Evolutionary Biology

1. Insect Immune Defenses Insects have sophisticated immune systems Immune responses always include the deployment of cocktails of defense molecules including antimicrobial peptides. Why has natural selection sculpted such immune defenses? Recent research in our lab, using the mealworm beetle, indicates that interactions between immune effectors, and especially the highly abundant antimicrobial peptides (AMPs) are often synergistic. In vivo they show emergent properties that are not yet understood. We are currently starting to explore these emergent effects. 2. Bacterial Adaptations to insect defenses Bacteria can easily evolve resistance against most conventional antibiotics but much less so against antimicrobial peptides such as those produced and deployed by insects. Through a combination of experimental evolution of bacteria (S. aureus and E. coli) and theoretical modeling we have identified important reasons for this difference. Bacteria evolve AMP resistance through conserved defense mechanism. They can also develop phenotypic resistance, an important but so far mostly overlooked aspect of host-microbe interactions. AMPs differ in their pharmacodynamics and they kill very fast, usually within minutes. Also, AMPs do not increase mutagenesis of bacteria nor do they increase recombination rate. 3. Evolution of Metamorphosis At least 60% of all animals are holometabolous insects. Yet, there is no clear explanation why this extreme life style,