise

Capturing Paradise: Alfred Russel Wallace's Red Bird of Paradise

Ornithology Collection

Entomology Collection

Wallace's books available as free ebooks from Project Gutenberg

The mammals of Sulawesi

Author
by Kevin Rowe
Publish date
6 January 2012
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Kevin is the Senior Curator of Mammals at Museum Victoria. He reports on his recent expedition to the mountains of Sulawesi, Indonesia in this series of blog posts.

I recently returned from an expedition into the heart of Sulawesi's central mountain forests. Shrouded in the cool moisture of clouds, these forests appear to be made of moss erupting from the ground. Halfway between Asia and Australia, the native species on this island are neither Australian nor Asian but a unique mix of lineages from the two great continents.

Cloud forest of Sulawei The mountain rainforest of Sulawesi, Indonesia.
Image: Kevin Rowe
Source: Museum Victoria
 

Together with Anang S. Achmadi, Curator of Mammals from the Museum Zoologicum Bogoriense (the national museum of Indonesia) and a team of local guides, I hiked two days from the rice fields of Mamasa to a field camp at 2600 m in the mountains above.

the Sulawesi expedition team The Sulawesi expedition team.
Image: Kevin Rowe
Source: Museum Victoria
 

campsite in Sulawesi Base camp for the Sulawesi expedition.
Image: Kevin Rowe
Source: Museum Victoria
 

Led by our local guides, including 84 year-old village-elder, Pak Daud, we encountered a pristine, primordial forest rich in biodiversity. Streams dissect the plateau spreading the daily afternoon showers across the landscape and to the fertile rice fields in the valleys below. The endangered mountain anoa (a pygmy water buffalo found only in the mountains of Sulawesi) run in large numbers, bear cuscus (relatives of Australia's brushtail possums) climb through the tree tops, dozens of orchid and pitcher plant species cling to the moss that covers everything, and a diverse assemblage of rodents survive in large numbers. We came in search of these rodents found nowhere else on earth, but which may help us understand the relationship between Australia's native rodents and Asia's.

hiking in Sulawesi Hiking through mountain terrain in Sulawesi.
Image: Kevin Rowe
Source: Museum Victoria
 

Over three weeks of surveys in these remote forests, we detected 34 species of small mammals (< 1 kg), a healthy number for any forest. Consider that there are about the same number of small mammals across the entire State of Victoria. The rodents in these mossy mountain forests are characterised by a range of morphological oddities, such as giant woolly rats, Eropeplus, small arboreal mice, Haeromys, spiny rats, Maxomys, tiny arboreal squirrels, Prosciurillus, large terrestrial squirrels, Hyosciurus, and a collection of shrew rats that, like shrews, specialise on eating invertebrates. These shrew rats include two species of the soft-furred Tateomys and one species of the short-legged Melasmothrix.

Rodents of Sulawesi. Rodents of Sulawesi. Left: small arboreal mouse Haeromys montanus. | Right: giant woolly rat Eropeplus canus
Image: Kevin Rowe
Source: Museum Victoria
 

Two species of shrew rats from Sulawesi Two species of shrew rats from Sulawesi. Left: Tateomys rhinogradoides | Right: Tateomys macocercus
Image: Kevin Rowe
Source: Museum Victoria
 

We also detected two shrew rat genera that have not been seen since the 1970s including three individuals each of the puppy-faced Crunomys and the rare, worm-eating, gangly-legged Sommeromys, previously known from a single specimen.

Two genera of shrew rats from Sulawesi. Two general of shrew rats that were found for the first time since the 1970s. Above: Crunomys sp. | Below: Sommeromys sp.
Image: Kevin Rowe
Source: Museum Victoria
 

Brittle star bands

Author
by Kate C
Publish date
18 February 2011
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Over the past ten years, MV curator Tim O’Hara has been snooping through museum collections all over the world, collecting data about brittle stars for a major mapping exercise. He compiled nearly 7000 samples from 250 common species of brittle stars from 24 different museums and discovered something quite unexpected about their distribution.

Brittle stars, or ophiuroids, are echinoderms closely related to sea stars. They have five long, flexible arms attached to a central body. Unlike sea stars, brittle stars are quite active and fast-moving. They are ideal for this kind of large-scale mapping study because they are found all over the globe in a variety of habitats.

Conocladus australis A brittle star (Conocladus australis) from southern Australia wrapped around a whip-coral.
Image: Julian Finn
Source: Museum Victoria
 

Biogeographers – scientists that study the patterns of distribution of life – have long observed that certain species are associated with particular environments. This makes sense; an animal has particular requirements of temperature, salinity, depth, food availability, and won’t survive where these conditions don’t exist. However in the deep-sea, environmental factors are not very variable - deep water is cold and dark everywhere. Correspondingly, it has been assumed that the fauna in the deep-sea won’t vary much, or at most, certain species would be confined to particular oceans.

It turns out this assumption is not necessarily true. Tim's brittle star study found that there are distinct bands of species distribution not only in shallow water environments, where conditions can be very variable and distinct, but in the deep-sea. Deep-sea brittle stars are found in the same latitudinal bands as their shallow-water relatives, and it’s not yet clear why.

Brittle star distribution map Map showing the overlapping distribution of tropical, temperate and polar brittle stars.
Image: Tim O'Hara
Source: Museum Victoria
 

Tim thinks the pattern he's discovered might be related to the life history of brittle stars. As he explains, the distinct bands might be due to the way currents disperse larvae. “A lot of these animals have very yolky eggs and there’s a theory that in cold water, eggs go into suspended animation and float on the currents for perhaps a year. Some don’t need to feed – they have all the energy they need to go through metamorphosis to juvenile stage.”

“It’s a funny strategy that an animal would just throw eggs into the current and hope for the best, but obviously it’s successful because they get around. We’re doing a lot of genetic work at the moment over this study area and we’re getting things that are almost identical 7000km apart.”

Tim’s study, co-authored by Ashley Rowden and Nicholas Bax, was published in Current Biology. This project was generated as part of the Marine Biodiversity Hub, a multi-institutional research program funded by the Australian Government’s Department of Sustainability, Environment, Water, Population and Communities.

Links:

O'Hara,Timothy D., Ashley A. Rowden, Nicholas J. Bax. A Southern Hemisphere Bathyal Fauna Is Distributed in Latitudinal Bands, Current Biology, 8 February 2011 (Vol. 21, Issue 3, pp. 226-230)

Marine Biodiversity Hub

Discussion of this study elsewhere:

Deep-sea News

The Age: 'Scientists discover deep-sea creatures play in the same band'

Echinoblog

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