Heath goannas - a species of giant, scavenging lizard - act as natural clean-up crews by clearing maggot-ridden animal carcasses from the landscape.

The theory of coevolution says that when closely interacting species drive evolutionary changes in each other this can lead to speciation - the evolution of new species. But until now, real-world evidence for this has been scarce.

Now a team of researchers has found evidence that coevolution is linked to speciation by studying the evolutionary arms race between cuckoos and the host birds they exploit.

Bronze-cuckoos lay their eggs in the nests of small songbirds. Soon after the cuckoo chick hatches, it pushes the host’s eggs out of the nest. The host not only loses all its own eggs, but spends several weeks rearing the cuckoo, which takes up valuable time when it could be breeding itself.

Each species of bronze-cuckoo closely matches the appearance of their host’s chicks, fooling the host parents into accepting the cuckoo.

The study shows how these interactions can cause new species to arise when a cuckoo species exploits several different hosts. If chicks of each host species have a distinct appearance, and hosts reject odd-looking nestlings, then the cuckoo species diverges into separate genetic lineages, each mimicking the chicks of its favoured host. These new lineages are the first sign of new species emerging.

The study is published today in the journal Science.

“This exciting new finding could potentially apply to any pairs of species that are in battle with each other. Just as we’ve seen with the cuckoo, the coevolutionary arms race could cause new species to emerge - and increase biodiversity on our planet,” said Professor Kilner in the University of Cambridge’s Department of Zoology, a co-author of the report.

The striking differences between the chicks of different bronze-cuckoo lineages correspond to subtle differences in the plumage and calls of the adults, which help males and females that specialise on the same host to recognise and pair with each other.

“Cuckoos are very costly to their hosts, so hosts have evolved the ability to recognise and eject cuckoo chicks from their nests,’’ said Professor Naomi Langmore at the Australian National University, Canberra, lead author of the study. 

She added: “Only the cuckoos that most resemble the host’s own chicks have any chance of escaping detection, so over many generations the cuckoo chicks have evolved to mimic the host chicks.”

The study revealed that coevolution is most likely to drive speciation when the cuckoos are very costly to their hosts, leading to a ‘coevolutionary arms race’ between host defences and cuckoo counter-adaptations.

A broad scale analysis across all cuckoo species found that those lineages that are most costly to their hosts have higher speciation rates than less costly cuckoo species and their non-parasitic relatives.

“This finding is significant in evolutionary biology, showing that coevolution between interacting species increases biodiversity by driving speciation,” said Dr Clare Holleley at the Australian National Wildlife Collection within CSIRO, Canberra, senior author of the report.

The study was made possible by the team’s breakthrough in extracting DNA from eggshells in historical collections, and sequencing it for genetic studies.

The researchers were then able to combine two decades of behavioural fieldwork with DNA analysis of specimens of eggs and birds held in museums and collections.

The study involved an international team of researchers at the University of Cambridge, Australian National University, CSIRO (Australia’s national science agency), and the University of Melbourne. It was funded by the Australian Research Council.

Reference: Langmore, N.E. et al: ‘Coevolution with hosts underpins speciation in brood-parasitic cuckoos.’ Science, May 2024. DOI: 10.1126/science.adj3210

Adapted from a press release by the Australian National University.

Two decades of cuckoo research have helped scientists to explain how battles between species can cause new species to arise

This exciting new finding could potentially apply to any pairs of species that are in battle with each other...the coevolutionary arms race could cause new species to emerge - and increase biodiversity on our planetRebecca KilnerMark LethleanMale wren (left) brings food to a cuckoo fledgling (right)

The text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright ©University of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

YesLicence type: Attribution-Noncommerical

A study involving the University of Cambridge has used virtual recreations of the earliest animal ecosystems, known as marine animal forests, to demonstrate the part they played in the evolution of our planet.

Using state-of-the-art computer simulations of fossils from the Ediacaran time period - approximately 565 million years ago - scientists discovered how these animals mixed the surrounding seawater. This may have affected the distribution of important resources such as food particles and could have increased local oxygen levels.

Through this process, the scientists think these early communities could have played a crucial role in shaping the initial emergence of large and complex organisms prior to a major evolutionary radiation of different forms of animal life, the so-called Cambrian ‘explosion’.

Over long periods of time, these changes might have allowed life forms to perform more complicated functions, like those associated with the evolution of new feeding and movement styles.

The study was led by the Natural History Museum and is published today in the journal Current Biology.

Dr Emily Mitchell at the University of Cambridge’s Department of Zoology, a co-author of the report, said: “It’s exciting to learn that the very first animals from 580 million years ago had a significant impact on their environment, despite not being able to move or swim. We’ve found they mixed up the water and enabled resources to spread more widely - potentially encouraging more evolution.”

Scientists know from modern marine environments that nutrients like food and oxygen are carried in seawater, and that animals can affect water flow in ways that influence the distribution of these resources.

To test how far back this process goes in Earth’s history, the team looked at some of the earliest examples of marine animal communities, known from rocks at Mistaken Point, Newfoundland, Canada. This world-famous fossil site perfectly preserves early life forms thanks to a cover of volcanic ash (sometimes referred to as an ‘Ediacaran Pompeii’).

Although some of these life forms look like plants, analysis of their anatomy and growth strongly suggests they are animals. Owing to the exceptional preservation of the fossils, the scientists could recreate digital models of key species, which were used as a basis for further computational analyses.

First author Dr Susana Gutarra, a Scientific Associate at the Natural History Museum, said: “We used ecological modelling and computer simulations to investigate how 3D virtual assemblages of Ediacaran life forms affected water flow. Our results showed that these communities were capable of ecological functions similar to those seen in present-day marine ecosystems.”

The study showed that one of the most important Ediacaran organisms for disrupting the flow of water was the cabbage-shaped animal Bradgatia, named after Bradgate Park in England. The Bradgatia from Mistaken Point are among some of the largest fossils known from this site, reaching diameters of over 50 centimetres.

Through their influence on the water around them, the scientists believe these Ediacaran organisms might have been capable of enhancing local oxygen concentrations. This biological mixing might also have had repercussions for the wider environment, possibly making other areas of the sea floor more habitable and perhaps even driving evolutionary innovation.

Dr Imran Rahman, lead author and Principal Researcher at the Natural History Museum, said: “The approach we’ve developed to study Ediacaran fossil communities is entirely new in palaeontology, providing us with a powerful tool for studying how past and present marine ecosystems might shape and influence their environment.”

The research was funded by the UK Natural Environment Research Council and the US National Science Foundation.

Reference: Gutarra-Diaz, S.“Ediacaran marine animal forests and the ventilation of the oceans.” May 2024, Current Biology. DOI: 10.1016/j.cub.2024.04.059

Adapted from a press release by the Natural History Museum

3D reconstructions suggest that simple marine animals living over 560 million years ago drove the emergence of more complex life by mixing the seawater around them

It’s exciting to learn that the very first animals from 580 million years ago had a significant impact on their environment, despite not being able to move or swim.Emily MitchellHugo Salais, Metazoa StudioArtistic recreation of the marine animal forest

The text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright ©University of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

YesLicence type: Attribution-Noncommerical

Researchers have evaluated different types of pig farming – including woodland, organic, free range, RSPCA assured, and Red Tractor certified, to assess each systems’ impact across four areas: land use (representing biodiversity loss), greenhouse gas emissions, antibiotics use and animal welfare. Their study concludes that none of the farm types performed consistently well across all four areas – a finding that has important implications for increasingly climate conscious consumers, as well as farmers themselves.

However, there were individual farms that did perform well in all domains, including an indoor Red Tractor farm, an outdoor bred, indoor finished RSPCA assured farm and fully outdoor woodland farm. “Outliers like these show that trade-offs are not inevitable,” said lead author Dr Harriet Bartlett, Research Associate at the University of Oxford's Smith School of Enterprise and the Environment, who was formerly at the University of Cambridge.  

“Somewhat unexpectedly we found that a handful of farms perform far better than average across all four of our environmental and welfare measures,” added senior author Andrew Balmford, Professor of Conservation Science at the University of Cambridge. However, none of the current label or assurance schemes predicted which farms these would be.

“The way we classify farm types and label pork isn’t helpful for making informed decisions when it comes to buying more sustainable meat. Even more importantly, we aren’t rewarding and incentivising the best-performing farmers. Instead of focusing on farm types or practices, we need to focus on meaningful outcomes for people, the planet and the pigs – and assess, and reward farms based on these,” said Bartlett.

The findings also show that common assumptions around food labelling can be misplaced. For instance, Organic farming systems, which consumers might see as climate and environmentally friendly, have on average three times the CO2 output per kg of meat of more intensive Red Tractor or RSPCA assured systems and four times the land use. However, these same systems use on average almost 90% fewer antibiotic medicines, and result in improved animal welfare compared with production from Red tractor or RSPCA assured systems.

The way we classify livestock farms must be improved, Bartlett says, because livestock production is growing rapidly, especially pork production, which has quadrupled in the past 50 years and already accounts for 9% of greenhouse gas emissions from livestock. Pig farming also uses more antibiotics than any other livestock sector, and 8.5% of all arable land.

“Our findings show that mitigating the environmental impacts of livestock farming isn’t a case of saying which farm type is the best,” said Bartlett. “There is substantial scope for improvement within types, and our current means of classification is not identifying the best farms for the planet and animals overall. Instead, we need to identify farms that successfully limit their impacts across all areas of societal concern, and understand, promote and incentivise their practises.”

The study reached its conclusions using data from 74 UK and 17 Brazilian breed-to-finish systems, each made up of 1-3 farms and representing the annual production of over 1.2 million pigs. It is published today in the journal Nature Food.

“To the best of our knowledge, our dataset covers by far the largest and most diverse sample of pig production systems examined in any single study,” said Bartlett.

James Wood, Professor of Equine and Farm Animal Science at the University of Cambridge, commented: “This important study identifies a key need to clarify what different farm labels should indicate to consumers; there is a pressing need to extend this work into other farming sectors. It also clearly demonstrates the critical importance that individual farmers play in promoting best practice across all farming systems.”

Trade-offs in the externalities of pig production are not inevitable was authored by academics at the University of Oxford, University of Cambridge and the University of São Paulo.

The research was funded by the Biotechnology and Biological Sciences Research Council (BBSRC).

Reference: Bartlett, H.,‘Trade-offs in the externalities of pig production are not inevitable.’ Nature Food, April 2024. DOI: 10.1038/s43016-024-00921-2

Adapted from a press release by the University of Oxford.

Farmers don’t have to choose between lowering environmental impact and improving welfare for their pigs, a new study has found: it is possible to do both. But this is not reflected in the current food labelling schemes relied on by consumers.

The way we classify farm types and label pork isn’t helpful for making informed decisions when it comes to buying more sustainable meat.Harriet BartlettCharity Burggraaf/ GettyTwo pigs on a farm

The text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright ©University of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

YesLicence type: Attribution-Noncommerical