Central to evolutionary biology is the evolution of species, i.e., speciation. This phenomenon is important as it explains the biodiversity that we observe in the staggering variety of fossil and extant life forms. Evolution can only happen in the presence of genetic variation which is continuously generated by recombination and, ultimately, mutation. Genetic variation that increases individual fitness can result in the evolution of adaptations by natural selection. This makes genetic variation essential for the survival of local populations, species, and biodiversity in a changing environment.

The research group studies the evolutionary genetic mechanisms of population differentiation and reproductive isolation in the course of evolution. We concentrate on traits and mechanisms involved in the development of reproductive isolation, as well as on analyzing and modeling the resulting population genetic structure and phylogeographic patterns.

Three main lines of research

Our research is clustered according to the following three lines of research:

(1) Evolution of host and mate choice.

Host and mate choice are two quantitative genetic traits that play a significant role in speciation. Switches in host choice are often linked to speciation events, probably because because host specificity reduces genetic exchange between populations adapted to different host plant species. Mate choice can lead directly to reproductive isolation and is often a matter of chemical communication by means of highly specific sex pheromones. We study the following issues:

The phenotypic effects, organization, and regulation of quantitative trait genes involved in the sex pheromone communication system, oviposition choice, and larval performance of the ermine moth genus Yponomeuta on various host plants. Of special interest are genes for receptor proteins in sensory cells (specifically recognizing plant and mate odours) and pheromone production genes.

The relative contributions of natural selection and genetic drift to the fixation of speciation genes at the population level.

(2) Evolutionary genetics of host-symbiont relationships and mode of reproduction

Symbiosis between bacteria and arthropods is extremely widespread and diverse in its phenotype. These bacterial infections have important effects on host fitness, adaptation, and reproductive isolation and as well as on the evolution of host reproductive systems. We focus on the evolutionary consequences of infections with intracellular microorganisms on the mode of reproduction and speciation of spider mite hosts. We study the following issues:

The role of cytoplasmic incompatibility inducing microorganisms on reproductive isolation and speciation of the mites.

Evolutionary genetics of microbe-induced parthenogenesis in thelytokous mites; effects on host adaptation, clonal genetic diversity, and host-symbiont coevolution.

(3)   Patterns and processes shaping population structure and phylogeography.

Current population structure is the result of historic events and processes. Phylogeography in combination with coalescence theory enables us to reconstruct the evolutionary trajectory of current population structure. This provides insights in the factors that have been and probably still are important in speciation and species distribution. Nowadays, the distribution and coherence of the populations of a species are under high pressure from human activities (pollution, global change, fragmentation and decline of habitat). Changes in biodiversity as a result of degradation and recovery of ecosystems are modeled by investigating landscape, metapopulation, and evolutionary dynamics. We study the following issues:                

Phylogeography and genetic population structure of, among other things, marine zooplankton.

Modeling metapopulation structure and evolutionary dynamics of ecosystems under stress.

The methods we use are molecular genetic analyses (DNA, allozymes), experimentation both in the field as well as under controlled conditions in the laboratory (chemical ecological and genetical analyses) and modeling.

Although the main focus is on answering fundamental questions on speciation in arthropods, the knowledge generated is also used to formulate effective strategies for nature conservation (mostly in the Netherlands and SE Asia), sustainable development, and for biological control.