Rapid and Predictable Evolution of Admixed Populations Between TwoDrosophilaSpecies Pairs

Abstract

In this article, Matute et al. report an experiment in which they generated eight interspecific admixed populations using two species pairs of Drosophila. They found that in both species pairs, and across all experimental replicates... The consequences of hybridization are varied, ranging from the origin of new lineages, introgression of some genes between species, to the extinction of one of the hybridizing species. We generated replicate admixed populations between two pairs of sister species of Drosophila: D. simulans and D. mauritiana; and D. yakuba and D. santomea. Each pair consisted of a continental species and an island endemic. The admixed populations were maintained by random mating in discrete generations for over 20 generations. We assessed morphological, behavioral, and fitness-related traits from each replicate population periodically, and sequenced genomic DNA from the populations at generation 20. For both pairs of species, species-specific traits and their genomes regressed to those of the continental species. A few alleles from the island species persisted, but they tended to be proportionally rare among all sites in the genome and were rarely fixed within the populations. This paucity of alleles from the island species was particularly pronounced on the X-chromosome. These results indicate that nearly all foreign genes were quickly eliminated after hybridization and that selection against the minor species genome might be similar across experimental replicates.

Loss of ecologically important genetic variation in late generation hybrids reveals links between adaptation and speciation

“…Therefore, similar to a recent study (Matute et al. 2020) that showed a removal of derived alleles after extensive hybridization, we believe that negative genetic interactions remove derived alleles and caused the hybrid to revert to a state similar to the common ancestor. However, our results also reveal the importance of understanding dominance for combining divergent genomes.…”

Widespread introgression across a phylogeny of 155Drosophilagenomes

“…This number should be treated as an approximate lower bound and we cannot rule out the possibility that the true number is substantially higher. Studies in contemporary Drosophila species suggest that selection may constrain the evolution of mixed ancestry, at least in naturally occurring (Cooper et al, 2018;Meiklejohn et al, 2018; and experimental admixed populations (Matute et al, 2020). The results we have presented here utilized phylogenetic signals to show that introgression has nonetheless occurred and left a detectable signal within the genomes of many extant Drosophila.…”

Paracoccidioides brasiliensis Isolated from Nine-Banded Armadillos (Dasypus novemcinctus) Reveal Population Structure and Admixture in the Amazon Basin

“…Admixtures are now known to be much more common than previously thought [ 12 ]. The possibility of hybridization and admixture generating allelic combinations that can be selected upon will depend on the density of alleles that increased fitness in the recipient population, the density of hybrid incompatibilities, and the recombination rates between positively and negatively selected alleles [ 47 , 48 , 49 ]. In this report, we focused on the magnitude of gene exchange between populations of the most-extensively sampled species of Paracoccidioides and P. brasiliensis sensu stricto.…”