One of creationism’s favourite assertions is that evolution cannot produce “new genetic information” without an intelligent designer. What usually goes missing is a clear definition of information, an explanation of why known genetic mechanisms cannot generate novelty, or any evidence of the supposed designer doing anything. Meanwhile, evolutionary biologists continue to investigate the natural processes by which genomes change and organisms acquire new capabilities. A new study of ants provides another example of how productive that scientific approach can be.
As reported in Science Advances, an international team led by Dr Lukas Schrader has investigated the contribution of transposable elements, commonly called “jumping genes”, to ant evolution. These mobile DNA sequences can move or copy themselves within genomes. Their activity can be disruptive, but it can also supply material for evolutionary innovation. The research links their activity to the expansion of gene families, including those encoding the odour receptors so important to ants’ chemical communication.
The researchers compared genomes from 163 ant species, representing twelve of the sixteen living subfamilies. They identified independent bursts of transposable-element activity in the ancestors of major ant groups, preceding their rapid diversification following the Cretaceous–Palaeogene, or K–Pg, mass extinction approximately 66 million years ago. The findings support a connection between changes within genomes and the evolutionary opportunities created by a profoundly altered world.
The evolutionary significance is straightforward. A mass extinction changes the conditions under which survivors live: ecological relationships are disrupted, resources become available in different ways, and opportunities arise as ecosystems recover. A genetic variant that previously offered little advantage may become useful under these new conditions. Natural selection can then favour organisms carrying it. Neither the mutation nor the environmental upheaval needs to anticipate the outcome.
Nor does genetic novelty require a complete, finished gene to appear from nowhere. Duplication supplies additional copies of existing sequences, which can subsequently diverge; changes to the regulation and arrangement of DNA can also alter what an organism does. Calling the starting material “existing information” does nothing to prevent its descendants from acquiring new functions. The relevant questions concern what changed, how it changed, and what consequences followed—not whether creationists are willing to call the result “information”.
Here, the specific finding is an association between mobile DNA, expanding gene families and subsequent diversification. It should not be inflated into a claim that every extra receptor acquired a demonstrated new function, or that the asteroid impact directly produced particular beneficial mutations. Nevertheless, the study supplies evidence for a natural route connecting genomic change with evolutionary diversification, precisely where the creationist argument substitutes an assertion of impossibility.
For young-Earth creationists, there is the additional inconvenience of the timescale. This diversification followed an extinction event some 66 million years ago—thousands of times further into the past than their entire supposed history of the Universe allows. Ant evolution was already unfolding in a world unimaginably ancient by biblical standards. What emerges is a history of genetic change, environmental catastrophe and opportunities exploited by surviving lineages, without foresight or a predetermined destination.
In a recent paper published in Biocontaminant, a group of environmental and public health scientists from China and the United States warn of the growing threat to public health from a group of dangerous free-living single-celled amoebae, the most notorious of which is Naegleria fowleri, also known as the brain-eating amoeba.
This complex, eukaryotic organism bears all the hallmarks of what Discovery Institute fellows William A. Dembski and Michael J. Behe insist is compelling evidence for intelligent design — complex specified genetic information and irreducible complexity — so, if we accept their argument, we have to conclude that whatever designer they imagine is doing this designing must also be the one who designed these nasty little ways to make people sick and die by having their brains eaten, like in some grotesque zombie apocalypse.
N. fowleri normally lives in soil and water, where it feeds on bacteria and other micro-organisms, but if it manages to get into a victim’s nose it can track along the olfactory nerves to the brain, where it treats brain cells the way it treats soil-borne organisms and sets about eating them. Infections are almost invariably fatal. What makes them particularly dangerous is their ability to survive extreme conditions that would kill most micro-organisms, such as high temperatures and strong disinfectants like chlorine, so they can persist in water supplies that most people regard as safe.
An additional hazard is that these amoebae can also act as carriers for other pathogens such as Legionella pneumophila, Chlamydia, and Mycobacterium tuberculosis. By providing these pathogens with protection from disinfection, the amoeba can enhance their pathogenicity and prolong their survival in the environment.
It would be hard to find a better example than N. fowleri of what creationists insist must be intelligently designed, so it follows that there are probably few better examples of the sheer malevolent evil of any designer of such creatures, from the perspective of the humans infected with it. For creationists to retreat into the traditional excuse of blaming ‘the Fall’ is to abandon the claim that irreducible complexity and complex specified genetic information are definitive evidence of intelligent design, and to retreat instead into religious fundamentalism and Bible literalism.
10,000 years or so before creationism's little god created the small flat planet with a dome over it, thinking it was a universe, as described in the creation myth in the Bible, there was a mass extinction due to global climate change.
In addition to the loss of the Ice Age megafauna, such as the woolly mammoth, woolly rhinoceros, cave lions, etc. over most of Eurasia and North America when temperatures rose at the end of the last glaciation, we also lost a lot of the Ice Age-adapted plants.
But, because plants tend not to fossilise so readily as the bones of large mammals, we didn't know until now, just how extensive this loss was, and more importantly, what a similar rise in temperatures is going to mean for the extant flora.
To redress this gap, a team of researchers from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), Germany, have analysed DNA recovered from plant remains in the sediment of lakes in Siberia and Alaska. In doing so, they have discovered how the temperature affects the way plants interact, tending to support one another in cold weather and competing with one another in warm weather. A rise in ambient temperature meant increasing competition and loss of mutual support.
This article caught my eye because it concerns the birds in a wood which is local to me - Wytham Wood, near Oxford, to which I have licensed access. This is reputedly the most intensively studied area of woodland in the world, belonging, as it does, to Oxford University.
Wytham Woods form an iconic location that has been the subject of continuous ecological research programmes, many dating back to the 1940s. The estate has been owned and maintained by the University of Oxford since 1942. The Woods are often quoted as being one of the most researched pieces of woodland in the world, and their 1000 acres are designated as a Site of Special Scientific Interest.
The wooded parts of the Wytham Estate comprise ancient semi-natural woodland (dating to the last Ice Age), secondary woodland (dating to the seventeenth century), and modern plantations (1950s and 60s). The fourth key habitat is the limestone grassland found at the top of the hill. Other smaller habitats include a valley-side mire and a series of ponds.
The site is exceptionally rich in flora and fauna, with over 500 species of plants, a wealth of woodland habitats, and 800 species of butterflies and moths.
Through intensive observation over successive years, researchers are able to measure changes in behaviour of species such as the Great Tit, Parus major with some of the best examples of observational biology in the form of research papers. For example, a few years ago a team of researchers showed that the British race of Great tits were diverging from their European relatives with changes in the beaks probably reflecting the fact that we in Britain provide feeding stations for birds to sustain them through the winter much more frequently than other Europeans, so the British Great tits are evolving so they can get the food in the bird feeders in British gardens.
In the following article, ecologist, David López Idiáquez, a Postdoctoral Research Associate in Behavioural and Evolutionary Ecology, University of Oxford, explains how their research is measuring how Great tits are responding to climate change. His article is reprinted here from The Conversation under a Creative Commons license, reformatted for stylistic consistency, with photographs from Internet sources:
An interesting paper has just been published which illustrates how chaos theory and catastrophe theory are related and explain the appearance of 'punctuated equilibrium' in the fossil record. It concerns the small environmental change that can trigger a large phenotypic change in the growth and shape of fungal hyphae.
One of the more annoying things to emerge in evolutionary biology during the last 30 years or so is the idea that 'Punctuated Evolution' (PE) somehow either falsifies or replaces Darwinian evolution as the explanation for biodiversity. Of course, it does neither. The term was invented by Stephen J Gould and Niles Eldredge, to explain the appearance of sudden change in the geological column, where species appear to remain unchanged for prolonged periods of time, then change, in what, with the compression of time in the geological column, looks like instantaneously.
Sadly, the term quickly became entangled with both American nationalism and creationism; the latter because it appears to refute the person whom creationists think is the arch prophet of the 'evil' of evolution - Charles Darwin, the leading figure in creationist demonology - as though the entire body of evolutionary biology hangs on the authority of one 19th century biologist; the former because it appears to have replaced one of the most famous scientific theories with one 'discovered' by Americans, so asserting American pre-eminence in science.
Tell me about 'Punctuated Equilibrium'; who popularized the idea and the arguments for and against it.
Punctuated equilibrium is a theory in evolutionary biology that suggests that the tempo of evolution is not constant but rather characterized by periods of relatively rapid change (punctuation) interspersed with prolonged periods of stability (equilibrium). This concept was popularized by paleontologists Niles Eldredge and Stephen Jay Gould in their 1972 paper "Punctuated Equilibria: An Alternative to Phyletic Gradualism."
Arguments for punctuated equilibrium include:
Fossil Record: Eldredge and Gould argued that the fossil record often shows long periods of stasis, where species exhibit little morphological change over millions of years, followed by relatively rapid bursts of evolutionary change when new species appear.
Lack of Transitional Forms: They also pointed out that the fossil record frequently lacks the transitional forms predicted by gradualism, which suggests that evolution may occur in more rapid bursts.
Genetic Mechanisms: Some genetic models also support the idea of punctuated equilibrium, suggesting that small populations undergoing rapid change due to factors like genetic drift and founder effects can lead to rapid speciation.
Arguments against punctuated equilibrium include:
Lack of Evidence: Critics argue that punctuated equilibrium is based more on interpretation of the fossil record rather than direct evidence from genetic or ecological studies.
Sampling Bias: Some scientists suggest that the apparent gaps in the fossil record may be due to incomplete sampling rather than actual periods of stasis.
Mechanistic Explanation: Critics also question the mechanisms underlying punctuated equilibrium, arguing that it may be difficult to explain how rapid evolutionary change occurs in the absence of significant environmental pressures or genetic changes.
Overall, punctuated equilibrium remains a subject of debate within evolutionary biology, with proponents arguing that it provides a more accurate description of patterns of evolution observed in the fossil record, while critics suggest that it may overemphasize the importance of long periods of stasis and rapid bursts of change.
Figure 1. Flows of non-native insects between North America (NA), Europe (EU), and Australasia (AU). Numbers indicate the total count of species established from donor to recipient, with flow widths being proportional to these counts. Overlapping flows on the donor side indicate the fraction of species that established in both recipient regions.
It's an observable, and often regrettable fact of biology that the majority of invasive species tend to be from Europe into North America and Australia and not vice versa. That’s not to say there are no migrations the other way, but the distribution is highly asymmetric, so is unlikely to be due to chance alone.
There have been several attempts to explain this in terms of the North American and Australian environment being inherently more amenable to invasion, and the European environment being less so. However, historically, Europe has been repeatedly invaded by insect species from Asia, so the latter explanation is unlikely.
It is generally assumed that insects are spread inadvertently by trade in goods, when insects 'stow away' in packages, the holds of ships, etc., but research led by Dr. Rylee Isitt of the University of New Brunswick, and published in the journal NeoBiota, shows that after accounting for patterns of international trade, the number of insects that have spread from Europe into North America, Australia, and New Zealand far exceeds expectations.
The question is then, is there something different about European insects that makes them better at invading new territories; are they more numerous? Or is there something else at work here?
The same research found no evidence for these ideas:
Figure 2. Cumulative discoveries (observed and modelled) and establishments (modelled) of non-native insects exchanged between Europe (EU), North America (NA), and Australasia (AU) versus cumulative import value (inflation-corrected to 2020 British pounds sterling, billions), 1827–2014. Alternating background shading indicates decadal increments, with shading omitted prior to the 1940s for clarity.
So, what's going on?
Dr. Isitt and collaborators have proposed that the abundance of European insect invaders may be a result of deliberate introductions of non-native plants into Europe's colonies. Plants introduced into European colonies could have promoted the spread of European insects into North America and Australia by two different means.
This is, of course, consistent with a basic prediction of the Theory of Evolution by Natural Selection. If an environmental change creates an opportunity for a species to expand its territory, then it will expand into that new territory, where if there is any competition, natural selection will determine the outcome. However, if the change in the environment is the introduction of a food resource that was previously absent, there is unlikely to be much competition, so the invasive species gets a free ride.
And of course, as Europeans have colonised new lands such as North America, Australia and New Zealand, so they have taken their traditional staple food plants with them, created a perfect environment for European insects to tag along and become established just as the human colonists and their plants have.
The geographical exchange of non-native species can be highly asymmetrical, with some world regions donating or receiving more species than others. Several hypotheses have been proposed to explain such asymmetries, including differences in propagule pressure, source species (invader) pools, environmental features in recipient regions, or biological traits of invaders. We quantified spatiotemporal patterns in the exchange of non-native insects between Europe, North America, and Australasia, and then tested possible explanations for these patterns based on regional trade (import values) and model estimates of invader pool sizes. Europe was the dominant donor of non-native insect species between the three regions, with most of this asymmetry arising prior to 1950. This could not be explained by differences in import values (1827–2014), nor were there substantial differences in the sizes of modelled invader pools. Based on additional evidence from literature, we propose that patterns of historical plant introductions may explain these asymmetries, but this possibility requires further study.
Introduction
Non-native insects have been implicated in displacing native species, altering the composition of ecological communities, damaging economically important trees and food crops, vectoring diseases, and more (Kenis et al. 2009; Bradshaw et al. 2016). An intriguing aspect of insect invasions is that some regions appear to have donated disproportionately more non-native insects during biotic exchange than others. For example, considerably more phytophagous forest insects have invaded North America from Europe than the reverse (Niemelä and Mattson 1996.1), and Europe has contributed a large fraction of New Zealand’s non-native insect fauna (Edney-Browne et al. 2018). Consequently, the question of why such asymmetries may occur has fascinated ecologists for decades, with several mutually compatible hypotheses offered: (1) differences in the magnitude of invasion vectors, such as international trade, may lead to differences in the arrival and establishment rates of non-native species; (2) differences in the size of potential invader pools may drive differences in the numbers of species being donated to other regions; (3) environmental differences (e.g., climate and availability of host plants) in recipient regions may promote or inhibit invasion; and (4) biological traits of insects native to some regions may make them better at invading or competing than insects native to other regions (Vermeij 1991, 1996; Niemelä and Mattson 1996; Visser et al. 2016.1).
The latter two hypotheses are often tested on a single insect order or guild and at smaller spatial scales (e.g., Rigot et al. 2014; Guyot et al. 2015; Rassati et al. 2016.2), but less commonly on multiple insect orders and multiple geographical regions. Testing them requires regional knowledge of the nature of recipient environments and their ecological communities, and of the biological traits of the invaders, information that is often available only for certain regions or certain insect groups/guilds. The former two hypotheses are more approachable, given the availability of datasets on international trade, regional insect richness, and modelling approaches that can estimate invader pool sizes.
Our research goals were firstly to test for the existence of asymmetries in the cumulative numbers of insect invaders, across all taxa, exchanged between three world regions of interest: North America, Europe, and Australasia (limited to Australia and New Zealand). These regions were chosen due to their histories of anthropogenic interactions and exchange of species, existing literature suggesting asymmetrical exchange of insects between them (see above), and the availability of data. Secondly, if clear asymmetries were found, we aimed to determine if they could be explained by differences in propagule pressure (using the value of international trade as a proxy) or by differences in estimates of invader pool sizes. We did not statistically test hypotheses (3) and (4), above, but considered them as possible explanations for asymmetries that could not be explained by hypotheses (1) and (2).
It's good to see how the basic principles of environment-led evolution (which often starts with migration into new territory) underpins the observable phenomenon of invasive insect species and what governs their movements. Earth is, of course, a dynamic and changing place where these sorts of migrations in response to environmental change have been going on for hundreds of millions of years. Recently however, Man has become a major factor in this process, the consequences of which are still being played out. One thing we can be sure of though is that there is no place for supernatural magic in the explanation for it.
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As expected of scientific research papers, this one deals with events that occurred in that vast expanse of time before creationists think Earth was created, when 99.97% of Earth's history occurred.
This one, published open access in eLife, explains how the ancestors of modern elephants and their recently extinct relatives, the mammoths, got their long flexible trunks and used them for their unique feeding method.
The paper by lead author, Chunxiao Li, and colleagues from the Key Laboratory of Vertebrate Evolution and Human Origins of the Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China, and including Burt Wolff of the Department of Earth, Ocean and Atmospheric Science, Florida State University, Tallahassee, FL, USA and Fajun Sun of the Department Environmental Science & Technology, University of Maryland, MD, USA, "combines multiple analyses to reconstruct feeding behaviours in the extinct longirostrine elephantiforms - elephant-like mammals characterised by elongated lower jaws and tusks."
It seems that, as they grew larger, for reasons not yet fully understood, but possibly to give a larger 'vat' in which to ferment their high-cellulose diet, these early ancestors of the elephants had to evolve a longer jaw to reach the grasses and shrubs on which they grazed. The trunk extended as part of this process of facial elongation. This in turn created the opportunity for the end of the truck to play a part in holding the plants as they were cut off by the incisor teeth at the end of the lower jaw. This was more of an advantage in the open grasslands that Platybelodon inhabited, so, when climate change meant loss of habitat and eventual extinction for the two related gomphotheres, Platybelodon's prehensile trunk gave it enough advantage to survive.
A press release by eLife explains the research and its significance for understanding how elephants got their trunks:
A team of researcher from Utah University's Department of Watershed Sciences in Quinney College of Natural Resources and the Ecology Center, led by Jaron Adkins, has investigated why there is a rich diversity of species in some areas and a paucity of species in others. Not surprisingly, given what we know of how diversity evolves due to environmental selectors, they found a close link between diversity and the environment, especially rainfall, and the result of rainfall, or a lack of it - plant growth.
A Pharmacy shop sign displays the outside temperature of 46 Celsius degrees (114.8 F) in downtown Rome, July 18, 2023.
AP Photo/Domenico Stinellis
As I have commented before, probably the most dangerous delusion fostered by the Abrahamic religions, is that Earth was given to humankind for our exclusive use and that we are being watched over by a benevolent magic guardian in the sky who will ensure that no long-term harm will come to us and our planet. This delusion could well result in us making this planet, our life-support system in the cosmos, uninhabitable by all but a small number of species such as bacteria and cockroaches.
Fundamentalist 'loving' Christians jibber excitedly about the 'end times', looking forward to the day when their imaginary friend comes to Earth and kills everyone who disagrees with them so they can have everything for themselves, but the only end times we face are the end times for all of us, just assuredly as a space man systematically destroying his own spaceship.
So, what is causing the record temperatures we are experiencing this year, where records are not only being broken almost every day, but being broken by record margins? In the following article, reprinted from The Conversation, Andrew King, Senior Lecturer in Climate Science, The University of Melbourne gives six reasons for these record temperatures. His article is reprinted under a Creative Commons licence, reformatted for stylistic purposes:
Back in the late 1960's, when I was a student at Oxford Polytechnic (Now Oxford Brookes University) studying for an HNC in Applied Biology, one of the modules (on which apparently the National Council for Academic Awards (NCAA) insisted) was 'General Studies', i.e., anything which broadened our education away from the narrowness of a specialised subject, such as Applied Biology.
Part of that was an assignment to investigate an aspect of man-made environmental pollution, Rachal Carson's 'Silent Spring' being a recent publication and a nascent green movement beginning to emerge. The subject I decided on was to investigate what happened to the millions of tons of vulcanized rubber from road vehicle tyres that needed to be replaced annually because tyres wore away on the roads. It stood to reason that that rubber either entered the atmospheres as dust, or, more likely, got washed off the roads and into road-side ditches and eventually into the waterways and from there to the sea.
The question was, what effect did this fine rubber dust have on the environment and how much of it ended up in the food chain?
I was shocked to discover, after several days searching the literature available to me in the college library (if only we had had the Internet in those days!) that there was not a scrap of scientific data on the subject. There were no published papers on the question whatsoever. Either no-one had thought it worth investigating, no-one had identified the problem, or no-one was prepared to fund the research. And yet millions of tons of vulcanized rubber were being turned into tyres and from then into rubber dust on our roads, and it was all going somewhere, but no-one knew where!
In desperation, and with a project to complete, I abandoned my research and instead looked at the environmental effects of DDT, then extensively used as an insecticide, and about which some alarming news was emerging - extermination of brown pelicans in American lakes treated with DDT to kill mosquitoes, because DDT is adsorbed onto particulate matter which is ingested by the small organisms eaten by fish and so concentrated up the food chain, at the apex of which were brown pelicans; loss of peregrine falcons because DDT reduced egg shell thickness, leading to a loss of broods, again the result of DDT being concentrated up the food chain and killing the apex predators.
So, news that, some 54 years later, researchers at Griffin University, Australia, have published a paper in Environmental Science & Technology, dealing with a closely related problem - the problem of microplastics and tire [sic] wear products in urban stormwater.
Sadly, the research paper is behind a paywall, but a Griffin University news release explains the research and its significance:
In an example of how the environment, and in this case probably the availability of different food items, can cause changes on which natural selection can act, a study by an international team or reserchers led by Pablo Salmón of Lund University, Sweden, has shown that great tits, Parus major living in an urban environment have paler breasts than those living in a forest environment.
Although this is probably not an evolutionary change, i.e., a change in the frequency of alleles in the population gene pools, as the cause is probably dietary difference, it illustrates how an environmental change can produce changes in features on which natural selection can act to bring about true evolutionary changes, and so begin the process of allopatric speciation.
Of course, there will be creationists who will misrepresent the scientific fact of evolution, either deliberately, or mendaciously in order to mislead others, who will dismiss this as "not evolution", not for the reason given above but because "they're still great tits/still birds" and haven't grown a new structure or turned into an unrelated taxon.
The research is explained in a Lund University press release:
If you change an organism's environment, the Theory of Evolution by Natural Selection (TOE) predicts that the organism will evolve to fit into that changed environment. One such change could be the removal of an apex predator, as happened when humans erected the 'dingo fence', stretching more than 5,600 Km (about 3,500 miles) across Australia in the 1950, but was in a state of disrepair until 1975, which is thus the effective start of environmental isolation southeast of the fence.
The purpose of the fence was to protect domestic sheep from dingoes, Canis dingo, the wild Australian canid and only Australian placental mammal other than bats. Dingoes have been Australia's apex predator for some 10,000 years, maybe longer, so have been an important part of the ecosystem and the main, if not only, predator on red kangaroos, Osphranter rufus since then.
So, when wildlife to the southeast of the 'dingo fence' had their apex predator removed, the TOE predicts that there should be observable evolutionary change, and this is what a team of scientist led by Dr Rex Mitchel of the College of Science and Engineering, Flinders University, Adelaide, South Australia may have found when they studied the Red Kangaroos either side of the fence. Although, as they point out, evolutionary change in about 45 years, or about 17 red kangaroo generations, would be unusual and, with a limited dataset more work is needed to check that other factors are not the cause of the observed changes, for example, reduced stress in the protected area.
Four of the team: Vera Weisbecker, Associate Professor, Flinders University; Corey J. A. Bradshaw, Matthew Flinders Professor of Global Ecology and Models Theme Leader for the ARC Centre of Excellence for Australian Biodiversity and Heritage, Flinders University; Frédérik Saltré, Research Fellow in Ecology for the ARC Centre of Excellence for Australian Biodiversity and Heritage, Flinders University, and Dr D Rex Mitchell, have written about their research in The Conversation.
Their article is reprinted here under a Creative Commons licence, reformatted for stylistic consistency:
‘An exciting possibility’: scientists discover markedly different kangaroos on either side of Australia’s dingo fence
Australia’s dingo fence is an internationally renowned mega-structure. Stretching more than 5,600 kilometres, it was completed in the 1950s to keep sheep safe from dingoes. But it also inadvertently protects some native species.
This makes the fence an unintentional experiment in the relationship between predators and prey. Our new research examined how the fence affects a favourite prey of the dingo: red kangaroos.
We found young kangaroos on the side exposed to dingoes grew more quickly than their protected counterparts. This has potentially big repercussions for the health of these juveniles.
The merits of the dingo fence are hotly debated, and there have been calls to pull it down or move it. That’s why we must seek a better understanding of how the fence affects the animals that live along it.
Australia’s dingo fence runs for more than 5,600 kilometres.
Image source: Shutterstock
‘Stressful’ lives
The dingo fence, formally known as the “wild dog barrier fence”, runs through Queensland, New South Wales and South Australia. It protects sheep and cattle to the southeast.
Extensive fencing can fragment habitats and disrupt ecosystems. Maintaining the fence costs about A$10 million per year. For these and other reasons, some have suggested the fence be pulled down.
But how would removing the fence affect kangaroos that have lived without dingoes for up to 70 years? Our research sought to answer this question.
We assessed 166 red kangaroos from two isolated populations on either side of the fence in far northwest NSW. We did this using data collected as part of a licensed shooting program. We compared population size, age structure, sex ratio, growth rate and skull shape.
We expected kangaroos north of the fence – those hunted by dingoes – to differ from their dingo-free cousins to the south. That’s because their lives are more stressful, especially for young kangaroos and females that are killed by dingoes more often than adult males.
Female and young red kangaroos are targeted by dingoes.
Image source: Shutterstock
What we found
As anticipated, we found more young and female kangaroos in the dingo-protected population south of the fence. But the story is more complex than that.
Young kangaroos south of the fence, up to about the age of four years, grew more slowly than those in the north. They were substantially smaller and lighter than their dingo-exposed counterparts.
This raises an exciting possibility: that the growth of kangaroos south of the fence has slowed in the absence of the dingo threat.
But maybe there was just more plant food available in the north, where there are fewer kangaroos compared to the south. Was this the reason the northern kangaroos grew more quickly?
As it turns out, no. We assessed the vegetation on each side of the fence using a decade of satellite measurements. We found there was probably less, not more, food overall for kangaroos in the north compared to the south.
More detailed investigation is needed into whether the types of plants differed on each side of the fence. But our results suggest the different growth rates were driven by predators, not food availability.
There was probably less vegetation north of the dingo fence than in the south
Image source: Shutterstock
This raises important questions
The differences between populations are even more striking considering the dingo fence in the area we studied was in disrepair until 1975. Before then, dingoes and kangaroos probably moved freely. So the changes we observed could have come about in as little as 17 kangaroo generations.
This would be unusually fast for an evolutionary adaptation. Instead, we suspect it’s the result of a more immediate response to the absence of dingoes, such as lower concentrations of stress-related hormones. These affect the health of mammals, and might have affected kangaroo growth rates in this case.
After about the age of four, the protected kangaroos had caught up and were the same size as their unprotected counterparts. But the unprotected kangaroos would have invested a lot more bodily resources into growing so quickly.
This would have left less energy for the animals to develop important functions such as their immune or reproductive systems. Or they might have had less fat reserves.
Conversely, protected kangaroos might have been healthier, or more fertile, because of their slower growth rates.
The research raises questions about how mammals respond to changes such as the absence of dingoes.
Image source: Shutterstock
Understanding the mammal response
Our study involved only a single sample at one point in time. But it’s the first to comprehensively assess differences in a dingo prey species on either side of a fence.
Our results provide an insight into how prey populations might fare if the dingo fence is removed. But the implications are potentially even broader.
We must now investigate whether other native mammal species share similar differences across the fence. If so, this could help us predict how animals elsewhere in Australia are coping with rapid environmental change.
Vera Weisbecker, Associate Professor, Flinders University; Corey J. A. Bradshaw, Matthew Flinders Professor of Global Ecology and Models Theme Leader for the ARC Centre of Excellence for Australian Biodiversity and Heritage, Flinders University; Frédérik Saltré, Research Fellow in Ecology for the ARC Centre of Excellence for Australian Biodiversity and Heritage, Flinders University, and Rex Mitchell, Postdoctoral Fellow, Flinders University
Decommissioning the dingo barrier fence has been suggested to reduce destructive dingo control and encourage a free transfer of biota between environments in Australia. Yet the potential impacts that over a century of predator exclusion might have had on the population dynamics and developmental biology of prey populations has not been assessed. We here combine demographic data and both linear and geometric morphometrics to assess differences in populations among 166 red kangaroos (Osphranter rufus)—a primary prey species of the dingo—from two isolated populations on either side of the fence. We also quantified the differences in aboveground vegetation biomass for the last 10 years on either side of the fence. We found that the age structure and growth patterns, but not cranial shape, differed between the two kangaroo populations. In the population living with a higher density of dingoes, there were relatively fewer females and juveniles. These individuals were larger for a given age, despite what seems to be lower vegetation biomass. However, how much of this biomass represented kangaroo forage is uncertain and requires further on-site assessments. We also identified unexpected differences in the ontogenetic trajectories in relative pes length between the sexes for the whole sample, possibly associated with male competition or differential weight-bearing mechanics. We discuss potential mechanisms behind our findings and suggest that the impacts of contrasting predation pressures across the fence, for red kangaroos and other species, merit further investigation.
The dingo barrier fence extends from southeast Queensland to the Great Australian Bight in South Australia. The study location (black rectangle): Quinyambie and Mulyungarie stations are adjacent properties located on the western side of the South Australia–New South Wales border (black dotted line) and separated by the fence.
Changes in cranial shape throughout ontogeny in Osphranter rufus. Orbs represent cranial shape predicted for younger individuals. Mesh represents shape predicted for older individuals. Relative braincase size and incisor size become smaller during growth.
What is now needed is detailed DNA analysis of the two populations because any differences would be definitive evolutionary change.
That should be a small crumb of comfort for creationists who must continue to hope that no such differences are found in red Kangaroos or other wildlife either side if the dingo fence, but I wonder how many of them would be prepared to bet their house on the probability of none being found.
