Abstract
Adaptation requires genetic variation, but founder populations are generally genetically depleted. Here we sequence two populations of an inbred ant that diverge in phenotype to determine how variability is generated. Cardiocondyla obscurior has the smallest of the sequenced ant genomes and its structure suggests a fundamental role of transposable elements (TEs) in adaptive evolution. Accumulations of TEs (TE islands) comprising 7.18% of the genome evolve faster than other regions with regard to single-nucleotide variants, gene/exon duplications and deletions and gene homology. A non-random distribution of gene families, larvae/adult specific gene expression and signs of differential methylation in TE islands indicate intragenomic differences in regulation, evolutionary rates and coalescent effective population size. Our study reveals a tripartite interplay between TEs, life history and adaptation in an invasive species.
Highlights
Adaptation requires genetic variation, but founder populations are generally genetically depleted
The invasive, inbreeding ant Cardiocondyla obscurior (Fig. 1) provides a suitable model to study how species adapt to novel habitats in spite of constraints imposed by invasion history, life history or both
Our results suggest that transposable elements (TEs) islands might function as spring wells for genetic diversification in founder populations of this invasive species
Summary
Adaptation requires genetic variation, but founder populations are generally genetically depleted. Low genetic and phenotypic variation is common in founder populations, where only one or a few genotypes are isolated from a source population Under such conditions, reduced effective population size (Ne) should decrease selection efficiency and increase genetic drift, resulting in only weak selection against mildly deleterious alleles which can accumulate[2]. These effects should be even stronger in inbreeding species[3] and taxa with generally low Ne such as social insects[4]. The distinct organization of TE islands, their gene composition and their regulation by the genome adds compelling evidence for the role of TEs as players in differentiation, adaptation and speciation
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