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.

Sibling species and sex chromosome differentiation in Simulium neornatipes (Diptera: Simuliidae)

1984 ◽  
Vol 26 (3) ◽  
pp. 318-325 ◽  
Author(s):  
D. G. Bedo
Keyword(s):  
Polytene Chromosome ◽  
Sibling Species ◽  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Close Association ◽  
Chromosome Analysis ◽  
Sex Linkage ◽  
Direct Role ◽  
Chromosome Differentiation ◽  
Close Relationship

Polytene chromosome analysis of five Simulium neornatipes populations not only confirms the existence of the two sibling species, S. neornatipes 1 and 2, proposed earlier but reveals a third. S. neornatipes 3. These sibling species share a common standard polytene chromosome banding sequence which differs from the Australian S. ornatipes complex standard by five fixed inversions. The sharing of polymorphic inversions between the ornatipes and neornatipes complexes indicates their close relationship. The neornatipes species are distinguished from each other by additional fixed inversions and differentiated sex chromosomes. Extensive sex chromosome differentiation involving chromosome III has occurred in S. neornatipes 1 and 2. A period of incomplete sex-linkage allowing reassortment of inversions must have preceded the currently observed strong sex-linkage of differentiated sex chromosomes to account for the complex array of sex chromosomes found. The close association of sex chromosome differentiation with speciation in black flies is discussed in relation to appropriate speciation mechanisms. It is concluded that the rearrangements themselves have no direct role in the speciation process.Key words: sibling species, sex chromosomes, Simuliidae.

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)’.

Ultrastructural analysis of the X1X2X3O sex chromosome system during the spermatogenesis of Tegenaria domestica (Arachnida)

1982 ◽  
Vol 58 (1) ◽  
pp. 411-422
Author(s):  
R. Benavente ◽  
R. Wettstein ◽  
M. Papa
Keyword(s):  
Synaptonemal Complex ◽  
Chromosome Pairing ◽  
Sex Chromosomes ◽  
Ultrastructural Study ◽  
Chromosome Structure ◽  
Sex Chromosome ◽  
X Chromosomes ◽  
Sex Chromosome System ◽  
Available Information ◽  
Dense Chromatin

An ultrastructural study was performed on the sex chromosomes (male X1X2X3O) during the spermatogenesis of Tegenaria domestica (Arachnida, Agelenidae). This study was carried out using random and serially cut sections. During pachytene and diplotene the three X chromosomes are longitudinally paired. Each of these consists of a central core of condensed chromatin, surrounded by a field of dense chromatin projections through which the chromosomes are in contact with one another. These projections may be responsible for the recognition and pairing of the sex chromosomes and in some way participate in their non-disjunction during anaphase I. A study of the structure and behaviour of the sex chromosomes during spermatogenesis is also presented. The available information on non-synaptonemal complex-mediated chromosome pairing and a systematization of sex chromosome structure in spiders are discussed.

Pattern of X–Y chromosome pairing in the Japanese field vole, Microtus montebelli

Genome ◽  
1997 ◽  
Vol 40 (6) ◽  
pp. 829-833 ◽  
Author(s):  
P. M. Borodin ◽  
M. B. Rogatcheva ◽  
K. Koyasu ◽  
K. Fukuta ◽  
K. Mekada ◽  
...  
Keyword(s):  
Synaptonemal Complex ◽  
Chromosome Pairing ◽  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Chromosomal Evolution ◽  
The Other ◽  
Field Vole ◽  
Y Chromosomes ◽  
The One ◽  
Ancestral Type

Pairing of X and Y chromosomes at meiotic prophase in males of Microtus montebelli was analyzed. The sex chromosomes form a synaptonemal complex at pachytene and end-to-end association at diakinesis – metaphase I in two species of the genus Microtus (M. montebelli and M. oeconomus) only, while they do not pair at all in the other species of this genus that have been studied so far. These data confirm that M. montebelli and M. oeconomus are very closely related in their origin. It is suggested that the sex chromosomes of M. montebelli and M. oeconomus display the ancestral type of X–Y pairing. The lack of X–Y pairing in most species of Microtus appeared after the split in lineage that led to M. oeconomus and M. montebelli on the one hand and the remaining species on the other.Key words: Microtus montebelli, arvicoline phylogeny, synaptic sex chromosome, synaptonemal complex, chromosomal evolution.

The population structure of Simulium vittatum (Zett.): the IIIL-1 and IS-7 sibling species

1981 ◽  
Vol 59 (10) ◽  
pp. 1857-1883 ◽  
Author(s):  
Klaus Rothfels ◽  
David Featherston
Keyword(s):  
United States ◽  
Population Structure ◽  
Salivary Gland ◽  
Sibling Species ◽  
Sex Chromosome ◽  
Geographic Pattern ◽  
Northeastern United States ◽  
Simulium Vittatum ◽  
Cytological Characteristics ◽  
Wide Zone

This paper describes two sibling species in Simulium vittatum (Zett.) on the basis of their salivary gland chromosomes. The IIIL-1 sibling is characterized by a Y chromosome carrying the IIIL-1 inversion; the IS-7 sibling is characterized by the IS-7 X chromosome. The basic banding sequences are identical in the two sibling species. The siblings differ however in the relative frequencies of standard and inverted sequences for a number of autosomal polymorphisms that they share. Standard sequences are predominant in the IIIL-1 sibling and inverted sequences in the IS-7 type. The IIIL-1 sibling is distributed from the Atlantic, south to the Gulf of Mexico and west to the Saskatchewan–Alberta border. The IS-7 sibling ranges from the Atlantic to Alaska, but so far has not been found south of Pennsylvania. The sibling species are sympatric over a wide zone extending through parts of Quebec, Ontario, and northeastern United States via Michigan, Wisconsin, and Minnesota to Saskatchewan and Alberta. It is argued that the two sibling species originated in the region of the present sympatry. Evidence for this conclusion derives from the geographic pattern of sex chromosome and autosome polymorphism in North America and from cytological characteristics of certain extraterritorial populations (Iceland).

Sex chromosome polymorphism in the Simulium tuberosum complex (Lundström) (Diptera: Simuliidae)

1984 ◽  
Vol 62 (4) ◽  
pp. 647-658 ◽  
Author(s):  
G. F. Mason
Keyword(s):  
United States ◽  
Sibling Species ◽  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Distinct Species ◽  
Chromosome Polymorphism ◽  
Northeastern United States ◽  
Primary Zone ◽  
Heteromorphic Sex Chromosomes ◽  
Unusual Chromosome

These studies on the Simulium tuberosum complex have revealed the presence of a number of closely related sibling species which are distinguished by the banding pattern on their sex chromosomes. Collections were made over wide geographic areas of North America and the distributions of the various types found were recorded. Included are areas in northeastern United States with sites at which a number of the sibling species are sympatric. At these sites the separation of one taxa from another is not clear and a number of intra- and inter-sibling sex chromosome polymorphisms were detected. Included in these polymorphs were larvae with unusual chromosome combinations, including females with heteromorphic sex chromosomes. Arguments are made for some of the divisions as distinct species and for sex chromosome polymorphism in others. Based on the evidence of the geographic distribution, it is suggested that the area of sympatry in which polymorphism in all of the division of the complex was found is a primary zone of speciation.

Polytene chromosomes of three species of blackflies in the Simulium pictipes group (Diptera: Simuliidae)

1975 ◽  
Vol 53 (8) ◽  
pp. 1147-1164 ◽  
Author(s):  
Daniel G. Bedo
Keyword(s):  
Salivary Gland ◽  
Chromosome Number ◽  
Sibling Species ◽  
Sex Chromosomes ◽  
Polytene Chromosomes ◽  
Fluorescence Staining ◽  
Haploid Chromosome Number ◽  
Quinacrine Fluorescence ◽  
Individual Bands ◽  
Staining Methods

The salivary gland chromosomes of members of the Simulium pictipes group were examined by conventional staining and quinacrine fluorescence staining methods which proved to be a useful tool to show otherwise hidden details, especially in expanded centromere regions. Three cytologically definable species were found, one of which must represent a previously unrecognized species. Simulium longistylatum Shewell was the only species among the three siblings identified with certainty. The remaining pair were designated as S. pictipes A and S. pictipes B. In all three siblings the haploid chromosome number was three. Specific differences include a simple and a complex inversion, a shift of basal bands between the short arms of the second and third chromosome, details of the sex chromosomes, and the amount of DNA in certain individual bands and expanded centromere regions. Y chromosome markers are located in a different element of the complement in each of the three species, a unique situation within closely related blackfly sibling species. These findings are discussed in connection with the evolution of sex chromosomes and sibling species. A cytophylogeny is presented.

Sex chromosome pairing and sex chromatin bodies in W–Z translocation strains of Ephestia kuehniella (Lepidoptera)

Genome ◽  
1994 ◽  
Vol 37 (3) ◽  
pp. 426-435 ◽  
Author(s):  
František Marec ◽  
Walther Traut
Keyword(s):  
Chromosome Pairing ◽  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Ephestia Kuehniella ◽  
Z Chromosome ◽  
W Chromosome ◽  
Wild Type ◽  
Electron Microscopic ◽  
Sex Chromatin ◽  
Mediterranean Flour Moth

Structure and pairing behavior of sex chromosomes in females of four T(W;Z) lines of the Mediterranean flour moth, Ephestia kuehniella, were investigated using light and electron microscopic techniques and compared with the wild type. In light microscopic preparations of pachytene oocytes of wild-type females, the WZ bivalent stands out by its heterochromatic W chromosome strand. In T(W;Z) females, the part of the Z chromosome that was translated onto the W chromosome was demonstrated as a distal segment of the neo-W chromosome, displaying a characteristic non-W chromosomal chromomere–interchromomere pattern. This segment is homologously paired with the corresponding part of a complete Z chromosome. In contrast with the single ball of heterochromatic W chromatin in highly polyploid somatic nuclei of wild-type females, the translocation causes the formation of deformed or fragmented W chromatin bodies, probably owing to opposing tendencies of the Z and W chromosomal parts of the neo-W. In electron microscopic preparations of microspread nuclei, sex chromosome bivalents were identified by the remnants of electron-dense heterochromatin tangles decorating the W chromosome axis, by the different lengths of the Z and W chromosome axes, and by incomplete pairing. No heterochromatin tangles were attached to the translocated segment of the Z chromosome at one end of the neo-W chromosome. Because of the homologous pairing between the translocation and the structurally normal Z chromosome, pairing affinity of sex chromosomes in T(W;Z) females is significantly improved. Specific differences observed among T(W;Z)1–4 translocations are probably due to the different lengths of the translocated segments.Key words: Mediterranean flour moth, sex chromosomes, sex chromatin, translocations, synaptonemal complexes, microspreading.

scholarly journals Genomic landscape of reproductive isolation in Lucania killifish: The role of sex chromosomes and salinity

2019 ◽  
Author(s):  
Emma L. Berdan ◽  
Rebecca C. Fuller ◽  
Genevieve M. Kozak
Keyword(s):  
Reproductive Isolation ◽  
Salinity Tolerance ◽  
Sex Chromosomes ◽  
Genetic Architecture ◽  
Sex Chromosome ◽  
Salinity Gradient ◽  
Chromosome 1 ◽  
Hybrid Male ◽  
Bluefin Killifish ◽  
Sex Locus

ABSTRACTUnderstanding how speciation occurs and how reproductive barriers contribute to population structure at a genomic scale requires elucidating the genetic architecture of reproductive isolating barriers. In particular, it is crucial to determine if loci underlying reproductive isolation are genetically linked or if they are located on sex chromosomes, which have unique inheritance and population genetic properties. Bluefin killifish (Lucania goodei) and rainwater killifish (L. parva) are closely related species that have diverged across a salinity gradient and are reproductively isolated by assortative mating, hybrid male infertility, viability of hybrid offspring at high salinities, as well as reduced overall fitness of F2 offspring and backcrosses to L. goodei. We conducted QTL mapping in backcrosses between L. parva and L. goodei to determine the genetic architecture of sex determination, mate attractiveness, fertility, and salinity tolerance. We find that the sex locus appears to be male determining and located on a chromosome that has undergone a Robertsonian fusion in L. parva relative to L. goodei. We find that the sex locus on the fused chromosome is involved in several genomic incompatibilities, which affect the survival of backcrossed offspring. Among the backcrossed offspring that survived to adulthood, we find that one QTL for male attractiveness to L. goodei females is closely linked to this sex locus on chromosome 1. Males homozygous for L. goodei alleles at the sex locus laid more eggs with L. goodei females. QTL associated with salinity tolerance were spread across the genome but did not tend to co-localize with reproductive isolation. Thus, speciation in this system appears to be driven by reinforcement and indirect selection against hybrids rather than direct natural selection for salinity tolerance. Our work adds to growing evidence that sex chromosome evolution may contribute to speciation.

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