Tag Archives: genomes

Research: Extinction of dinosaurs led to swift evolution of bird genomes

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About 66 million years ago, at the end of the Cretaceous period, a 10 km-wide asteroid struck Earth near what is now the town of Chicxulub in Mexico. The impact wiped out about 75% of Earth's animal and plant species, including groups such as non-avian dinosaurs and ammonites. A new study identifies key changes in bird genomes caused by the end-Cretaceous mass extinction that ultimately contributed to the remarkable diversity of modern birds.

This painting depicts an asteroid impact in the shallow tropical ocean of the sulfur-rich Yucatan Peninsula in what is now southeastern Mexico. The impact of this massive asteroid, which occurred about 65 million years ago, is believed to have wiped out the dinosaurs and many other species on Earth. The painting shows a Pterodactylus, a flying reptile with a wingspan of up to 50 feet, gliding above low tropical clouds. Image by Donald E. Davis/NASA.

“By studying the DNA of modern birds, we can detect patterns in gene sequences that changed shortly after one of the most significant events in Earth's history,” said Dr Jake Barb, from the University of Michigan.

“The signatures of these events appear to be imprinted in the genomes of survivors in ways that are detectable tens of millions of years later.”

An organism's genome is made up of four nucleotide molecules designated by the letters A, T, G, and C. The order of these nucleotides in the genome defines the blueprint of life.

The DNA code can evolve in ways that change the overall composition of DNA nucleotides across the genome.

These changes in composition are important in determining what genetic variations are possible and contribute to an organism's evolutionary potential, or ability to evolve.

Dr. Belf and his colleagues found that the mass extinction caused a change in nucleotide composition.

The researchers also found that these changes appear to be related to the birds' development as young birds, their adult size, and their metabolism.

For example, in the approximately 3 to 5 million years following the mass extinction at the end of the Cretaceous period, surviving bird lineages tended to decrease in body size.

The development of hatchlings has also changed, with more species becoming 'altricial'.

“This means that when they hatch they are still in a fetal state and need to be fed by their parents, and it may take several weeks for them to fledge,” Dr Barb said.

“Birds that are ready to fend for themselves immediately after hatching, like chickens and turkeys, are called 'precocious.'”

“We found that adult body size and pre-hatching developmental patterns are two important traits of bird biology that we can link to the genetic changes we are detecting.”

“One of the most important challenges in evolutionary biology and ornithology is unraveling the relationships between the major bird groups. The structure of the extant bird phylogenetic tree is difficult to determine.”

Over the past 15 years, researchers have been trying to solve this problem by applying increasingly large genomic datasets.

So far, they have used genomic data to study the evolution of bird genomes using statistical models based on strong assumptions.

These traditional models allow researchers to reconstruct the history of genetic change, but they typically assume that the makeup of DNA, i.e. the proportions of A, T, G and C nucleotides, remains constant throughout evolutionary history.

The study authors developed software tools to more closely track DNA composition over time and across different branches of the tree of life.

This tool allowed us to relax the assumption that DNA's composition is constant.

“This allows us to vary our models of DNA evolution across the evolutionary tree and identify places where there may have been changes in DNA makeup,” said Professor Steven Smith, from the University of Michigan.

“In this new study, these changes were clustered within about five million years of the end-Cretaceous mass extinction,” Dr Belff added.

This approach also allowed the team to estimate which bird traits are most closely associated with changes in DNA composition.

“This is an important type of genetic change that we think is associated with mass extinctions,” Dr Barb said.

“To our knowledge, changes in DNA composition have never before been so clearly linked to the end-Cretaceous mass extinction.”

“We know that mass extinctions can have dramatic effects on biodiversity, ecosystems and the forms of life,” said Professor Daniel Field, from the University of Cambridge.

“Our study highlights that these extinction events can have even larger effects on organismal biology by altering key aspects of genome evolution.”

“This study improves our understanding of the dramatic biological impact of mass extinction events and highlights that the mass extinction that wiped out the giant dinosaurs was one of the most biologically consequential events in the entire history of the Earth.”

By relaxing typical assumptions used in evolutionary biology, the researchers are developing more nuanced insights into the sequence of events in birds' early history.

“We haven't typically thought of changes in DNA configurations and models across the tree of life as changes that indicate something interesting happened at a particular time and place,” Prof Smith said.

“This study shows that we've probably missed something.”

of study Published in the journal Scientific advances.

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Jacob S. Belf others2024. Genomic and life-history evolution link bird diversification and the end-Cretaceous mass extinction. Scientific advances 10(31); doi: 10.1126/sciadv.adp0114

This article is a version of a press release provided by the University of Michigan.

Source: www.sci.news

The genomes of the greater bilby and the kobilby were sequenced by researchers

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Working with Indigenous rangers and conservation managers, University of Sydney And elsewhere, they sequenced the genomes of living organisms. Greater Bilby (Macrotis lagotis) And then it went extinct Lesser Bilby (Macrotis leuca).

Greater Bilby (Macrotis lagotis), 1988. Image credit: Queensland Government/CC BY 4.0.

The bilby is a unique marsupial and the only member of its family. Sugar gliderThese include the extant greater bilby and the extinct kobilby.

These animals are culturally significant to Aboriginal Australians and their common name is of Yuwaaraai origin. Bilba.

Bilbies were once an important source of meat for the desert people and their prized long black tails with white fluffy tips were used in cultural practices linked to deep symbolism of love and marriage.

Aboriginal knowledge, bilby song lineages, rituals and stories exist across Australia, connecting places and people, and even in areas where bilbies are now locally extinct, strong connections with the species continue.

The loss of indigenous knowledge and land management practices due to species decline is recognised as a threat to the survival of bilbies in the area.

Historically, the greater bilby was widespread, distributed across both arid and temperate regions, while the kobilby was restricted to the desert.

The decline of both bilby species has been attributed to the introduction of wild pests into Australia by European settlers, particularly predation by cats and foxes, competition with European rabbits, and changes in cultural fire practices.

Sadly, the Lesser Bilby is now extinct, having last been reported alive in 1931, although it may have survived in some desert areas until the 1960s and was well known to indigenous people of the Central Desert.

“The greater bilby reference genome is one of the highest quality marsupial genomes to date and is presented as nine segments representing each of the bilby chromosomes,” said Professor Carolyn Hogg from the University of Sydney.

“It provides insights into biology, evolution and population management.”

Professor Hogg and his colleagues used DNA from zoo animals to sequence the greater bilby's genome.

They also created the first genome of the extinct lesser bilby from the skull of a specimen collected in 1898.

“This research helps us understand what gives bilbies their unique sense of smell and how they survive in the desert without drinking water,” Prof Hogg said.

“Importantly, this genome is being used to manage bilby metapopulations in zoos, fenced reserves and islands.”

“By selecting individuals for transplant and release, we can maximize genetic diversity and improve the population's ability to adapt to a changing world.”

The authors also used the bilby genome to develop a more accurate fecal testing method to complement existing traditional land use practices by Indigenous rangers.

“We know a lot about bilbies – where they live, what they eat and how to track them,” says Scott West, a ranger at Kiwirrkurra Aboriginal Reserve in Western Australia.

“It's great to use an iPad for mapping and a camera for surveillance.”

“DNA studies will also help us to understand if the bilbies are related, where they come from and how far they may have migrated.”

“By using old and new methods together we can get useful information about bilbies and how to care for them – it's a two-way science.”

of result Published in the journal Natural Ecology and Evolution.

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CJ Hogg othersCombining genomes of extant and extinct bilbies with Indigenous knowledge will improve conservation of Australia's native marsupials. Nat Ecol EvolPublished online July 1, 2024; doi: 10.1038/s41559-024-02436-2

Source: www.sci.news

Study finds that butterfly and moth genomes have remained remarkably stable over 250 million years of evolution

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This stability exists despite the incredible diversity in wing patterns, sizes, and caterpillar morphology across more than 160,000 species worldwide today, according to one study. new paper It was published in the magazine natural ecology and evolution.

lissandra belargas. Image credit: Eric Silvestre.

Butterflies and moths (in order) Lepidoptera) make up 10% of all described animal species and are extremely important pollinators and herbivores in many ecosystems.

In a new study, Professor Mark Blaxter and colleagues from the Wellcome Sanger Institute set out to understand the processes driving the evolution of chromosomes in this highly diverse group.

They analyzed and compared more than 200 high-quality chromosome-level genomes of butterflies and moths.

They identified 32 ancestral chromosomal components; Merian element Thanks to the work of pioneering 17th century entomologist Maria Sibylla Merian, most butterfly and moth species have remained intact since their last common ancestor more than 250 million years ago.

With the exception of a single ancient fusion event between two chromosomes that led to the 31 chromosomes found in most species today, the chromosomes of most modern species correspond directly to these ancestral Merian elements.

Researchers discovered that not only are chromosomes incredibly stable, but the order of genes within them is also stable.

They discovered several species with small changes, mainly involving the fusion of small autosomes and sex chromosomes. This highlights the role of chromosome length as a driver of evolutionary change.

However, scientists believe that the blue butterfly (lissandra) and the group containing cabbage butterflies (Pieris) ignored these genomic structure constraints.

These groups underwent large-scale chromosomal reshuffling, including large-scale chromosome reshuffling through chromosome breakage and fission and fusion.

This study improves our understanding of the factors that lead to genetic diversity in these insects. This will guide efforts to protect and conserve specific species facing unique challenges and environmental changes related to climate change.

“The chromosomes of most butterflies and moths living today can be directly traced back to 32 ancestral Merian elements that existed 250 million years ago,” said Dr. Charlotte Wright, researcher at the Wellcome Sanger Institute. said.

“It is surprising that even though the species has diversified extensively, its chromosomes have remained surprisingly intact.”

“This calls into question the idea that stable chromosomes may limit species diversification. Indeed, this feature may be the basis for building diversity. We We hope to find clues about rare groups that have circumvented these rules.”

“Studies like this that allow us to delve into these evolutionary processes are only possible through efforts like the Darwin Tree of Life Project, which generate high-quality, publicly available genome assemblies,” Blaxter said. the professor said.

“We are stepping up these efforts with Project Psyche, where we aim to sequence all 11,000 butterfly and moth species in Europe in collaboration with collaborators across the continent.”

“As important pollinators, herbivores, and food sources in a variety of ecosystems, and as powerful indicators of ecosystem health, a deeper understanding of the biology of butterflies and moths through Project Psyche will This will be useful for future research on adaptation and speciation for biodiversity conservation.”

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CJ light other. Comparative genomics reveals the dynamics of chromosome evolution in Lepidoptera. Nat Ecole Evol, published online on February 21, 2024. doi: 10.1038/s41559-024-02329-4

Source: www.sci.news