Evolution at 'Sutures' and 'Centers': Recombination Can Aid Adaptation of Spatially Structured Populations on Rugged Fitness Landscapes

摘要

Epistatic interactions among genes can give rise to rugged fitness landscapes, in which multiple “peaks” of high-fitness allele combinations are separated by “valleys” of low-fitnessgenotypes. How populations traverse rugged fitness landscapes is a long-standing questionin evolutionary biology. Sexual reproduction may affect how a population moves within arugged fitness landscape. Sex may generate new high-fitness genotypes by recombination,but it may also destroy high-fitness genotypes by shuffling the genes of a fit parent with agenetically distinct mate, creating low-fitness offspring. Either of these opposing aspects ofsex require genotypic diversity in the population. Spatially structured populations may harbor more diversity than well-mixed populations, potentially amplifying both positive and negative effects of sex. On the other hand, spatial structure leads to clumping in which mating ismore likely to occur between like types, diminishing the effects of recombination. In thisstudy, we use computer simulations to investigate the combined effects of recombinationand spatial structure on adaptation in rugged fitness landscapes. We find that spatiallyrestricted mating and offspring dispersal may allow multiple genotypes inhabiting suboptimal peaks to coexist, and recombination at the “sutures” between the clusters of thesegenotypes can create genetically novel offspring. Sometimes such an offspring genotypeinhabits a new peak on the fitness landscape. In such a case, spatially restricted matingallows this fledgling subpopulation to avoid recombination with distinct genotypes, as matesare more likely to be the same genotype. Such population “centers” can allow nascentpeaks to establish despite recombination. Spatial structure may therefore allow an evolvingpopulation to enjoy the creative side of sexual recombination while avoiding its destructiveside.