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Genetics to the rescue

27 05 2025

Procreating with a relative is taboo in most human societies for many reasons, but they all stem from avoiding one thing in particular — inbreeding increases the risk of genetic disorders that can seriously compromise a child’s health, life prospects, and survival.

While we all inherit potentially harmful mutations from our parents, the effects of these mutations are often partially or completed masked if we possess two alternative variants of a gene — one from each parent. However, the children of closely related parents are more likely to inherit the same copies of harmful mutations. This is known as ‘inbreeding depression’.

But inbreeding depression can happen in any species, with the risk increasing as populations become smaller. Because many species are rapidly declining in abundance and becoming isolated from one another predominantly due to habitat destruction, invasive species, and climate change, the chances of inbreeding are also increasing.

Not only are such populations more susceptible to random disturbances, they are also victim of reduced population growth rates arising from inbreeding depression. This produces what is generally known as the ‘extinction vortex‘ — the smaller your population, the more you inbreed and produce sub-optimal offspring, leading to even more population decline and eventually extinction.

One emergency intervention that can ‘rescue’ such inbred populations from extinction (at least in the short term) is to introduce unrelated individuals from other populations in an attempt to increase genetic diversity, and therefore, the rate of population growth. While somewhat controversial because some fear introducing diseases or eroding local-area specialisation (so-called ‘outbreeding depression’), the risk-benefit ratio of this ‘genetic rescue’ is now widely considered to be worth it.

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Tags: bandicoot, demographic stochasticity, devil, EPBC Act, genetic drift, genetic load, genetic rescue, koala, marsupials, microsatellite DNA, mitochondrial DNA, mtDNA, natural selection, possum, quoll, single-nucleotide polymorphisms, SNPs, whole-genome sequencing, woylie
Categories : Australia, conservation, demography, extinction, extinction debt, extinction vortex, genetic diversity, genetics, inbreeding depression, mammal, threatened species

“Overabundant” wildlife usually isn’t

12 07 2019

koalacrosshairs Late last year (10 December) I was invited to front up to the ‘Overabundant and Pest Species Inquiry’ at the South Australian Parliament to give evidence regarding so-called ‘overabundant’ and ‘pest’ species.

There were the usual five to six Ministers and various aides on the Natural Resources Committee (warning here: the SA Parliament website is one of the most confusing, archaic, badly organised, and generally shitty government sites I’ve yet to visit, so things require a bit of nuanced searching) to whom I addressed on issues ranging from kangaroos, to dingoes, to koalas, to corellas. The other submissions I listened to that day were (mostly) in favour of not taking drastic measures for most of the human-wildlife conflicts that were being investigated.

Forward seven months and the Natural Resources Committee has been reported to have requested the SA Minister for Environment to allow mass culling of any species (wildlife or feral) that they deem to be ‘overabundant’ or a ‘pest’.

So, the first problem is terminological in nature. If you try to wade through the subjectivity, bullshit, vested interests, and general ignorance, you’ll quickly realise that there is no working definition or accepted meaning for the words ‘overabundant’ or ‘pest’ in any legislation. Basically, it comes down to a handful of lobbyists and other squeaky wheels defining anything they deem to be a nuisance as ‘overabundant’, irrespective of its threat status, ecological role, or purported impacts. It is, therefore, entirely subjective, and boils down to this: “If I don’t like it, it’s an overabundant pest”. Read the rest of this entry »

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Tags: dingo, environment, fur seals, Government of South Australia, Kangaroo, koala, little corella, Natural Resources Committee, South Australia
Categories : alien species, animal welfare, Australia, biodiversity, climate change, community ecology, conservation, decline, dingo, ecology, ecosystem, ecosystem function, environmental policy, exploitation, fish, fisheries, harvest, human-wildlife conflict, impact, invasive species, kangaroo, management, meso-predator release, predation, predator, science, South Australia, sustainability, threatened species, top-down ecology

Koala extinctions past, present, and future

12 06 2019

Photo by John Llewelyn

Koalas are one of the most recognised symbols of Australian wildlife. But the tree-living marsupial koala is not doing well throughout much of its range in eastern Australia. Ranging as far north as Cairns in Queensland, to as far west as Kangaroo Island in South Australia, the koala’s biggest threats today are undeniably deforestation, road kill, dog attacks, disease, and climate change.

With increasing drought, heatwaves, and fire intensity and frequency arising from the climate emergency, it is likely that koala populations and habitats will continue to decline throughout most of their current range.

But what was the distribution of koalas before humans arrived in Australia? Were they always a zoological feature of only the eastern regions?

The answer is a resounding ‘no’ — the fossil record reveal a much more complicated story.

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Tags: climate envelope, Eucalypt, Eucalyptus, koala, marsupial, niche, Phascolarctos, Phascolarctos cinereus, potential niche, SDM
Categories : Australia, biodiversity, biogeography, climate change, climate shift, conservation, conservation biology, conservation ecology, decline, deforestation, ecology, extinction, fragmentation, habitat loss, mammal, modelling, niche model, palaeo-ecology, research, science, southern Australia, species distribution model, threatened species, vegetation

Job: Koala Data Research Technician

6 03 2017

koala If you live in South Australia, and in Adelaide especially, you would have had to be living under a rock not to have heard of the Great Koala Counts 1 and 2. So I’m not really writing this for those sotto pietra types. If you are a regular reader of CB.com, you’ll also know that I’ve been involved in helping analyse the data from GKC1, as well as improving the design of the GKC2.

Well, the data are in for GKC2 and we need help to analyse them. Just as a little reminder, the GKCs are designed to provide better data to estimate the distribution and density of koalas in South Australia (especially in the Mount Lofty Ranges). We’ve already written one scientific article from GKC1, but we now have a more expansive and quality-controlled dataset, so it’s now time to write the second. Read the rest of this entry »

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Tags: data, employment, job, koala, marsupial, part-time, research assistant, technician
Categories : conservation, niche model, South Australia, southern Australia, species distribution model

Putting the ‘science’ in citizen science

30 04 2014

How to tell if a koala has been in your garden. © Great Koala Count

When I was in Finland last year, I had the pleasure of meeting Tomas Roslin and hearing him describe his Finland-wide citizen-science project on dung beetles. What impressed me most was that it completely flipped my general opinion about citizen science and showed me that the process can be useful.

I’m not trying to sound arrogant or scientifically elitist here – I’m merely stating that it was my opinion that most citizen-science endeavours fail to provide truly novel, useful and rigorous data for scientific hypothesis testing. Well, I must admit that I still believe that ‘most’ citizen-science data meet that description (although there are exceptions – see here for an example), but Tomas’ success showed me just how good they can be.

So what’s the problem with citizen science? Nothing, in principle; in fact, it’s a great idea. Convince keen amateur naturalists over a wide area to observe (as objectively) as possible some ecological phenomenon or function, record the data, and submit it to a scientist to test some brilliant hypothesis. If it works, chances are the data are of much broader coverage and more intensively sampled than could ever be done (or afforded) by a single scientific team alone. So why don’t we do this all the time?

If you’re a scientist, I don’t need to tell you how difficult it is to design a good experimental sampling regime, how even more difficult it is to ensure objectivity and precision when sampling, and the fastidiousness with which the data must be recorded and organised digitally for final analysis. And that’s just for trained scientists! Imagine an army of well-intentioned, but largely inexperienced samplers, you can quickly visualise how the errors might accumulate exponentially in a dataset so that it eventually becomes too unreliable for any real scientific application.

So for these reasons, I’ve been largely reluctant to engage with large-scale citizen-science endeavours. However, I’m proud to say that I have now published my first paper based entirely on citizen science data! Call me a hypocrite (or a slow learner). Read the rest of this entry »