Reproductive Isolation Between Isozyme Groups of Glycine tomentella (Leguminosae), and Spontaneous Doubling in Their Hybrids

1986 ◽  
Vol 34 (5) ◽  
pp. 523 ◽  
Author(s):  
MJ Doyle ◽  
JE Grant ◽  
AHD Brown
Keyword(s):  
Chromosome Number ◽  
Reproductive Isolation ◽  
Hybrid Sterility ◽  
Gene Pools ◽  
Single Chromosome ◽  
Glycine Tomentella ◽  
Hybrid Plants ◽  
Genomic Divergence ◽  
Close Relationship ◽  
Mother Cells

Previous studies of infraspecific isozyme variation in Glycine tornentella have recognised five tetraploid (TI, T2, ... T5) and seven diploid (Dl, D2, ... D7) subspecific groups. This report analyses the meiosis in pollen mother cells of 31 new tetraploid hybrids, 10 diploid hybrids and three diploid by tetraploid combinations. A close relationship, over the range of diversity, was observed between isozyme similarity of the parents of hybrids and chromosome pairing at meiosis. In general, hybrids between parents belonging to the same isozyme group were fertile whereas hybrids between groups were sterile. In the tetraploids, the fertility of interregional hybrids when the accessions belonged to the same group confirmed the widespread distribution of groups T1 and T4. Alternatively, the sterility of intraregional hybrids between groups showed that groups can coexist and remain as separate gene pools. Each isozyme group apparently had a single chromosome number (TI and T5 had 2n = 78; T2, T3 and T4 had 2n = 80). Some otherwise sterile hybrid plants produced rare progeny with elevated chromosome num- ber, probably from the functioning of unreduced male and female gametes. Considerable genomic divergence was apparent from the hybrids between diploid groups, comparable with that found between recognised Glycine species. Again isozyme groups had a characteristic chromosome number (Dl and D2 had 2n = 38, the remainder had 2n = 40). Thus reproductive isolation through reduced formation of bivalents at meiosis operated both between and within cytotypes (2n = 38, 40, 78, 80) of G. tornentella. The pattern of hybrid sterility was as predicted from the analysis of isozyme similarity, confirming the grouping as a meaningful classification within this diverse species.

scholarly journals Rapid Evolution of Assortative Fertilization between Recently Allopatric Species of Drosophila

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
Yasir H. Ahmed-Braimah ◽  
Bryant F. McAllister
Keyword(s):  
Reproductive Isolation ◽  
Phylogenetic Analyses ◽  
Hybrid Sterility ◽  
Rapid Evolution ◽  
Fertilization Success ◽  
Good Resolution ◽  
Genetic Changes ◽  
Close Relationship ◽  
Virilis Group ◽  
Consequent Reduction

The virilis group of Drosophila represents a relatively unexplored but potentially useful model to investigate the genetics of speciation. Good resolution of phylogenetic relationships and the ability to obtain fertile hybrid offspring make the group especially promising for analysis of genetic changes underlying reproductive isolation separate from hybrid sterility and inviability. Phylogenetic analyses reveal a close relationship between the sister species, Drosophila americana and D. novamexicana, yet excepting their contemporary allopatric distributions, factors that contribute to reproductive isolation between this species pair remain uncharacterized. A previous report has shown reduced progeny numbers in laboratory crosses between the two species, especially when female D. novamexicana are crossed with male D. americana. We show that the hatch rate of eggs produced from heterospecific matings is reduced relative to conspecific matings. Failure of eggs to hatch, and consequent reduction in hybrid progeny number, is caused by low fertilization success of heterospecific sperm, thus representing a postmating, prezygotic incompatibility. Following insemination, storage and motility of heterospecific sperm is visibly compromised in female D. novamexicana. Our results provide evidence for a mechanism of reproductive isolation that is seldom reported for Drosophila species, and indicate the rapid evolution of postmating, prezygotic reproductive barriers in allopatry.

scholarly journals Male meiosis and pollen morphology in diploid Indonesian wild bananas and cultivars

The Nucleus ◽  
2021 ◽  
Author(s):  
Fajarudin Ahmad ◽  
Yuyu S. Poerba ◽  
Gert H. J. Kema ◽  
Hans de Jong
Keyword(s):  
Hybrid Sterility ◽  
Pollen Grains ◽  
Chromosome Analysis ◽  
Male Meiosis ◽  
Enzyme Treatment ◽  
Unreduced Gamete ◽  
Ploidy Levels ◽  
Scientific Disciplines ◽  
Sterile Pollen ◽  
Mother Cells

AbstractBreeding of banana is hampered by its genetic complexity, structural chromosome rearrangements and different ploidy levels. Various scientific disciplines, including cytogenetics, linkage mapping, and bioinformatics, are helpful tools in characterising cultivars and wild relatives used in crossing programs. Chromosome analysis still plays a pivotal role in studying hybrid sterility and structural and numerical variants. In this study, we describe the optimisation of the chromosome spreading protocol of pollen mother cells focusing on the effects of standard fixation methods, duration of the pectolytic enzyme treatment and advantages of fluorescence microscopy of DAPI stained cell spreads. We demonstrate the benefits of this protocol on meiotic features of five wild diploid Musa acuminata bananas and a diploid (AA) cultivar banana “Rejang”, with particular attention on pairing configurations and chromosome transmission that may be indicative for translocations and inversions. Pollen slides demonstrate regular-shaped spores except “Rejang”, which shows fertile pollen grains of different size and sterile pollen grains, suggesting partial sterility and unreduced gamete formation that likely resulted from restitutional meiotic divisions.

Systematic Status of a Midwater Population of Freshwater Sculpin (Cottus) from Lake Washington, Seattle, Washington

1975 ◽  
Vol 32 (1) ◽  
pp. 21-28 ◽  
Author(s):  
K. W. Larson ◽  
G. W. Brown Jr.
Keyword(s):  
Reproductive Isolation ◽  
Canal System ◽  
Systematic Status ◽  
Close Relationship ◽  
Lake Washington ◽  
Freshwater Sculpin

A population of freshwater sculpin from Lake Washington differs from other species of the typically benthic genus Cottus in that individuals migrate nightly to the surface and midwaters. Individuals are phenotypically and biochemically similar to Cottus aleuticus, but have a longer, more terete body, a larger cephalic pore and canal system, shorter pelvic fins, and a higher frequency of individuals with seven branchiostegal rays per side.A close relationship between the Lake Washington population and C. aleuticus seems indicated because of their phenotypic and biochemical similarities and because of the existence of individuals in other Northwest lakes that appear intermediate in character between C. aleuticus and the Lake Washington population. The decision as to the specific status of the Lake Washington population is deferred until more is known of its degree of reproductive isolation from C. aleuticus and of the existence of these possibly intermediate populations.

Reproductive Isolation and the Integrity of Two Sympatric Species of Choristoneura (Lepidoptera: Tortricidae)

1953 ◽  
Vol 85 (4) ◽  
pp. 141-151 ◽  
Author(s):  
Stanley G. Smith
Keyword(s):  
Reproductive Isolation ◽  
Hybrid Sterility ◽  
Sympatric Species ◽  
Evolutionary Divergence ◽  
Gene Exchange ◽  
Hybrid Breakdown ◽  
Temporal Isolation ◽  
Isolating Mechanisms ◽  
Spatial Isolation ◽  
Mechanical Isolation

According to Dobzhansky (1951a, p. 262) “Species are … groups of populations the gene exchange between which is limited or prevented by one, or by a combination of several, reproductive isolating mechanisms”. This definition follows from his concept of a species not as a static unit but as a stage in the process of evolutionary divergence. Limitation or prevention of gene exchange is a property of geographic and reproductive isolation (Mayr, 1912), the various types of which Dobzhansky lists as follows:I. Geographic or Spatial IsolationII. Reproductive IsolationA. Ecological IsolationB. Seasonal or Temporal IsolationC. Sexual, Psychological or Ethnological IsolationD. Mechanical IsolationE. Gametic IsolationF. Hybrid InviabilityG. Hybrid SterilityH. Hybrid Breakdown

Coenocytism, ameiosis, and chromosome diminution in intergeneric hybrids in the perennial Triticeae

Genome ◽  
1988 ◽  
Vol 30 (5) ◽  
pp. 766-775 ◽  
Author(s):  
Richard R.-C. Wang
Keyword(s):  
Intergeneric Hybrid ◽  
Chromosome Elimination ◽  
Intergeneric Hybrids ◽  
Pollen Grain ◽  
Unreduced Gamete ◽  
Pollen Mother Cells ◽  
Psathyrostachys Juncea ◽  
Hybrid Plants ◽  
Mother Cells ◽  
Pollen Grain Wall

Three different pathways of ameiotic microsporogenesis were observed in some intergeneric hybrids of the perennial Triticeae grasses. In one of the hybrids between Pseudoroegneria spicata ssp. inermis and Psathyrostachys juncea, pollen mother cells remained as premeiotic interphase cells when the pollen grain wall started to form. The microspores in such an ameiotic plant are presumably unreduced. Coenocyte formation coupled with ameiosis occurred in two hybrid plants of Psathyrostachys huashanica × Secale montanum. Less than 10% of the pollen mother cells had one nucleus. An average of 4.44 nuclei, ranging from 1 to 25 per pollen mother cell, was observed. The nuclei in coenocytes remained unfused when the pollen grain wall was formed. Nucleus splitting followed by cytoplasmic budding or cleavage, possibly a process of chromosome diminution or elimination, replaced meiotic divisions in most of the pollen mother cells in one plant of Leymus angustus × Hordeum bulbosum and two plants of Thinopyrum elongatum × Psathyrostachys juncea. It is evident that these meiotic abnormalities are under genetic control. Probable locations for these genes controlling these phenomena are suggested.Key words: coenocyte, ameiosis, chromosome diminution, chromosome elimination, microsporogenesis, unreduced gamete, polyploidy, intergeneric hybrid.

Apospory in Paspalum thunbergii

2004 ◽  
Vol 52 (1) ◽  
pp. 81 ◽  
Author(s):  
Guohua Ma ◽  
Xuelin Huang ◽  
Nanxian Zhao ◽  
Qiusheng Xu
Keyword(s):  
Chromosome Number ◽  
Developmental Stage ◽  
Pollen Viability ◽  
Paraffin Section ◽  
Embryo Sac ◽  
Low Frequency ◽  
The Other ◽  
Egg Cell ◽  
Successive Generations ◽  
Mother Cells

The cytology, development of aposporous embryo sac, pro-embryo and pseudogamy in Paspalum thunbergii Kunth ex Steud. was studied. P. thunbergii was found to be a tetraploid cytotype, with a chromosome number of 40. Meiosis of the pollen mother cells was irregular, pollen viability was low and multiporate pollens were often observed. Megasporogenesis began normally; however, the megaspore deteriorated at the developmental stage of tetrad, while one to five specific nucellar cells became active and began enlarging, and then developed into aposporous embryo sacs. The mature aposporous sacs usually had three nuclei characterised by one egg cell and two polar nuclei. The egg cell developed spontaneously to form pro-embryos prior to anthesis. When several aposporous sacs occurred in the same ovule, usually one sac near the micropyle was involved in pseudogamy, while the other sacs were not involved. Low frequency of twin-embryo seedlings was observed after seeds matured. Examination of three successive generations by paraffin-section and clearing methods revealed that no sexual sac was present. Therefore, the species P. thunbergii is considered to be an obligate apomict that reproduces by apospory.

Genome constitution of the Australian hexaploid grass Elymus scabrus (Poaceae: Triticeae)

Genome ◽  
1993 ◽  
Vol 36 (1) ◽  
pp. 147-151 ◽  
Author(s):  
J. Torabinejad ◽  
R. J. Mueller
Keyword(s):  
Chromosome Pairing ◽  
Interspecific Hybrids ◽  
Intergeneric Hybrid ◽  
Meiotic Pairing ◽  
Genome Constitution ◽  
Psathyrostachys Juncea ◽  
Hybrid Plants ◽  
Thinopyrum Bessarabicum ◽  
Mother Cells ◽  
Metaphase I

Eight intergeneric hybrid plants were obtained between Elymus scabrus (2n = 6x = 42, SSYY??) and Australopyrum pectinatum ssp. retrofractum (2n = 2x = 14, WW). The hybrids were vegetatively vigorous but reproductively sterile. Examination of pollen mother cells at metaphase I revealed an average of 16.63 I, 5.29 II, 0.19 III, and 0.05 IV per cell for the eight hybrids. The average chiasma frequency of 6.77 per cell in the above hybrids strongly supports the presence of a W genome from A. pectinatum ssp. retrofractum in E. scabrus. Meiotic pairing data of some other interspecific hybrids suggest the existence of the SY genomes in E. scabrus. Therefore, the genome constitution of E. scabrus should be written as SSYYWW. Two other hybrid plants resulted from Elymus yezoensis (2n = 4x = 28, SSYY) crosses with A. pectinatum ssp. pectinatum (2n = 2x = 14, WW). Both were weak and sterile. An average of 0.45 bivalents per cell were observed at metaphase I. This clearly indicates a lack of pairing between W genome of Australopyrum and S or Y genomes of E. yezoensis. In addition, six hybrid plants of E. scabrus with Psathyrostachys juncea (2n = 2x = 14, NN) and one with Thinopyrum bessarabicum (2n = 2x = 14, JJ) were also obtained. The average bivalents per cell formed in both combinations were 2.84 and 0.70, respectively. The results of the latter two combinations showed that there is no N or J genome in E. scabrus.Key words: wide hybridization, chromosome pairing, genome analysis, Australopyrum, Elymus.

Synthetic and natural hybrids of Psathyrostachys huashanica

Genome ◽  
1987 ◽  
Vol 29 (6) ◽  
pp. 811-816 ◽  
Author(s):  
Richard R. -C. Wang
Keyword(s):  
Intergeneric Hybrid ◽  
Meiotic Pairing ◽  
Psathyrostachys Huashanica ◽  
Spike Morphology ◽  
Natural Hybrids ◽  
Close Relationship ◽  
Synthetic Hybrids ◽  
Meiotic Analyses ◽  
Mother Cells ◽  
The Relationship

Three synthetic hybrids and two natural hybrids involving Psathyrostachys huashanica are reported. Gross spike morphology of the hybrids of Pseudoroegneria cognata and Pseudoroegneria spicata ssp. inermis with P. hauashanica was not as indicative of hybridity as in other hybrids involving P. huashanica. Meiotic analyses of these two synthetic hybrids confirmed that little homology exists between the genomes S and Nh. Coenocytism in the hybrids P. huashanica × Secale montanum led to the formation of pseudomicrospores in nondehiscent anthers. No metaphase through telophase chromosome stages could be observed and thus the relationship between genomes Nh and R could not be assessed. Intermediate spike morphology of, and the sterility in, natural hybrids of P. huashanica with P. fragilis and P. juncea substantiated their hybridity. High meiotic pairing in hybrids between P. huashanica and P. fragilis, averaging 1.03 I + 6.48 II, indicated a close relationship between the two species. Occasional high pairing and frequent abnormal meiosis, manifested by degenerating prophase pollen mother cells (PMCs) and empty anthers lacking PMCs of later stages, in the hybrid P. huashanica × P. juncea suggested a more distant relationship between the parental species. It is concluded that P. fragilis is more closely related to P. huashanica than P. juncea. Key words: hybrid (intergeneric), hybrid (interspecific), genome, coenocyte, chromosome diminution, Psathyrostachys, Pseudoroegneria, Secale.

scholarly journals The genetics of postzygotic isolation in the Drosophila virilis group.

Genetics ◽  
1989 ◽  
Vol 121 (3) ◽  
pp. 527-537 ◽  
Author(s):  
H A Orr ◽  
J A Coyne
Keyword(s):  
Reproductive Isolation ◽  
X Chromosome ◽  
Related Species ◽  
Hybrid Sterility ◽  
Drosophila Virilis ◽  
Female Sterility ◽  
Postzygotic Isolation ◽  
Male And Female ◽  
Virilis Group ◽  
Drosophila Virilis Group

Abstract In a genetic study of postzygotic reproductive isolation among species of the Drosophila virilis group, we find that the X chromosome has the largest effect on male and female hybrid sterility and inviability. The X alone has a discernible effect on postzygotic isolation between closely related species. Hybridizations involving more distantly related species also show large X-effects, although the autosomes may also play a role. In the only hybridization yet subjected to such analysis, we show that hybrid male and female sterility result from the action of different X-linked loci. Our results accord with genetic studies of other taxa, and support the view that both Haldane's rule (heterogametic F1 sterility or inviability) and the large effect of the X chromosome on reproductive isolation result from the accumulation by natural selection of partially recessive or underdominant mutations. We also describe a method that allows genetic analysis of reproductive isolation between species that produce completely sterile or inviable hybrids. Such species pairs, which represent the final stage of speciation, cannot be analyzed by traditional methods. The X chromosome also plays an important role in postzygotic isolation between these species.

scholarly journals Parental population range expansion before secondary contact promotes heterosis

2020 ◽  
Author(s):  
Ailene MacPherson ◽  
Silu Wang ◽  
Ryo Yamaguchi ◽  
Loren H. Riesesberg ◽  
Sarah P. Otto
Keyword(s):  
Reproductive Isolation ◽  
Range Expansion ◽  
Genomic Analysis ◽  
Population Expansion ◽  
Ancestral Population ◽  
Secondary Contact ◽  
Hybrid Zones ◽  
Deleterious Alleles ◽  
Genomic Divergence ◽  
Slightly Deleterious Mutations

AbstractPopulation genomic analysis of hybrid zones is instrumental to our understanding of the evolution of reproductive isolation. Many temperate hybrid zones are formed by the secondary contact between two parental populations that had undergone post-glacial range expansion. Here we show that explicitly accounting for historical parental isolation followed by range expansion prior to secondary contact is fundamental for explaining genetic and fitness patterns in these hybrid zones. Specifically, ancestral population expansion can result in allele surfing, neutral or slightly deleterious mutations drift high frequency at the front of the expansion. If these surfed deleterious alleles are recessive, they can contribute to substantial heterosis in hybrids produced at secondary contact, counteracting negative-epistatic interactions between BDMI loci and hence can deteriorate reproductive isolation. Similarly, surfing at neutral loci can alter the expected pattern of population ancestry and suggests that accounting for historical population expansion is necessary to develop accurate null genomic models in secondary-contact hybrid zones. Furthermore, this process should be incorporated in macroevolutionary models of divergence as well, since such heterosis facilitated by parental-range expansion could dampen genomic divergence established in the past.

Sign in / Sign up

Export Citation Format

Share Document