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Alex Slavenko @alexsla.bsky.social · 07/03/2026

A succinct summary of a fantastic study by my colleagues at Cesar Australia 🧪🌏

Alex Slavenko @alexsla.bsky.social · 24/02/2026

So this should be a last resort tactic, and only employed after careful consideration of all biological, legal and ethical implications and careful testing. But we think it can be done, and might be beneficial. So we do think the option should be on the table, and we encourage discussion. Fin.

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Alex Slavenko @alexsla.bsky.social · 24/02/2026

Parrots often hybridise in captivity and the wild. Adding eastern genetics might ugment genetic diversity and adaptive potential through genetic mixing, and maybe even broaden the western realised niche breadth, faciliating range expansion. But there are also risks such as outbreeding depression.

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Alex Slavenko @alexsla.bsky.social · 24/02/2026

Now, the western ground parrot is in really big trouble. Only two extant populations remain, and one of them likely suffered a fair bit from recent wildfires (www.abc.net.au/news/2026-01...). We end our paper with a potentially controversial recommendation: should we try hybridising the two species?

abc.net.au

Fire rips through habitat of critically endangered parrot

Experts estimate 11,000 hectares of core habitat for the critically endangered parrot has been lost to a recent fire.

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Alex Slavenko @alexsla.bsky.social · 24/02/2026

That way we ended up with two species - one pretty widespread in the temperate coastal heathlands of Australia's southeast, and one restricted to the Mediterranean coastal heatlands of Australia's southwest. Enter Europeans, invasive predators & pathogens, habitat clearing and changing fire regimes.

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Alex Slavenko @alexsla.bsky.social · 24/02/2026

However, as the Nullarbor plain dried up, a biogeographic barrier was formed, which likely led to the formation of an eastern and western population. Then, what we think happened is that the eastern incipient species experienced a really big niche expansion by spreading to more mesic habitats.

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Alex Slavenko @alexsla.bsky.social · 24/02/2026

So putting it together, we get a pretty interesting story - platycercine climatic niches are shaped by their occupied biomes. The extents of these biomes have shifted through time. The ancestral ground parrot was likely distributed in the Mediterranean biome along Australia's southern coast.

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Alex Slavenko @alexsla.bsky.social · 24/02/2026

This analysis indicates that the 2Mya mark is more or less when the Nullarbor plain switches from pre-dominantly meditteranean to predominantly arid, which what is also indicated by lots of geological and fossil evidence.

Proportion of the Nullarbor plain classified as either Mediterranean or arid biome through time.

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Alex Slavenko @alexsla.bsky.social · 24/02/2026

To look at it from another angle, we esimated paleobiomes by training a random forest classifier for biome based on extant bioclimatic layers and a biome map for Australia, then projecting it backwards through time on paleoclimate layers. Notice the expanding extent of the arid biome.

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Alex Slavenko @alexsla.bsky.social · 24/02/2026

The SDMs certainly support this - notice how habitat suitability in the Nullarbor plain fluctuates at first, then drops to pretty much 0 after 2 Mya, more or less the upper boundary for the divergence date estimate based on phylogenomic analysis (doi.org/10.1206/0003...).

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Alex Slavenko @alexsla.bsky.social · 24/02/2026

We also constructed SDMs and projected them backwards in time using paleoclimatic layers. This was important to test a long-standing hypothesis that their divergence was driven by the progressive aridification of the Nullarbor plain during the Pleistocene–Holocene. doi.org/10.1002/ece3...

doi.org

A species assemblage approach to comparative phylogeography of birds in southern Australia

In order to compare demographic histories of ten broadly co-distributed birds that are wholly or patchily discontinuous in semi-arid habitats between the continent's south-west and south-east mesic z....

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Alex Slavenko @alexsla.bsky.social · 24/02/2026

What about thermal maxima? The greatest support was for a non-phylogenetic white noise model. Not that surprising: heat tolerance is considered more physiologically constrained than cold tolerance, meaning weaker phylogenetic signal in thermal maxima. And that's what our data certainly look like.

Phenogram showing evolution of climatic niche dimensions in Australian platycercines.

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Alex Slavenko @alexsla.bsky.social · 24/02/2026

The fitted evolutionary models then support different adaptive optima for thermal minima and rainfall for different biomes. Essentially, temperate biomes associated with cold and wet niches, tropics with warm and wet, arid and mediterranean with dry.

Parameter estimates from fitted trait evolution models, showing rates and optima for three climatic niche dimensions.

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Alex Slavenko @alexsla.bsky.social · 24/02/2026

Basically, we used historical biogeographic models to infer likely biome histories. These tell us, for instance, that the ancestral ground parrot was likely a Mediterranean biome species, or that the ancestor of the genus Neophema was likely a temperate biome species.

Phylogeny of Australian platycercines, with observed (at the tips) and inferred (pie charts at internal nodes) biome occupancy histories.

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Alex Slavenko @alexsla.bsky.social · 24/02/2026

How did these differences in realised niches evolve? We fitted some trait evolution models to try and uncover these, and see if climatic niche dimensions (temperature maxima and minima, rainfall) co-evolve with occupied biome, using a simplified four-biome classification scheme for Australia.

A map showing the extent of different biomes in Australia, based on a simplified four-biome classification scheme.

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Alex Slavenko @alexsla.bsky.social · 24/02/2026

The ground parrots also have very unique habitat requirements, as we can see in this dendrogram showing habitat similarity clusters. They really like coastal heathlands. But they're also quite different from one another, with a lot of western records from mallee woodlands and shrublands.

Dendrogram showing species clustering based on habitat similarity.

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Alex Slavenko @alexsla.bsky.social · 24/02/2026

Basically, it occurs over a really wide range of temperatures and rainfall zones. The western ground parrot's niche is tiny in comparison, but is also almost completely nested within the eastern ground parrot's niche. This indicates niche expansion in the eastern ground parrot following speciation.

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Alex Slavenko @alexsla.bsky.social · 24/02/2026

We first identified the realised climatic and habitat niches of all Aussie platycercines based on their occurrence records. There's a lot of variation, but the key result we want to point out is that the eastern ground parrot has an enormous climatic niche, much larger than all others.

Boxplots showing estimated climatic niche sizes, based on temperature extremes and annual rainfall patterns.

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Alex Slavenko @alexsla.bsky.social · 24/02/2026

Pezoporus is part of the subfamily Platycercinae, which includes Australian rosellas, bluebonnets, ringnecks, etc. but not lorikeets, lories or cockatoos. Platycercines are found throughout Australia, giving us a broad range of climates and habitats to compare and contrast.

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Alex Slavenko @alexsla.bsky.social · 24/02/2026

We were interested in the dynamics of speciation between the two ground parrots, and particularly in how their climatic and habitat niches differ and how such differences evolved. But we also wanted a broader context for this comparison, so we included other close relatives in the analysis.

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Alex Slavenko @alexsla.bsky.social · 24/02/2026

The two species are ecologically similar, mostly inhabiting coastal heathlands in southeastern and southwestern Australia. However, while the eastern species is relatively widespread, the western is more restricted in distribution and has declined greatly over past decades.

Occurrence record map for eastern (Pezoporus wallicus, in shades of green) and western (Pezoporus flaviventris, in shades of red) ground parrots. Darker colours represent older records.

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Alex Slavenko @alexsla.bsky.social · 24/02/2026

The other members of the genus are ground parrots. Currently two species are recognised, the eastern ground parrot (P. wallicus) and the western ground parrot (P. flaviventris, photo by Brent Barrett CC BY-NC-ND 2.0). In the past, P. flaviventris was considered a subspecies of P. wallicus.

Photo of a western ground parrot (Pezoporus flaviventris) in coastal heatland.

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Alex Slavenko @alexsla.bsky.social · 24/02/2026

First, a brief introduction to the focal taxa. The genus Pezoporus contains three species. One of them is the very cool and very enigmatic night parrot (P. occidentalis) which is occurs throughout the arid Australian interior but observations are sparse and its biology is poorly known.

Illustration of night parrots (Pezoporus occidentalis).

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Alex Slavenko @alexsla.bsky.social · 24/02/2026

New paper alert! 🚨🌏🧪 We've just published a neat little study in Journal of Biogegraphy, looking at the climatic and habitat niches of ground parrots and how they've evolved. Let's dive in a bit deeper! onlinelibrary.wiley.com/doi/10.1111/...

onlinelibrary.wiley.com

Breaking New Ground: Niche Divergence and Expansion in Ground Parrots (Pezoporini: Platycercinae)

Aim The two species of ground parrots (Pezoporus wallicus and P. flaviventris) are morphologically and behaviourally similar, yet geographically disjunct and genetically distinct. We investigated th.....

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Alex Slavenko @alexsla.bsky.social · 22/01/2026

An excellent and thorough rebuttal of the extremely flawed paper by Wallach & Lundgren (2025). 🧪🌏

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Alex Slavenko @alexsla.bsky.social · 17/04/2025

And to do this, they try to paint the conservation community as suffering from "bias, groupthink, and overconfidence" - all while their own very clear biases are showing in every page of this paper.

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Alex Slavenko @alexsla.bsky.social · 17/04/2025

Wallach & Lundgren are not dumb, nor are they bad scientists. They're disingenuous scientists. They know exactly what they're doing, which is trying to discredit the well-supported role of invasive predators in driving extinction, because they don't think we should kill invasive predators.

wildlifecoexistence.org

Compassionate Conservation | The International Wildlife Coexistence Network

The king parrot is eating my pomegranates and teaching me to accommodate thieves in my life. Arian Wallach I don’t know what he wants from me,” says Arian W ...

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Alex Slavenko @alexsla.bsky.social · 17/04/2025

But as we've seen, their own sweeping claims are based on some pretty dodgy tactics, very liberal interpretation of some results, and consistent downplaying of any result that is inconsistent with their own preconceived idea - that foxes and cats did not (and do not) drive Aussie mammal extinction.

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Alex Slavenko @alexsla.bsky.social · 17/04/2025

Wallach & Lundgren summarise: "Sweeping claims have been made about introduced predators with ambiguous, weak, and—in most cases—no evidence. This challenges the notion that a core paradigm of conservation biology is evidence based, at least in Australia."

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Alex Slavenko @alexsla.bsky.social · 17/04/2025

This means the species they studied had ample time to evolve to live in the presence of foxes. You know who didn't? The one that had prey naiveté, that were more vulnerable to fox predation, and went extinct long before Wooster et al. came around to run their experiments. Classic survivorship bias.

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Alex Slavenko @alexsla.bsky.social · 17/04/2025

Obviously, there's a bit of a problem here. The study was conducted in 2018 and 2019 - small mammals in Australia have lived in the presence of foxes for decades. 104 and 108 years, specifically, in the sites Wooster et al. studied, where invasive predators are also protected and not controlled.

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Alex Slavenko @alexsla.bsky.social · 17/04/2025

One specific study they mention in detail is Wooster et al. 2024, which showed that "small mammal responses to fox scent was essentially the same outside the foxes’ native range (Australia) as inside (Israel and United States)" nsojournals.onlinelibrary.wiley.com/doi/full/10....

nsojournals.onlinelibrary.wiley.com

Prey responses to foxes are not determined by nativeness

Introduced predators are thought to be responsible for the decline and extinction of their native prey. The prey naivety hypothesis provides a mechanism for these declines, suggesting that native pre...

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Alex Slavenko @alexsla.bsky.social · 17/04/2025

But Wallach & Lundgren claim there is no evidence for this, citing some studies to support this, including a few they were themselves authors on. Remember that bit about overlap in authors? Funny how that's suddenly not a problem. Anyway.

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Alex Slavenko @alexsla.bsky.social · 17/04/2025

We've known this is a thing ever since Darwin bashed in the head of a fox with a geological hammer. en.wikipedia.org/wiki/Darwin%...

en.wikipedia.org

Darwin's fox - Wikipedia

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Alex Slavenko @alexsla.bsky.social · 17/04/2025

Wallach & Lundgren also claim there is no mechanism for foxes and cats driving extinction in Australia. That's a pretty bold claim, considering we do have one - prey naiveté. Aussie mammals evolved without eutherian predators like cats and foxes present, and so are more vulnerable to predation

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Alex Slavenko @alexsla.bsky.social · 17/04/2025

Regardless of those examples, the point here is not whether other factors can cause failures (they can) but what *did* cause the recorded failure. If predation by foxes and cats causes the reintroduction to fail, that's pretty compelling evidence they caused the extirpation in the first place.

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Alex Slavenko @alexsla.bsky.social · 17/04/2025

They also cite a paper on failure of brown treecreeper reintroduction in Australia - but that paper not report which predators caused the failure. In fact, they attribute it more to aggressive behaviour by noisy miners, which would be more of a competitive interaction.

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Alex Slavenko @alexsla.bsky.social · 17/04/2025

They also claim that reintroduction failures are not good evidence because "reintroduction programs are foiled by native predators as well". As support, they cite two studies from South Africa - which, unlike Australia, has many native predators remaining.

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Alex Slavenko @alexsla.bsky.social · 17/04/2025

Wallach & Lundgren have no argument against this, other than "Although there could be other reasons why extinctions concentrated in this body mass and in that region, to our knowledge, no competing hypotheses have been put forward". What, pray tell, are these competing hypotheses?

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Alex Slavenko @alexsla.bsky.social · 17/04/2025

One of the key points of evidence for fox and cat-driven extinctions is that many of the extinct Aussie mammals fall within the 'critical weight range' of 35 g-5.5 kg, just the right prey size for cats and foxes. onlinelibrary.wiley.com/doi/10.1111/...

onlinelibrary.wiley.com

Body mass and extinction risk in Australian marsupials: The ‘Critical Weight Range’ revisited

Australian mammals have suffered an exceptionally high rate of decline and extinction over the last two hundred years. Body mass is linked to extinction risk in Australian mammals, but the nature of ...

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Alex Slavenko @alexsla.bsky.social · 17/04/2025

Then, they go about explaining why they think foxes and cats do not drive extinctions. Remember their claim I started the thread with? That they're not aiming to prove or disprove the hypothesis? Here's where that claim falls apart.

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Alex Slavenko @alexsla.bsky.social · 17/04/2025

And this is for the species they themselves admitted has the best evidence! With no studies not in support! I think this begs the question, what do Wallach & Lundgren consider sufficient support? When will they admit that foxes and cats are to blame for an extinction?

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Alex Slavenko @alexsla.bsky.social · 17/04/2025

The online supplementary again offers even less tempered language, that makes Wallach & Lundgren's position very clear: "Cats are among a range of ecological variables negatively correlated with rat abundance, but causality cannot be inferred due to confounding variables."

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Alex Slavenko @alexsla.bsky.social · 17/04/2025

Also, if overlap in authors is an issue, I'd like to point out Wallach and Lundgren are authors on many of the papers cited in this study. So....

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Alex Slavenko @alexsla.bsky.social · 17/04/2025

Can anyone think why there might be overlap in study sites for a species that is widely extirpated from the majority of its historical range and is now restricted to only a ew small populations? Anyone?

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Alex Slavenko @alexsla.bsky.social · 17/04/2025

Alas, "We do not agree that one can go further to claim that there is sufficient evidence that cats are the cause of the threatened status of rabbit rats, because the studies are not fully independent (the articles overlap in data, study sites, and authors)".

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Alex Slavenko @alexsla.bsky.social · 17/04/2025

See how they downplay the evidence in the 20 species with supportive population data. For brush-tailed rabbit rats, "We identified six population studies, all in support, of which five met basic qualities for testing predator–prey interactions". Sounds good right?

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