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Incomplete Sterility of Chromosomal Hybrids : Implications for Karyotype Evolution and Homoploid Hybrid Speciation

Lukhtanov, Vladimir A. ; Dincă, Vlad ; Friberg, Magne LU ; Vila, Roger and Wiklund, Christer (2020) In Frontiers in Genetics 11.
Abstract

Heterozygotes for major chromosomal rearrangements such as fusions and fissions are expected to display a high level of sterility due to problems during meiosis. However, some species, especially plants and animals with holocentric chromosomes, are known to tolerate chromosomal heterozygosity even for multiple rearrangements. Here, we studied male meiotic chromosome behavior in four hybrid generations (F1–F4) between two chromosomal races of the Wood White butterfly Leptidea sinapis differentiated by at least 24 chromosomal fusions/fissions. Previous work showed that these hybrids were fertile, although their fertility was reduced as compared to crosses within chromosomal races. We demonstrate that (i) F1 hybrids are highly heterozygous... (More)

Heterozygotes for major chromosomal rearrangements such as fusions and fissions are expected to display a high level of sterility due to problems during meiosis. However, some species, especially plants and animals with holocentric chromosomes, are known to tolerate chromosomal heterozygosity even for multiple rearrangements. Here, we studied male meiotic chromosome behavior in four hybrid generations (F1–F4) between two chromosomal races of the Wood White butterfly Leptidea sinapis differentiated by at least 24 chromosomal fusions/fissions. Previous work showed that these hybrids were fertile, although their fertility was reduced as compared to crosses within chromosomal races. We demonstrate that (i) F1 hybrids are highly heterozygous with nearly all chromosomes participating in the formation of trivalents at the first meiotic division, and (ii) that from F1 to F4 the number of trivalents decreases and the number of bivalents increases. We argue that the observed process of chromosome sorting would, if continued, result in a new homozygous chromosomal race, i.e., in a new karyotype with intermediate chromosome number and, possibly, in a new incipient homoploid hybrid species. We also discuss the segregational model of karyotype evolution and the chromosomal model of homoploid hybrid speciation.

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publication status
published
subject
keywords
chromosome, fertility, hybridization, inverted meiosis, inviability, Lepidoptera, Pieridae, segregation
in
Frontiers in Genetics
volume
11
article number
583827
publisher
Frontiers Media S. A.
external identifiers
  • scopus:85094596996
  • pmid:33193715
ISSN
1664-8021
DOI
10.3389/fgene.2020.583827
language
English
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yes
id
aee26aa1-37fc-41e5-85e6-1f7a7b63ce61
date added to LUP
2020-11-16 14:29:49
date last changed
2021-06-16 06:10:45
@article{aee26aa1-37fc-41e5-85e6-1f7a7b63ce61,
  abstract     = {<p>Heterozygotes for major chromosomal rearrangements such as fusions and fissions are expected to display a high level of sterility due to problems during meiosis. However, some species, especially plants and animals with holocentric chromosomes, are known to tolerate chromosomal heterozygosity even for multiple rearrangements. Here, we studied male meiotic chromosome behavior in four hybrid generations (F1–F4) between two chromosomal races of the Wood White butterfly Leptidea sinapis differentiated by at least 24 chromosomal fusions/fissions. Previous work showed that these hybrids were fertile, although their fertility was reduced as compared to crosses within chromosomal races. We demonstrate that (i) F1 hybrids are highly heterozygous with nearly all chromosomes participating in the formation of trivalents at the first meiotic division, and (ii) that from F1 to F4 the number of trivalents decreases and the number of bivalents increases. We argue that the observed process of chromosome sorting would, if continued, result in a new homozygous chromosomal race, i.e., in a new karyotype with intermediate chromosome number and, possibly, in a new incipient homoploid hybrid species. We also discuss the segregational model of karyotype evolution and the chromosomal model of homoploid hybrid speciation.</p>},
  author       = {Lukhtanov, Vladimir A. and Dincă, Vlad and Friberg, Magne and Vila, Roger and Wiklund, Christer},
  issn         = {1664-8021},
  language     = {eng},
  month        = {10},
  publisher    = {Frontiers Media S. A.},
  series       = {Frontiers in Genetics},
  title        = {Incomplete Sterility of Chromosomal Hybrids : Implications for Karyotype Evolution and Homoploid Hybrid Speciation},
  url          = {http://dx.doi.org/10.3389/fgene.2020.583827},
  doi          = {10.3389/fgene.2020.583827},
  volume       = {11},
  year         = {2020},
}