PD Dr. Anneke H. van Heteren
Section Mammalogy
Head of Section Mammalogy
curator
Research
How organisms respond to and adapt to their abiotic and biotic surroundings is essential for understanding ecology and evolution. Form and associated function are the means by which organisms interact with their environment. As a result, research in this area is essential for a comprehensive understanding of evolution, organismal function and the ecology of life, as well as biodiversity.
Fossils provide our only direct window into evolutionary processes in the distant past. As such, a profound knowledge of fossils and their position and role in the earth’s palaeoecosystems is crucial for expanding our understanding of the development of modern biodiversity and, arguably, its future. Phenomics is the systematic study of phenotypical organismal traits dependent on large amounts of phenotypic data. This approach offers potent and versatile tools, such as geometric morphometrics and microstructure analysis. These tools enable the representation of shape in statistically robust mathematical models, addressing morphological variation and functional morphology across all bio-systematic levels, as well as within ontogenetic and evolutionary dimensions.
In this context, we delve into various subjects. One aspect involves comprehending how squirrels adapt to seasonality, climate and competition. Another area of research involves comprehending the population dynamics of locally endangered edible dormice. We are a dynamic team with a growing list of publications.
Red squirrel ecology: Adaptations to seasonality, climate and competition
Common grey squirrels (Sciurus caroliniensis) are an invasive species in Europe. They tend to outcompete red squirrels (Scuirus vulgaris) which could disappear from Europe within decades. This research programme is important and urgent, because understanding the processes that cause plastic changes in their bones and comprehending their adaptive flexibility will advance present and future nature conservation projects. Our preliminary finite element analyses on the humeri show that there are large morphological differences within a single subspecies that could greatly affect interspecific biomechanical comparisons. Likewise, preliminary microstructure analyses show that bone microarchitecture parameters, such as bone volume, differ significantly between individuals that died in different seasons, which is strongly suggestive of intraindividual changes throughout the year, and which might be caused by seasonal dietary fluctuations.
We gather numerical micro- and macroanatomical data from an extensive dataset and perform a statistical evaluation to understand the response of squirrel bone to climate and interspecies competition at the individual, population and evolutionary levels. We amalgamate finite element data, geometric morphometrics, histology, Raman spectroscopy and microstructure data.
Edible dormouse ecology: Linking morphology and genetics
The edible dormouse (Glis glis) is the largest dormouse (family Gliridae) and the only extant species in the genus Glis. It is native to the deciduous and mixed forest zone of Europe and south-western Asia. The species is vulnerable to forest fragmentation and is of conservation concern along its northern range, which includes Germany, where populations are fragmented due to deforestation and poor forest management. The edible dormouse has deeply divergent phylogenetic lineages and represents a rare case (at least among mammalian species) of sympatric and allopatric reproductive isolation. This project initially documents phenotypic and genotypic variability of the edible dormouse in the Alpine foothills from the Late Pleistocene onward. The faunas of alpine areas are particularly meaningful for determining general principles of biodiversity dynamics because the Alps are particularly affected by changes associated with climate change, including increased human land use. Subsequently, this project will be expanded over larger geographic and temporal scales.
Marine mammal palaeoecology
In 2021, I set up field work in Hengchun, southern Taiwan, in collaboration with Dr. Yang (National Museum of Natural Science, Taiwan). Dr. Yang and I co-lead an international excavation team of over 35 technicians, students, and volunteers. We excavated about a nearly complete fossil baleen whale. This is the most complete fossil whale found, not only in Taiwan, but in the whole of Southeast Asia, and the only complete whale fossil from the Pleistocene (since such geologically young material usually still lies on the sea floor). The specimen is possibly a grey whale, but the tympanic bullae were not preserved, so we will use geometric morphometrics on the mandible and the scapula, as well as peptide mass finger printing to confirm this species attribution. Bones of two additional marine mammals have been found. These latter two are possibly dolphins, but they are still mostly in the sediment, so a more precise determination is not possible now. Furthermore, additional marine mammal bones have been found suggesting that this might be a cetacean Lagerstätte.
The Hengchun fossil site is an exclusive opportunity to study an assemblage of multiple Pleistocene species of marine mammals. We describe their morphology in detail, including the relative sizes of bones, which is impossible on the isolated Pleistocene marine mammal material that has been found to date. We compare them with their extant counterparts in the light of environmental change. We also do taphonomical and palaeopathological studies to determine whether these animals possibly died in a single event or whether they were deposited here over a longer period. Additionally, dating will be performed, as well as palaeoecological analyses based on associated invertebrate, micro- and nannofossils.
Extreme ecomorphological adaptations in vertebrates
To understand how and why size evolution and other extreme adaptations take place, I primarily use phenomics to identify specific adaptations. We use various approaches, including geometric morphometrics, traditional morphometrics, microanatomical bone analysis, histology and finite element analysis. We are interested in extreme adaptations in general, rather than in a specific taxon: how and why extreme adaptations come about. It is exactly in these extreme cases that we have great opportunities to learn more about how evolution and ecology function. The research questions vary from case to case, but are generally variations of the following: How extreme is the adaptation? Why was this adaptation necessary? How was this adaptation acquired? Examples include extreme dietary adaptations focused on carnivores, the role island dwarfing plays in human and mammalian evolution, and the evolution of gigantism.