The maintenance of populations at small sizes can lead to the accumulation of deleterious mutations that undermine the fitness of individuals. However, subsequent return to large population size can result in the fixation of beneficial mutations at other loci that compensate for these negative effects. Such an advantageous association can be disrupted during outcrossing, thereby leading to a fitness decline in hybrids and representing a first step in the formation of new species.
This research represents the first experimental test of the role of compensatory mutations in the evolution of reproductive incompatibility. Using the nematode model system C. elegans, this project attempts to: 1) subject multiple lines to a regime of deleterious mutation accumulation by maintenance at small population sizes with a knockout of a key DNA mismatch repair gene; 2) initiate fitness recovery in mutationally degraded lines via the accumulation of compensatory mutations under large population sizes, thereby creating line-specific coadapted gene complexes and 3) test for diminished fitness in hybrid progeny.
This study will test the role of inter-locus gene interactions in the evolution of reproductive incompatibility, evaluate the validity of a key model of speciation, and have implications for conservation management practices.
