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Genomic Architecture Drives the Rapid Origin of New Species

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Date and time:��

Thursday, February 6, 2014 - 2:00pm

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ECCR 257

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A long-standing problem in evolutionary biology has been determining whether and how gradual, incremental changes at the gene level can account for rapid speciation and bursts of adaptive radiation. Using genome-scale computer simulations, we demonstrate that gradual adaptive change can generate nonlinear population transitions, resulting in the rapid formation of new, reproductively isolated species. We show that these transitions occur via a mechanism rooted in a basic property of biological heredity: the organization of genes in genomes. Genomic organization of genes facilitates two processes: (i) the buildup of statistical associations among large numbers of genes, and (ii) the action of divergent selection on persistent combinations of alleles. When a population has accumulated a critical amount of standing, divergently selected variation, the combination of these two processes allows many mutations of small effect to act synergistically and precipitously split one population into two discontinuous, reproductively isolated groups. Factors such as frequency-dependent selection, epistasis, assortative mating, “magic traits,” founder effects, and/or reduced recombination can act in concert with this mechanism, but are not required for rapid species splitting. Our results explain alternative stable states of population divergence, discrete phases of speciation, and the rapid emergence of multilocus barriers to gene flow. In so doing, the models predict genome-wide patterns of divergence across the speciation continuum in terms of metrics that are empirically measurable. This approach is a step toward aligning population genomic theory with modern empirical studies and transforming that theory into one with more predictive power.