Conservation: So easy a child could do it

13 09 2013

child's playI don’t like to talk about my family online. Call me paranoid, but there are a lot of crazy people out there who don’t like what scientists like me are saying (bugger the evidence). Yes, like many climate scientists, I’ve also been threatened. That’s why my personal life remains anonymous except for a select group of people.

But I’ve mentioned my daughter before on this blog, and despite a few people insinuating that I am a bad parent because of what I said, I am happy that I made the point that climate change is a scary concept of which our children must at least be cognisant.

My daughter’s story today is a little less confronting, but equally enlightening. It’s also a little embarrassing as a scientist who has dedicated my entire research career to the discipline of conservation biology.

As a normal six year-old without the ability to refrain from talking – even for a moment – I hear a lot of stories. Many of them are of course fantastical and ridiculous, but those are just part of a healthy, imaginative childhood (I am proud to say though that she is quite clear about the non-existence of fictitious entities like faeries, easter bunnies and gods).

Every once in a while, however, there are snippets of wisdom that ooze out from the cracks in the dross. In the last few months, my daughter has independently and with no prompting from me come up with two pillars of conservation science: (i) protected areas and (ii) biodiversity corridors. Read the rest of this entry »





Biogeography comes of age

22 08 2013

penguin biogeographyThis week has been all about biogeography for me. While I wouldn’t call myself a ‘biogeographer’, I certainly do apply a lot of the discipline’s techniques.

This week I’m attending the 2013 Association of Ecology’s (INTECOL) and British Ecological Society’s joint Congress of Ecology in London, and I have purposefully sought out more of the biogeographical talks than pretty much anything else because the speakers were engaging and the topics fascinating. As it happens, even my own presentation had a strong biogeographical flavour this year.

Although the species-area relationship (SAR) is only one small aspect of biogeography, I’ve been slightly amazed that after more than 50 years since MacArthur & Wilson’s famous book, our discipline is still obsessed with SAR.

I’ve blogged about SAR issues before – what makes it so engaging and controversial is that SAR is the principal tool to estimate overall extinction rates, even though it is perhaps one of the bluntest tools in the ecological toolbox. I suppose its popularity stems from its superficial simplicity – as the area of an (classically oceanic) island increases, so too does the total number of species it can hold. The controversies surrounding such as basic relationship centre on describing the rate of that species richness increase with area – in other words, just how nonlinear the SAR itself is.

Even a cursory understanding of maths reveals the importance of estimating this curve correctly. As the area of an ‘island’ (habitat fragment) decreases due to human disturbance, estimating how many species end up going extinct as a result depends entirely on the shape of the SAR. Get the SAR wrong, and you can over- or under-estimate the extinction rate. This was the crux of the palaver over Fangliang He (not attending INTECOL) & Stephen Hubbell’s (attending INTECOL) paper in Nature in 2011.

The first real engagement of SAR happened with John Harte’s maximum entropy talk in the process macroecology session on Tuesday. What was notable to me was his adamant claim that the power-law form of SAR should never be used, despite its commonness in the literature. I took this with a grain of salt because I know all about how messy area-richness data can be, and why one needs to consider alternate models (see an example here). But then yesterday I listened to one of the greats of biogeography – Robert Whittaker – who said pretty much the complete opposite of Harte’s contention. Whittaker showed results from one of his papers last year that the power law was in fact the most commonly supported SAR among many datasets (granted, there was substantial variability in overall model performance). My conclusion remains firm – make sure you use multiple models for each individual dataset and try to infer the SAR from model-averaging. Read the rest of this entry »





Want to work with us?

22 03 2013
© Beboy-Fotolia

© Beboy-Fotolia

Today we announced a HEAP of positions in our Global Ecology Lab for hot-shot, up-and-coming ecologists. If you think you’ve got what it takes, I encourage you to apply. The positions are all financed by the Australian Research Council from grants that Barry Brook, Phill Cassey, Damien Fordham and I have all been awarded in the last few years. We decided to do a bulk advertisement so that we maximise the opportunity for good science talent out there.

We’re looking for bright, mathematically adept people in palaeo-ecology, wildlife population modelling, disease modelling, climate change modelling and species distribution modelling.

The positions are self explanatory, but if you want more information, just follow the links and contacts given below. For my own selfish interests, I provide a little more detail for two of the positions for which I’m directly responsible – but please have a look at the lot.

Good luck!

CJA Bradshaw

Job Reference Number: 17986 & 17987

The world-leading Global Ecology Group within the School of Earth and Environmental Sciences currently has multiple academic opportunities. For these two positions, we are seeking a Postdoctoral Research Associate and a Research Associate to work in palaeo-ecological modelling. Read the rest of this entry »





Native invaders divide loyalties

7 09 2012

California sea lion at Bonneville fish ladder. Credit: U.S. National Oceanic and Atmospheric Administration

As if to mimic the weirder and weirder weather human-caused climate disruption is cooking up for us, related science stories seem to come in floods and droughts. Yes, research trends become fashionable too (imagine a science fashion show? – but I digress…).

Only yesterday, the ABC published an opinion piece on the controversies surrounding which species we call ‘native’ and ‘invasive’ (based on a recent paper published in Global Ecology and Biogeography), and in June this year, Salvador Herrando-Pérez wrote a great little article on the topic entitled “The invader’s double edge“.

Then today, I received a request to publish a guest post here on ConservationBytes.com from Lauren Kuehne, a research scientist in Julian Olden‘s lab at the University of Washington in Seattle. The topic? Why, the controversies surrounding invasive species, of course! Lauren’s following article demonstrates yet again that it’s not that simple.

A drawback to the attention garnered by high-profile invasive species is the tendency to infer that every non-native species is bad news, the inverse assumption being that all native species must be ‘good’. While this storyline works well for Hollywood films and faerie tales, in ecology the truth is rarely that simple. A new review article in the September issue of Frontiers in Ecology and the Environment, describes the challenges and heartbreaks when native species run amok in the sense of having negative ecological impacts we typically associate with non-native species. Examples in the paper range from unchecked expansions of juniper trees in sagebrush ecosystems with wildfire suppression, to overgrazing by elk (wapiti) released from predation following the removal of wolves and mountain lions. Read the rest of this entry »





Global Ecology postgraduate opportunities

12 08 2012

I should have published these ages ago, but like many things I have should have done earlier, I didn’t.

I also apologise for a bit of silence over the past week. After coming back from the ESP Conference in Portland, I’m now back at Stanford University working with Paul Ehrlich trying to finish our book (no sneak peaks yet, I’m afraid). I have to report that we’ve completed about about 75 % it, and I’m starting to feel like the end is in sight. We hope to have it published early in 2013.

So here they are – the latest 9 PhD offerings from us at the Global Ecology Laboratory. If you want to get more information, contact the first person listed as the first supervisor at the end of each project’s description.

1. Optimal survey and harvest models for South Australian macropods (I’ve advertised this before, but so far, no takers):

The South Australia Department of Environment, Water and Natural Resources (DEWNR) is custodian of a long-term macropod database derived from the State’s management of the commercial kangaroo harvest industry. The dataset entails aerial survey data for most of the State from 1978 to present, annual population estimates, quotas and harvests for three species: red kangaroo (Macropus rufus), western grey kangaroo (Macropus fuliginosus), and the euro (Macropus robustus erubescens).

DEWNR wishes to improve the efficiency of surveys and increase the precision of population estimates, as well as provide a more quantitative basis for setting harvest quotas.

We envisage that the PhD candidate will design and construct population models:

  • to predict population size/densities with associated uncertainty, linking fluctuations to environmental variability (including future climate change projections)
  • to evaluate the efficiency of spatially explicit aerial surveys
  • to estimate demographic parameters (e.g., survival rate) from life tables and
  • to estimate spatially explicit sustainable harvest quotas

 Supervisors: me, A/Prof. Phill Cassey, Dr Damien Fordham, Dr Brad Page (DEWNR), Professor Michelle Waycott (DEWNR).

2. Correcting for the Signor-Lipps effect

The ‘Signor-Lipps effect’ in palaeontology is the notion that the last organism of a given species will never be recorded as a fossil given the incomplete nature of the fossil record (the mirror problem is the ‘Jaanusson effect’, where the first occurrence is delayed past the true time of origination). This problem makes inference about the timing and speed of mass extinctions (and evolutionary diversification events) elusive. The problem is further complicated by the concept known as the ‘pull of the recent’, which states that the more time since an event occurred, the greater the probability that evidence of that event will have disappeared (e.g., erased by erosion, hidden by deep burial, etc.).

In a deep-time context, these problems confound the patterns of mass extinctions – i.e., the abruptness of extinction and the dynamics of recovery and speciation. This PhD project will apply a simulation approach to marine fossil time series (for genera and families, and some individual species) covering the Phanerozoic Aeon, as well as other taxa straddling the K-T boundary (Cretaceous mass extinction). The project will seek to correct for taphonomic biases and assess the degree to which extinction events for different major taxa were synchronous.

The results will also have implications for the famous Sepkoski curve, which describes the apparent logistic increase in marine species diversity over geological time with an approximate ‘carrying capacity’ reached during the Cenozoic. Despite recent demonstration that this increase is partially a taphonomic artefact, a far greater development and validation/sensitivity analysis of underlying statistical models is needed to resolve the true patterns of extinction and speciation over this period.

The approach will be to develop a series of models describing the interaction of the processes of speciation, local extinction and taphonomic ‘erasure’ (pull of the recent) to simulate how these processes interact to create the appearance of growth in numbers of taxa over time (Sepkoski curve) and the abruptness of mass extinction events. The candidate will estimate key parameters in the model to test whether the taphonomic effect is strong enough to be the sole explanation of the apparent temporal increase in species diversity, or whether true diversification accounts for this.

Supervisors: me, Prof. Barry Brook

3. Genotypic relationships of Australian rabbit populations and consequences for disease dynamics

Historical evidence suggests that there were multiple introduction events of European rabbits into Australia. In non-animal model weed systems it is clear that biocontrol efficacy is strongly influenced by the degree of genetic diversity and number of breed variants in the population.

The PhD candidate will build phylogenetic relationships for Australian rabbit populations and develop landscape genetic models for exploring the influence of myxomatosis and rabbit haemorrhagic disease virus (RHDV) on rabbit vital rates (survival, reproduction and dispersal) at regional and local scales. Multi-model synthesis will be used to quantify the relative roles of environment (including climate) and genotype on disease prevalence and virulence in rabbit populations.

Supervisors: A/Prof Phill Cassey, Dr Damien Fordham, Prof Barry Brook Read the rest of this entry »





The invader’s double edge

15 06 2012

The Ogasawara Archipelago (Bonin Islands,) encompasses several tens of small islands ~ 1000 km from mainland Japan. In 2011, UNESCO declared this archipelago a World Heritage Site. Some regard them as the “Galapagos of the Orient”, owing to their biological singularity, e.g., endemism rates of ~ 50 % of > 500 species of plants, or ~ 90 % of > 100 species of terrestrial snails. Photos show patches of native scrub (left) and introduced sheoak forest (right), close-ups of the two study species Ogasawarana discrepans (left) and O. optima (right), and empty shells with (top right, bottom) and without (top left) rat scars (Courtesy of Satoshi Chiba).

Another great post by Salvador Herrando-Pérez that challenges our views on invasive species (some would do well to heed his words when it comes to species like dingos). I mentioned in his last post that he had just recently submitted his PhD thesis, and now I’m proud to say that it has been examined with no recommended changes required. What a truly rare accolade. Congratulations, Salva.

A blunt instrument of ecological restoration is the elimination of introduced species. However, when introduced species become custodians of native wildlife, a dilemma emerges between re-establishing historical ecosystem conditions or instead, accepting foreign species for the benefits they might also bring.

Right after birth, we all enter a culture where what is ‘good’ or ‘bad’ has already been determined. Later on, if those values remain unchallenged, individuals assume them to be true and act accordingly (which is neither ‘good’ nor ‘bad’ necessarily… it is just so). Science is therefore the only recourse humans have to check such values by  reducing the subjectivity of our judgements about why natural phenomena occur.

But scientists also work in a context of ‘pre-established truths’ (because, believe it or not, most of us are human too). The late Larry Slobodkin referred to our professional biases as ‘reifications’; i.e.,

“…reification consists of accepting a designation as if it has empirical meaning when, in fact, its existence has either never been tested or it has been found empty” (1).

Slobodkin underlined invasive species as an icon of reification. Indeed, people (with and without a scientific background) tend to demonise species that are not native and extremely abundant – experts even debate whether this is another sort of xenophobia (2). Thus, zebra mussels (Dreissena polymorpha), cane toads (Rhinella marinus) or caulerpa algae (Caulerpa taxifolia) are commonly referred to as ‘alien’, ‘invasive’ or ‘noxious’. Technically, we now call them ‘biological pollution’ (3). Such epithets are loaded with moral and pejorative connotations to qualify organisms that affect the range of facets of human well-being (aesthetics, economy, ethics, health). Read the rest of this entry »





Can Australia afford the dingo fence?

18 05 2012

I wrote this last night with Euan Ritchie of Deakin University in response to some pretty shoddy journalism that misrepresented my comments (and Euan’s work). Our article appeared first in The Conversation this morning (see original article).

We feel we have to set the record straight after some of our (Bradshaw’s) comments were taken grossly out of context, or not considered at all (Ritchie’s). A bubbling kerfuffle in the media over the last week compels us to establish some facts about dingoes in Australia, and more importantly, about how we as a nation choose to manage them.

A small article in the News Ltd. Adelaide Advertiser appeared on 11 May in which one of us (Bradshaw) was quoted as advocating the removal of the dingo fence because it was not “cost effective” (sic). Despite nearly 20 minutes on the telephone explaining to the paper the complexities of feral animal management, the role of dingoes in suppressing feral predators, and the “costs” associated with biodiversity enhancement and feral control, there wasn’t a single mention of any of this background or justification.

Another News Ltd. article denouncing Ritchie’s work on the role of predators in Australian ecosystems appeared in The Weekly Times the day before, to which Ritchie responded in full.

So it’s damage control, and mainly because we want to state categorically that our opinion is ours alone, and not that of our respective universities, schools, institutes or even Biosecurity SA (which some have claimed or insinuated, falsely, that we represent). Biosecurity SA is responsible for, inter alia, the dingo fence in South Australia. Although our opinions differ on its role, we are deeply impressed, grateful and supportive of their work in defending us from biological problems. Read the rest of this entry »





Give way to the invader

25 01 2012

By weird coincidence, Salvador Herrando-Pérez (student blogger extra-ordinaire – see his previous posts on evolution, pollination, bird losses, taxonomic inflation, niche conservatism, historical biogeography, ecological traps and ocean giants) has produced a post this week expanding on the problem of roads. Also weirdly coincidental is that both Salva and I are in his home country of Spain this week.

Australia’s > 800,000-km road network would go 60 times around the equator of our planet. Confined to the boundaries of any one country, roads are a conspicuous component of the landscape, and shape the dispersion, survival and reproduction of many plants and animals in urban and remote areas.

Those who drive (or are driven by) will be familiar with the image of a crushed kangaroo on the roadside (a hedgehog in Europe), or the sticky mosaic of insects smashed against the windscreen after a high-speed run. Mortality by collision is one of the many effects that roads can have on the demography of organisms – including humans. Those effects encompass

  • physical alteration of terrestrial and aquatic habitats,
  • chemical pollution leakage during road construction and maintenance, and from asphalt compounds during storms,
  • alteration of animal behaviour (e.g., change in home range, or in patterns of flight or vocalisation),
  • access to remote areas by hunters, fishermen and gatherers in general, and
  • intense habitat fragmentation1-3.

However, some species get around those negative impacts by using the roads as pathways to new territories, thereby eluding barriers like seas, mountains, rivers, dense vegetation, or competition for vital resources with other species. Read the rest of this entry »





Government pulls plug on Asian honeybee eradication

3 03 2011

Here’s another one from the bee man, Tobias Smith (PhD candidate at the University of Queensland). Tobias recently blogged about bee basics here on ConservationBytes.com (something I highly recommend for anyone interested on brushing up on bee facts and dispelling a few myths), so I asked him to follow up with this very important piece on the future of pollination in Australia. It concerns a nasty little invader recently dubbed the “flying cane toad” (not my analogy).

http://www.flickr.com/photos/angela-and-andrew/1196369580/in/faves-lornet/

© 中國蜂

Over the last few weeks there has been much media attention given to the Asian honeybee (Apis cerana) incursion in far north Queensland. The Asian honeybee was first detected near Cairns in May 2007. Since then an effort to eradicate the bee has been made. This peaked during 2010, when over 40 bee eradication personnel were employed to hunt and destroy in areas around Cairns, the Atherton Tablelands, and other nearby locations.

In late January this year, the committee established to manage the eradication program (governments and industry), decided to pull the plug on eradication efforts (on money to pay for efforts that is). They decided it was no longer possible to achieve eradication (a majority decision, not a unanimous decision). The position to stop resources for eradication is not supported by industry, or ecological commentators. Arguments have been made that this is the only window of opportunity for eradication (for ever!), and that more resources need to be put towards it now, while there is still a chance of success.

A few points to be made about the Asian honeybee in Australia: Read the rest of this entry »





Invaders beware

1 11 2010

Recently, the Global Ecology Group at the University of Adelaide has had the immense privilege and pleasure of welcoming a new senior member to the fold – Dr. Phill Cassey. The slightly Pommefied-Kiwi-Now-Coming-To-Terms-With-Being-Australian ;-)  represents a wonderful new addition to our lab’s expertise and vision.

Phill is a distinguished Australian Research Council Future Fellow. He conducts research on the subject of human contributions to changes in biodiversity through the dual processes of species extinction and introduction. Phill’s research encompasses a broad range of analytical and applied skills and has led to significant advances in the discipline of global change biology.

Phill has also hit the ground running here in Adelaide, and now offers two PhD projects for people interested to work at the forefront of invasive species research in Australia. Students will be members of the School for Earth and Environmental Sciences, which includes world-class researchers in the disciplines of Ecology and Evolutionary Biology and Global Ecology as well as ongoing research links with the South Australian Museum, Adelaide Zoo, and State Herbarium of South Australia. Successful candidates will be part of a strong research group with a highly successful and innovative culture of scientific communication and study. Read the rest of this entry »





Blog Action Day 2010 – Water neutrality and its biodiversity benefits

16 10 2010

In my little bid to participate in Change.org’s Blog Action Day 2010 – Water, I’ve re-hashed a post from 2008 on ‘water neutrality’. This will also benefit my recently joined readers, and re-invigorate a concept I don’t think has received nearly enough attention globally (or even in parched Australia where I live). So here we go:

The world’s freshwater ecosystems are in trouble. We’ve extracted, poisoned, polluted, damned and diverted a large proportion of the finite (and rather small!) amount of freshwater on the planet. Now, most people might immediately see the problem here from a selfish perspective – no clean, abundant water source = human disease, suffering and death. Definitely something to avoid, and a problem that all Australians are facing (i.e., it’s not just restricted to developing nations). Just look at the Murray-Darling problem.

In addition to affecting our own personal well-being, freshwater ecosystems are thought to support over 10000 fish species worldwide (see also a recent post on Africa’s freshwater biodiversity’s susceptibility to climate change), and the majority of amphibians and aquatic reptiles. Current estimates suggest that about 1/3 of all vertebrate biodiversity (in this case, number of species) is confined to freshwater. As an example, the Mekong River system alone is thought to support up to 1700 different species of fish.

So, what are some of the ways forward? The concept of ‘water neutrality’ is essentially the wet version of carbon neutrality. It basically means that water usage can be offset by interventions to improve freshwater habitats and supply. Read the rest of this entry »





PhD scholarships in marine plant ecology and conservation

12 05 2010

Two new APAI (Australian Postgraduate Award – Industry) PhD scholarships are available at the University of Adelaide, both in marine ecology and conservation.

Molecular Systematics and Ecology of Marine Macroalgae

Dr. Frederico Gurgel at the University of Adelaide is seeking 2 PhD students interested in working on several aspects of the marine green macroalgal genus Caulerpa. Honour students are also welcome to apply. APAI PhD scholarships are the best-paid scholarships from the Australian Research Council (fees + AU$26,000 p.a. for 3 yrs). Possible co-advisors: Prof. Corey Bradshaw (University of Adelaide/South Australian Research and Development Institute – SARDI), Dr. Jason Tanner (SARDI), and Dr. Marty Deveney (SARDI). External collaborators: Dr. Peter Grewe (CSIRO Marine), Dr. John Runcie (University of Sydney). Starting date: any time.

Integrative approach to the study of Caulerpa taxifolia in Australia: Ecological, Physiology, Phylogeography and DNA barcoding

The students will perform comparative ecological and physiological assays among Australian native and invasive strains of C. taxifolia (and related species) to study their response (e.g., growth, reproduction, photosynthesis, gene expression) to distinct abiotic factors and global climate change scenarios (e.g., pCO2, pH, temperature, light, salinity, nutrients). Students will perform a multi-marker comparative phylogeographic study among 14 invasive (NSW and SA) and 4 native (QLD, NT, WA) populations to determine the origin of introduced populations in temperate Australia. Students will build a dual-marker DNA barcode database of all species of Caulerpa in Australia as a tool to identify morphologically compromised specimens. Additionally, they will perform a molecular-assisted evolutionary (phylogenetic) study of the genus and develop demographic models to predict the fate of Caulerpa populations under different abiotic scenarios. The students will have the option to choose the components of the project they desire.

Desirable skills: 4WD and manual driving, snorkelling, SCUBA diving certification (open water minimum), molecular biology experience.

For more information please contact Dr. Fred Gurgel (e-mail or telephone: +61 8 8222 9291).

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Inbreeding bad for invasives too

18 02 2010

I just came across this little gem of a paper in Molecular Ecology (not, by any stretch, a common forum for biodiversity conservation-related papers). It’s another one of those wonderful little experimental manipulation studies I love so much (see previous examples here and here).

I’ve written a lot before about the loss of genetic diversity as a contributing factor to extinction risk, via things like Allee effects and inbreeding depression. I’ve also posted blurbs about our work and that of others on what makes particular species prone to become extinct or invasive (i.e., the two sides of the same evolutionary coin). Now Crawford and Whitney bring these two themes together in their paper entitled Population genetic diversity influences colonization success.

Yes, the evolved traits of a particular species will set it up either to do well or very badly under rapid environmental change, and invasive species tend to be those with rapid generation times, defence mechanisms, heightened dispersal capacity and rapid growth. However, such traits generally only predict a small amount in the variation in invasion success – the other being of course propagule pressure (a composite measure of the number of individuals of a non-native species [propagule size] introduced to a novel environment and the number of introduction events [propagule number] into the new host environment).

But, that’s not all. It turns out that just as reduced genetic diversity enhances a threatened species’ risk of extinction, so too does it reduce the ‘invasiveness’ of a weed. Using experimentally manipulated populations of the weedy herb Arabidopsis thaliana (mouse-ear cress; see if you get the joke), Crawford & Whitney measured greater population-level seedling emergence rates, biomass production, flowering duration and reproduction in high-diversity populations compared to lower-diversity ones. Maintain a high genetic diversity and your invasive species has a much higher potential to colonise a novel environment and spread throughout it.

Of course, this is related to propagule pressure because the more individuals that invade/are introduced the more times, the higher the likelihood that different genomes will be introduced as well. This is extremely important from a management perspective because it means that well-mixed (outbred) samples of invasive species probably can do a lot more damage to native biodiversity than a few, genetically similar individuals alone. Indeed, most introductions probably don’t result in a successful invasion mainly because they don’t have the genetic diversity to get over the hump of inbreeding depression in the first place.

The higher genetic (and therefore, phenotypic) variation in your pool of introduced individuals, the great the chance that at least a few will survive and proliferate. This is also a good bit of extra proof for our proposal that invasion and extinction are two sides of the same evolutionary coin.

CJA Bradshaw

ResearchBlogging.orgCrawford, K., & Whitney, K. (2010). Population genetic diversity influences colonization success Molecular Ecology DOI: 10.1111/j.1365-294X.2010.04550.x

Bradshaw, C., Giam, X., Tan, H., Brook, B., & Sodhi, N. (2008). Threat or invasive status in legumes is related to opposite extremes of the same ecological and life-history attributes Journal of Ecology, 96, 869-883 DOI: 10.1111/j.1365-2745.2008.01408.x

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Salamander Longshanks – breed them out

3 02 2010

© M. Dawson

Patrick McGoohan in his role as the less-than-sentimental King Edward ‘Longshanks’ in the 1995 production of ‘Braveheart’ said it best in his references to the invocation of ius primæ noctis:

If we can’t get them out, we’ll breed them out

What a charmer.

Dabbling in molecular ecology myself over the past few years with some gel-jockey types (e.g., Dick Frankham [author of Introduction to Conservation Genetics], Melanie Lancaster, Paul Sunnucks, Yuji Isagi inter alios), I’m quite fascinated by the application of good molecular techniques in conservation biology. So when I came across the paper by Fitzpatrick and colleagues entitled Rapid spread of invasive genes into a threatened native species in PNAS, I was quite pleased.

When people usually think about invasive species, they tend to think ‘predator eating naïve native prey’ or ‘weed outcompeting native plant’. These are all big problems (e.g., think feral cats in Australia or knapweed in the USA), but what people probably don’t think about is the insidious concept of ‘genomic extinction’. This is essentially a congener invasive species breeding with a native one, thus ‘diluting’ the native’s genome until it no longer resembles its former self. A veritable case of ‘breeding them out’.

Who cares if at least some of the original genome remains? Some would argue that ‘biodiversity’ should be measured in terms of genetic diversity, not just species richness (I tend to agree), so any loss of genes is a loss of biodiversity. Perhaps more practically, hybridisation can lead to reduced fitness, like we observed in hybridised fur seals on Macquarie Island.

Fitzpatrick and colleagues measured the introgression of alleles from the deliberately introduced barred tiger salamander (Ambystoma tigrinum mavortium) into threatened California tiger salamanders (A. californiense) out from the initial introduction site. While most invasive alleles neatly stopped appearing in sampled salamanders not far from the introduction site, three invasive alleles persisted up to 100 km from the introduction site. Not only was the distance remarkable for such a small, non-dispersing beastie, the rate of introgression was much faster than would be expected by chance (60 years), suggesting selection rather than passive genetic drift. Almost none of the native alleles persisted in the face of the three super-aggressive invasive alleles.

The authors claim that the effects on native salamander fitness are complex and it would probably be premature to claim that the introgression is contributing to their threatened status, but they do raise an important management conundrum. If species identification rests on the characterisation of a specific genome, then none of the native salamanders would qualify for protection under the USA’s Endangered Species Act. They believe then that so-called ‘genetic purity’ is an impractical conservation goal, but it can be used to shield remaining ‘mostly native’ populations from further introgression.

Nice study.

CJA Bradshaw

ResearchBlogging.orgFitzpatrick, B., Johnson, J., Kump, D., Smith, J., Voss, S., & Shaffer, H. (2010). Rapid spread of invasive genes into a threatened native species Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.0911802107

Lancaster, M., Bradshaw, C.J.A., Goldsworthy, S.D., & Sunnucks, P. (2007). Lower reproductive success in hybrid fur seal males indicates fitness costs to hybridization Molecular Ecology, 16 (15), 3187-3197 DOI: 10.1111/j.1365-294X.2007.03339.x

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Computer-assisted killing for conservation

12 01 2010

Many non-Australians might not know it, but Australia is overrun with feral vertebrates (not to mention weeds and invertebrates). We have millions of pigs, dogs, camels, goats, buffalo, deer, rabbits, cats, foxes and toads (to name a few). In a continent that separated from Gondwana about 80 million years ago, this allowed a fairly unique biota to evolve, such that when Aboriginals and later, Europeans, started introducing all these non-native species, it quickly became an ecological disaster. One of my first posts here on ConservationBytes.com was in fact about feral animals. Since then, I’ve written quite a bit on invasive species, especially with respect to mammal declines (see Few people, many threats – Australia’s biodiversity shame, Shocking continued loss of Australian mammals, Can we solve Australia’s mammal extinction crisis?).

So you can imagine that we do try to find the best ways to reduce the damage these species cause; unfortunately, we tend to waste a lot of money because density reduction culling programmes aren’t usually done with much forethought, organisation or associated research. A case in point – swamp buffalo were killed in vast numbers in northern Australia in the 1980s and 1990s, but now they’re back with a vengeance.

Enter S.T.A.R. – the clumsily named ‘Spatio-Temporal Animal Reduction’ [model] that we’ve just published in Methods in Ecology and Evolution (title: Spatially explicit spreadsheet modelling for optimising the efficiency of reducing invasive animal density by CR McMahon and colleagues).

This little Excel-based spreadsheet model is designed specifically to optimise the culling strategies for feral pigs, buffalo and horses in Kakadu National Park (northern Australia), but our aim was to make it easy enough to use and modify so that it could be applied to any invasive species anywhere (ok, admittedly it would work best for macro-vertebrates).

The application works on a grid of habitat types, each with their own carrying capacities for each species. We then assume some fairly basic density-feedback population models and allow animals to move among cells. We then hit them virtually with a proportional culling rate (which includes a hunting-efficiency feedback), and estimate the costs associated with each level of kill. The final outputs give density maps and graphs of the population trajectory.

We’ve added a lot of little features to maximise flexibility, including adjusting carrying capacities, movement rates, operating costs and overheads, and proportional harvest rates. The user can also get some basic sensitivity analyses done, or do district-specific culls. Finally, we’ve included three optimisation routines that estimate the best allocation of killing effort, for both maximising density reduction or working to a specific budget, and within a spatial or non-spatial context.

Our hope is that wildlife managers responsible for safeguarding the biodiversity of places like Kakadu National Park actually use this tool to maximise their efficiency. Kakadu has a particularly nasty set of invasive species, so it’s important those in charge get it right. So far, they haven’t been doing too well.

You can download the Excel program itself here (click here for the raw VBA code), and the User Manual is available here. Happy virtual killing!

CJA Bradshaw

P.S. If you’re concerned about animal welfare issues associated with all this, I invite you to read one of our recent papers on the subject: Convergence of culture, ecology and ethics: management of feral swamp buffalo in northern Australia.

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ResearchBlogging.orgC.R. McMahon, B.W. Brook,, N. Collier, & C.J.A. Bradshaw (2010). Spatially explicit spreadsheet modelling for optimising the efficiency of reducing invasive animal density Methods in Ecology and Evolution : 10.1111/j.2041-210X.2009.00002.x

Albrecht, G., McMahon, C., Bowman, D., & Bradshaw, C. (2009). Convergence of Culture, Ecology, and Ethics: Management of Feral Swamp Buffalo in Northern Australia Journal of Agricultural and Environmental Ethics, 22 (4), 361-378 DOI: 10.1007/s10806-009-9158-5

Bradshaw, C., Field, I., Bowman, D., Haynes, C., & Brook, B. (2007). Current and future threats from non-indigenous animal species in northern Australia: a spotlight on World Heritage Area Kakadu National Park Wildlife Research, 34 (6) DOI: 10.1071/WR06056





Coming to grips with the buffalo problem

7 09 2009

Clive McMahon (left) & colleaguesA good friend and colleague of mine, Dr. Clive McMahon, is visiting Adelaide for the next few weeks from Darwin. We’re attacking a few overdue manuscripts and sampling a few of Adelaide’s better drops of value-added grape juice, so I asked him to do a guest post on ConservationBytes.com about his work. So here it is, something perhaps even few Australians know much about, let alone overseas folks. If you can recall that very strange scene in the film Crocodile Dundee where the old croc hunter casts a gestured spell over a horned beast, then you’ll probably appreciate this post.

Yes, there are plenty of them in northern Australia

Invasive and feral species can be important drivers of biodiversity loss. Australia, like many other isolated islands has developed an ancient, unique and diverse ecosystem. This unique ecosystem has been under extreme pressure ever since humans arrived around 40000-60000 years ago. One of the more damaging and economically important introduced species in Australia is the Asian swamp buffalo (Bubalus bubalis). Ironically, swamp buffalo are listed as Endangered by the IUCN, and current estimates suggest that there are probably less than 4000 in their native habitats in Asia.

© B. Salu, Kakadu National Park

© B. Salau, Kakadu National Park

The first 16 buffalo were introduced to Australia in 1826 on Melville Island, and then to the mainland at Cobourg Peninsula a year later from Kupang (now West Timor, Indonesia). Another 18 buffalo were obtained from Kisar Island (northeast of modern Timor-Leste) and introduced to the Cobourg. In 1843, another 49 were introduced. When the first Cobourg settlement was abandoned in 1849, all the buffalo were released, and the population spread rapidly throughout the Northern Territory. Over the next 65 years, numbers and distribution increased to an estimated 350000 in the 1960s and 1970s and densities exceeded 25 km-2 in ‘prime’ habitat. However, the population was severely reduced during the 1980s and 1990s in parts of its range under the Brucellosis-Tuberculosis Eradication Campaign (BTEC). Although largely successful in eradicating buffalo from pastoral lands in the short term, there was no ongoing broad-scale management of numbers and the present-day population of free-ranging buffalo has recovered to former densities in some areas.

© C. Speed

© C. Speed

Buffalo were then and still are major problem in Australia due mainly to the environmental damage they cause, such as saltwater intrusion of wetlands and trampling of sensitive habitats, their potential threat to Australia’s livestock industry as hosts for disease, and the danger they pose to human safety. Given these ecological, economic and social impacts, there is an urgent need to manage buffalo numbers.

An important step to inform management of introduced and invasive species is to determine the history of introduction and quantify the rate of spread from introduction sites. Contemporary genetic techniques in conjunction with demographic and life history information are useful tools for understanding the dynamics, population structure, biology and colonisation dynamics of plants and animals, including invasive species such as buffalo.

We are currently in the final stages of providing the first detailed analysis of the buffalo population structure (demographic and genetic) to (1) establish the rate and most probable history of spread using detailed genetic information sampled from 8 sub-populations, (2) quantify the genetic distance and mixing rates between populations and (3) describe the age structure and therefore the demographic performance of this very successful invasive species.

Firstly to get an idea of genetic structure and relatedness, we collected a total of 430 small skin biopsies from buffalo across the Northern Territory, representing eight geographically distinct populations. To determine what has made the buffalo such a successful invader it is important to know the survival and breeding performance; we also constructed seven life tables based on culled samples at different densities and in different environments to work out what are the critical components of the population – i.e., where management intervention would be most successful.

As expected from a bottlenecked population, genetic variation is low compared to the that found in swamp buffalo from India and South East Asia. Despite this reduced genetic variation, the Australian population has thrived and spread outwards from introduction sites and into culled sites at high rates over the last 160 years (covering ~ 224 000 km2 in that time).

Although buffalo in Australia experienced two major periods of population reduction since their introduction, a small proportion (estimated at ~ 20 %) escaped the BTEC reduction in the eastern part of its north Australian range. BTEC did not operate with uniformity across the entire range of buffalo, concentrating its destocking efforts in a general area from the western coast of the Northern Territory to west of the Mann River in Arnhem Land, and south roughly to Kakadu National Park’s southern border. Coincidently and not surprisingly, it is in this area that we observe most migration activity.

The subpopulation structure detected here suggests that each population, while connected over generational time scales, generally remains in its immediate vicinity over the course of management-tractable periods. Therefore, management aimed at protecting Australia’s lucrative livestock industry trading under Australia’s disease-free status will benefit directly from this knowledge. For example, the localised introduction and subsequent rapid detection of disease could be efficiently managed from local culls because short-term movements of long-distance are less likely. Our results showcase how management of animals for disease control can be effectively informed via genetic studies and so avoid the need for expensive broad-scale intervention.

Our analyses of the age structure of buffalo reveals that buffalo have the capacity to recover swiftly after control because of high survival and fertility rates. Survival in the juvenile age classes was consistently the most important modifier of population growth. In populations where juvenile animals are harvested annually, fertility determined rebound potential. Thus, management aimed at long-term control of densities should focus primarily on the sustained culling of adult females and their offspring.

Given that numbers of buffalo are increasing and that buffalo are extremely well-adapted to the monsoonal tropics (unlike cattle, buffalo can maintain body condition and positive growth during times of food shortages), they are vulnerable to extended periods of harsh conditions. Climate change predictions herald increasing rainfall in the region, thereby potentially reducing the pressure on juvenile survival. As such, buffalo population growth could conceivably increase, making future management much more difficult. In essence, we need a large, evidence-based density reduction programme in place soon to prevent the worst ecological damage to Australia’s sensitive and unique ecosystems.

Check back here for announcements of upcoming publications arising from our work.

Clive McMahon & CJA Bradshaw

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Destroyed or Destroyer?

23 03 2009

Last year our group published a paper in Journal of Ecology that examined, for the first time, the life history correlates of a species’ likelihood to become invasive or threatened.

The paper is entitled Threat or invasive status in legumes is related to opposite extremes of the same ecological and life-history attributes and was highlighted by the Editor of the journal.

The urgency and scale of the global biodiversity crisis requires being able to predict a species’ likelihood of going extinct or becoming invasive. Why? Well, without good predictive tools about a species’ fate, we can’t really prepare for conservation actions (in the case of species more likely to go extinct) or eradication (in the case of vigorous invasive species).

We considered the problem of threat and invasiveness in unison based on analysis of one of the largest-ever databases (8906 species) compiled for a single plant family (Fabaceae = Leguminosae). We chose this family because it is one of the most speciose (i.e., third highest number of species) in the Plant kingdom, its found throughout all continents and terrestrial biomes except Antarctica, its species range in size from dwarf herbs to large tropical trees, and its life history, form and functional diversity makes it one of the most important plant groups for humans in terms of food production, fodder, medicines, timber and other commercial products. Choosing only one family within which to examine cross-species trends also makes the problem of shared evolutionary histories less problematic from the perspective of confounded correlations.

We found that tall, annual, range-restricted species with tree-like growth forms, inhabiting closed-forest and lowland sites are more likely to be threatened. Conversely, climbing and herbaceous species that naturally span multiple floristic kingdoms and habitat types are more likely to become invasive.

Our results support the idea that species’ life history and ecological traits correlate with a fate response to anthropogenic global change. In other words, species do demonstrate particular susceptibility to either fate based on their evolved traits, and that traits generally correlated with invasiveness are also those that correlate with a reduced probability of becoming threatened.

Conservation managers can therefore benefit from these insights by being able to rank certain plant species according to their risk of becoming threatened. When land-use changes are imminent, poorly documented species can essentially be ranked according to those traits that predispose them to respond negatively to habitat modification. Here, species inventories combined with known or expected life history information (e.g., from related species) can identify which species may require particular conservation attention. The same approach can be used to rank introduced plant species for their probability of spreading beyond the point of introduction and threatening native ecosystems, and to prioritise management interventions.

I hope more taxa are examined with such scrutiny so that we can have ready-to-go formulae for predicting a wider array of potential fates.

CJA Bradshaw

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Classics: Invasion Meltdown

26 10 2008

One for the Classics page…

melting_rat_by_xenatalhaoui-d71xr1yDaniel Simberloff is probably best known for his work on the implications of invasive (non-indigenous) species for biodiversity, although he has contributed to a wide range of conservation disciplines.

A seminal paper that he co-wrote with Betsy Von Holle is one I consider to be a conservation Classic: their 1999 paper in the inaugural issue of Biological Invasions entitled Positive interactions of nonindigenous species: Invasional meltdown?

The establishment of non-indigenous species can have severe negative impacts on ecosystems. Introduced species that become invasive (widespread and locally dominant) transform habitats, degrade ecosystem services, reduce biodiversity and are some of the greatest threats to ecosystems today (perhaps nearly as important as habitat loss and over-exploitation).

The so-called ‘invasion meltdown‘ describes the process by which the negative impacts induced on native ecosystems by one invading non-indigenous species are exacerbated by interactions with another exotic species.

Although there isn’t a lot of information on invasion meltdowns, one good example comes from Christmas Island in tropical Australia. The introduced yellow crazy ant (Anoplolepis gracilipes) exploded in numbers when another exotic species, a scale insect, was introduced about the same time that a native scale insect species also had a local outbreak.  Because ants protect scale insects from predators and parasites in return for scale honeydew, the crazy ant suddenly had a much more abundant food source, leading to the huge increase in the ant population. This large ant population devastated the population of native red crab (Gecarcoidea natalis) and resulted in massive increase in forest undergrowth due to reduced herbivory by crabs (see O’Dowd et al. 2003). The great decline in red crabs may also make the island more vulnerable to other plant invasions.

What did Simberloff & Van Holle’s idea and subsequent examples of invasion meltdowns teach us? I believe their paper really hit home the idea that invasive species were not only a threat to biodiversity, but the self-reinforcing mutualisms of invasive species could rival other forms of human-induced biodiversity decline. Indeed, many of the effects of invasive species will be reinforced by global climate change through increasing temperatures, rising sea levels and changing rainfall patterns that increase the potential range and spread of invading species, so the problem is only going to get worse. This is why the U.N. began the Global Invasive Species Programme (GISP), and world-wide, countries are attempting to restrict the flow of invasive species so that their negative effects are lessened. Identifying the extent of the problem has stimulated a lot of people to act accordingly.

CJA Bradshaw

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