scholarly journals Genetics of morphological differences and hybrid sterility between Drosophila sechellia and its relatives

1991 ◽  
Vol 57 (2) ◽  
pp. 113-122 ◽  
Author(s):  
Jerry A. Coyne ◽  
John Rux ◽  
Jean R. David
Keyword(s):  
Genetic Analysis ◽  
X Chromosome ◽  
Sibling Species ◽  
Male Genitalia ◽  
Hybrid Sterility ◽  
Drosophila Sechellia ◽  
Ovariole Number ◽  
The Difference ◽  
Male Hybrid ◽  
Morphological Differences

SummaryWe conducted classical genetic analysis of the difference in male genitalia and hybrid sterility between the island-dwelling sibling species Drosophila sechellia and D. mauritiana. At least two loci (one on each autosome) are responsible for the genital difference, with the X chromosome having no significant effect. In contrast, male hybrid sterility is caused by at least four gene loci distributed among all major chromosomes, with those on the X chromosome having the largest effect.We also show that the large difference in ovariole number between D. sechellia and its mainland relative D. simulans is due to at least two gene substitutions, one on each major autosome. The X and the left arm of the second chromosome, however, have no significant effect on the character. This implies that the evolution of reduced ovariole number involved relatively few gene substitutions.These results extend previous findings that morphological differences between Drosophila species are caused by genes distributed among all chromosomes, while hybrid sterility and inviability are due primarily to X-linked genes. Because strong X-effects on male sterility have been found in all three pairwise hybridizations among D. simulans, D. sechellia and D. mauritiana, these effects must have evolved at least twice independently.

scholarly journals X-Chromosome involvement in male hybrid sterility from Glossina morsitans sub-species crosses

Heredity ◽  
1980 ◽  
Vol 45 (3) ◽  
pp. 405-410 ◽  
Author(s):  
C F Curtis ◽  
P A Langley ◽  
M A Trewern
Keyword(s):  
X Chromosome ◽  
Hybrid Sterility ◽  
Glossina Morsitans ◽  
Male Hybrid

Genetic basis of sterility in hybrid males from crosses of Glossina morsitans morsitans and Glossina morsitans centralis (Diptera: Glossinidae)

1987 ◽  
Vol 65 (3) ◽  
pp. 640-646 ◽  
Author(s):  
R. H. Gooding
Keyword(s):  
X Chromosome ◽  
Hybrid Sterility ◽  
Glossina Morsitans Morsitans ◽  
Marker Genes ◽  
Genetic Constitution ◽  
Glossina Morsitans ◽  
Y Chromosomes ◽  
Weak Evidence ◽  
Glossina Morsitans Centralis ◽  
Male Hybrid

Glossina morsitans morsitans Westwood and Glossina morsitans centralis Machado carrying from one to three marker genes on each chromosome were hybridized. F1 females were backcrossed and the resulting backcross males were tested for their ability to inseminate and to fertilize both G. m. morsitans and G. m. centralis; these abilities were then related to the genetic constitution of each male. Hybrid males having an X chromosome from one subspecies and a Y chromosome from the other were sterile, as were about half the males having X and Y chromosomes from the same subspecies. There is weak evidence for autosomal involvement in hybrid sterility but this involvement is not through genetical recombination between the loci Ao and Xo, nor does it depend upon the number of autosomes from the same taxon as the sex chromosomes. Hybrid males descending from G. m. morsitans females could not fertilize G. m. centralis although they could inseminate them. F1 hybrid females had lower than expected intrachromosomal recombination in the X chromosome and in linkage group II, and hybrid females tended to use autosomes of G. m. centralis origin more frequently than chromosomes from G. m. morsitans. Models for evolution of the maternally inherited sterility factor(s) suggest that G. m. centralis is ancestral to G. m. morsitans. Use of hybrid males descending from female G. m. morsitans for genetic control of G. m. centralis is proposed.

scholarly journals A Quantitative Genetic Analysis of Male Sexual Traits Distinguishing the Sibling Species Drosophila simulans and D. sechellia

Genetics ◽  
1999 ◽  
Vol 153 (4) ◽  
pp. 1683-1699 ◽  
Author(s):  
Stuart J Macdonald ◽  
David B Goldstein
Keyword(s):  
Genetic Analysis ◽  
Sibling Species ◽  
Reproductive Traits ◽  
Drosophila Simulans ◽  
Directional Selection ◽  
Posterior Lobe ◽  
Sex Comb ◽  
Tooth Number ◽  
Comb Tooth ◽  
Shape And Size

Abstract A quantitative trait locus (QTL) genetic analysis of morphological and reproductive traits distinguishing the sibling species Drosophila simulans and D. sechellia was carried out in a backcross design, using 38 markers with an average spacing of 8.4 cM. The direction of QTL effects for the size of the posterior lobe was consistent across the identified QTL, indicating directional selection for this trait. Directional selection also appears to have acted on testis length, indicating that sexual selection may have influenced many reproductive traits, although other forms of directional selection cannot be ruled out. Sex comb tooth number exhibited high levels of variation both within and among isofemale lines and showed no evidence for directional selection and, therefore, may not have been involved in the early speciation process. A database search for genes associated with significant QTL revealed a set of candidate loci for posterior lobe shape and size, sex comb tooth number, testis length, tibia length, and hybrid male fertility. In particular, decapentaplegic (dpp), a gene known to influence the genital arch, was found to be associated with the largest LOD peak for posterior lobe shape and size.

scholarly journals Genetics of sexual isolation in male hybrids of Drosophila simulans and D. mauritiana

1996 ◽  
Vol 68 (3) ◽  
pp. 211-220 ◽  
Author(s):  
Jerry A. Coyne
Keyword(s):  
Genetic Analysis ◽  
Y Chromosome ◽  
Sibling Species ◽  
Previous Analysis ◽  
Sexual Isolation ◽  
Drosophila Simulans

SummarySexual isolation between the sibling species D. simulans and D. mauritiana is due largely to the rejection of D. simulans males by D. mauritiana females. Genetic analysis shows that genes on the X and third chromosomes contribute to the differences between males causing sexual isolation, while the Y chromosome, second chromosome and cytoplasm have no effect. These chromosome effects differ from those observed in a previous analysis of sexual isolation in hybrid females, implying that different genes cause sexual isolation in the two sexes.

scholarly journals Sex and death: from cell fate specification to dynamic control of X-chromosome structure and gene expression

2018 ◽  
Vol 29 (22) ◽  
pp. 2616-2621 ◽  
Author(s):  
Barbara J. Meyer
Keyword(s):  
Gene Expression ◽  
Cell Fate ◽  
X Chromosome ◽  
Chromosome Structure ◽  
Dynamic Control ◽  
Three Dimensional ◽  
X Chromosomes ◽  
Meiotic Chromosomes ◽  
The Difference ◽  
Developmental Decision

Determining sex is a binary developmental decision that most metazoans must make. Like many organisms, Caenorhabditis elegans specifies sex (XO male or XX hermaphrodite) by tallying X-chromosome number. We dissected this precise counting mechanism to determine how tiny differences in concentrations of signals are translated into dramatically different developmental fates. Determining sex by counting chromosomes solved one problem but created another—an imbalance in X gene products. We found that nematodes compensate for the difference in X-chromosome dose between sexes by reducing transcription from both hermaphrodite X chromosomes. In a surprising feat of evolution, X-chromosome regulation is functionally related to a structural problem of all mitotic and meiotic chromosomes: achieving ordered compaction of chromosomes before segregation. We showed the dosage compensation complex is a condensin complex that imposes a specific three-­dimensional architecture onto hermaphrodite X chromosomes. It also triggers enrichment of histone modification H4K20me1. We discovered the machinery and mechanism underlying H4K20me1 enrichment and demonstrated its pivotal role in regulating higher-order X-chromosome structure and gene expression.

scholarly journals Reading the bed morphology of a mountain stream: a geomorphometric study on high-resolution topographic data

2010 ◽  
Vol 14 (2) ◽  
pp. 393-405 ◽  
Author(s):  
S. Trevisani ◽  
M. Cavalli ◽  
L. Marchi
Keyword(s):  
High Resolution ◽  
Ad Hoc ◽  
Flow Direction ◽  
Spatial Scales ◽  
Mountain Stream ◽  
Topographic Data ◽  
The Difference ◽  
Morphological Differences ◽  
High Level ◽  
Local Anomalies

Abstract. High-resolution topographic data expand the potential of quantitative analysis of the earth surface, improving the interpretation of geomorphic processes. In particular, the morphologies of the channel beds of mountain streams, which are characterised by strong spatial variability, can be analysed much more effectively with this type of data. In this study, we analysed the aerial LiDAR topographic data of a headwater stream, the Rio Cordon (watershed area: 5 km2), located in the Dolomites (north-eastern Italy). The morphology of the channel bed of Rio Cordon is characterised by alternating step pools, cascades, and rapids with steps. We analysed the streambed morphology by means of ad hoc developed morphometric indices, capable of highlighting morphological features at a high level of spatial resolution. To perform the analysis and the data interpolation, we carried out a channel-oriented coordinate transformation. In the new coordinate system, the calculation of morphometric indices in directions along and transverse to the flow direction is straightforward. Three geomorphometric indices were developed and applied as follows: a slope index computed on the whole width of the channel bed, directional variograms computed along the flow direction and perpendicular to it, and local anomalies, calculated as the difference between directional variograms at different spatial scales. Directional variograms in the flow direction and local anomalies have proven to be effective at recognising morphologic units, such as steps, pools and clusters of large boulders. At the spatial scale of channel reaches, these indices have demonstrated a satisfactory capability to outline patterns associated with boulder cascades and rapids with steps, whereas they did not clearly differentiate between morphologies with less marked morphological differences, such as step pools and cascades.

BIOSYSTEMATICS OF THE GENUS EUXOA (LEPIDOPTERA: NOCTUIDAE). XVIH. COMPARATIVE BIOLOGY AND EXPERIMENTAL TAXONOMY OF THE SIBLING SPECIES EUXOA RIDMGSIANA (GRT.) AND EUXOA MAIMES (SM.)

1985 ◽  
Vol 117 (4) ◽  
pp. 481-493 ◽  
Author(s):  
J.R. Byers ◽  
D.L. Struble ◽  
J.D. Lafontaine
Keyword(s):  
Life Cycle ◽  
Reproductive Isolation ◽  
Sibling Species ◽  
Mate Recognition ◽  
Recognition System ◽  
Flight Period ◽  
Interspecific Differences ◽  
Mate Recognition System ◽  
The Difference ◽  
Species Specific

AbstractThe species previously recognized as Euxoa ridingsiana (Grt.) is shown to be composed of a sympatric pair of sibling species, Euxoa ridingsiana (Grt.) and Euxoa maimes (Sm.), which in the laboratory will produce viable F1 hybrids but no F2. Results of F1 sib and backcrosses show that the F1 males are fertile and the F1 females are infertile. In mating-bias tests conducted in laboratory cages, 74% of matings were conspecific and 26% interspecific. Differences in the diel periodicities of mating, which are about 2 h out of phase, may account for the mating bias. The duration of development of E. ridingsiana in the laboratory and its seasonal flight period in the field are about 2 weeks in advance of that of E. maimes. However, there is considerable overlap of the flight periods and, with the tendency of females of both species to mate several times, it is unlikely that the difference in seasonal emergence is enough to effect reproductive isolation. It is evident that, under natural conditions, reproductive isolation can be maintained entirely by species-specific sex pheromones. This mechanism of reproductive isolation is, however, apparently ineffective when moths are confined in cages in the laboratory.Biogeographic considerations suggest that the differences in life-cycle timing and mating periodicities might have been adaptations to adjust development and reproduction to prevailing ancestral environments. If the initial differentiation of the 2 species occurred in isolation and included at least an incipient shift in the pheromonal mate-recognition system, it is possible that upon reestablishment of contact between ancestral populations the differences in life-cycle timing and mating periodicities acting in concert could have effected substantial, albeit incomplete, reproductive isolation. Subsequent selection to reinforce assortative mating to preserve coadapted gene complexes could then have resulted in differentiation of discrete pheromonal systems and attainment of species status.

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