Prestigious feature in journal Science on the reproduction of prehistoric flying reptiles

Reblogged from http://www.lincoln.ac.uk/news/2017/12/1421.asp

For many years, palaeontologists have been uncovering the mysteries of reptiles, dinosaurs and other animals which roamed the earth more than 150 million years ago.

Now, in a fascinating feature for one of the world’s leading academic journals, Science, Dr Charles Deeming from the University of Lincoln, UK, shines a light on the reproductive biology of the pterosaurs – winged reptiles that flourished throughout the age of dinosaurs.

Dr Deeming, an avian and reptilian reproduction specialist in the School of Life Sciences at the University has studied pterosaur reproduction for 12 years. He has reviewed new research by an international team of research led by Xiaolin Wang which examined a find of more than 200 pterosaur eggs and associated embryos belonging to a pterosaur species known as Hamipterus tianshanensis.

The study by Wang et al, published in the same edition of the journal, also investigated lines of arrested growth in bone sections, enabling the age of the animal to be estimated.

Writing in the Perspectives section of Science today (1st December 2017), Dr Deeming explained: “The fact that these flying reptiles even laid eggs was only recently confirmed in 2004, with the report of two eggs from China, and one from Argentina that contained well-developed pterosaur embryos.

“We now know that pterosaur eggs had soft, parchment like shells comparable to those laid by modern-day lizards. Wang et al’s study supports this interpretation, as does a previous study of a smaller number of eggs from the same site. The fossilised eggs show little evidence of shell calcification, and many show a dimpling of the shell as seen in dead, dehydrated lizard eggs.

“Due to the nature of the shells, scientists believe that pterosaur eggs were buried, precluding any form of contact incubation by the parents. Adults may have attended or defended nests, which would explain the presence of adult skeletons in the specimen reported by Wang et al.

Wang et al suggests that pterosaurs nested in colonies, but Dr Deeming suggests that appropriate nesting sites might have been in short supply. Like modern-day sea turtles, female pterosaurs may have inadvertently dug up existing nests, revealing previously buried eggs, which could result in them drying out.

Dr Deeming added: “It is rare in studies of pterosaurs to find data which can provide such an insight into the development of an extinct species from the earliest stage to maturity, but care is needed when assessing the developmental stage of embryos from what remains a limited data set.

“We now have many questions to address: were the eggs buried in sand or covered in vegetation? Was clutch size limited to two (as suggested by previous fossil finds)? Why are so many of the eggs showing signs of dehydration? Hopefully additional finds of equally spectacular fossils will help us answer such questions for pterosaurs and allow us to paint an increasingly complete picture of reproduction in these extinct species.”

Dr Deeming’s article is available to read in full online here: http://science.sciencemag.org/content/358/6367/1124

To access the research paper by Wang et al visit:
http://science.sciencemag.org/content/358/6367/1197

Lizards facing mass extinction

Climate change could lead to dozens of lizard species becoming extinct within the next 50 years, according to new research published this week.

Globally it has been observed that lizards with viviparous reproduction (retention of embryos within the mother’s body) are being threatened by changing weather patterns. A new study suggests that the evolution of this mode of reproduction, which is thought to be a key successful adaptation, could, in fact, be the species’ downfall under global warming.

Dr Daniel Pincheira-Donoso, from the School of Life Sciences at the University of Lincoln (UK), is the lead author of the paper detailing these amazing predictions, published in the scientific journal Global Ecology and Biogeography.

Researchers, including academics from the University of Exeter, investigated the hypothesis that historical invasions of cold climates by Liolaemus lizards – one of the most diverse groups of vertebrates on earth – have only been possible due to their evolution to viviparity (live birth) from oviparity (laying eggs). Remarkably, once these species evolve viviparity, the process is mostly irreversible and they remain restricted to colder climates.

By analysing this evolutionary transition in the lizards’ reproductive modes and projecting the future impact of climate change, the scientists discovered that increasing temperatures in the species’ historically cold habitats would result in their areas of distribution being significantly reduced. As a consequence, if global warming continues at the same rate, viviparous lizards are facing extinction in the next few decades.

Dr Daniel Pincheira-Donoso is one of the few people in the world who works on the ecology and evolution of these lizard species.

He said: “Lizards’ reproduction is largely linked to climatic temperatures and viviparous species are usually found in cold environments. When reptiles initially moved to colder areas they needed to evolve emergency measures to succeed in these harsh places, and we believe viviparity is one of these key measures. However, this transition is mostly one-directional and unlikely to be reversed. Rapid changes in the environment’s temperature would demand rapid re-adaptations to secure the species’ survival. Through the research we found that over the next 50 years nearly half of the area where these species occur may disappear, causing multiple extinction due to climate change.”

Overall the conclusion is that although viviparity allowed lizards in the past to invade and adapt to live in cold environments, and was therefore a key trait for evolutionary success, it will now ultimately lead to multiple events of extinction.

Dr Pincheira-Donoso said: “These lizards are one of the most diverse groups of animals, and are able to adapt to remarkably diverse conditions. Unfortunately, a reduction in cold environments will reduce their areas of existence, which means that their successful evolutionary history may turn into a double-edged sword of adaptation. Their extinction would be an atrocious loss to biodiversity.”

Dr Dave Hodgson, from the University of Exeter, said: “Climate change must not be underestimated as a threat to modern patterns of biodiversity. Our work shows that lizard species which birth live young instead of laying eggs are restricted to cold climates in South America: high in the Andes or towards the South Pole. As the climate warms, we predict that these special lizard species will be forced to move upwards and towards the pole, with an increased risk of extinction.”

The work formed part of Dr Pincheira-Donoso’s post-doctoral work, which was funded by the Leverhulme Trust.

The paper ‘The evolution of viviparity opens opportunities for a lizard radiation but drives it into a climatic cul-de-sac’ is published in the latest issue of the peer-reviewed journal Global Ecology and Biogeography.

Dr Pincheira-Donoso will now continue his research at the University of Lincoln by developing projects to investigate the ecology of evolutionary adaptations and its interactions with human-induced climate change.

To read the full paper go to http://onlinelibrary.wiley.com/doi/10.1111/geb.12052/abstract

Avian experts gather for first scientific conference of its kind

Scientists from across the world will gather at the University of Lincoln for the first ever scientific conference focussed on the construction and function of bird nests.

Running for three days from 10th September 2012 at the Think Tank, the conference has been organised by Dr Charles Deeming from the University’s School of Life Sciences, a renowned academic expert on avian reproductive biology.

The aim is to bring together scientists interested in how birds build their nests to provide the appropriate environment to incubate eggs and rear chicks.

Dr Deeming said: “Up to now nests have been perceived as just the receptacle for eggs and chicks, however, there is an increasing amount of information to suggest they are a lot more than that. One of the areas we are interested in is using the study of nests to understand climate change. The conference will explore how nests function, how they are constructed and the decision making process behind that.”

Delegates from 12 different countries, including Australia and North America, will be attending the conference.