Incompletely isolated species provide an opportunity to investigate the genetic mechanisms and evolutionary forces that maintain distinct species in the face of ongoing gene flow. Here, we use field surveys and reduced representation sequencing to characterize the patterns of reproductive isolation, admixture and genomic divergence between populations of the outcrossing wildflower
Invasive species can impact native populations through competition, predation, habitat alteration, and disease transmission, but also genetically through hybridization. Potential outcomes of hybridization span the continuum from extinction to hybrid speciation and can be further complicated by anthropogenic habitat disturbance. Hybridization between the native green anole lizard (
- Award ID(s):
- 1655221
- NSF-PAR ID:
- 10401003
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Molecular Ecology
- Volume:
- 32
- Issue:
- 11
- ISSN:
- 0962-1083
- Page Range / eLocation ID:
- p. 2930-2944
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Mimulus guttatus and selfingM. nasutus . Focusing on a single site where these two species have come into secondary contact, we find that phenological isolation is strong, although incomplete, and is likely driven by divergence in response to photoperiod. In contrast to previous field studies, which have suggested that F1‐hybrid formation might be rare, we discover patterns of genomic variation consistent with ongoing introgression. Strikingly, admixed individuals vary continuously from highly admixed to nearly pureM. guttatus , demonstrating ongoing hybridization and asymmetric introgression fromM. nasutus intoM. guttatus . Patterns of admixture and divergence across the genome show that levels of introgression are more variable than expected by chance. Some genomic regions show a reduced introgression, including one region that overlaps a critical photoperiodQTL , whereas other regions show elevated levels of interspecific gene flow. In addition, we observe a genome‐wide negative relationship between absolute divergence and the local recombination rate, potentially indicating natural selection againstM. nasutus ancestry inM. guttatus genetic backgrounds. Together, our results suggest thatMimulus speciation is both ongoing and dynamic and that a combination of divergence in phenology and mating system, as well as selection against interspecific alleles, likely maintains these sympatric species. -
Abstract Hybridization facilitates recombination between divergent genetic lineages and can be shaped by both neutral and selective processes. Upon hybridization, loci with no net fitness effects introgress randomly from parental species into the genomes of hybrid individuals. Conversely, alleles from one parental species at some loci may provide a selective advantage to hybrids, resulting in patterns of introgression that do not conform to random expectations. We investigated genomic patterns of differential introgression in natural hybrids of two species of Caribbean anoles,
Anolis pulchellus andA. krugi in Puerto Rico. Hybrids exhibitA. pulchellus phenotypes but possessA. krugi mitochondrial DNA, originated from multiple, independent hybridization events, and appear to have replaced pureA. pulchellus across a large area in western Puerto Rico. Combining genome‐wide SNP datasets with bioinformatic methods to identify signals of differential introgression in hybrids, we demonstrate that the genomes of hybrids are dominated bypulchellus ‐derived alleles and show only 10%–20%A. krugi ancestry. The majority ofA. krugi loci in hybrids exhibit a signal of non‐random differential introgression and include loci linked to genes involved in development and immune function. Three of these genes (delta like canonical notch ligand 1, jagged1 and notch receptor 1) affect cell differentiation and growth and interact with mitochondrial function. Our results suggest that differential non‐random introgression for a subset of loci may be driven by selection favouring the inheritance of compatible mitochondrial and nuclear‐encoded genes in hybrids. -
Abstract As humans cause the redistribution of species ranges, hybridization between previously allopatric species is on the rise. Such hybridization can have complex effects on overall fitness of native species as new allelic combinations are tested. Widespread species introductions provide a unique opportunity to study selection on introgressed alleles in independent, replicated populations. We examined selection on alleles that repeatedly introgressed from introduced rainbow trout (
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Hybridization is among the evolutionary mechanisms most frequently hypothesized to drive the success of invasive species, in part because hybrids are common in invasive populations. One explanation for this pattern is that biological invasions coincide with a change in selection pressures that limit hybridization in the native range. To investigate this possibility, we studied the introduction of the brown anole (
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Abstract When organisms experience secondary contact after allopatric divergence, genomic regions can introgress differentially depending on their relationships with adaptation, reproductive isolation, recombination, and drift. Analyses of genome‐wide patterns of divergence and introgression could provide insight into the outcomes of hybridization and the potential relationship between allopatric divergence and reproductive isolation. Here, we generate population genetic data (26,262 SNPs; 353 individuals) using a reduced‐representation sequencing approach to quantify patterns of ancestry, differentiation, and introgression between a pair of ecologically distinct mammals—the desert woodrat (
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