Both models and case studies suggest that chromosomal inversions can facilitate adaptation and speciation in the presence of gene flow by suppressing recombination between locally adapted alleles. Until recently, however, it has been laborious and time-consuming to identify and genotype inversions in natural populations. Here we apply RAD sequencing data and newly developed population genomic approaches to identify putative inversions that differentiate a sand dune ecotype of the prairie sunflower (Helianthus petiolaris) from populations found on the adjacent sand sheet. We detected seven large genomic regions that exhibit a different population structure than the rest of the genome and that vary in frequency between dune and non-dune populations. These regions also show high linkage disequilibrium and high heterozygosity between, but not within haplotypes, consistent with the behavior of large inversions, an inference subsequently validated in part by comparative genetic mapping.Genome-environment association analyses show that key environmental variables, including vegetation cover and soil nitrogen, are significantly associated with inversions. The inversions co-locate with previously described "islands of differentiation," and appear to play an important role in adaptive divergence and incipient speciation within H. petiolaris.
Chromosomal inversions have the potential to play an important role in evolution by reducing recombination between favorable combinations of alleles. Until recently, however, most evidence for their likely importance derived from dipteran flies, whose giant larval salivary chromosomes aided early cytogenetic studies. The widespread application of new genomic technologies has revealed that inversions are ubiquitous across much of the plant and animal kingdoms. Here we review the rapidly accumulating literature on inversions in the plant kingdom and discuss what we have learned about their establishment and likely evolutionary role. We show that inversions are prevalent across a wide range of plant groups. We find that inversions are often associated with locally favored traits, as well as with traits that contribute to assortative mating, suggesting that they may be key to adaptation and speciation in the face of gene flow. We also discuss the role of inversions in sex chromosome formation, and explore possible parallels with inversion establishment on autosomes. The identification of inversion origins, as well as the causal variants within them, will advance our understanding of chromosomal evolution in plants.
With more than 300 affected individuals living in Quebec, autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is the most common of all inherited recessive ataxias in the province 1 . Though most families originate from the regions of Charlevoix and Saguenay-Lac-St-Jean (SLSJ), cases are found in other regions of Quebec. The high carrier rate for the c.8844delT spastic ataxia of Charlevoix-Saguenay (SACS) gene mutation explains the higher prevalence of ARSACS in French-Canadians
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