scholarly journals Higher levels of sex chromosome heteromorphism are associated with markedly stronger reproductive isolation

2014 ◽  
Vol 5 (1) ◽  
Author(s):  
Thiago G. Lima
Keyword(s):  
Reproductive Isolation ◽  
Sex Chromosome ◽  
Chromosome Heteromorphism

scholarly journals X-Linked Signature of Reproductive Isolation in Humans is Mirrored in a Howler Monkey Hybrid Zone

2020 ◽  
Vol 111 (5) ◽  
pp. 419-428 ◽  
Author(s):  
Marcella D Baiz ◽  
Priscilla K Tucker ◽  
Jacob L Mueller ◽  
Liliana Cortés-Ortiz
Keyword(s):  
Reproductive Isolation ◽  
X Chromosome ◽  
Hybrid Zone ◽  
Sex Chromosome ◽  
Genomic Sequence ◽  
Alouatta Palliata ◽  
Model Systems ◽  
Howler Monkey ◽  
Autosomal Snps ◽  
Outlier Region

Abstract Reproductive isolation is a fundamental step in speciation. While sex chromosomes have been linked to reproductive isolation in many model systems, including hominids, genetic studies of the contribution of sex chromosome loci to speciation for natural populations are relatively sparse. Natural hybrid zones can help identify genomic regions contributing to reproductive isolation, like hybrid incompatibility loci, since these regions exhibit reduced introgression between parental species. Here, we use a primate hybrid zone (Alouatta palliata × Alouatta pigra) to test for reduced introgression of X-linked SNPs compared to autosomal SNPs. To identify X-linked sequence in A. palliata, we used a sex-biased mapping approach with whole-genome re-sequencing data. We then used genomic cline analysis with reduced-representation sequence data for parental A. palliata and A. pigra individuals and hybrids (n = 88) to identify regions with non-neutral introgression. We identified ~26 Mb of non-repetitive, putatively X-linked genomic sequence in A. palliata, most of which mapped collinearly to the marmoset and human X chromosomes. We found that X-linked SNPs had reduced introgression and an excess of ancestry from A. palliata as compared to autosomal SNPs. One outlier region with reduced introgression overlaps a previously described “desert” of archaic hominin ancestry on the human X chromosome. These results are consistent with a large role for the X chromosome in speciation across animal taxa and further, suggest shared features in the genomic basis of the evolution of reproductive isolation in primates.

Karyotypes of side-necked turtles (Testudines: Pleurodira)

1980 ◽  
Vol 58 (5) ◽  
pp. 828-841 ◽  
Author(s):  
James J. Bull ◽  
John M. Legler
Keyword(s):  
Sex Chromosome ◽  
Ancestral Condition ◽  
Chromosome Heteromorphism

Karyotypes are presented for 13 of the 14 genera of side-necked turtles (suborder Pleurodira, families Pelomedusidae and Chelidae). Pelomedusids have low diploid numbers and few microchromosomes (2n = 26–36); the five largest chromosomes are homologous in the three genera. Chelids have high diploid numbers and many microchromosomes (2n = 50–64) and are similar in this respect to cryptodires (2n = 50–66). The pelomedusid karyotype is regarded as derived, probably from an ancestral condition like that seen in chelids. Gross karyotypic differences are slight or nil within genera and among closely related pleurodiran genera. Triploidy probably occurs in Platemys platycephala (family Chelidae) which has 96 chromosomes. No sex chromosome heteromorphism was observed.

Cytological evidence for population-specific sex chromosome heteromorphism in Palaearctic green toads (Amphibia, Anura)

2007 ◽  
Vol 32 (4) ◽  
pp. 763-768 ◽  
Author(s):  
G. Odierna ◽  
G. Aprea ◽  
T. Capriglione ◽  
S. Castellano ◽  
E. Balletto
Keyword(s):  
Sex Chromosome ◽  
Cytological Evidence ◽  
Chromosome Heteromorphism

scholarly journals Ancestral and neo-sex chromosomes contribute to population divergence in a dioecious plant

2019 ◽  
Author(s):  
Felix E.G. Beaudry ◽  
Spencer C.H. Barrett ◽  
Stephen I. Wright
Keyword(s):  
Gene Flow ◽  
Reproductive Isolation ◽  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Demographic History ◽  
Population Divergence ◽  
Effective Population ◽  
Dioecious Plant ◽  
Fusion Event ◽  
Contemporary Gene Flow

ABSTRACTEmpirical evidence from several animal groups suggests that sex chromosomes may disproportionately contribute to reproductive isolation. This occurs particularly when sex chromosomes are associated with turnover of sex determination systems resulting from structural rearrangements to the sex chromosomes. We investigated these predictions in the dioecious plant Rumex hastatulus, which is comprised of populations of two sex chromosome cytotypes. Using population genomic analyses, we investigated the demographic history of R. hastatulus and explored the contributions of ancestral and neo-sex chromosomes to population genetic divergence. Our study revealed that the cytotypes represented genetically divergent populations with evidence for historical but not contemporary gene flow between them. In agreement with classical predictions, we found that the ancestral X chromosome was disproportionately divergent compared with the rest of the genome. Excess differentiation was also observed on the Y chromosome, even when using measures of differentiation that control for differences in effective population size. Our estimates of the timing of the origin of the neo-sex chromosomes in R. hastatulus are coincident with cessation of gene flow, suggesting that the chromosomal fusion event that gave rise to the origin of the XYY cytotype may have also been a key driver of reproductive isolation.

scholarly journals Sex chromosomes in meiotic, hemiclonal, clonal and polyploid hybrid vertebrates: along the ‘extended speciation continuum'

2021 ◽  
Vol 376 (1833) ◽  
pp. 20200103 ◽  
Author(s):  
Matthias Stöck ◽  
Dmitrij Dedukh ◽  
Radka Reifová ◽  
Dunja K. Lamatsch ◽  
Zuzana Starostová ◽  
...  
Keyword(s):  
Reproductive Isolation ◽  
Sex Chromosomes ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Dominance Hierarchies ◽  
Speciation Continuum ◽  
Well Differentiated ◽  
Evolution Understanding ◽  
Meiotic Aberrations ◽  
Male Heterogamety

We review knowledge about the roles of sex chromosomes in vertebrate hybridization and speciation, exploring a gradient of divergences with increasing reproductive isolation (speciation continuum). Under early divergence, well-differentiated sex chromosomes in meiotic hybrids may cause Haldane-effects and introgress less easily than autosomes. Undifferentiated sex chromosomes are more susceptible to introgression and form multiple (or new) sex chromosome systems with hardly predictable dominance hierarchies. Under increased divergence, most vertebrates reach complete intrinsic reproductive isolation. Slightly earlier, some hybrids (linked in ‘the extended speciation continuum') exhibit aberrant gametogenesis, leading towards female clonality. This facilitates the evolution of various allodiploid and allopolyploid clonal (‘asexual’) hybrid vertebrates, where ‘asexuality' might be a form of intrinsic reproductive isolation. A comprehensive list of ‘asexual' hybrid vertebrates shows that they all evolved from parents with divergences that were greater than at the intraspecific level (K2P-distances of greater than 5–22% based on mtDNA). These ‘asexual' taxa inherited genetic sex determination by mostly undifferentiated sex chromosomes. Among the few known sex-determining systems in hybrid ‘asexuals', female heterogamety (ZW) occurred about twice as often as male heterogamety (XY). We hypothesize that pre-/meiotic aberrations in all-female ZW-hybrids present Haldane-effects promoting their evolution. Understanding the preconditions to produce various clonal or meiotic allopolyploids appears crucial for insights into the evolution of sex, ‘asexuality' and polyploidy. This article is part of the theme issue ‘Challenging the paradigm in sex chromosome evolution: empirical and theoretical insights with a focus on vertebrates (Part II)’.

Sibling species of the blackfly Prosimulium onychodactylum (Simuliidae, Diptera): a salivary gland chromosome study

1983 ◽  
Vol 61 (12) ◽  
pp. 2816-2835 ◽  
Author(s):  
Lester J. Newman
Keyword(s):  
Salivary Gland ◽  
Reproductive Isolation ◽  
Sibling Species ◽  
Chromosome Pairing ◽  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Homologous Pairing ◽  
Chromosome Markers ◽  
Chromosome Arm ◽  
Backcross Hybrids

Larvae of the morphospecies Prosimulium onychodactylum collected from two streams in northern Oregon are divided into 11 sibling species based on fixed and polymorphic inversions. The sibling species have differentiated sex chromosomes; each sibling species falls into one of two groups based on the chromosome arm which carries the sex chromosome markers. Males exhibit lack of homologous pairing or inversion heterzygosity and females have complete chromosome pairing or inversion homozygosity. There is a succession of sibling species which mature in the streams from January through September. Mature larvae of each sibling species are present for about 6 weeks; some are synchronic while others are allochronic. Some of the sibling species occur in the same stream and others are in different streams. Sibling species which are both synchronic and sympatric appear to be reproductively isolated. Reproductive isolation may not be complete for sibling species which are normally allopatric or allochronic; small numbers of F1 and backcross hybrids were found between some of these sibling species. The division of the morphospecies into sibling species was also observed in collections from Washington through northern California.

Muller's Ratchet and the evolution of supernumerary chromosomes

Genome ◽  
1990 ◽  
Vol 33 (6) ◽  
pp. 818-824 ◽  
Author(s):  
David M. Green
Keyword(s):  
Genetic Information ◽  
Sex Chromosome ◽  
Chromosome Complement ◽  
Evolutionary Constraint ◽  
Supernumerary Chromosomes ◽  
Muller's Ratchet ◽  
Heteromorphic Sex Chromosomes ◽  
Muller’S Ratchet ◽  
Over Time ◽  
Chromosome Heteromorphism

Supernumerary chromosomes arise from portions of the normal chromosome complement through nondisjunction, fragmentation, or other mechanisms. Once present in the genome, they are subject to virtually the same genetic conditions that affect the evolutionary degeneration of heteromorphic sex chromosomes. Y or W chromosomes occur only in the presence of X or Z chromosomes, respectively, just as supernumeraries never occur except in the presence of the complete regular karyotype containing their progenitor sequences. Thus, mechanisms that can account for the evolution of sex-chromosome heteromorphism can also be invoked to explain the degeneration process of supernumerary chromosomes after their origination. Incipient supernumeraries initially have genes identical with those on progenitor chromosomes. This frees them from the evolutionary constraint of carrying nonduplicated genetic information, just as in Y and W chromosomes during early stages of sex-chromosome differentiation. The degeneration of supernumerary chromosomes may thus proceed via the mechanism of Muller's Ratchet. This hypothesis predicts that supernumerary chromosomes should lose functional loci, lose sequence homology with the regular genome, and gain heterochromatin over time, resulting in multiple heteromorphic forms of degenerate supernumeraries within and between populations, as is commonly observed.Key words: supernumerary chromosomes, B chromosomes, evolution, origin, Muller's Ratchet.

scholarly journals Karyotype characterization and ZZ/ZW sex chromosome heteromorphism in two species of the catfish genus Ancistrus Kner, 1854 (Siluriformes: Loricariidae) from the Amazon basin

2007 ◽  
Vol 5 (3) ◽  
pp. 301-306 ◽  
Author(s):  
Renildo R. de Oliveira ◽  
Eliana Feldberg ◽  
Maeda B. dos Anjos ◽  
Jansen Zuanon
Keyword(s):  
Sex Chromosomes ◽  
Amazon Basin ◽  
Sex Chromosome ◽  
Brazilian Amazon ◽  
Modal Number ◽  
Phylogenetic Relations ◽  
Karyotypic Formula ◽  
Pericentric Inversions ◽  
Acrocentric Chromosomes ◽  
Chromosome Heteromorphism

We present karyotypic characteristics and report on the occurrence of ZZ/ZW sex chromosomes in Ancistrus ranunculus (rio Xingu) and Ancistrus sp. "Piagaçu" (rio Purus), of the Brazilian Amazon. Ancistrus ranunculus has a modal number of 2n=48 chromosomes, a fundamental number (FN) of 82 for both sexes, and the karyotypic formula was 20m+8sm+6st+14a for males and 19m+9sm+6st+14a for females. Ancistrus sp. "Piagaçu" presented 2n=52 chromosomes, FN= 78 for males and FN= 79 for females. The karyotypic formula was 16m+8sm+2st+26a for males and 16m+9sm+2st+25a for females. The high number of acrocentric chromosomes in karyotype of Ancistrus sp. "Piagaçu" differs from the majority of Ancistrini genera studied so far, and may have resulted from pericentric inversions and translocations. The lower number of chromosomes in A. ranunculus indicates that centric fusions also occurred in the evolution of Ancistrus karyotypes. We conclude that karyotypic characteristics and the presence of sex chromosomes can constitute important cytotaxonomic markers to identify cryptic species of Ancistrus. However, sex chromosomes apparently arose independently within the genus and thus do not constitute a reliable character to analyze phylogenetic relations among Ancistrus species.

scholarly journals Sex Chromosome Heteromorphism and the Fast-X Effect in Poeciliids

2021 ◽  
Author(s):  
Iulia Darolti ◽  
Lydia J. M. Fong ◽  
Judith E. Mank
Keyword(s):  
X Chromosome ◽  
Sex Chromosomes ◽  
Poecilia Reticulata ◽  
Sex Chromosome ◽  
Comparative Approach ◽  
Sequence Evolution ◽  
Chromosome Differentiation ◽  
Poeciliid Fish ◽  
Sex Chromosome System ◽  
Chromosome Heteromorphism

AbstractAn accelerated rate of sequence evolution on the X chromosome compared to autosomes, known as Fast-X evolution, has been observed in a range of heteromorphic sex chromosomes. However, it remains unclear how early in the process of sex chromosome differentiation the Fast-X effect becomes detectible. Recently, we uncovered an extreme variation in sex chromosome heteromorphism across Poeciliid fish species. The common guppy, Poecilia reticulata, Endler’s guppy, P. wingei, and the swamp guppy, P. picta, appear to share the same XY system and exhibit a remarkable range of heteromorphism. The sex chromosome system is absent in recent outgroups, including P. latipinna and Gambusia holbrooki. We combined analyses of sequence divergence and polymorphism data across Poeciliids to investigate X chromosome evolution as a function of hemizygosity and reveal the causes for Fast-X effects. Consistent with the extent of Y degeneration in each species, we detect higher rates of divergence on the X relative to autosomes and a strong Fast-X effect in P. picta, while no change in the rate of evolution of X-linked relative to autosomal genes in P. reticulata. In P. wingei, the species with intermediate sex chromosome differentiation, we see an increase in the rate of nonsynonymous substitutions on the older stratum of divergence only. We also use our comparative approach to test different models for the origin of the sex chromosomes in this clade. Taken together, our study reveals an important role of hemizygosity in Fast-X and suggests a single, recent origin of the sex chromosome system in this clade.

Cytogenetics of the Holarctic black fly Simulium noelleri (Diptera: Simuliidae)

2001 ◽  
Vol 79 (11) ◽  
pp. 1972-1979 ◽  
Author(s):  
Peter H Adler ◽  
Eugenie A Kachvorian
Keyword(s):  
Reproductive Isolation ◽  
Type Species ◽  
Sex Chromosome ◽  
Polytene Chromosomes ◽  
Single Species ◽  
Species Group ◽  
Western Canada ◽  
Black Fly ◽  
Standard Map ◽  
Species Groups

The polytene chromosomes of Simulium noelleri from 16 sites in Armenia, Canada, England, Germany, Russia, and Sweden were analyzed. A standard map is proposed for the S. noelleri species-group that is 11 fixed inversions removed from the original standard map of the subgenus Simulium. Based on one shared subterminal inversion in the IIIL arm, the S. noelleri species-group is in a trichotomy with the S. bezzi and S. ornatum species-groups. Reproductive isolation of S. noelleri and S. decorum is demonstrated chromosomally at sites where both occur together. All analyzed populations of S. noelleri are considered conservatively to represent a single species, although at least three cytotypes are recognized, based primarily on different sex-chromosome systems. Cytotype A, representing the type species of S. noelleri, occurs in Germany, England, and western Russia. Cytotype B occupies Sweden and western Canada, emphasizing the intimate connection between the northern Nearctic and Palearctic simuliid faunas. Cytotype C is known only from Armenia.

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