A Tale of Two Lakes: Divergent Evolutionary Trajectories of Two Daphnia Populations Experiencing Distinct Environments.

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Most studies of local adaptation substitute the correlation between spatial distance and environmental heterogeneity for the temporal dynamics over which local adaptation evolves. The availability of detailed ecological and genomic information from lake sediments provides an opportunity to study local adaptation with unparalleled clarity from the temporal perspective. Inference can be further enhanced by including multiple lakes along ecological axes to further isolate the effects of ecological change in driving local adaptation. Lakes throughout the world face the impact of numerous anthropogenically induced environmental changes. Top among these is the eutrophication of freshwaters from agriculture, development, and land-use change. Here, we use the genetic information recorded in lake sediments of two lakes experiencing contrasting histories of land-use change to study the evolution of local adaptation in the lakes' Daphnia pulicaria populations. Utilizing nextRAD derived single-nucleotide polymorphisms (SNPs) in resurrected clonal lineages, we studied the evolutionary trajectories of Daphnia pulicaria in both lakes. Using gene-environment correlations and F st tests for selection, we found SNPs that appear to be under selection in both lakes. Specifically, we found more outlier SNPs in the highly impacted lake using F st-based tests for selection. Conversely, gene-environment tests revealed the reverse pattern. We discuss numerous facets of experimental design that must be considered when using resurrection ecology to study local adaptation and critically evaluate how they may have impacted the of this investigation.