Chromosomal inversion polymorphisms in two sympatric ascidian lineages - Sorbonne Université
Journal Articles Genome Biology and Evolution Year : 2021

Chromosomal inversion polymorphisms in two sympatric ascidian lineages

Abstract

Chromosomal rearrangements can reduce fitness of heterozygotes and can thereby prevent gene flow. Therefore, such rearrangements can play a role in local adaptation and speciation. In particular, inversions are considered to be a major potential cause for chromosomal speciation. There are two closely related, partially sympatric lineages of ascidians in the genus Ciona, which we call type-A and type-B animals in the present study. While these invertebrate chordates are largely isolated reproductively, hybrids can be found in wild populations, suggesting incomplete prezygotic barriers. Although the genome of type-A animals has been decoded and widely used, the genome for type-B animals has not been decoded at the chromosomal level. In the present study, we sequenced the genomes of two type-B individuals from different sides of the English Channel (in the zone of sympatry with type-A individuals) and compared them at the chromosomal level with the type-A genome. While the overall structures were well conserved between type A and type B, chromosomal alignments revealed many inversions differentiating these two types of Ciona; it is probable that the frequent inversions have contributed to separation between these two lineages. In addition, comparisons of the genomes between the two type-B individuals revealed that type B had high rates of inversion polymorphisms and nucleotide polymorphisms, and thus type B might be in the process of differentiation into multiple new types or species. Our results suggest an important role of inversions in chromosomal speciation of these broadcasting spawners.

Domains

Genetics
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Dates and versions

hal-03192575 , version 1 (08-04-2021)

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Yutaka Satou, Atsuko Sato, Hitoyoshi Yasuo, Yukie Mihirogi, John Bishop, et al.. Chromosomal inversion polymorphisms in two sympatric ascidian lineages. Genome Biology and Evolution, 2021, ⟨10.1093/gbe/evab068/6209075⟩. ⟨hal-03192575⟩
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