Evolution of lacertid lizards
The Old-World clade of Lacertidae gained recently attention as a result of their newly discovered sistergroup relationship with the legless, burrowing Amphisbaenia. Lacertids can be subdivided into a Palearctic and an African radiation, with the latter showing an inverse latitudinal diversity gradient having the highest species numbers in arid and semiarid regions on both sides of the Equator. Our research focuses especially on the African clade, which we investigate both morphologically and ecologically and with special emphasis on the desert lacertids from the Sahara and the Kalahari/Namib. Desert lacertids show a remarkable degree of ecomorphological convergence, which might be induced, among other things, by changes in their life history as an evolutionary response to climate and habitat. Also, we are interested in the fossil history of the Lacertidae, which we use as additional evidence to decipher the clade’s patterns of diversification and to gain new calibration points for molecular clock studies.
Origin and evolution of the Amphisbaenia
The burrowing amphisbaenians are one of the greatest enigmas of Squamata, and only recently – also through studies from our lab – was it revealed that they share a common ancestry with the four-limbed, fully terrestrial lacertid lizards (see above). Next to working on their evolutionary origin, we are also concentrating on the ingroup evolution of Amphisbaenia. Current research in this area involves detailed osteological studies of all modern amphisbaenian genera, which we investigate using CT technology, and a careful reassessment of the amphisbaenian fossil record. In collaboration with the lab of Hussam Zaher in Sao Paulo, we combine this morphological information with molecular data in order to unravel the clade’s morphological evolution and biogeographic history. Preliminary data suggest that several of the supposedly “unique” amphisbaenian features evolved several times independently within the clade. In this context, we became also interested in other examples of body elongation and limb reduction, and the evolution of plasticity in the vertebral column.
Diversification of caenophidian snakes
Caenophidian snakes are the most speciose clade of Serpentes, and include all species that people would normally consider a “typical” snake. The Caenophidia appear to have diversified dramatically since the Oligocene, but the reasons for this diversification are poorly understood and have largely remained speculative. In a collaborative project with Jason Head from the University of Cambridge, we are currently assessing the fossil record of modern snakes in a quantitative framework, and try to test the different hypotheses that have been put forward to explain Caeonophidia’s apparent boost in Neogene diversification. In addition, we are investigating the morphology and evolution of selected clades of Colubroidea.
Middle ear evolution in diapsid reptiles
The evolution of the middle ear has been a long-time interest in the lab. While previous research has dealt with parareptiles and early amniotes, our focus is now on the Diapsida. To this day it is still unknown how often an impedance-matching middle ear evolved within the clade, which is why we track the evolution of this complex from the base of the clade up to its modern members. In this respect, we have also taken advantage of the great fossil vertebrate collection at the Museum für Naturkunde Berlin, particularly the Tendaguru dinosaurs, and recently studied in detail the braincase and inner ear structure of the ornithischian dinosaur Dysalotosaurus lettowvorbecki. So although dinosaurs are normally blacklisted in the lab, we are sometimes moving over to the dark side.
The Late Cretaceous sediments of Sudan are known to yield a fascinating variety of micro- and macrovertebrates, ranging from small salamanders up to giant crocodiles and dinosaurs. Also, some of the oldest and most diverse snake faunas have been reported from these deposits. Detailed information, however, has remained fragmentary, and only little is known about the environment in which these animals lived. In a collaborative field project together with David Evans (Royal Ontario Museum Toronto), Nicole Klein (Uni Bonn), Robert Bussert (TU Berlin) and our partner institutions in Sudan (Al Neelain University, Museum of Natural History Khartoum) we have been prospecting and excavating at various sites and formations in the Saharan desert of Sudan. We have so far completed two successful field seasons, during which we discovered new fossil-bearing localities and several new taxa. Whereas fossils from Sudan were previously only known from bonebeds, we now also discovered sites that preserve completely articulated skeletons.
Late Miocene Vertebrates of Arabia
In the Al Gharbia (western) region of the United Arab Emirates outcrop rocks of around 7 million years age, a time known as the late Miocene epoch. Work in the 1980s and 90s led by Andrew Hill (Yale University) and the late Peter Whybrow (Natural History Museum, London) led to the discovery and description of a wide range of animal fossils from this region. Since, 2003, a team led by Faysal Bibi (MfN), Andrew Hill (Yale), and Mark Beech (Abu Dhabi Tourism and Culture Authority) has more than doubled the previous findings and greatly expanded the number of sites. Our findings include skeletal remains of diverse mammals, fish, birds, and herps which are all in different stages of analysis, and are providing new information on the ancient climate, ecology, and biogeographic relationships of what is today the Arabian desert region. Click here for more info.
Physical environmental change has been proposed as one of the main drivers of mammalian evolution. Ecological traits modulate the response of organisms to such changes, potentially affecting their capability to shift their geographic distributions, the composition of community assemblages and even their speciation and extinction rates. We use ruminants — e.g. deer, antelopes, giraffes — as a model faunal set for exploring the connections between environmental change, ecological traits, and evolution. This includes a synthesis of both fossil and extant taxa into a single phylogenetic framework, and the calculation of phylogenetic community structure metrics to reconstruct the diversity dynamics (e.g. speciation, extinction patterns) of paleo-communities. The timing of main evolutionary and ecological events can then be compared to the ever-growing record of physical environmental change in order to establish correlations and test existing hypotheses on the relationships of environment and mammalian evolution.
We develped a new open-access database, the ecoClimate.org database, to enable researcher to use homogeneous climatic layers for working in macroecology and paleobiogeography. In ecoClimate.org there are GIS layers from 9 different climatic models with a cell resolution of 0.5 degrees, for the past (Pliocene, Late Glacial Maximum, Holocene), present (pre-industrial, historic, present), and future (4 different rcps) climatic scenarios.
Species Distribution Modeling
Ecological Niche Models (ENM) allow us to map the species geographic ranges and investigate the effects of climate changes and human impact on species potential distributions. We are collaborating with different international researchers to implement ENM at local and global scales for understanding extinction processes, migrations and the impact of current global changes.
[and under construction:]
Evolution and Paleoecology of African Antelopes
Paleo Food Webs