Environment Institute

mosquitoAustralia’s Ross River Virus (RRV) could be the next mosquito-borne global epidemic according to a new research study led by the University of Adelaide and The Australian National University.

The virus has been thought to be restricted largely to Australia and Papua New Guinea where it is harboured by marsupial animals, specifically kangaroos and wallabies, and spread by mosquitoes.

Published online ahead of print in the International Journal of Infectious Diseases, the research shows that the virus may have been circulating silently in the South Pacific ever since a large epidemic of more than 500,000 cases in 1979-80, thought to have been started by an infected Australian tourist who travelled to Fiji.

“Ross River Virus is found naturally in Australia, where it was circulating in kangaroos and wallabies long before the arrival of the first Australians over 40,000 years ago,” says one of the project leaders Professor Phil Weinstein, Professorial Research Fellow with the University of Adelaide’s School of Biological Sciences.

“When humans arrived, first Aboriginal Australians and then Europeans, they were bitten by the same mosquitoes and became infected: they had all of the sore joints, fever, rash, and fatigue that we associate with the disease today. Although RRV has never killed anyone, it can be extremely debilitating for several months, and up to years in a few unlucky individuals.”

The 1979 epidemic in the Pacific Islands Countries and Territories was the first time that RRV had ‘escaped’ from its marsupial reservoir. But without marsupials, the epidemic burned itself out the following year – or so it was thought.

“The first clues about local transmission in the Pacific Islands came when more recent tourists from New Zealand and Canada who had been to the South Pacific, but not Australia, were diagnosed with RRV when they returned home,” Professor Weinstein says.

In partnership with French collaborators in Tahiti and France, the researchers tested blood samples of American Samoans.

“We were surprised to find that of those who were born after the 1979-1980 epidemic and had lived in American Samoa their whole lives, a massive 63% had antibodies to RRV, strongly suggesting local transmission of the virus after 1980,” says Dr Colleen Lau, NHMRC Research Fellow in ANU’s College of Medicine, Biology and Environment.

“There are no marsupials in American Samoa, so the only reasonable conclusion is that the virus was able to circulate in local mammals rather than marsupials. If RRV can circulate in non-marsupials in the South Pacific, then it can find a home anywhere in the world.

“Isolation of the virus from non-marsupials will provide us with definitive evidence that RRV can become endemic globally.”

Professor Weinstein says: “With the large number of Australians now travelling, it would not be unreasonable to expect one or more tourists to carry RRV overseas to seed a new epidemic. With the right conditions, this could take off globally in exactly the same way that Zika did.”

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famelab-square-31Are you the next great science communicator? If so, FameLab wants you to compete in the world’s largest science communication competition.

FameLab challenges budding science communicators to explain a scientific concept to a general audience in just 3 minutes. To enter the competition, contestants must submit a video entry showcasing their communication prowess.

Several entrants will be selected from this pool to compete in the semi-finals in NSW, QLD, VIC and WA. The overall national winner will then receive an all-expenses paid trip to the UK to represent Australia in the international FameLab challenge. While in the UK, the winner will be mentored by industry elites and meet other young science communicators from around the world.

Last year, the Environment Institute’s very own Erin Fagan-Jeffries topped the nation and represented Australia at the international event. If you need some inspiration, you can listen to her presentation available as a podcast on ABC radio national.

Applications for FameLab 2017 are now open and close on 24 February, 2017. For more details, head to the FameLab website.

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Some of the obvious and cryptic differences between human races (Dr Rosedale)

As Charles Darwin noted, the physical differences between individuals of a species are  important for their future survival and success (or not). However there are also many not so obvious differences (known as cryptic variation) between individuals that give us important insights into the evolutionary and ecological history of a species. This information is important for how we make use of and conserve a range of our native biodiversity.

Across the range of a species, populations experience different environments that can cause local adaptation. For example, the skin colour of our human ancestors was selected by the latitude they lived at: higher sun intensities at low latitudes selected for darker skin tones as protection against the damaging effects of UV rays; lower sun intensities at high latitudes selected for lighter skin tones to ensure sufficient UV exposure for vitamin D production. Some differences among populations can also be cryptic, i.e. not apparent to the naked eye. Again, taking a human example, the enzyme lactase is produced by infants to break down the sugar lactose present in breast milk. In many modern human populations, lactase production does not continue into adulthood as it is no longer required. However, in descendants of populations that shifted from a hunter-gatherer to an agricultural lifestyle, where the farming of cattle provided milk as an extra food source for human adults, selection has resulted in a life-long tolerance of lactose through continued lactase production.

As well as adaptive differences between populations, neutral or non-adaptive genetic differences can also accumulate. Geographic isolation between populations can reduce or prevent breeding between individuals. This reproductive isolation means that genes are not shared among populations. Over time, random mutations in neutral (non-functional) regions of the genome will accumulate (a process known as genetic drift) resulting in distinct genetic signatures . These neutral genetic differences can provide important insights into historical colonisation and evolutionary processes and are the basis for commercial human ancestry tests that can inform your ethnic make-up.

From humans to plants

To understand something about the evolutionary and demographic history of the narrow-leaf hopbush (Dodonaea viscosa), an important plant used for habitat restoration in Southern Australia, researchers at the University of Adelaide carried out an assessment of neutral genetic diversity.

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The narrow-leaf hopbush, Dodonaea viscosa (Flickr)

The team sampled populations from Kangaroo Island in the south, through the Flinders Ranges, and up to the Gammon Ranges in the north (~700 kms away) – to develop a picture of how closely related populations are. Using a novel genotyping technique, they analysed a set of neutral genetic markers that were common among the sampled populations. This analysis gave a measure of how genetically similar individual plants are within populations (the genetic diversity of the populations) as well as between the different sampling sites (how genetically differentiated the populations are).

The sampled populations could be grouped into three genetically distinct clusters: a Kangaroo Island cluster (see map; blue), a Flinders/Gammon Ranges cluster (see map;green), and a cluster of populations from the eastern portion of its range (see map;red). The Kangaroo Island cluster (blue) appears simple enough to explain, with the geographic separation between the island and mainland populations reducing the capacity for pollen and/or seed migration and leading to genetic isolation.

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The distinction between populations from the Flinders/Gammon Ranges populations (green) and the eastern portion of the species range (red) was more surprising. The authors offer two potential explanations. They suggest that the difference in environmental conditions between the two areas (with lower temperatures and higher rainfall on the Ranges) may have led to isolation-by- environment: where plants in the two different clusters may have adapted to their local conditions, resulting in them having a genetic makeup only suitable for those conditions. So, even if pollen and seed is transferred between the Eastern and Flinders/Gammon Ranges populations, any resultant offspring will most probably not survive or at least will be less competitive than offspring from local parent plants. This is akin to a lactose intolerant person having to survive in a land where milkshakes and cheese are the dominant foodstuffs – they just do not have the genetic disposition to do well in this environment.

Alternatively, the different genetic signatures may reflect the hidden historical origins of populations. During past ice ages we known that species retreated to southern regions of the Australian continent to escape the arid conditions of more central areas. This resulted in the formation of refugia – areas that acted as safe havens for species, providing suitable environmental conditions and buffering them from climatic change. There are thought to have been many refugial areas along the southern coastline of Australia during the ice ages, where more mesic conditions were maintained. In inter-glacial periods, like we are in now, species expand out from these refugia as other areas become suitable for them to inhabit. The Flinders Ranges has been identified as one such refugium, for plant and animal species, and the high genetic diversity of the populations in the Flinders Ranges identified in this study suggests that it may also have played a refugial role for the hopbush in the past. Under this scenario, the eastern portion of the range of the hop bush (red) may represent the edge of an ancient expansion from a south-eastern refugium that occurred millennia ago, and now occurs alongside the local refusal populations of the Flingers and Gammon Ranges (green). If this second hypothesis is correct then it is no wonder that these two sets of populations demonstrate such distinct genetic signatures.

And why are these findings important? Well, the Australian continent has experienced unprecedented land use change since the arrival of the first Europeans. Swathes of land have been cleared for agriculture, resulting in the destruction and fragmentation of native habitats. There are now increasing efforts to protect and restore areas of native vegetation. Restoration efforts require sources of good-quality native seed and the seed needs to be from plants that will thrive in the restored area. The hopbush is commonly used in restoration throughout South Australia and is a dominant understorey species in many habitats. By getting a clearer understanding of the genetic connectivity of populations across the region, better informed decisions can be made as to where to source seed from for restoration. For example, the movement of seed between the Flinders ranges and the drier eastern regions should be avoided as the resultant plants may not be well adapted to the different environmental conditions, compromising well meaning restoration efforts.

 

This study has been published in the journal Nature Scientific Reports and is available open-access here:

Access ResearchBytes article on the research. This research also featured on The Conversation.

Reference

Matthew J. Christmas, Ed Biffin, Martin F. Breed & Andrew J. Lowe. 2017. Targeted capture to assess neutral genomic variation in the narrow-leaf hopbush across a continental biodiversity refugium. Scientific Reports, doi: 10.1038/srep41367.

This article was written by Matt Christmas and edited by Andrew Lowe. The article first appeared on Biodiversity Revolution.

 

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Elsevier is now offering the option to prepare and upload audio slides that will appear on the same page as your publication. AudioSlides are short, webcast-style presentations that are shown next to online articles on ScienceDirect. This format gives authors the opportunity to present their research in their own words, helping readers understand quickly what […]

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Australia’s arid zone has spread throughout history, and has had a transformative impact on many species. New research has investigated the evolutionary history of spiny trapdoor spiders, in response to changes in Australia’s arid environment. Published in Molecular Phylogenetics and Evolution, and co-authored by the Environment Institute’s Professor Andy Austin, the paper has been ranked as […]

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The future is always uncertain but it’s best to be prepared, especially when it comes to potential disasters. The Bushfire and Natural Hazards CRC (BNHCRC) has published a report exploring the risk of future disasters within Greater Adelaide. The Futures Greater Adelaide 2050: An exploration of disaster risk and the future report is designed to help decision makers plan […]

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Reaching a maximum length of 18 metres and weighing up to 21 tons, the whale shark (Rhincodon typus) is the world’s largest fish and is found circumglobally in tropical and temperate seas. Though we know surprisingly little about the natural history and behaviour of these massive animals, they are known to gather seasonally in large […]

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The next Research Tuesdays forum will be presented by Professor Alan Cooper, founder of the Australian Centre for Ancient DNA. Title: Connected to Country When: 5:30pm, Tuesday, February 14, 2017 Where: Braggs Lecture Theatre Cost: Free, but bookings recommended Indigenous Australians have a remarkably deep cultural and spiritual connection to their country. Now, research at the […]

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The secrets of understudied Australian rangelands, which make up 81% of the continent, have been exposed in a new publication. The Terrestrial Ecosystem Research Network (TERN) has published results of a large, continental-scale research program, detailing precise information about the vegetation and soil of Australian rangelands. Published in PLOS ONE by lead author Dr Greg […]

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In December 2016, the Intelligent Water Decisions Group had three PhD students participate in the prestigious OzEWEX Summer Institute. They discovered that the Summer Institute was really beneficial. Read on to find out why.   What is the OzEWEX Summer institute? The acronym OzEWEX stands for the Australian Energy and Water Exchanges initiative. It is […]

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