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Abstract

Phenotypic evolution can occur more quickly than previously thought but understanding the genetic basis of rapid evolution is still in its infancy. Until recently it was difficult to detect such rapid adaptation at the genomic level. Four replicated experimental translocations of high-predation (HP)guppies to uncolonized low-predation (LP) habitats in northern Trinidad provide a unique opportunity to study this phenomenon. These transplanted guppies have evolved phenotypes similar to naturally-colonised low-predation populations in 8-10 generations. These adapted phenotypes persist in subsequent generations in lab environments, suggesting a prominent role for genetic adaptation. Here, we present results from whole genome scans of each experimental population, sampled 8-10 generations post introduction, and their high-predation source. Patterns of genome-wide variation indicated only minor changes from the source. However, examining runs of homozygosity revealed a bottleneck in one population, which agrees with population census data. Using a combination of haplotype genome scans and a novel multivariate approach based on allele frequency change vectors, we found signals of convergent evolution in all four populations. Specifically, we found a region on chromosome 15 under strong selection in three of the our populations, and our multivariate approach revealed more subtle parallel changes in allele frequency in all four populations across this region. Investigating patterns of genome-wide selection in this uniquely replicated experiment offers a remarkable insight into the mechanisms underlying rapid adaptation that could potentially be extrapolated to other species and populations experiencing rapidly changing environments.