Sibling species and sex chromosomes in Eusimulium vernum (Diptera: Simuliidae)

1985 ◽  
Vol 63 (9) ◽  
pp. 2145-2161 ◽  
Author(s):  
C. Brockhouse
Keyword(s):  
Sex Determination ◽  
Sibling Species ◽  
Sex Chromosomes ◽  
Polytene Chromosomes ◽  
Biological Species ◽  
Undescribed Species ◽  
Ecological Segregation ◽  
Sex Locus

The polytene chromosomes of larvae from samples of Eusimulium vernum, E. bicorne, and an undescribed species (designated here as Eusimulium "Yukon") were examined. Twelve cytotypes within E. vernum were distinguished, of which at least eight appear to be good biological species. These cytotypes, together with the two allied morphospecies, were related in a cytophylogeny. An ecological segregation between some of the siblings was observed. One cytotype apparently utilizes two (possibly three) separate chromosome (arms) in sex determination. Five of the total of six chromosome arms are involved in sex determination in the various members of this complex. The genetics of sex determination and the mechanisms of sex-locus shift are discussed in the context of these findings.

Cytotaxonomy of Simulium (Montisimulium) ghoomense (Diptera: Simuliidae) from the Darjeeling Hills, India

Zootaxa ◽  
2011 ◽  
Vol 2872 (1) ◽  
pp. 49
Author(s):  
WILLIE HENRY ◽  
SACHIN THAPA ◽  
PETER H. ADLER ◽  
SUBRATA KUMAR DEY ◽  
RAKESH VARMA
Keyword(s):  
Sibling Species ◽  
Sex Chromosomes ◽  
Polytene Chromosomes ◽  
Haploid Number ◽  
Total Complement ◽  
Chromosomal Map

The polytene chromosomes are mapped for a scarce Himalayan simuliid, Simulium (Montisimulium) ghoomense Datta, from the Darjeeling area of India. This species has three tightly paired polytene chromosomes with a haploid number of 3. Chromosomes I, II, and III account for 39.6%, 30.3%, and 30.1% of the total complement length, respectively. The centromeres of chromosomes II and III consistently form a putative partial chromocenter. Sex chromosomes are undifferentiated and polymorphisms and sibling species are lacking in a sample of 35 larvae. This is the first chromosomal map for a species in the subgenus Montisimulium in India.

scholarly journals Proto-sex locus in large yellow croaker provides insights into early evolution of the sex chromosome

2020 ◽  
Author(s):  
Zhiyong Wang ◽  
Shijun Xiao ◽  
Mingyi Cai ◽  
Zhaofang Han ◽  
Wanbo Li ◽  
...  
Keyword(s):  
Sex Determination ◽  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Draft Genome ◽  
Sex Reversal ◽  
Large Yellow Croaker ◽  
Larimichthys Crocea ◽  
Suppressed Recombination ◽  
Heterogametic Sex ◽  
Sex Locus

AbstractAutosomal origins of heterogametic sex chromosomes have been inferred frequently from suppressed recombination and gene degeneration manifested in incompletely differentiated sex chromosomes. However, the initial transition of an autosome region to a proto-sex locus has been not explored in depth. By assembling and analyzing a chromosome-level draft genome, we found a recent (evolved 0.26 million years ago), highly homologous, and dmrt1 containing sex-determination locus with slightly reduced recombination in large yellow croaker (Larimichthys crocea), a teleost species with genetic sex determination (GSD) and with undifferentiated sex chromosomes. We observed genomic homology and polymorphic segregation of the proto-sex locus between sexes. Expression of dmrt1 showed a stepwise increase in the development of testis, but not in the ovary. We infer that the inception of the proto-sex locus involves a few divergences in nucleotide sequences and slight suppression of recombination in an autosome region. In androgen-induced sex reversal of genetic females, in addition to dmrt1, genes in the conserved dmrt1 cluster, and the rest of the sex determination network were activated. We provided evidence that broad functional links were shared by genetic sex determination and environmental sex reversal.

A cytotaxonomic investigation of seven species in the Eusimulium vernum group (Diptera: Simuliidae)

1986 ◽  
Vol 64 (2) ◽  
pp. 296-311 ◽  
Author(s):  
Fiona F. Hunter ◽  
Victoria Connolly
Keyword(s):  
Sibling Species ◽  
North American ◽  
Banding Pattern ◽  
Polytene Chromosomes ◽  
The Other ◽  
Undescribed Species ◽  
Species Complexes

Using the banding pattern of Eusimulium vernum (Macquart) as a standard, the polytene chromosomes of seven North American members of the vernum group are described. These are Eusimulium aestivum (Davies, Peterson, and Wood), E. impar (Davies, Peterson, and Wood), E. gouldingi (Stone), E. croxtoni (Nickolson and Mickel), E. pugetense Dyar and Shannon, E. quebecense (Twinn), and an undescribed species provisionally designated Simulium sp. near furculatum/croxtoni. Two of these species, pugetense and quebecense, apparently are sibling species complexes. An inversion cladogram separates the seven species into two distinct lineages; aestivum, impar, pugetense, and quebecense belong to one and gouldingi, croxtoni, and Simulium sp. to the other.

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.

scholarly journals The Diversity and Evolution of Sex Chromosomes in Frogs

Genes ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 483
Author(s):  
Wen-Juan Ma ◽  
Paris Veltsos
Keyword(s):  
Sex Determination ◽  
Sex Chromosomes ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Comparative Genomic ◽  
Ancestral State ◽  
Heteromorphic Sex Chromosomes ◽  
Genomic Studies ◽  
Evolutionary Trajectories ◽  
Heterogametic Sex

Frogs are ideal organisms for studying sex chromosome evolution because of their diversity in sex chromosome differentiation and sex-determination systems. We review 222 anuran frogs, spanning ~220 Myr of divergence, with characterized sex chromosomes, and discuss their evolution, phylogenetic distribution and transitions between homomorphic and heteromorphic states, as well as between sex-determination systems. Most (~75%) anurans have homomorphic sex chromosomes, with XY systems being three times more common than ZW systems. Most remaining anurans (~25%) have heteromorphic sex chromosomes, with XY and ZW systems almost equally represented. There are Y-autosome fusions in 11 species, and no W-/Z-/X-autosome fusions are known. The phylogeny represents at least 19 transitions between sex-determination systems and at least 16 cases of independent evolution of heteromorphic sex chromosomes from homomorphy, the likely ancestral state. Five lineages mostly have heteromorphic sex chromosomes, which might have evolved due to demographic and sexual selection attributes of those lineages. Males do not recombine over most of their genome, regardless of which is the heterogametic sex. Nevertheless, telomere-restricted recombination between ZW chromosomes has evolved at least once. More comparative genomic studies are needed to understand the evolutionary trajectories of sex chromosomes among frog lineages, especially in the ZW systems.

scholarly journals Unusually High Recombination Rate Detected in the Sex Locus Region of the Honey Bee (Apis mellifera)

Genetics ◽  
1999 ◽  
Vol 153 (4) ◽  
pp. 1701-1708 ◽  
Author(s):  
Martin Beye ◽  
Greg J Hunt ◽  
Robert E Page ◽  
M Kim Fondrk ◽  
Lore Grohmann ◽  
...  
Keyword(s):  
Sex Determination ◽  
Physical Mapping ◽  
Recombination Rate ◽  
Heterozygote Advantage ◽  
Range Restriction ◽  
Group Iii ◽  
Single Sex ◽  
Complementary Sex Determination ◽  
Sex Locus ◽  
Map Distance

Abstract Sex determination in Hymenoptera is controlled by haplo-diploidy in which unfertilized eggs develop into fertile haploid males. A single sex determination locus with several complementary alleles was proposed for Hymenoptera [so-called complementary sex determination (CSD)]. Heterozygotes at the sex determination locus are normal, fertile females, whereas diploid zygotes that are homozygous develop into sterile males. This results in a strong heterozygote advantage, and the sex locus exhibits extreme polymorphism maintained by overdominant selection. We characterized the sex-determining region by genetic linkage and physical mapping analyses. Detailed linkage and physical mapping studies showed that the recombination rate is <44 kb/cM in the sex-determining region. Comparing genetic map distance along the linkage group III in three crosses revealed a large marker gap in the sex-determining region, suggesting that the recombination rate is high. We suggest that a “hotspot” for recombination has resulted here because of selection for combining favorable genotypes, and perhaps as a result of selection against deleterious mutations. The mapping data, based on long-range restriction mapping, suggest that the Q DNA-marker is within 20,000 bp of the sex locus, which should accelerate molecular analyses.

scholarly journals Cytogenetic Analysis of the Asian Box Turtles of the Genus Cuora (Testudines, Geoemydidae)

Genes ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 156
Author(s):  
Lorenzo Clemente ◽  
Sofia Mazzoleni ◽  
Eleonora Pensabene ◽  
Tomáš Protiva ◽  
Philipp Wagner ◽  
...  
Keyword(s):  
Sex Determination ◽  
Sex Chromosomes ◽  
Wide Distribution ◽  
Iucn Red List ◽  
Telomeric Repeats ◽  
Rdna Loci ◽  
Box Turtles ◽  
Genotypic Sex Determination ◽  
Poorly Differentiated ◽  
Almost All

The Asian box turtle genus Cuora currently comprises 13 species with a wide distribution in Southeast Asia, including China and the islands of Indonesia and Philippines. The populations of these species are rapidly declining due to human pressure, including pollution, habitat loss, and harvesting for food consumption. Notably, the IUCN Red List identifies almost all species of the genus Cuora as Endangered (EN) or Critically Endangered (CR). In this study, we explore the karyotypes of 10 Cuora species with conventional (Giemsa staining, C-banding, karyogram reconstruction) and molecular cytogenetic methods (in situ hybridization with probes for rDNA loci and telomeric repeats). Our study reveals a diploid chromosome number of 2n = 52 chromosomes in all studied species, with karyotypes of similar chromosomal morphology. In all examined species, rDNA loci are detected at a single medium-sized chromosome pair and the telomeric repeats are restricted to the expected terminal position across all chromosomes. In contrast to a previous report, sex chromosomes are neither detected in Cuoragalbinifrons nor in any other species. Therefore, we assume that these turtles have either environmental sex determination or genotypic sex determination with poorly differentiated sex chromosomes. The conservation of genome organization could explain the numerous observed cases of interspecific hybridization both within the genus Cuora and across geoemydid turtles.

scholarly journals The maintenance of polygenic sex determination depends on the dominance of fitness effects which are predictive of the role of sexual antagonism

2021 ◽  
Author(s):  
Richard P Meisel
Keyword(s):  
Sex Determination ◽  
Sex Chromosomes ◽  
House Fly ◽  
Sexual Antagonism ◽  
Antagonistic Effects ◽  
Fitness Effects ◽  
Y Chromosomes ◽  
Sexually Antagonistic Selection ◽  
The Individual ◽  
Polygenic Sex Determination

Abstract In species with polygenic sex determination, multiple male- and female-determining loci on different proto-sex chromosomes segregate as polymorphisms within populations. The extent to which these polymorphisms are at stable equilibria is not yet resolved. Previous work demonstrated that polygenic sex determination is most likely to be maintained as a stable polymorphism when the proto-sex chromosomes have opposite (sexually antagonistic) fitness effects in males and females. However, these models usually consider polygenic sex determination systems with only two proto-sex chromosomes, or they do not broadly consider the dominance of the alleles under selection. To address these shortcomings, I used forward population genetic simulations to identify selection pressures that can maintain polygenic sex determination under different dominance scenarios in a system with more than two proto-sex chromosomes (modeled after the house fly). I found that overdominant fitness effects of male-determining proto-Y chromosomes are more likely to maintain polygenic sex determination than dominant, recessive, or additive fitness effects. The overdominant fitness effects that maintain polygenic sex determination tend to have proto-Y chromosomes with sexually antagonistic effects (male-beneficial and female-detrimental). In contrast, dominant fitness effects that maintain polygenic sex determination tend to have sexually antagonistic multi-chromosomal genotypes, but the individual proto-sex chromosomes do not have sexually antagonistic effects. These results demonstrate that sexual antagonism can be an emergent property of the multi-chromosome genotype without individual sexually antagonistic chromosomes. My results further illustrate how the dominance of fitness effects has consequences for both the likelihood that polygenic sex determination will be maintained as well as the role sexually antagonistic selection is expected to play in maintaining the polymorphism.

The cytotaxonomy of three species in the jenningsi-group of the subgenus Simulium (Diptera: Simuliidae) in New York State

1984 ◽  
Vol 62 (3) ◽  
pp. 347-354 ◽  
Author(s):  
A. Elizabeth Gordon
Keyword(s):  
New York ◽  
Sex Determination ◽  
Sibling Species ◽  
New York State ◽  
York State ◽  
Ancestral Condition ◽  
Finger Lakes ◽  
Finger Lakes Region

The chromosomal constitutions of three species in the jenningsi-group in the Adirondacks and the Finger Lakes Region in New York State are detailed. No sibling species were found in Simulium jenningsi, S. fibrinflatum, or S. luggeri in these areas. The species were found to differ by 6 fixed inversions and by 19 floating inversions. 4 of which are related to sex determination in S. jenningsi. The major chromosomal differences between the venustutm-group and the jenningsi-group are detailed. The ancestral condition for each arm was determined using ex-group and L′ analyses. A phylogenetic sequence for these three species from the ancestral condition is proposed.

Genetic and cytogenetic analysis of the fruit fly Rhagoletis cerasi (Diptera: Tephritidae)

Genome ◽  
2008 ◽  
Vol 51 (7) ◽  
pp. 479-491 ◽  
Author(s):  
Ilias Kounatidis ◽  
Nikolaos Papadopoulos ◽  
Kostas Bourtzis ◽  
Penelope Mavragani-Tsipidou
Keyword(s):  
Salivary Gland ◽  
Sex Chromosomes ◽  
Cytogenetic Analysis ◽  
Polytene Chromosomes ◽  
Fruit Fly ◽  
Pest Species ◽  
Heteromorphic Sex Chromosomes ◽  
Weak Points ◽  
Heterogametic Sex ◽  
Rhagoletis Cerasi

The European cherry fruit fly, Rhagoletis cerasi , is a major agricultural pest for which biological, genetic, and cytogenetic information is limited. We report here a cytogenetic analysis of 4 natural Greek populations of R. cerasi, all of them infected with the endosymbiotic bacterium Wolbachia pipientis . The mitotic karyotype and detailed photographic maps of the salivary gland polytene chromosomes of this pest species are presented here. The mitotic metaphase complement consists of 6 pairs of chromosomes, including one pair of heteromorphic sex chromosomes, with the male being the heterogametic sex. The analysis of the salivary gland polytene complement has shown a total of 5 long chromosomes (10 polytene arms) that correspond to the 5 autosomes of the mitotic nuclei and a heterochromatic mass corresponding to the sex chromosomes. The most prominent landmarks of each polytene chromosome, the “weak points”, and the unusual asynapsis of homologous pairs of polytene chromosomes at certain regions of the polytene elements are also presented and discussed.

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