Dr Serjoscha Evers, from the Department of Geosciences at the University of Fribourg, was awarded a SNSF Ambizione grant for his groundbreaking research into the ?Macroevolutionary Patterns of Shape Evolution in Turtles,? a project that will run until 2025.
In this ambitious project - well worth the aptly named Ambizione grant it received - Dr Evers makes full use of his background as a palaeobiologist to study the evolution of shelled turtles through time and macroevolutionary events (such as the mass extinction that marked the end of the Cretaceous period, killing off 75% of plant and animal life on earth).
Whereas most evolutionary history of species has typically relied on the study of the morphological changes of a single body part from diverse groups, such as the skull of birds or mammals, Dr Evers rightly points out that an animal's body part does not evolve in a vacuum, but is dependent upon the changes taking place elsewhere in the anatomy. For instance, since the evolution of the limbs of an animal may permit it to move from an aquatic to a terrestrial living environment, this environmental change will probably also cause the animal to change its diet, resulting in a modification of its mandibles.
Not content to propose such a novel idea, Dr Evers also makes use of different data sets which are not usually brought together in order to gain a single “big picture” model of macroevolutionary patterns: he is studying turtles that appear as fossils (c. 20 species) as well as others that are still extant (c. 100 species), and will define the relationship and evolution between different turtle species (phylogeny) not only by way of analysing DNA samples, the traditional method which however also presents well-established problems, but also through an examination of turtles' shape with some cutting-edge CT scanning of the type on display here (left).
Why turtles, you ask? Because they present themselves as the logical choice for such an overarching study, notably due to their extremely long evolutionary history and the fact that they often appear as fossils, both of which may at least partly be explained by their hard protective shells. These may also form part of the reason why turtles have evolved in a very conservative way compared to other classes of animals: one simply has to think of the fact that a species of turtle tends to very much look like another type of turtle, whereas mammals are particularly morphologically diverse, being represented for instance by the Homo sapiens, the whale, or the horse. Turtles are also particularly good subjects to study macroevolutionary patterns of geological and climatic change because of their ecological diversity - they inhabit marine, freshwater and terrestrial spaces. You can see, on the right the differences between an aquatic turtle's flipper and a land turtle's hand.
What Dr Evers proposes in this study, then, is to trace the evolution of turtles' whole bodies, the rate at which this evolution takes place, as well as the relationship between the evolution of each body part and the rest of the body (coevolution), in order to understand how turtles evolved, and test specific theses, such as whether the selective survival of some species of turtles during the mass extinction at the end of the Cretaceous period was due to their eating hard-shelled food (durophagy). More than this, the research will also tackle some wider-ranging questions and hypotheses about macroevolution. One of these is for instance the basic question of how evolution really happens is it at a constant and relatively slow rate, as Darwin proposed, or does it rather happen in relatively short bursts of rapid evolution? It will be possible to correlate the changes in evolutionary rate compiled in this study with macroevolutionary influences, such as climate change or mass extinctions, and get answers this way. Another question of import is whether, and how, the modification of one part of the anatomy causes other body parts to evolve, or inversely imposes constraints on them (such as, presumably, the evolutionary conservatism of turtles because of their hard shell). Further, Dr Evers will test his hypothesis that parts of the anatomy that are presumably particularly important ecologically (e.g. the limbs for locomotion, or the mandibles for feeding) will show an accelerated evolution during macroevolutionary events such as mass extinctions.
After a prized M.Sc in Geological Sciences at LMU Munich and a distinguished D.Phil in Environmental Research from the University of Oxford, the University of Fribourg was very fortunate to attract Dr Evers to its Geosciences Department, first as a Postdoctoral Researcher in Professor Walter Joyce's SNSF project since 2019, and, since September 2021, as an Ambizione fellow.
Thinking of applying for Ambizione funding? The next deadline for application will be on 1 November 2022. Please contact us at email@example.com for any question, advice, or support you might need during the application process!
Want to know more about Dr Evers, his research, and turtles? The following articles are related to this project
Joyce WG, Mäuser M, Evers SW. 2021. Two turtles with soft tissue preservation from the platy limestones of Germany provide evidence for marine flipper adaptations in Late Jurassic thalassochelydians. PLoS ONE16(6): e0252355; doi: 10.1371/journal.pone.0252355
[this paper looks specifically at the hand anatomy of an extinct type of turtle to assess its ecology]
Bronzati M, Benson RBJ, Evers SW, Ezcurra MD, Cabreira SF, Choiniere J, Dollman KN, Paulina-Carabajal A, Radermacher V, Roberto-da-Silva L, Sobral G, Stocker MR, Witmer LM, Langer MC, Nesbitt SJ. 2021. Deep evolutionary diversification of semicircular canals in archosaurs. Current Biology 31(12): 2520– 2529; doi: 10.1016/j.cub.2021.03.086
[This article uses 3D shapes and statistical tools to look at ecomorphology and evolutionary rates. It is not on turtles, but shows well the type of research Dr Evers does]
Evers SW, Benson RBJ. 2019. A new phylogenetic hypothesis of turtles with implications for the number of evolutionary transitions to marine lifestyles supports an Early Cretaceous origin and rapid diversification of Chelonioidea. Palaeontology 62(1): 93–134; doi: 10.11117pala.12384
[This is one of Dr Evers's doctoral papers in which he derives a turtle tree of life, integrating a flurry ofinformation from 3D digitized turtles, including fossils. It received the Best Paper Award 2019 in the journal Palaeontology]