Deadly combinations. Hybrid incompatibilities in the parasitic wasp genus Nasonia

PhD ceremony: Ms. T. Ferber-Koevoets, 14.30 uur, Academiegebouw, Broerstraat 5, Groningen

Dissertation: Deadly combinations. Hybrid incompatibilities in the parasitic wasp genus Nasonia

Promotor(s): prof. L.W. Beukeboom

Faculty: Mathematics and Natural Sciences

Since Darwins “The Origin of Species”, much research into the processes that play a role in speciation has been performed. The PhD research of Tosca Koevoets focused on the early stages of speciation.

When different groups are no longer in contact, they will slowly diverge from each other. Eventually these groups will have changed genetically so much, that combining the DNA of different species is no longer possible, which follows from problems found in the hybrid offspring. These problems in the early stages of speciation appear to be different in males compared to females. To find the reason for this difference, parasitic wasp species from the genus Nasonia were used. Wasps have no sex chromosomes. Females of these wasps develop from fertilized eggs and males from unfertilized eggs; females thus have twice the amount of DNA of males. Both males and females were monitored for genetic problems that arise upon crossing two Nasonia species. In wasps, males proved also more vulnerable to hybridization than females. This vulnerability even increases under stress. This is because males have less genetic variability, but also merely because they have less DNA. Through a genetic technique we can force fertilized eggs (normally destined to be female) to develop as males. In this way it could be assessed whether being male or the amount of DNA was the most important factor. Of course the answer was in the middle: both facets are important. This research demonstrated that genetic interactions, the amount of DNA and the genetic variation are important aspects of speciation.