Format: ORAL

Lise Huseby1 Anne Brysting2 Christian Brochmann1 Lovisa Gustafsson1 Johanna Leppl3

1 Natural History Museum of Oslo, University of Oslo, Norway 2 Department of Biosciences, University of Oslo, Norway 3 Natural Research Institute, Finland

The Bateson-Dobzhansky-Muller (BDM) model posits that the evolution of intrinsic postzygotic barriers occurs when independent mutations become fixed in diverging populations. If we assume that new mutations become fixed at rate n, then the number of pair of potentially interacting loci that could contribute to reproductive isolation between the populations accumulates at rate n2. This is the snowball theory, which so far only has been empirically tested in interspecific studies in Solanum, Eucalyptus, and Drosophila. In this project we aim to address whether a snowball effect also can be detected within a species using the outcrossing species Arabidopsis lyrata as a model. We will 1) identify the number of loci responsible for reproductive isolation between populations assumed to represent different divergence times, and 2) test for a correlation between the number of loci contributing to reproductive isolation and population divergence. We selected three populations, previously demonstrated to produce varying degrees of F1 sterility in experimental crossing studies. We produced three F1 hybrid populations and crossed two individuals from each of them to produce three F2 populations, each comprising 500 individuals. We currently perform quantitative trait loci (QTL) mapping of reproductive isolation (pollen fertility) in the F2 populations using genotype data from restriction-site associated DNA sequencing. Preliminary results indicate a declining trend in fertility with respect to population divergence.