Chronic heat stress resistance in Caenorhabditis remanei
Organisms are subjected to a wide range of stressful conditions throughout their lifetime. Environmental stress can drive a population to adapt to novel conditions by yielding selective advantages to subsets of the population. Understanding the genetic architecture of stress responses is important because it helps researchers evaluate how characteristics of interest may respond to selection. Selection can drive sub-populations to diverge from each other, but gene flow can homogenize them. Migration-selection dynamics are one of the fundamental aspects of population divergence and speciation, but they have not been rigorously investigated in an experimental context. The goal of this research is to dissect the genetic basis of chronic heat stress, a model complex trait, in the nematode Caenorhabditis remanei and to understand how gene flow affects rates of adaptation to a novel environment. Populations of C. remanei were evolved in pairs to novel (31°C) and ancestral (20°C) environments. We tested the effect of gene flow between the sub-populations with 0 and 5 percent migration rates. Female fecundity information was collected to estimate the extent of adaptation in the heat-stress-evolved population. The migration treatment stunted the rate of adaptation to the novel environment, though population divergence still occurred. We expect genomic changes in the descendant lines that lead to adaptation. Whole genome sequencing data from both the ancestral and descendant populations will be compared on a locus-by-locus basis. The migration treatment is expected to reduce signatures of differentiation from weakly selected loci and to enhance signatures associated with loci of large effect.