Authorship contributions: BR and TJV conceived the work and designed the methodology. BR carried out the simulations and performed data analysis. BR initially drafted, and BR and TJV jointly revised the manuscript.Acknowledgements: We thank Morgan Holder and Wesley Price for assistance in conducting initial explorations of the simulation model and software.
AbstractThe role of genetic architecture in adaptation to novel environments has received considerable attention when the source of adaptation variation is de novo mutation. Relatively less is known when the source of adaptive variation is inter- or intraspecific hybridization. We model hybridization between divergent source populations and subsequent colonization of an unoccupied novel environment using individual-based simulations in order to understand the influence of genetic architecture on the timing of colonization and the mode of adaptation. We find that two distinct categories of genetic architecture facilitate rapid colonization but that they do so in qualitatively different ways. For few and/or tightly linked loci, the mode of adaptation is via the recovery of adaptive parental genotypes. With many unlinked loci, the mode of adaptation is via the generation of novel hybrid genotypes. The first category results in the shortest colonization lag phases across the widest range of parameter space, but further adaptation is mutation limited. The second category takes longer and is more sensitive to genetic variance and dispersal rate, but can facilitate adaptation to environmental conditions which exceed the tolerance of parental populations. These findings have implications for understanding the origins of biological invasions and the success of hybrid populations.
Yellow starthistle (Centaurea solstitialis) is a highly invasive species that has been a model system for the potential contribution of evolution to invader traits. Here, we report the construction of a chromosome-scale reference genome for C. solstitialis using a combination of PacBio HiFi and Dovetail Omni-C technologies, and functional gene annotation with RNAseq. We validate the reference genome using a restriction site-associated DNA (RAD)-based genetic map from an F2 mapping population. We find that syntenic comparisons to other taxa in the Asteraceae reveal a chromosomal fusion in the lineage of C. solstitialis, and widespread fission in globe artichoke (Cynara cardunculus). Using a QTL analysis from the mapping population (derived from a cross between native and invading parents) we identify 13 QTL underpinning size traits that are associated with adaptation in the invaded range, including a putative large-scale chromosomal inversion that has a pleiotropic and overdominant effect on key invader traits.
Invasive species can interact with native relatives in a variety of ways which may jeopardize their long-term coexistence. Here we show that interactions with an invasive species of guava (Psidium guajava) appear to be driving the local exclusion and regional decline of guayabillo (Psidium galapageium), a tree species endemic to the Galápagos archipelago. We find evidence consistent with recent historic exclusion of guayabillo from the highlands of San Cristóbal Island, signatures of ongoing demographic decline in sympatric populations at lower elevations, and evidence suggesting that the four coinhabited islands represent points along a time series of regional decline, with the extent of guayabillo decline depending on the date that guava was introduced to each island. Based on these results, we then use the percentage of guava cover surrounding guayabillo populations to target populations that are at imminent risk of exclusion to aid in prioritizing management targets.
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