The propagation of admixture-derived adaptive radiation potential

Adaptive radiations frequently show remarkable repeatability where single lineages undergo multiple independent episodes of adaptive radiation in distant places and long separate timepoints. Increasing evidence suggests that genetic variation generated through hybridization between distantly related lineages can promote adaptive radiation. This mechanism, however, requires rare coincidence in space and time between the hybridization event and opening of ecological opportunity, because hybridization generates large genetic variation only in the site where it occurred and the elevated genetic variation will persist only for a short period. Hence, hybridization seems unlikely to explain recurrent adaptive radiation in the same lineage. Contrary to these expectations, our evolutionary computer simulations demonstrate that admixture variation can geographically spread and persist for long periods if certain conditions are present such that ecological and/or geographic mechanisms split the hybrid population into isolated sub-lineages. Subsequent secondary hybridization of some of these can reestablish genetic polymorphisms from the ancestral hybridization in places far from the birthplace of the hybrid-clade and long after the ancestral hybridization event. Consequently, simulations revealed conditions where exceptional genetic variation, once generated through a rare and unlikely hybridization event, can facilitate multiple adaptive radiations exploiting ecological opportunities available at distant points in time and space.

Methods
Source code of the individual-based computer simulation model and final output files from simulations.