Spatial heterogeneity in resources alters selective dynamics in Drosophila melanogaster

Environmental features can alter the behaviours and phenotypes of
organisms evolving within them influencing the dynamics of natural and
sexual selection. Experimental environmental manipulation, particularly
when conducted in experiments where the dynamics of the purging of
deleterious alleles are compared, has demonstrated both direct and
indirect effects on the strength and direction of selection. However, many
of these experiments are conducted with fairly simplistic environments
when it is not always clear how or why particular forms of spatial
heterogeneity influence behaviour or selection. Using Drosophila
melanogaster, we tested three different spatial environments designed to
determine if spatial constraint of critical resources influences the
efficiency of natural and sexual selection. We conducted two allele
purging experiments to 1) assess effects of these spatial treatments on
selective dynamics of six recessive mutations, and 2) determine how these
dynamics changed when sexual selection was relaxed and spatial area
reduced for 2 of the mutants. Allele purging dynamics depended on spatial
environment, however the patterns of purging rates between the
environments differed across distinct deleterious mutations. We also
tested two of the mutant alleles, and demonstrate sexual selection
increased the purging rate.