scholarly journals Intrapopulation Chromosomal Polymorphism in Mazama gouazoubira (Cetartiodactyla; Cervidae): The Emergence of a New Species?

2018 ◽  
Vol 154 (3) ◽  
pp. 147-152 ◽  
Author(s):  
Mirela P. Valeri ◽  
Iara M. Tomazella ◽  
José M.B. Duarte
Keyword(s):  
Karyotype Evolution ◽  
Chromosomal Rearrangements ◽  
Chromosomal Polymorphism ◽  
Centric Fusion ◽  
Deer Species ◽  
Balanced Polymorphism ◽  
Gamete Formation ◽  
Lack Of Information ◽  
Mazama Gouazoubira ◽  
A New Species

Mazama gouazoubira is a small deer species widely distributed in South America. Previous studies have shown that this species presents intraspecific chromosomal polymorphisms, which could affect fertility due to the effects of chromosomal rearrangements on gamete formation. Important aspects regarding the karyotype evolution of this species and the genus remain undefined due to the lack of information concerning the causes of this chromosomal variation. Nineteen individuals belonging to the Mazama gouazoubira population located in the Pantanal were cytogenetically evaluated. Among the individuals analyzed, 9 had B chromosomes and 5 carried a heterozygous centric fusion (2n = 69 and FN = 70). In 3 individuals, the fusion occurred between chromosomes X and 16, in 1 individual between chromosomes 7 and 21, and in another individual between chromosomes 4 and 16. These striking polymorphisms could be explained by several hypotheses. One is that the chromosome rearrangements in this species are recent and not fixed in the population yet, and another hypothesis is that they represent a balanced polymorphism and that heterozygotes have an adaptive advantage. On the other hand, these polymorphisms may negatively influence fertility and raise questions about sustainability or reproductive isolation of the population.

Patterns of genome duplication within the Brassica napus genome

Genome ◽  
2003 ◽  
Vol 46 (2) ◽  
pp. 291-303 ◽  
Author(s):  
I A.P Parkin ◽  
A G Sharpe ◽  
D J Lydiate
Keyword(s):  
Brassica Napus ◽  
Genome Duplication ◽  
Chromosomal Rearrangements ◽  
Centric Fusion ◽  
Linkage Groups ◽  
Gross Chromosomal Rearrangements ◽  
A Genome ◽  
C Genome ◽  
Homologous Locus ◽  
Duplicate Loci

The progenitor diploid genomes (A and C) of the amphidiploid Brassica napus are extensively duplicated with 73% of genomic clones detecting two or more duplicate sequences within each of the diploid genomes. This comprehensive duplication of loci is to be expected in a species that has evolved through a polyploid ancestor. The majority of the duplicate loci within each of the diploid genomes were found in distinct linkage groups as collinear blocks of linked loci, some of which had undergone a variety of rearrangements subsequent to duplication, including inversions and translocations. A number of identical rearrangements were observed in the two diploid genomes, suggesting they had occurred before the divergence of the two species. A number of linkage groups displayed an organization consistent with centric fusion and (or) fission, suggesting this mechanism may have played a role in the evolution of Brassica genomes. For almost every genetically mapped locus detected in the A genome a homologous locus was found in the C genome; the collinear arrangement of these homologous markers allowed the primary regions of homoeology between the two genomes to be identified. At least 16 gross chromosomal rearrangements differentiated the two diploid genomes during their divergence from a common ancestor.Key words: genome evolution, Brassicaeae, polyploidy, homoeologous linkage groups.

scholarly journals Ein Neuer Copepode (Cyclopoida: Gnathostoma) von den Westindischen Inseln: Halicyclops Antiguaensis n. sp.

1983 ◽  
Vol 53 (2) ◽  
pp. 262-266 ◽  
Author(s):  
Hans-Volkmar Herbst
Keyword(s):  
New Species ◽  
West Indies ◽  
The Third ◽  
Lack Of Information ◽  
A New Species

In a well on the island of Antigua (West Indies), one female of a new species of Halicyclops was found, described as H. antiguaensis n. sp. The male still remains unknown. The new species belongs to the thermophilus group of Halicyclops , characterized by a spiniform protuberance on each side of the genital somite, the end of which is curved backward, and a spine formula of the third exopodite segment of P1-P4 of 3, 4, 4, 3. It differs from H. thermophilus Kiefer, 1929, H. spinifer Kiefer, 1935, H. venezuelaensis Lindberg, 1954, and H. dedeckeri Brownell, 1983, by the relatively short spines on P5. The new species is closely related to H. latus Shen & Tai, 1964, but in this species the furca and segment 3 of the 4th endopodite are relatively longer. Due to lack of information on the length of the furcal setae of the species of Shen & Tai, further comparison is impossible.

scholarly journals Impact of Chromosomal Rearrangements on the Interpretation of Lupin Karyotype Evolution

Genes ◽  
2019 ◽  
Vol 10 (4) ◽  
pp. 259 ◽  
Author(s):  
Karolina Susek ◽  
Wojciech Bielski ◽  
Katarzyna B. Czyż ◽  
Robert Hasterok ◽  
Scott A. Jackson ◽  
...  
Keyword(s):  
Karyotype Evolution ◽  
Chromosomal Rearrangements ◽  
Chromosome Mapping ◽  
Artificial Chromosome ◽  
Basic Chromosome Number ◽  
Plant Genome ◽  
Old World ◽  
Whole Genome Duplications ◽  
Genome Duplications

Plant genome evolution can be very complex and challenging to describe, even within a genus. Mechanisms that underlie genome variation are complex and can include whole-genome duplications, gene duplication and/or loss, and, importantly, multiple chromosomal rearrangements. Lupins (Lupinus) diverged from other legumes approximately 60 mya. In contrast to New World lupins, Old World lupins show high variability not only for chromosome numbers (2n = 32–52), but also for the basic chromosome number (x = 5–9, 13) and genome size. The evolutionary basis that underlies the karyotype evolution in lupins remains unknown, as it has so far been impossible to identify individual chromosomes. To shed light on chromosome changes and evolution, we used comparative chromosome mapping among 11 Old World lupins, with Lupinus angustifolius as the reference species. We applied set of L. angustifolius-derived bacterial artificial chromosome clones for fluorescence in situ hybridization. We demonstrate that chromosome variations in the species analyzed might have arisen from multiple changes in chromosome structure and number. We hypothesize about lupin karyotype evolution through polyploidy and subsequent aneuploidy. Additionally, we have established a cytogenomic map of L. angustifolius along with chromosome markers that can be used for related species to further improve comparative studies of crops and wild lupins.

Karyotype, C-banding, and Ag-NOR analysis in Diplodus bellottii (Sparidae, Perciforms). Intra-individual polymorphism involving heterochromatic regions

Genome ◽  
1993 ◽  
Vol 36 (4) ◽  
pp. 672-675 ◽  
Author(s):  
A. Amores ◽  
G. Martinez ◽  
J. Reina ◽  
M. C. Alvarez
Keyword(s):  
Karyotype Evolution ◽  
Karyotype Analysis ◽  
Centric Fusion ◽  
Active Regions ◽  
Chromosome Polymorphism ◽  
Terminal Position ◽  
C Banding ◽  
Metacentric Pair ◽  
Pericentric Inversions ◽  
Nucleolus Organizers

A karyotype analysis was carried out in nine specimens of the Sparid species Diplodus bellottii using conventional staining, as well as C-banding and Ag-NOR banding techniques, showing, respectively, 2n = 46 and fundamental number (FN) = 54, and scarce heterochromatic areas irregularly distributed and up to four NOR active regions that were C positive. When compared with the karyotypes of other related species, one centric fusion giving rise to a large metacentric pair and several pericentric inversions seem to have been involved in the karyotype evolution. An intra-individual polymorphism was detected in one specimen, resulting in two karyotypic forms in roughly identical proportion, owing to a larger C-band by the NOR regions, appearing either in a terminal position of the short arms of pair 2 or in telomeric position of pair 3. These findings suggest that the extra heterochromatic segment responsible for the heteromorphism apparently only involves associated heterochromatin and not the NORs themselves. This C-positive block seems to have eventually been transferred between heterologous NOR chromosomes by a somatic event, facilitated by the physical proximity of NOR pairs in the nucleolus.Key words: Sparidae, karyotype, heterochromatin, nucleolus organizers, chromosome polymorphism.

scholarly journals Chromosomal Polymorphism and Speciation: The Case of the Genus Mazama (Cetartiodactyla; Cervidae)

Genes ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 165
Author(s):  
David Javier Galindo ◽  
Gabriela Siqueira Martins ◽  
Miluse Vozdova ◽  
Halina Cernohorska ◽  
Svatava Kubickova ◽  
...  
Keyword(s):  
Chromosomal Polymorphism ◽  
Centric Fusion ◽  
Mean Value ◽  
Fish Analysis ◽  
Fertility Reduction ◽  
Sperm Fish ◽  
The Family ◽  
Chromosomal Variability ◽  
Testicular Histology ◽  
The Impact

Chromosomal polymorphism plays a major role in speciation processes in mammals with high rates of karyotypic evolution, as observed in the family Cervidae. One remarkable example is the genus Mazama that comprises wide inter- and intra-specific chromosomal variability. To evaluate the impact of chromosomal polymorphisms as reproductive barriers within the genus Mazama, inter-specific hybrids between Mazama gouazoubira and Mazama nemorivaga (MGO × MNE) and intra-specific hybrids between cytotypes of Mazama americana (MAM) differing by a tandem (TF) or centric fusion (Robertsonian translocations—RT) were evaluated. MGO × MNE hybrid fertility was evaluated by the seminal quality and testicular histology. MAM hybrids estimation of the meiotic segregation products was performed by sperm-FISH analysis. MGO × MNE hybrids analyses showed different degrees of fertility reduction, from severe subfertility to complete sterility. Regarding MAM, RT, and TF carriers showed a mean value for alternate segregation rate of 97.74%, and 67.23%, and adjacent segregation rate of 1.80%, and 29.07%, respectively. Our results suggested an efficient post-zygotic barrier represented by severe fertility reduction for MGO × MNE and MAM with heterozygous TF. Nevertheless, RT did not show a severe effect on the reproductive fitness in MAM. Our data support the validity of MGO and MNE as different species and reveals cryptic species within MAM.

Orientation and segregation of Robertsonian trivalents in Dichroplus pratensis (Acrididae)

Genome ◽  
1988 ◽  
Vol 30 (6) ◽  
pp. 947-955 ◽  
Author(s):  
Claudio J. Bidau ◽  
Patricia M. Mirol
Keyword(s):  
Chiasma Frequency ◽  
Centric Fusion ◽  
South American ◽  
Meiotic Segregation ◽  
Sperm Production ◽  
Position Effects ◽  
Balanced Polymorphism ◽  
Abnormal Sperm ◽  
Pairing Behavior ◽  
Different Populations

Pairing behavior, metaphase I orientation, and anaphase I segregation of centric fusion trivalents were studied in 26 single, 15 double, and 2 triple male fusion heterozygotes of the polymorphic South American melanopline grasshopper Dichroplus pratensis. They represent the seven different fusions and their combinations already described in different populations of the species. Our analysis showed the following: (1) pairing behavior is very regular in all trivalents; (2) frequencies of linear orientation was very low irrespective of the trivalent involved; (3) reorientation seems to occur frequently since frequencies of abnormal segregation and aneuploid second division cells were invariably lower than those of nonconvergent orientation; (4) aneuploidy and abnormal sperm production increases with increasing number of fusions; (5) chiasma frequency and localisation is relevant to trivalent orientation since trivalents with nonconvergent orientations showed proximal and interstitial chiasmata more frequently than convergently oriented ones. The results are in agreement with the hypothesis that these polymorphisms are old and stable, and confirm that for the maintenance of a balanced polymorphism, if this polymorphism is adaptive because of its consequences on recombination, position effects, etc., changes tending to stabilise trivalent orientation and segregation are central.Key words: Dichrophus pratensis, grasshopper, Robertsonian trivalent, meiotic orientation, meiotic segregation.

Chromosomal changes in vertebrate evolution

1977 ◽  
Vol 199 (1136) ◽  
pp. 377-397 ◽  
Keyword(s):  
Population Structure ◽  
Reproductive Biology ◽  
Chromosome Banding ◽  
Chromosomal Rearrangements ◽  
Chromosomal Polymorphism ◽  
Vertebrate Evolution ◽  
Factors Influencing ◽  
Extant Species ◽  
Chromosomal Changes ◽  
Karyotypic Change

The immense variety of karyotypes found in extant species is unmistakable evidence that the process of evolution is associated with karyotypic change. The question whether the chromosome changes are a cause or a consequence of speciation has been debated intensely for many years and, as is often the case with biological problems, there has been no unequivocal answer. Evolution operates along different lines in different groups of organisms. In animals, reproductive biology and population structure are important factors influencing the rate of karyotypic change. Still, the most extreme chromosomal rearrangements are not necessarily found in the most specialized species. A great number of chromosome banding techniques has made it possible to study chromosomes of vertebrates in great detail. Some applications of these techniques to problems of chromosomal polymorphism in relation to mammalian speciation are presented.

Extraordinary and extensive karyotypic variation: A 48-fold range in chromosome number in the gall-inducing scale insect Apiomorpha (Hemiptera: Coccoidea: Eriococcidae)

Genome ◽  
2000 ◽  
Vol 43 (2) ◽  
pp. 255-263 ◽  
Author(s):  
Lyn G Cook
Keyword(s):  
Chromosome Number ◽  
Chromosomal Rearrangements ◽  
Chromosomal Polymorphism ◽  
Chromosomal Evolution ◽  
Scale Insect ◽  
Closely Related Species ◽  
Host Genus ◽  
Species Complexes ◽  
Species Groups ◽  
Karyotypic Variation

Chromosome number reflects strong constraints on karyotype evolution, unescaped by the majority of animal taxa. Although there is commonly chromosomal polymorphism among closely related taxa, very large differences in chromosome number are rare. This study reports one of the most extensive chromosomal ranges yet reported for an animal genus. Apiomorpha Rübsaamen (Hemiptera: Coccoidea: Eriococcidae), an endemic Australian gall-inducing scale insect genus, exhibits an extraordinary 48-fold variation in chromosome number with diploid numbers ranging from 4 to about 192. Diploid complements of all other eriococcids examined to date range only from 6 to 28. Closely related species of Apiomorpha usually have very different karyotypes, to the extent that the variation within some species- groups is as great as that across the entire genus. There is extensive chromosomal variation among populations within 17 of the morphologically defined species of Apiomorpha indicating the existence of cryptic species-complexes. The extent and pattern of karyotypic variation suggests rapid chromosomal evolution via fissions and (or) fusions. It is hypothesized that chromosomal rearrangements in Apiomorpha species may be associated with these insects' tracking the radiation of their speciose host genus, Eucalyptus. Key words: Apiomorpha, cytogenetics, chromosomal evolution, holocentric.

Chromosomal rearrangements in rock wallabies, Petrogale (Marsupialia: Macropodidae). II. G-banding analysis of Petrogale godmani

Genome ◽  
1989 ◽  
Vol 32 (6) ◽  
pp. 935-940 ◽  
Author(s):  
M. D. B. Eldridge ◽  
P. G. Johnston ◽  
R. L. Close ◽  
P. S. Lowry
Keyword(s):  
Chromosomal Rearrangements ◽  
Centric Fusion ◽  
Common Ancestry ◽  
Chromosome 4 ◽  
Chromosome 5 ◽  
Separate Species ◽  
Submetacentric Chromosome ◽  
Ancestral Chromosome ◽  
Banding Analysis ◽  
Cape York

Chromosomal rearrangements in the two currently recognised races of Petrogale godmani were examined using C- and G-banding. The nominate race P. godmani godmani (2n = 20) was found to possess an inverted chromosome 5 and an acrocentric 6–10 fusion, which can be derived from a 6–10 centric fusion by a centromeric transposition. The Cape York race (2n = 22) was found to retain the ancestral submetacentric chromosome 4 and the ancestral chromosome 5. Thus despite their genie similarity, the two races clearly have major chromosomal differences and should be regarded as separate species. Petrogale g. godmani shares two derived chromosomes with another Queensland taxon, the assimilis race of P. assimilis, indicating recent common ancestry. The Cape York race retains characteristics of an ancestral stock of Petrogale and its genic similarity with P. g. godmani could therefore be the result of extensive introgression.Key words: chromosomal rearrangements, G-banding, Marsupialia, Petrogale.

scholarly journals Unusual chromosomal polymorphism of the common shrew, Sorex araneus L., in southern Belarus

2021 ◽  
Vol 15 (2) ◽  
pp. 159-169
Author(s):  
Iryna A. Kryshchuk ◽  
Victor N. Orlov ◽  
Elena V. Cherepanova ◽  
Yuri M. Borisov
Keyword(s):  
Chromosomal Rearrangements ◽  
Common Shrew ◽  
Chromosomal Polymorphism ◽  
Sorex Araneus ◽  
Chromosomal Form ◽  
Acrocentric Chromosomes ◽  
The Common ◽  
Common Shrew Sorex Araneus

Analysis of the frequency of karyotypes and chromosomal rearrangements in the distributional ranges of four metacentric races of Sorex araneus Linnaeus, 1758 has revealed features that are not typical for polymorphic populations of this species. The frequency of the acrocentric karyotype and heterozygotes for fusion of acrocentric chromosomes turned out to be significantly higher than expected in case of random crossing. As an explanation for the unusual polymorphism, it has been suggested that metacentric races may hybridize with acrocentric populations that remained from the ancient chromosomal form.

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