Welcome to the pages of our working group. Main subjects of our research are the evolution of fertilization proteins in primates and other mammals, and the evolution of parasitism - and this always in the light of the phylogenetic relationships of the investigated organisms.
Molecular Evolution of Sperm-egg Interaction
We study the evolution of sperm-egg interaction in the light of sexual selection taking mating systems and physical measures such as sexual size dimorphism as proxies of species-specific levels of male competition. Much of our past work focused on the evolution of sperm ligands called zonadhesin (ZAN) and sperm adhesion molecule 1 (SPAM1) that both interact with female molecules. Our analyses revealed that species-specific substitution rates (see dN/dS in below figure) of the genes encoding ZAN and SPAM1 are lower in primate species with strong sexual dimorphism of body weight that live in harems ("uni-male breeding").
Combining two-dimensional gel electrophoresis, Western blotting, and mass spectrometry we were able to determine 99 human sperm proteins. Subsequent analyses of sequence evolution revealed that sperm proteins showing phosphorylation in humans evolve at lower rates across mammals than sperm proteins that are non-phosphorylated in humans (see above figure; after Schumacher et al. 2013). This suggests that evolutionary conservation prevails across phosphorylated sperm proteins while adaptive evolution of phosphosites is the exception. Importantly, we also found evidence that increased numbers of protein-protein interaction partners and, hence, increased functional constraint represents the deeper reason behind the higher evolutionary conservation of phosphorylated sperm proteins.
Phylogenetic Relations of Thorny-headed Worms and "Rotifers"
Besides evolutionary analyses of diverse genes and gene copies, we investigate the phylogenetic relations of thorny-headed worms (Acanthocephala) and their "rotiferan" relatives. Juvenile acanthocephalans mature in the body cavities of insects, myriapods and crustaceans (intermediate host), while adult worms live and reproduce in the intestinal tract of vertebrates including primates (definitive host). Based on molecular data we found evidence that the acanthocephalan endoparasitism evolved from free-living ancestors via an epizoic stage (see below figure). This conclusion gained support from recent large scale phylogenomic analyses on data including all relevant subgroups (Syndermata in the below figure; see Wey-Fabrizius et al. 2014). Accordingly, acanthocephalans and their relatives can serve as a model for the evolution of endoparasitism.
In a another study we mapped presence/absence data on lateral and apical sensory organs on a tree topology inferred from mtDNA data (see Weber et al. 2013). Our data suggest that paired lateral sensory organs evolved once in the acanthocephalan stem lineage while two apical sensory organs first emerged and then fused to an unpaired structure inside Archiacanthocephala. However, also reduction of lateral sensory organs occured, namely in palaeacanthocephalans. Thus, acanthocephalan sensory organs represent another example for the enormous plasticity in the evolution of endoparasites.
Many of these findings would not have been possible without financial support from the German Research Council (DFG) and the Johannes Gutenberg University and closely cooperating colleagues (see publications).
Osteological Teaching Collection - Portrait 1 (free access)