Lizards from cold climates may face rapid extinctions in next 60 years, study shows - via Herp Digest

by Dave Rogers, Nottingham Trent University

Lizards that produce live young are significantly more likely to be driven to extinction through climate change than those that lay eggs, new research suggests.

The study, involving Nottingham Trent University and the University of Lincoln, suggests that live-bearing lizards face high risks of extinction within the next 60 years, driven predominantly by rising temperatures.

Researchers investigated how strategies for reproduction that live-bearing (viviparous) or egg-laying (oviparous) modern lizards evolved in the past can affect their chance to survive ongoing climate change caused by humans.

As part of the work, the team argue they have confirmed the emerging 'cul-de-sac' theory, which suggests that live-bearing reproduction evolved in lizards that colonized cold climates, such as high elevations and latitudes.

This adaptation, however, is dragging them to extinction.

The theory—developed by NTU's Dr. Daniel Pincheira-Donoso—suggests that following colonization of those harsh environments, mothers 'retained' the eggs in their bodies to act as incubators, and this provided embryos with stable conditions of temperature and oxygen.

It is thought that, over time, this egg retention evolved into birthing live young.

Reproducing live young is not very effective in hot environments, however, and once reptiles evolve in this way, they remain 'trapped' in cold areas.

As climate warming rapidly progresses towards higher elevations and latitudes, the 'suitable' cold climates where live birthing species live will be pushed towards mountain tops and continent edges until lizards run out of space and are eventually wiped out.

The study looked at three groups of highly-diverse lizards from South America: one which only has viviparous species, one with only oviparous species, and one which has evolved both forms of reproduction.

To investigate whether ongoing climate change will cause extinctions predicted by the theory, the researchers used computational modeling of current climate change, combined with real data on the conditions that lizards live under.

Their team, led by Dr. Pincheira-Donoso, found that live-bearing species will displace towards the mountain tops at significantly faster speeds than egg-laying species—displacing at a rate of 0.3% of the current geographical range per year.

While this means that viviparous lizards will face high extinction risks within just six decades, oviparous species will remain largely unaffected. Of all the climatic factors studied, temperature was the dominant factor responsible for these extinctions.

"Human-induced climate change has forced the modern world to face one of the most severe periods of global-scale extinctions of species since life began," said researcher Dr. Daniel Pincheira-Donoso, a bioscientist at Nottingham Trent University.

He said: "Our results highlight the extent of the extinction crisis that modern biodiversity is currently facing. By 2080, more than half of the current 'cold lands' in the area we investigated in South America will have become warm, leading current resident species to extinction.

"Extinction risks are known to increase as a result of rapid climatic alterations and environmentally sensitive species traits that fail to adapt to those changes.

"Viviparous lizards appear to have undergone a 'double-edged adaptation' – life births evolved because it was the critical adaptation that reptiles needed to colonize cold climates, but it will also accelerate their extinctions.

"This work provides us with an opportunity to identify specific areas that need more urgent protection—such as high mountain elevations where extinction risks will concentrate.

"This phenomenon would apply to other reptiles, such as snakes, anywhere in the world.”

Researcher Manuel Jara, who was at the University of Lincoln when the work was carried out, added: "Live-bearing lizards are predicted to follow their dramatically shrinking cool habitats, increasing their risk of extinction."

More information: Manuel Jara et al. Alternative reproductive adaptations predict asymmetric responses to climate change in lizards, Scientific Reports (2019). DOI: 10.1038/s41598-019-41670-8

Journal information: Scientific Reports 

Pregnant fossil shows bird and crocodile ancestors gave birth to live young

A 245 million-year-old fossil is the first evidence of live births in one of the major groups of animals 
 

Stephan Lautenschlager
Thursday 16 February 2017 00:00 GM

Giving birth to live young is one of the traits we use to distinguish mammals from other animals. But certain kinds of lizards, snakes and amphibians, both living and extinct, also reproduce without laying eggs. In fact, live birth (or viviparity) has evolved more than 100 separate times in non-mammal species throughout history. It seems to have been a common reproductive strategy in particular for extinct aquatic reptiles, such as the fish-like ichthyosaurs, plesiosaurs and mosasaurs that lived at the same time as the dinosaurs.

But one group of animals known as Archosauromorpha, which includes crocodiles, birds and their ancestors the dinosaurs, has never been known to give birth – until now. A recently unearthed fossil, described in a new study by a team of scientists from China, the US, UK and Australia, shows that an ancient species of archosauromorph was giving birth about 245 million years ago.

The newly described specimen belongs to the species Dinocephalosaurus orientalis and was found in sediments from the early Triassic period in Yunnan Province, China. Dinocephalosaurus had a body length of around a metre but with an elongated neck of nearly twice that length. Its skull was relatively small and equipped with needle-like teeth adapted to catch fish and squids.

Continued

Ancient reptile's birth fossilised

By Ella Davies

Reporter, BBC Nature

A rare fossil has revealed how marine reptiles evolved to give birth to live young, scientists say.

The fossilised Chaohusaurus was discovered in central China's Anhui Province and includes the remains of three babies.

The animals lived 248 million years ago and are the earliest of the marine reptiles from the Mesozoic Era.

Experts suggest the position of the babies shows that giving birth to live young evolved on land, not in the sea.

The findings were published in the journal PLoS One.

Continued

An ancestor of snakes and lizards could have given birth to live young research shows

December 2013: Ancestors of snakes and lizards are likely to have given birth to live young, rather than laid eggs, and over time could have switched back and forth, say scientists.

“This is a very unusual and controversial finding, and a major overturn of an accepted school of thought,” said Alex Pyron from the George Washington University. “Before, researchers long assumed that the ancestor of snakes and lizards laid eggs, and that if a species switched to live birth, it never reverted back. We found this wasn’t the case.”

The findings push researchers’ understanding of the evolution of live birth a lot further back in time to 175 million years ago, showing that live birth has a much more ancient past as a strategy than previously believed. 

Continued

Fossil 'suggests plesiosaurs did not lay eggs' (via Dawn Holloway)

Scientists say they have found the first evidence that giant sea reptiles - which lived at the same time as dinosaurs - gave birth to live young rather than laying eggs.


They say a 78 million-year-old fossil of a pregnant plesiosaur suggests they gave birth to single, large young.

Writing in Science, they say this also suggests a degree of parental care.

The fossil, the first of a pregnant plesiosaur found, is at the US Natural History Museum of Los Angeles County.

After being excavated from a ranch in Kansas, US, the 5m-long fossil skeleton Polycotylus latippinus lay for two decades in the basement of the Los Angeles museum waiting to be chiselled from its rocky casing.

Immature skeleton
Two years ago when researchers began to piece the bones together they quickly realised that they were in fact dealing with two separate animals; an adult plesiosaur and a smaller juvenile.

The study's authors report that the juvenile was unlikely to have been eaten by the larger reptile because its tiny bones showed no evidence of bite marks, and its soft, immature skeleton suggested an animal only two-thirds of the way through its development.

For more than 200 years palaeontologists have speculated about how these colossal Cretaceous animals reproduced.

Many believed the plesiosaur was too cumbersome to drag itself up the beach to lay eggs, and so must have given birth to live young.

"[The find] provides the first direct evidence for live birth in plesiosaur," said palaeontologist Adam Smith from the Thinktank Centre, Birmingham Science Museum, UK.

"It's a very interesting find...[and] has been a long time coming."

Doting parents?
"The lack of fossil evidence of a pregnant plesiosaur was frustrating," explained the study's lead author Frank O'Keefe, from Marshall University in Huntington, US.

But he added: "What is really surprising about this fossil [is] that plesiosaurs [reproduce] differently to other marine reptiles... they give birth to one big baby instead of a lot of little babies."

By making comparisons with modern animals, such as whales, which give birth to larger, single young and then go on to care for them, Dr O'Keefe and his colleague, Luis Chiappe from the museum, attempt to infer something about plesiosaur behaviour.

In a similar way to land-dwelling dinosaurs, which are thought to have provided food for their nest-bound young, plesiosaurs, the authors suggest, might have been doting parents.

But Dr Smith was less convinced. He said that it was "certainly quite possible... but is very speculative".

P. latippinus's close relatives had three young at one time. It is possible the P. latippinus evolved to have only one, and care for it, he told BBC News, but more pregnant specimens are needed to be more certain of this.

Dr O'Keefe agreed, explaining that unlike on land where nests are preserved, studying the behaviour of ancient marine creatures is very difficult.

"When you get right down to it, behaviour doesn't fossilise, so we are stuck trying to make these inferences using modern animals where we can observe their behaviour," he explained.
http://www.bbc.co.uk/news/science-environment-14447187