Adaptive or neutral clines? Integrating genome-wide clinal and seasonal variation to infer natural selection in Drosophila melanogaster

• Autor(a) principal: Rodrigues, Murillo Fernando
• Data de Publicação: 2018
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Biblioteca Digital de Teses e Dissertações da USP
• Texto Completo: http://www.teses.usp.br/teses/disponiveis/41/41131/tde-26112018-153816/
• topic: Adaptação; Adaptação sazonal; Adaptation; Drosophila melanogaster; Drosophila melanogaster; Molecular variation; Natural selection; Seasonal adaptation; Seleção natural; Variação molecular

Spatial and temporal variation in the environment are ubiquitous. Traits are called clinal when they vary along an environmental gradient, and this is often interpreted as the result of spatially varying selection. Drosophila melanogaster is known to have many phenotypic and genotypic clines, replicated in many regions of the world. Recent studies have suggested that most clinal variation could be attributed to neutral, demographic processes. Because the environment varies in similar ways with latitude and across seasons, and seasonal variation is orthogonal to demography, one promising approach is to integrate clinal and seasonal variation to infer selection. Here, we test whether there is a genome-wide relationship between clinal and seasonal variation, and whether the pattern is consistent with selection. Also, we investigate the proportion of the variants that should be under latitudinal and seasonal selection to explain the pattern we uncovered. We estimate allele frequency from pooled samples of flies from eight different locations along the east coast of the US, and 13 samples collected in the spring and in the fall in Pennsylvania. We show that there is a genome-wide pattern of clinal variation mirroring seasonal variation. This pattern is stronger for exonic when compared to intergenic regions, consistent with natural selection. We find that the genome-wide relationship between clinal and seasonal variation could be explained by about 6.6% of our SNPs being under latitudinal and seasonal selection. Our results are consistent with the adaptive hypothesis of clinal variation and, together with other observations, leave little room for the role of demography in maintaining clines in D. melanogaster