Phylogeography of the antilopine wallaroos (Macropus antilopinus) across tropical northern Australia

Authors: Jessica J Wadley, Damien A Fordham, Vicki A Thomson, Euan G Ritchie and Jeremy J Austin

Published in: Ecology and Evolution (early view)


The distribution of antilopine wallaroo, Macropus antilopinus, is marked by a break in the species’ range between Queensland and the Northern Territory, coinciding with the Carpentarian barrier.

Previous work on M. antilopinus revealed limited genetic differentiation between the Northern Territory and Queensland M. antilopinus populations across this barrier. The study also identified a number of divergent lineages in the Northern Territory, but was unable to elucidate any geographic structure.

Here, we re-examine these results to (1) determine phylogeographic patterns across the range of M. antilopinus and (2) infer the biogeographic barriers associated with these patterns.

The tropical savannahs of northern Australia: from the Cape York Peninsula in the east, to the Kimberley in the west. We examined phylogeographic patterns in M. antilopinus using a larger number of samples and three mtDNA genes: NADH dehydrogenase subunit 2, cytochrome b, and the control region. Two datasets were generated and analyzed: (1) a subset of samples with all three mtDNA regions concatenated together and (2) all samples for just control region sequences that included samples from the previous study. Analysis included generating phylogenetic trees based on Bayesian analysis and intraspecific median-joining networks.

The contemporary spatial structure of M. antilopinus mtDNA lineages revealed five shallow clades and a sixth, divergent lineage. The genetic differences that we found between Queensland and Northern Territory M. antilopinus samples confirmed the split in the geographic distribution of the species. We also found weak genetic differentiation between Northern Territory samples and those from the Kimberley region of Western Australia, possibly due to the Kimberley Plateau–Arnhem Land barrier. Within the Northern Territory, two clades appear to be parapatric in the west, while another two clades are broadly sympatric across the Northern Territory. MtDNA diversity of M. antilopinus revealed an unexpectedly complex evolutionary history involving multiple sympatric and parapatric mtDNA clades across northern Australia.

These phylogeographic patterns highlight the importance of investigating genetic variation across distributions of species and integrating this information into biodiversity conservation.

Wadley JJ, Fordham DA, Thomson VA, Ritchie EG, Austin JJ (2016) Phylogeography of the antilopine wallaroo (Macropus antilopinus) across tropical northern Australia. Ecology and Evolution PDF DOI 


The Conversation: Why Victoria’s dingo and ‘wild dog’ bounty is doomed to miss its target

By Euan Ritchie (Deakin University) and Arian Wallach (University of Technology Sydney)


Dingo bounties are a really, really bad idea.

On any given night, many farmers go to sleep worrying about what they might wake up to in the morning. Few things are more stressful than seeing your livestock, such as sheep, lying dead or seriously injured in the paddock. Sometimes dingoes, free roaming and unowned (“feral”) dogs, and domestic dogs, or their hybrids, are responsible for such a scene. But what’s the best way to deal with this situation?

The Victorian government is set to reinstate a dingo and wild dog bounty scheme as a way to reduce livestock, especially sheep, being attacked and killed, in response to calls from farming and shooting groups.

Just what is a dingo?

One of the problems with managing dingoes is that the boundary between them and “wild dogs” is contentious. Some have even claimed that there are no pure dingoes in Victoria.

Defining what dingoes are is harder than you might think. There is considerable variation in how dingoes look, for example, in terms of their overall size and colour, as is common with many other members of the dog family (canids).

And if a dingo isn’t considered 100% “pure”, containing genes from domestic dogs, should hybrids be managed differently to dingoes?

Research suggests “pure” dingoes do exist in Victoria, albeit in smaller numbers than other regions.

Notably though, genetic samples in Victoria have been collected largely from areas close to towns, where there are likely more hybrid dogs, and less so from deep within Victoria’s more remote natural regions (the mallee, alpine, and Gippsland forests), where dingoes are often sighted.

Two other recent studies are important in the Victorian context. One suggests dingo characteristics prevail even within hybrids and another has found there are two distinct dingo populations. Importantly, the south east dingo population is at increased risk of extinction.

Many ecologists would argue that splitting hairs about dingo genetic “purity” is a moot point, because what really matters is what dingoes and dingo-dog hybrids are doing in the environment. This is because dingoes are known to have important ecological roles, including the suppression of feral species (such as cats, pigs, and goats), red foxes, and kangaroos.

How are wild dogs and dingoes managed in Victoria?

The decision to reinstate a dingo and wild dog bounty in Victoria is vexed. In 2007 the Victorian government established protection of dingoes, due to conservation concerns about the species, with hybridisation between dingoes and domestic dogs identified as a threatening process.

As a result, dingoes in Victoria are listed as a threatened species under the Flora and Fauna Guarantee Act 1988 and protected under the Wildlife Act 1975.

In Victoria wild dogs are classed as pest animals and can be legally controlled. However, the Victorian Department of Environment states that “dingoes are visually indistinguishable from wild dogs, making it impossible to ensure they are not inadvertently destroyed in wild dog control programs in any given area where both exist” and “dingoes are protected wildlife and it is an offence under the Wildlife Act 1975 to take or kill protected wildlife without an authorisation to do so”.

Management misfire

Legal and species identification issues aside, do bounties and lethal control of predators actually work?

In short, scientific evidence suggests the answer is largely no (see for instance here, here, here, here, and here).

There are a range of reasons cited for why bounties fail. These include:

  • an inability to sufficiently reduce numbers of the the target species and hence their impact, due to rapid breeding and/or immigration from other areas
  • corruption by those claiming bounties, whereby animals claimed for bounty payments have not actually been killed in the area where the bounty is intended to benefit
  • an inability to access some animals over large and/or remote areas
  • a disincentive to completely eradicate animals as this removes the source of income
  • disruption of predator social structures causing higher livestock predation.

Investing in predator-friendly farming

So what solutions do we have that might allow productive farms without the need to kill predators? A range of nonlethal solutions exist for protecting livestock, including improved husbandry techniques (such as corralling and herding), and in particular, a growing body of research suggests guardian animals provide a great step forward.

Nonlethal methods to protect livestock are also consistent with a growing social demand that both domestic and wild animals are treated humanely and ethically on farms.

Predator-friendly farming is growing across Australia, as you can see in the image above. Large livestock on large landholdings, such as beef cattle on thousands of square kilometre stations, are reducing conflict by enabling dingo packs to stabilize and by supporting healthier cows that are better able to defend their calves (top left).

Smaller farms are also employing protective strategies, including guardian dogs, even if the livestock species is large, such as dairy cows and buffalo, because lethal control on neighboring farms continues to disrupt the dingo’s social structure (bottom left).

Technological innovations in nonlethal methods for protecting livestock from predators have been developed in Australia and used worldwide, such as “Foxlights” (top right). And vulnerable stock, such as chickens, are being successfully protected with guardian dogs and enclosures (bottom right).

There are substantial gains to be made for agriculture, people, wild animals and the environment if decision-makers use scientific evidence and ethical analysis, rather than responding to lobby groups, as the basis for taxpayer-sponsored actions.

Education is also a key aspect of any change, and scientists are being proactive here too, providing guidance on new approaches to rangeland livestock management that are supported by research.

The fact is, bounty schemes don’t work. If instead the substantial funds currently being invested in bounties were invested in supporting farmers to move to more long-term, cost-effective, and more environmentally-friendly solutions, we may all be able to sleep better at night.

This article was originally published on The Conversation. Read the original article, including reader comments.

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Trophic cascades in 3D: Network analysis reveals how apex predators structure ecosystems

Authors: Arian D Wallach, Anthony H Dekker, Miguel Lurgi, Jose M Montoya, Damien A Fordham and Euan G Ritchie

Published in: Methods in Ecology and Evolution


Trophic cascade theory predicts that apex predators structure ecosystems by regulating mesopredator and herbivore abundance and behaviour. Studies on trophic cascades have typically focused on short linear chains of species interactions. A framework that integrates more realistic and complex interactions is needed to make broader predictions on ecosystem structuring.

Network analysis is used to study food webs and other types of species interaction networks. These often comprise large numbers of species but rarely account for multiple interaction types and strengths. Here we develop an intermediate complexity theoretical framework that allows specification of multiple interaction types and strengths for the study of trophic cascades. This ecological network is designed to suit data typically derived from field-based studies. The trophic cascade network contains fewer nodes than food webs, but provides semi-weighted directional links that enable different types of interactions to be included in a single model.

We use this trophic cascade network model to explore how an apex predator shapes ecosystem structure in an Australian arid ecosystem. We compared two networks that contrasted in the dominance of an apex predator, the dingo (Canis dingo), using published results ranking the direction and strength of key interactions. Nodes and links interacted dynamically to shape these networks. We examined how changes to an apex predator population affects ecosystem structure through their direct and indirect influences on different components of this ecological community.

Under strong apex predator influence, the network structure was denser and more complex, even, and top-down driven; and dingo predation and soil commensalism formed denser interactive modules. Under weak apex predator influence (e.g. reflecting predator control) the resulting network structure was frayed, with mesopredator predation and grazing forming modules.

Our study demonstrates that networks of intermediate complexity can provide a powerful tool for elucidating potential ecosystem-wide effects of apex predators, and predicting the consequences of management interventions such as predator control. Integrating trophic cascades, with their array of complex interactions, with the three-dimensional structure of ecological networks, has the potential to reveal ‘ecological architecture’ that neither captures on its own.

Wallach AD, Dekker AH, Lurgi M, Montoya JM, Fordham DA, Ritchie EG (2016) Trophic cascades in 3D: Network analysis reveals how apex predators structure ecosystems. Methods in Ecology and EvolutionPDF DOI

Invasive predators and global biodiversity loss

Authors: Tim S Doherty, Alistair S Glen, Dale G Nimmo, Euan G Ritchie and Chris R Dickman

Published in: Proceedings of the National Academy of Sciences


Invasive species threaten biodiversity globally, and invasive mammalian predators are particularly damaging, having contributed to considerable species decline and extinction. We provide a global meta-analysis of these impacts and reveal their full extent.

Invasive predators are implicated in 87 bird, 45 mammal, and 10 reptile species extinctions — 58% of these groups’ contemporary extinctions worldwide. These figures are likely underestimated because 23 critically endangered species that we assessed are classed as “possibly extinct.”

Invasive mammalian predators endanger a further 596 species at risk of extinction, with cats, rodents, dogs, and pigs threatening the most species overall.

Species most at risk from predators have high evolutionary distinctiveness and inhabit insular environments. Invasive mammalian predators are therefore important drivers of irreversible loss of phylogenetic diversity worldwide.

That most impacted species are insular indicates that management of invasive predators on islands should be a global conservation priority. Understanding and mitigating the impact of invasive mammalian predators is essential for reducing the rate of global biodiversity loss.

Doherty TS, Glen AS, Nimmo DG, Ritchie EG, Dickman CR (2016) Invasive predators and global biodiversity loss. Proceedings of the National Academy of Sciences PDF DOI


The Conversation: Invasive predators are eating the world’s animals to extinction – and the worst is close to home

By Tim Doherty (Deakin University), Chris Dickman (University of Sydney), Dale Nimmo (Charles Sturt University),  Euan Ritchie (Deakin University) and Al Glen (Landcare Research, New Zealand).

Feral cats are a major driver of global biodiversity loss, contributing to 26% of bird, mammal and reptile extinctions. Image credit: Mark Marathon via Wikimedia Commons

Feral cats are a major driver of global biodiversity loss, contributing to 26% of bird, mammal and reptile extinctions. Image credit: Mark Marathon via Wikimedia Commons

Invasive species are a threat to wildlife across the globe – and invasive, predatory mammals are particularly damaging.

Our research, recently published in Proceedings of the National Academy of Sciences, shows that these predators – cats, rats and foxes, but also house mice, possums and many others – have contributed to around 60% of bird, mammal and reptile extinctions. The worst offenders are feral cats, contributing to over 60 extinctions.

So how can we stop these mammals eating away at our threatened wildlife?

Counting the cost

Our study revealed that invasive predators are implicated in 87 bird, 45 mammal and 10 reptile extinctions — 58% of these groups’ contemporary extinctions worldwide.

Invasive predators also threaten 596 species classed as vulnerable, endangered or critically endangered on the International Union for the Conservation of Nature Red List. Combined, the affected species include 400 birds, 189 mammals and 149 reptiles.

Twenty-three of the critically endangered species are classed as “possibly extinct”, so the number of extinctions above is likely to be an underestimate.

Until now, these shocking statistics have been unknown, and the heavy toll of invasive predators on native biodiversity grossly underappreciated. Species extinctions attributed to invasive predators include the Hawaiian rail (Zapornia sandwichensis) and Australia’s lesser bilby (Macrotis leucura).

Who are the worst offenders?

We found that three canids (including the red fox and feral dogs), seven members of the weasel family or mustelids (such as stoats), five rodents, two primates, two mongooses, two marsupials and nine species from other families negatively impact threatened species. Some of these species, such as hedgehogs and brushtail possums, don’t immediately spring to mind as predators, yet they are known to prey on many threatened species.

Feral cats threaten the most species overall (430), including 63 that have become extinct. This equates to one-quarter of all bird, mammal and reptile extinctions – making the feral cat arguably the most damaging invasive species for animal biodiversity worldwide.

Five species of introduced rodent collectively threaten 420 species, including 75 extinctions. While we didn’t separate out the impacts of individual rodent species, previous work shows that black rats (Rattus rattus) threaten the greatest number of species, followed by brown rats (R. norvegicus) and Pacific rats (R. exulans).

The humble house mouse (Mus musculus) is another interesting case. Despite their small size, house mice have been recorded eating live chicks of albatrosses, petrels and shearwaters.

Other predators that threaten large numbers of species are the domestic dog (Canis familiaris), pig (Sus scrofa), small Indian mongoose (Herpestes auropunctatus), red fox (Vulpes vulpes) and stoat (Mustela erminea).

Island species most at risk

Species found only on islands (insular endemics) account for 81% of the threatened species at risk from predators.

The isolation of many islands and a lack of natural predators mean that insular species are often naive about new predators and lack appropriate defensive responses. This makes them highly vulnerable to being eaten and in turn suffering rapid population decline or, worse, extinction. The high extinction rates of ground-dwelling birds in Hawaii and New Zealand — both of which lack native mammalian predators — are well-known examples.

Accordingly, the regions where the predators threatened the greatest number of species were all dominated by islands – Central America and the Caribbean, islands of the Pacific, the Madagascar region, New Zealand and Hawaii.

Conversely, the continental regions of North and South America, Europe, Africa and Asia contain comparatively few species threatened by invasive predators. While Australia is a continent, it is also an island, where large numbers of native birds and mammals are threatened by cats and foxes.

Managing menacing mammals

Understanding and mitigating the impact of invasive mammal predators is essential for reducing the rate of global biodiversity loss.

Because most of the threatened species studied here live on islands, managing invasive predators on islands should be a global conservation priority. Invasive predators occur on hundreds of islands and predator control and eradication are costly exercises. Thus, it is important to prioritise island eradications based on feasibility, cost, likelihood of success and potential benefits.

On continents or large islands where eradications are difficult, other approaches are needed. This includes predator-proof fencing, top-predator restoration and conservation, lethal control, and maintenance of habitat structure.

Despite the shocking statistics we have revealed, there remain many unknowns. For example, only around 40% of reptile species have been assessed for the Red List, compared to 99% for birds and mammals. Very little is known about the impact of invasive predators on invertebrate species.

We expect that the number of species affected by invasive predators will climb as more knowledge becomes available.

This article was originally published on The Conversation. Read the original article, including reader comments.
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