scholarly journals Speciation towards tetraploidization after intermediate processes of non-sexual reproduction

2008 ◽  
Vol 363 (1505) ◽  
pp. 2921-2929 ◽  
Author(s):  
Carina Cunha ◽  
Ignacio Doadrio ◽  
Maria M Coelho
Keyword(s):  
Sexual Reproduction ◽  
Mating Systems ◽  
Diploid Hybrid ◽  
Polyploid Species ◽  
Animal Evolution ◽  
Sex Ratio Bias ◽  
First Time ◽  
Normal Meiosis ◽  
Experimental Crosses ◽  
Hybrid Forms

Polyploidy, hybridization and variation in mating systems are central issues for a deeper understanding of animal evolution. The Iberian species Squalius alburnoides represents an example combining all three phenomena. Previous studies showed that S. alburnoides populations are mainly composed of triploid and diploid hybrid forms (mainly females), and that the tetraploid forms are rare or absent. Both populations from the Douro drainage reveal a distinct scenario: tetraploid individuals represent 85.6–97.5% of the population, with no sex ratio bias observed. Based on the flow cytometry measurements of blood and spermatozoa cells, microsatellite loci and experimental crosses, we describe here, for the first time, two symmetric allotetraploid populations (CCAA) that resumed normal meiosis after undergoing intermediate processes of non-sexual reproduction to give rise to a new sexually reproducing polyploid species. Prezygotic (habitat selection and assortative mating) and postzygotic mechanisms (nonviable embryos) are responsible for the reproductive isolation from other forms of the S. alburnoides complex (e.g. CA, CAA). This example illustrates how hybrid polyploid complexes may lead to speciation.

Zygospore morphology in the conjugating green alga Spirotaenia diplohelica (Streptophyta, Zygnematophyceae, Mesotaeniaceae)

Phytotaxa ◽  
2017 ◽  
Vol 329 (3) ◽  
pp. 284
Author(s):  
PETER COESEL ◽  
ANDRÉ VANHOOF ◽  
KOOS MEESTERS
Keyword(s):  
Sexual Reproduction ◽  
Green Alga ◽  
Early Stage ◽  
First Time

The zygospore of the saccoderm desmid Spirotaenia diplohelica is described for the first time. The spore is most peculiar, for surrounded by a series of transparent, conical projections. In that feature it very much resembles the zygospore of Spirotaenia truncata. Contrary to Spirotaenia condensata and Spirotaenia obscura, no twin zygospores are produced and walls of empty gametangial cells do not solve in an early stage but tend to stick to the zygospore for some time. In view of those essentially different modes of sexual reproduction it is not to be excluded that species in the traditional genus Spirotaenia belong to different phylogenetic cladess.

Evidence for genetic suppression of heterogenetic chromosome pairing in polyploidy species of Solanum, sect. Petota

1983 ◽  
Vol 25 (5) ◽  
pp. 530-539 ◽  
Author(s):  
Jan Dvořák
Keyword(s):  
Chromosome Pairing ◽  
Interspecific Hybrids ◽  
Diploid Species ◽  
Diploid Hybrid ◽  
Polyploid Species ◽  
Chromosome Differentiation ◽  
Genetic Suppression ◽  
Solanum Sect ◽  
Paradoxical Results

Data on chromosome pairing in haploids and interspecific hybrids of Solanum, sect. Petota reported in the literature were used to determine whether the diploidlike chromosome pairing that occurs in some of the polyploid species of the section is regulated by the genotype or brought about by some other mechanism. The following trends emerged from these data. Most of the polyploid × polyploid hybrids had high numbers of univalents, which seemed to indicate that the polyploid species were constructed from diverse genomes. Haploids, except for those derived from S. tuberosum, had incomplete chromosome pairing. All hybrids from diploid × diploid crosses had more or less regular chromosome pairing, which suggested that all investigated diploid species have the same genome. Likewise, hybrids from polyploid × diploid crosses had high levels of chromosome pairing. These paradoxical results are best explained if it is assumed that (i) the genotypes of most polyploid species, but not those of the diploid species, suppress heterogenetic pairing, (ii) that nonstructural chromosome differentiation is present among the genomes of both diploid and polyploid species, and (iii) the presence of the genome of a diploid species in a polyploid × diploid hybrid results in promotion of heterogenetic pairing. It is, therefore, concluded that heterogenetic pairing in most of the polyploid species is genetically suppressed.

Étude comparée de la reproduction de Phymatolithon calcareum (Pallas) Adey & McKibbin et Lithothamnion corallioides (P. & H. Crouan) P. & H. Crouan (Corallinales, Rhodophyta), et reconsidérations sur la définition des genres

1998 ◽  
Vol 76 (8) ◽  
pp. 1433-1445 ◽  
Author(s):  
M L Mendoza ◽  
J Cabioch
Keyword(s):  
Sexual Reproduction ◽  
Type Species ◽  
Supporting Cell ◽  
Simple Type ◽  
Auxiliary Cell ◽  
Carpogonial Branch ◽  
Juvenile Stages ◽  
Fusion Cell ◽  
Main Components ◽  
First Time

The two CorallinalesPhymatolithon calcareum and Lithothamnion corallioides are the main components of European maerl communities. A large majority of the thalli are free-living branches borne on juvenile crusts that are rarely found. A detailed investigation of these juvenile stages has allowed the discovery of their reproductive features. Sexual reproduction of P. calcareum, the type-species of the genus, is described here for the first time and thus gives fundamental data for the generic definition. On the floor of the female conceptacle, a set of carpogonial branches is formed. Each fertilized carpogonium then fuses with the supporting cell of the carpogonial branch, which is also its auxiliary cell. A small fusion cell is thus formed, which produces upwards a small gonimoblast reduced to a short chain of carposporangia. In a mature conceptacle, the surface of the fertile floor thus appears entirely covered with small gonimoblasts. In the male conceptacle, mature spermatangia produced on the floor are typically dendroid; those produced on the walls are of a more simple type. The organization of the asexual conceptacle is briefly reviewed. The reproduction of L. corallioides is also newly described and compared with that previously reported for L. muelleri, the type-species of the genus.Key words: Corallinales, Phymatolithon, Lithothamnion, sexual reproduction, generic definition.

scholarly journals Sexual reproduction with variable mating systems can resist asexuality in a rock–paper–scissors dynamics

2015 ◽  
Vol 2 (7) ◽  
pp. 140383 ◽  
Author(s):  
Juan Carranza ◽  
Vicente Polo
Keyword(s):  
Mating System ◽  
Sexual Reproduction ◽  
Parameter Space ◽  
Mating Systems ◽  
Reproductive Mode ◽  
Long Term Effects ◽  
Diploid Population ◽  
Theoretical Question ◽  
Equal Contribution

While sex can be advantageous for a lineage in the long term, we still lack an explanation for its maintenance with the twofold cost per generation. Here we model an infinite diploid population where two autosomal loci determine, respectively, the reproductive mode, sexual versus asexual and the mating system, polygynous (costly sex) versus monogamous (assuming equal contribution of parents to offspring, i.e. non-costly sex). We show that alleles for costly sex can spread when non-costly sexual modes buffer the interaction between asexual and costly sexual strategies, even without twofold benefit of recombination with respect to asexuality. The three interacting strategies have intransitive fitness relationships leading to a rock–paper–scissors dynamics, so that alleles for costly sex cannot be eliminated by asexuals in most situations throughout the parameter space. Our results indicate that sexual lineages with variable mating systems can resist the invasion of asexuals and allow for long-term effects to accumulate, thus providing a solution to the persisting theoretical question of why sex was not displaced by asexuality along evolution.

scholarly journals Evidence of adoption, monozygotic twinning, and low inbreeding rates in a large genetic pedigree of polar bears

2015 ◽  
Author(s):  
René M. Malenfant ◽  
David W. Coltman ◽  
Evan S. Richardson ◽  
Nicholas J. Lunn ◽  
Ian Stirling ◽  
...  
Keyword(s):  
Mating Systems ◽  
Parentage Analysis ◽  
Hudson Bay ◽  
Polar Bears ◽  
Nucleotide Polymorphisms ◽  
Single Nucleotide ◽  
Monozygotic Twinning ◽  
Close Relatives ◽  
Free Ranging ◽  
First Time

Multigenerational pedigrees have been developed for free-ranging populations of many species, are frequently used to describe mating systems, and are used in studies of quantitative genetics. Here, we document the development of a 4449-individual pedigree for the Western Hudson Bay subpopulation of polar bears (Ursus maritimus), created from relationships inferred from field and genetic data collected over six generations of bears sampled between 1966 and 2011. Microsatellite genotypes for 22-25 loci were obtained for 2945 individuals, and parentage analysis was performed using the program FRANZ, including additional offspring-dam associations known only from capture data. Parentage assignments for a subset of 859 individuals were confirmed using an independent medium-density set of single nucleotide polymorphisms. To account for unsampled males in our population, we performed half-sib/full-sib analysis to reconstruct males using the program COLONY, resulting in a final pedigree containing 2957 assigned maternities and 1861 assigned paternities with only one observed case of inbreeding between close relatives. During genotyping, we identified two independently captured two-year-old males with identical genotypes at all 25 loci, showing--for the first time--a case of monozygotic twinning among polar bears. In addition, we documented six new cases of cub adoption, which we attribute to cub misidentification or misdirected maternal care by a female bereaved of her young. Importantly, none of these adoptions could be attributed to reduced female vigilance caused by immobilization to facilitate scientific handling, as has previously been suggested.

scholarly journals A Eurasia-wide polyploid species complex involving 6x Trifolium ambiguum, 2x T. occidentale and 4x T. repens produces interspecific hybrids with significance for clover breeding

2019 ◽  
Author(s):  
Warren Williams ◽  
Isabelle M Verry ◽  
Helal A Ansari ◽  
S Wajid Hussain ◽  
Ihsan Ullah ◽  
...  
Keyword(s):  
Chromosome Number ◽  
White Clover ◽  
Interspecific Hybrids ◽  
Species Complex ◽  
Embryo Rescue ◽  
Polyploid Species ◽  
Trifolium Ambiguum ◽  
Breeding Populations ◽  
Fertile Hybrids ◽  
First Time

Abstract Background Trifolium ambiguum occurs as a 2x, 4x, 6x polyploid series in W Asia, The 6x form is the most agronomically desirable, having strong rhizomatous spread and drought tolerance. These traits would be potentially very valuable if they could be transferred to white clover (T. repens) which is the most important agronomic clover species. However, to-date, no fertile interspecific hybrids with 6x T. ambiguum are available. Previously, 2x T. occidentale from W Europe has produced synthetic fertile hybrids with both 2x and 4x T. ambiguum and these were inter-fertile with white clover. Here we ask whether 2x T. occidentale can form fertile hybrids with 6x T. ambiguum and act as a genetic bridge to white clover and bring these species together as part of a common gene pool. Results Ten verified F1 (6x T. ambiguum x 2x T. occidentale) hybrids were produced by embryo rescue and seven were studied further. All four investigated for chromosome number were 2n=4x=32 and FISH confirmed the expected 21 T. ambiguum and 8 T. occidentale chromosomes. Hybrid fertility was extremely low but 2n female gametes functioned with white clover pollen to produce seeds. Derived plants were confirmed using FISH and were successfully backcrossed to white clover to produce partially fertile breeding populations. Conclusions Although T. occidentale and 6x T. ambiguum are widely separated by geography and ecological adaptation they have maintained enough genomic affinity to produce partially fertile hybrids. Inter-fertility of the hybrids with allotetraploid T. repens showed that T. occidentale can provide a genetic bridge between 6x T. ambiguum and white clover to produce plants with new phenotypes combining the traits of all three species. Use of this information should enable potentially valuable stress tolerance traits from 6x T. ambiguum to be used in white clover breeding for the first time.

scholarly journals Algal Sex Determination and the Evolution of Anisogamy

2019 ◽  
Vol 73 (1) ◽  
pp. 267-291 ◽  
Author(s):  
James Umen ◽  
Susana Coelho
Keyword(s):  
Sex Determination ◽  
Sexual Reproduction ◽  
Green Algae ◽  
Life Histories ◽  
Mating Systems ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Photosynthetic Eukaryotes ◽  
Sex Determination Mechanisms ◽  
Shed Light

Algae are photosynthetic eukaryotes whose taxonomic breadth covers a range of life histories, degrees of cellular and developmental complexity, and diverse patterns of sexual reproduction. These patterns include haploid- and diploid-phase sex determination, isogamous mating systems, and dimorphic sexes. Despite the ubiquity of sexual reproduction in algae, their mating-type-determination and sex-determination mechanisms have been investigated in only a limited number of representatives. These include volvocine green algae, where sexual cycles and sex-determining mechanisms have shed light on the transition from mating types to sexes, and brown algae, which are a model for UV sex chromosome evolution in the context of a complex haplodiplontic life cycle. Recent advances in genomics have aided progress in understanding sexual cycles in less-studied taxa including ulvophyte, charophyte, and prasinophyte green algae, as well as in diatoms.

Mating Systems

2001 ◽  
Author(s):  
Ann K. Sakai ◽  
David F. Westneat
Keyword(s):  
Sexual Reproduction ◽  
Mating Systems ◽  
Evolutionary Ecology ◽  
Genetic Material ◽  
Ecological Factors ◽  
Reproductive Traits ◽  
Female Reproduction ◽  
Selective Pressures ◽  
Evolutionary Changes ◽  
Sex Allocation Theory

The study of mating is one of the most active areas in evolutionary ecology. What fuels this research is curiosity about a stunning diversity of ways in which zygotes are formed. Many plants and some animals can reproduce without combining gametes. Many other plants combine gametes but do so within the same individual (selfing). Still other plants and animals require a gamete from another individual to stimulate reproduction but do not incorporate the genetic material contained in that gamete in the offspring. Finally, many organisms combine gametes produced from different individuals in sexual reproduction, but the ways in which these individuals get together to reproduce are also amazingly diverse and have major implications for how selection acts in these populations. Why are there so many different ways to reproduce? Answering this question is a major challenge for evolutionary ecologists. Our approach begins with how a variety of ecological factors affect selection on reproductive traits. Because many reproductive traits show genetic variation, diversity in selective pressures can lead to a diversity of evolutionary changes. Thus, understanding the evolutionary ecology of mating systems can help to interpret the significance of this variation and can provide new insight into related phenomena. For example, costs of female reproduction associated with development of offspring greatly impact other aspects of the life history, and males are often limited by mates (Savalli, this volume). Factors such as levels of selfing, inbreeding depression, and allocation of resources play a part in mating systems of both plants and animals (Waser and Williams, this volume), and sex allocation theory has been used in both plants and animals to explore the evolution of hermaphroditism and unisexuality (Campbell 2000; Orzack, this volume). This chapter explores some of the major forces affecting mating systems. Our treatments of plants and animals differ in emphasis, but our goal is to use the perspective of evolutionary ecology to define more fully the similarities, differences, and diversity in plant and animal mating systems, and to highlight potentially interesting yet currently unanswered questions. Diversity in patterns of zygote production arises in part from ecological factors influencing two issues: selection on the evolution of sexual reproduction itself and differentiation of the sexes.

Observations on the development of the male reproductive system in Gyrodactylus gasterostei Gläser, 1974 (Monogenea, Gyrodactylidae)

Parasitology ◽  
1985 ◽  
Vol 91 (3) ◽  
pp. 519-529 ◽  
Author(s):  
P. D. Harris
Keyword(s):  
Germ Cell ◽  
Sexual Reproduction ◽  
Reproductive System ◽  
Chromosome Complement ◽  
Mature Male ◽  
Male Reproductive System ◽  
Cell Divisions ◽  
Parasitic Flatworm ◽  
First Time

SUMMARYThe development of the male reproductive system in Gyrodactylus gasterostei has been followed using parasites of known age maintained on isolated hosts. The penis develops shortly after the parasite has given birth for the first time (at an age of 24–30 h at 13°C) and the first active spermatozoa appear after 40–50 h. Spermatogenesis occurs more rapidly in G. gasterostei than in any other parasitic flatworm (including those from warm-blooded hosts) in which it has been measured, and the onset of male maturity is further hastened by a reduction in the number of pre-spermatogenic germ cell divisions. Spermatogonia have a diploid chromosome complement of 12, and spermatocytes undergo meiosis to produce haploid spermatozoa. No evidence of aneuploidy in spermatozoa was obtained. Although the development of haploid spermatozoa suggests that sexual reproduction can occur, production of embryos by isolated flukes which lack a mature male system indicates that other means of reproduction may also be employed.

scholarly journals First report of the sexual stage of the flax pathogen Mycosphaerella linicola in France and its impact on pasmo epidemiology

2020 ◽  
Author(s):  
Delphine Paumier ◽  
Blandine Bammé ◽  
Annette Penaud ◽  
Romain Valade ◽  
Frédéric Suffert
Keyword(s):  
Sexual Reproduction ◽  
Late Summer ◽  
Sexual Stage ◽  
Plant Host ◽  
Temporal Shift ◽  
Developmental Dynamics ◽  
Autumn And Winter ◽  
Quantitative Impact ◽  
First Time

AbstractWe performed a three-year field survey in France to characterize the dynamics of sexual reproduction in Mycosphaerella linicola, the causal agent of pasmo, during the interepidemic period. Cohorts of fruiting bodies were sampled from linseed straw during the autumn and winter and carefully observed, focusing on pseudothecia, asci and ascospores. A sequence of experimental steps corresponding to Koch’s postulates confirmed in July 2014, for the first time in France and continental Europe, the widespread presence of the sexual stage of M. linicola in plant host tissues. The developmental dynamics of pseudothecia on straw, expressed as the change over time in the percentage of mature pseudothecia, was similar in all three years. Pseudothecia appeared in late summer, with peak maturity reached in October. A temporal shift, thought to be due to early autumn rainfall, was highlighted in one of the three years. These observations suggest that sexual reproduction plays a significant role in the epidemiology of pasmo in France. A resurgence of M. linicola infections in spring flax is thought to have occurred in recent years, due to the increase in the area under flax. The presence of the sexual stage of this pathogen probably increased the quantitative impact of residues of winter linseed (used for oil) and flax straw (left on the soil for retting and used for fibers) as an interepidemic ‘brown bridge’. This case study highlights how certain parts of a disease cycle, in this case the sexual phase, can become crucial due to changes in production conditions.

Sign in / Sign up

Export Citation Format

Share Document