Scientists complete conservation puzzle, shaping understanding of life on earth

An international team of scientists have completed the ‘atlas of life’ – the first global review and map of every vertebrate on Earth.

Led by researchers at the University of Oxford and Tel Aviv University, with contribution from the University of Lincoln, the 39 scientists have produced a catalogue and atlas of the world’s reptiles.

Tropiocolotes naterreri Simon
Tropiocolotes naterreri Simon

Maps showing the habitats of almost all birds, mammals and amphibians have been completed since 2006, but it was widely thought that many reptile species were too poorly known to be mapped. By linking this atlas with existing maps for birds, mammals and amphibians, the team has found many new areas where conservation action is vital.

Scientists have now produced the new reptile atlas, which covers more than 10,000 species of snakes, lizards and turtles/tortoises. The data completes the world map of 31,000 species of humanity’s closest relatives, including around 5,000 mammals, 10,000 birds and 6,000 frogs and salamanders.

The map has revealed unexpected trends and regions of biodiversity fragility. They include the Arabian Peninsula and the Levant, inland arid southern Africa, the Asian steppes, the central Australian deserts; the Brazilian caatinga scrubland, and the high southern Andes. The findings have been published in the journal Nature Ecology & Evolution.

Dr Daniel Pincheira-Donoso, an Evolutionary Biologist in the University of Lincoln’s School of Life Sciences, said: “After nearly ten years working as part of an international initiative to complete the atlas of living reptiles, we have been able to establish how the patterns of vertebrate global biodiversity are organised. We have then been able to proceed with analyses covering pretty much every single species of mammal, bird, amphibian and reptile in nature so that we can investigate the extent to which existing conservation schemes protect the stability of these organisms.

“Our work makes an important contribution to advancing the work that scientists around the world have already been doing to make informed decisions about areas of conservation priority and the allocation of funds, among other major modern challenges.”

Lead author Dr Uri Roll, now of the Ben Gurion University of the Negev, said: “Lizards especially tend to have weird distributions and often like hot and dry places, so many of the newly identified conservation priority areas are in drylands and deserts. These don’t tend to be priorities for birds or mammals, so we couldn’t have guessed them in advance.”

The maps have allowed conservationists to ask whether environmental efforts to date have been invested in the right way, and how they could be used most effectively.

Dr Richard Grenyer, Associate Professor in Biodiversity and Biogeography at Oxford University, added: “Thanks to tools like our atlas, scientists can for the first time look at the terrestrial Earth in its entirety, and make informed decisions about how to use conservation funding. This is not to say that the work done to date has been inaccurate: based on our knowledge at the time, conservationists have often made some really good decisions. But now conservation has the data and tools required to bring planning up to the same level as the businesses and governments who might have an eye on land for other uses. Maybe we’re actually a bit better, and we’re doing it in the open.”

The International Union for the Conservation of Nature (IUCN) are currently classifying the species featured in the map with a rating, from “critically endangered” to “least concern”. Once this work is complete, the interactive resource will be freely available for public access and use.

Its creation will allow a range of stakeholders, from countries, to conservation organisations, businesses and individuals, to understand the biodiversity in their surrounding environment, its importance and crucially, what they can do to better protect it.

Professor Shai Meiri from Tel Aviv University, who first planned the project more than ten years ago, explained: “Mapping the distributions of all reptiles was considered too difficult to tackle. But thanks to a team of experts on the lizards and snakes of some of the most poorly known regions of the world we managed to achieve this, and hopefully contribute to the conservation of these often elusive vertebrates that suffer from persecution and prejudice.”

How many ways are there to measure biological shape?

New research supports the use of cladistic data for quantifying the range of skull variation in a group of legless amphibians – the caecilians.

The rich and diverse array of biological shapes around us is astounding. Shape, however, may be an elusive concept. What do we actually measure, and how?

Dr Marcello Ruta, from the School of Life Sciences, University of Lincoln, UK, was part of a team who conducted an exploratory study of morphological disparity (i.e. range of shape variation), employing both traits that are used for reconstructing evolutionary family trees and geometric morphometric approaches. For their study, they used caecilians, a group of superficially earthworm-like amphibians distributed in the tropical regions of the southern hemisphere.

Cladistics is a branch of systematics (the field of biological classification) that seeks to reconstruct evolutionary family trees using information on characters (traits) observed in organisms and grouping them together based on whether or not they share unique characteristics inherited from a common ancestor. However, those traits hold great promise in that they can also be employed to quantify morphological differences, and these differences are the basis for analyses of shape disparity.

Traditionally, morphometric analyses can be used for quantifying disparity, for instance via linear measurements or constellations of data points, or landmarks. However, cladistic data offer a bonus, in that they can be used when measurements or landmarks cannot be readily applied to vastly divergent organisms.

Dr Ruta said: “Analyses of disparity requires a scalable comparative framework. The difficulties of applying geometric morphometrics to disparity analyses of groups with vastly divergent body plans are overcome partly by the use of cladistic characters. In all instances, we found no statistically significant difference. This suggests that cladistic and geometric morphometric data appear to summarise morphological variation in comparable ways. Our results support the use of cladistic data for characterising organismal disparity.”

The paper ‘Do cladistic and morphometric data capture common patterns of morphological disparity?’ has been published in the journal Palaeontology.

How the shape of eggs may explain evolutionary history of birds

The eggs of amniotes – mammals, reptiles and birds – come in a remarkable variety of shapes and sizes.

Evolutionary biologists have now addressed shape variety in terrestrial vertebrates’ eggs, pinpointing morphological differences between the eggs of birds and those of their extinct relatives, the theropod dinosaurs.

Researchers from the University of Lincoln, UK, examined eggshell geometry from the transition of theropods – a sub-order of the Saurischian dinosaurs – into birds, based on fossil records and studies of their living species.

The results suggest that the early birds from the Mesozoic (252 to 66 million years’ ago) laid eggs that had different shapes to those of modern birds. This may suggest that egg physiology and embryonic development was different in the earliest birds and so this may have implications for how some birds survived the Cretaceous-Palaeocene extinction event that wiped out the dinosaurs.

Their findings are published in the journal Royal Society Open Science.

Author Dr Charles Deeming, from Lincoln’s School of Life Sciences, explained: “These results indicate that egg shape can be used to distinguish between different types of egg-laying vertebrates. More importantly they suggest Mesozoic bird eggs differ significantly from modern day bird eggs, but more recently extinct Cenozoic birds do not. This suggests that the range of egg shapes in modern birds had already been attained in the Cenozoic.”

The origin of the amniotic egg (an egg which can survive out of water) is one of the key adaptations underpinning vertebrates’ transition from sea to land more than 300 million years ago. Modern amniotic eggs vary considerably in shape and size and it is believed this variety may reflect the different patterns of egg formation and development in these taxa.

Dr Deeming added: “From a biological perspective, it is self-evident that different egg shapes by birds, both past and present, might be associated with different nesting behaviours or incubation methods. However, hardly any research has been carried out on this topic and fossil data are insufficient to draw firm conclusions. We hope that future discoveries of associated fossil eggs and skeletons will help refine the general conclusions of this work.”

Dr Deeming and co-author Dr Marcello Ruta, also from the University of Lincoln, are now investigating how the highly variable amounts of yolk and albumen (egg white) in eggs of different species could be a possible determinant of bird egg shape.

D. Charles Deeming and Marcello Ruta ‘Egg shape changes at the theropod-bird transition, and a morphometric study of amniote eggs’ Royal Society Open Science
DOI: 10.1098/rsos.140311


Population density and testes size: more than meets the eye

A team of researchers has discovered that changes in population density can affect the size of animals’ testes and therefore impact on reproduction.

Across the animal kingdom, there is usually a positive relationship between sperm competing to fertilize eggs and the male reproductive effort in producing large ejaculates. This usually manifests in males evolving larger testes.

However, demographic and ecological processes may drastically alter the level of sperm competition and therefore the evolution of testes size.

A study has been conducted to find out whether testes size responds to natural fluctuations in density of 5 species of wild promiscuous voles.

The results have been published in Proceedings of the Royal Society B: Biological Sciences.

Females of many species mate with multiple males within a single reproductive cycle. When the sperm of two or more males compete for fertilisation, selection acts on a number of traits that enhance success such as sperm size and longevity. The number of sperm is key to success, which typically means males evolving larger testes.

Using long-term longitudinal data from five vole species in northern Finland, the team from the University of Jyvaskyla, Finland, University of Lincoln, UK, and the Finnish Forest Research Institute found that some species show the predicted increase in testes size with population density.

However, when density changed dramatically between years, this relationship can be reversed in some species.
Lead author Dr Ines Klemme from the University of Jyvaskyla, Finland, said: “Large changes in population density can affect competition not only for reproduction, but also for other resources such as space and food. These could potentially alter the ability of males to be able to produce reproductive tissue.”

Co-author Dr Carl Soulsbury, from the School of Life Sciences, University of Lincoln, added: “Knowing if testes size can respond to rapid and large natural changes in sperm competition is an important evolutionary question. The results suggest our understanding of sperm competition in fluctuating populations is still very limited.”

Ines Klemme, Carl D. Soulsbury, Heikki Henttonen ‘Contrasting effects of large density changes on relative testes size in fluctuating populations of sympatric vole species’ Proceedings of Royal Society B: Biological Sciences 2014 281, 20141291, published 13 August 2014

Video: The origin and evolution of an extraordinary lizard family

Life Sciences lecturer Dr Daniel Pincheira-Donoso and PhD student Manuel Jara have produced a video to showcase their research on the evolution of lizards.

Dr Daniel Pincheira-Donoso is one of the few people in the world who works on the ecology and evolution of the Liolaemus lizard species, exceptional and dominant components of the South American fauna.

An upcoming paper by Manuel reconstructs the evolutionary history of Liolaemus lizards based on the reconstruction of the climates that existed over the last 20-25 million years.

The video tells the story of their origins and dispersion.