Sequential Hermaphroditism

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Janet L. Leonard - One of the best experts on this subject based on the ideXlab platform.

  • SYMPOSIUM Williams ’ Paradox and the Role of Phenotypic Plasticity in Sexual Systems
    2016
    Co-Authors: Janet L. Leonard
    Abstract:

    Synopsis As George Williams pointed out in 1975, although evolutionary explanations, based on selection acting on individuals, have been developed for the advantages of simultaneous Hermaphroditism, Sequential Hermaphroditism and gonochorism, none of these evolutionary explanations adequately explains the current distribution of these sexual systems within the Metazoa (Williams ’ Paradox). As Williams further pointed out, the current distribution of sexual systems is explained largely by phylogeny. Since 1975, we have made a great deal of empirical and theoretical progress in under-standing sexual systems. However, we still lack a theory that explains the current distribution of sexual systems in animals and we do not understand the evolutionary transitions between Hermaphroditism and gonochorism. Empirical data, collected over the past 40 years, demonstrate that gender may have more phenotypic plasticity than was previously realized. We know that not only Sequential hermaphrodites, but also simultaneous hermaphrodites have phenotypic plasticity that alters sex allocation in response to social and environmental conditions. A focus on phenotypic plasticity suggests that one sees a continuum in animals between genetically determined gonochorism on the one hand and simultaneous Hermaphroditism on the other, with various types of Sequential Hermaphroditism and environmental sex determination as points along the spectrum. Here I suggest that perhaps the reason we have been unable to resolve Williams ’ Paradox is because the problem was not correctly framed. First, because, for example, simultaneous hermaph-roditism provides reproductive assurance or dioecy ensures outcrossing does not mean that there are no other evolu

  • Williams' Paradox and the Role of Phenotypic Plasticity in Sexual Systems
    Integrative and Comparative Biology, 2013
    Co-Authors: Janet L. Leonard
    Abstract:

    As George Williams pointed out in 1975, although evolutionary explanations, based on selection acting on individuals, have been developed for the advantages of simultaneous Hermaphroditism, Sequential Hermaphroditism and gonochorism, none of these evolutionary explanations adequately explains the current distribution of these sexual systems within the Metazoa (Williams' Paradox). As Williams further pointed out, the current distribution of sexual systems is explained largely by phylogeny. Since 1975, we have made a great deal of empirical and theoretical progress in understanding sexual systems. However, we still lack a theory that explains the current distribution of sexual systems in animals and we do not understand the evolutionary transitions between Hermaphroditism and gonochorism. Empirical data, collected over the past 40 years, demonstrate that gender may have more phenotypic plasticity than was previously realized. We know that not only Sequential hermaphrodites, but also simultaneous hermaphrodites have phenotypic plasticity that alters sex allocation in response to social and environmental conditions. A focus on phenotypic plasticity suggests that one sees a continuum in animals between genetically determined gonochorism on the one hand and simultaneous Hermaphroditism on the other, with various types of Sequential Hermaphroditism and environmental sex determination as points along the spectrum. Here I suggest that perhaps the reason we have been unable to resolve Williams' Paradox is because the problem was not correctly framed. First, because, for example, simultaneous Hermaphroditism provides reproductive assurance or dioecy ensures outcrossing does not mean that there are no other evolutionary paths that can provide adaptive responses to those selective pressures. Second, perhaps the question we need to ask is: What selective forces favor increased versus reduced phenotypic plasticity in gender expression? It is time to begin to look at the question of sexual system as one of understanding the timing and degree of phenotypic plasticity in gender expression in the life history in terms of selection acting on a continuum, rather than on a set of discrete sexual systems.

  • sexual selection lessons from hermaphrodite mating systems
    Integrative and Comparative Biology, 2006
    Co-Authors: Janet L. Leonard
    Abstract:

    Synopsis Over the last 130 years, research has established that (a) sexual selection exists and is widespread in the plant and animal kingdoms; (b) it does not necessarily entail sexual dimorphism; even hermaphrodites have it; (c) it does not require intelligence or a sophisticated sense of esthetics; even tapeworms and plants choose mates; and (d) it does not require brawn or even mobility for competition; plants may compete for pollinators, and broadcast spawning invertebrates may also compete for matings. Although discussions of sexual selection often focus on sexual dimorphism, several phenomena that are commonly associated with sexual selection are widespread and highly developed in hermaphrodites. These phenomena include (a) bizarre and expensive courtship and copulatory behavior, (b) multiple mating and sperm competition, (c) rapid evolution of genitalia, (d) special structures associated with courtship, and (e) sexual polymorphism. The skewed breeding sex ratios associated with Sequential Hermaphroditism have long been recognized as contributory to sexual selection. In many simultaneous hermaphrodites, although the sex ratio at mating may be one to one, the actual reproductive sex ratio may also be skewed, creating a high potential for sexual selection. Reproductive biology in hermaphroditic taxa also involves a lot of complexity unknown in dioecious taxa, such as sex change, facultative sex allocation and conditional reciprocity that offers opportunities to enrich our understanding of sexual selection and to test the assumptions and predictions of theory.

Nicolas Salamin - One of the best experts on this subject based on the ideXlab platform.

  • first draft genome of an iconic clownfish species amphiprion frenatus
    Molecular Ecology Resources, 2018
    Co-Authors: Anna Marcionetti, Victor Rossier, Joris A M Bertrand, Glenn Litsios, Nicolas Salamin
    Abstract:

    Clownfishes (or anemonefishes) form an iconic group of coral reef fishes, principally known for their mutualistic interaction with sea anemones. They are characterized by particular life history traits, such as a complex social structure and mating system involving Sequential Hermaphroditism, coupled with an exceptionally long lifespan. Additionally, clownfishes are considered to be one of the rare groups to have experienced an adaptive radiation in the marine environment. Here, we assembled and annotated the first genome of a clownfish species, the tomato clownfish (Amphiprion frenatus). We obtained 17,801 assembled scaffolds, containing a total of 26,917 genes. The completeness of the assembly and annotation was satisfying, with 96.5% of the Actinopterygii Benchmarking Universal Single-Copy Orthologs (BUSCOs) being retrieved in A. frenatus assembly. The quality of the resulting assembly is comparable to other bony fish assemblies. This resource is valuable for advancing studies of the particular life history traits of clownfishes, as well as being useful for population genetic studies and the development of new phylogenetic markers. It will also open the way to comparative genomics. Indeed, future genomic comparison among closely related fishes may provide means to identify genes related to the unique adaptations to different sea anemone hosts, as well as better characterize the genomic signatures of an adaptive radiation.

  • first draft genome assembly of an iconic clownfish species amphiprion frenatus
    bioRxiv, 2017
    Co-Authors: Anna Marcionetti, Victor Rossier, Joris A M Bertrand, Glenn Litsios, Nicolas Salamin
    Abstract:

    Clownfishes (or anemonefishes) form an iconic group of coral reef fishes, particularly known for their mutualistic interaction with sea anemones. They are characterized by particular life history traits, such as a complex social structure and mating system involving Sequential Hermaphroditism, coupled with an exceptionally long lifespan. Additionally, clownfishes are considered to be one of the rare group to have experienced an adaptive radiation in the marine environment. Here, we assembled and annotated the first genome of a clownfish species, the tomato clownfish ( Amphiprion frenatus ). We obtained a total of 17,801 assembled scaffolds, containing a total of 26,917 genes. The completeness of the assembly and annotation was satisfying, with 96.5% of the Actinopterygii BUSCOs (Benchmarking Universal Single-Copy Orthologs) being retrieved in A. frenatus assembly. The quality of the resulting assembly is comparable to other bony fish assemblies. This resource is valuable for the advancing of studies of the particular life-history traits of clownfishes, as well as being useful for population genetic studies and the development of new phylogenetic markers. It will also open the way to comparative genomics. Indeed, future genomic comparison among closely related fishes may provide means to identify genes related to the unique adaptations to different sea anemone hosts, as well as better characterize the genomic signatures of an adaptive radiation.

Frédérique Viard - One of the best experts on this subject based on the ideXlab platform.

  • The Size Advantage Model of Sex Allocation in the Protandrous Sex-Changer Crepidula fornicata: Role of the Mating System, Sperm Storage, and Male Mobility
    The American Naturalist, 2015
    Co-Authors: Thomas Broquet, Audrey Barranger, Emmanuelle Billard, Anastasia Bestin, Rémy Berger, Gaelle Honnaert, Frédérique Viard
    Abstract:

    Sequential Hermaphroditism is adaptive when the reproductive value of an individual varies with size or age, and this relationship differs between males and females. In this case, theory shows that the lifetime reproductive output of an individual is increased by changing sex (a hypothesis referred to as the size-advantage model). Sex-linked differences in size-fitness curves can stem from differential costs of reproduction, the mating system, and differences in growth and mortality between sexes. Detailed empirical data is required to disentangle the relative roles of each of these factors within the theory. Quantitative data are also needed to explore the role of sperm storage, which has not yet been considered with Sequential hermaphrodites. Using experimental rearing and paternity assignment, we report relationships between size and reproductive success of Crepidula fornicata, a protandrous (male-first) gastropod. Male reproductive success increased with size due to the polygamous system and stacking behavior of the species, but females nonetheless had greater reproductive success than males of the same size, in agreement with the size-advantage theory. Sperm storage appeared to be a critical determinant of success for both sexes, and modeling the effect of sperm storage showed that it could potentially accelerate sex change in protandrous species.

  • gregariousness and protandry promote reproductive insurance in the invasive gastropod crepidula fornicata evidence from assignment of larval paternity
    Molecular Ecology, 2006
    Co-Authors: Lise Dupont, Joelle Richard, Yvesmarie Paulet, Gerard Thouzeau, Frédérique Viard
    Abstract:

    According to the size-advantage hypothesis, protandric Sequential Hermaphroditism is expected when the increase in reproductive success with age or size is small for males but large for females. Interestingly, some protandrous molluscs have developed gregarious strategies that might enhance male reproductive success but at the cost of intraspecific competition. The gastropod Crepidula fornicata , a European invading species, is ideal for investigating mating patterns in a Sequential hermaphrodite in relation to grouping behaviour because individuals of different size (age) live in perennial stacks, fertilization is internal and embryos are brooded. Paternity analyses were undertaken in stacks sampled in three close and recently invaded sites in Brittany, France. Paternity assignment of 239 larvae, sampled from a set of 18 brooding females and carried out using five microsatellite loci, revealed that 92% of the crosses occurred between individuals located in the same stack. These stacks thus function as independent mating groups in which individuals may reproduce consecutively as male and female over a short time period, a pattern explained by sperm storage capacity. Gregariousness and sex reversal are promoting reproductive insurance in this species. In addition, females are usually fertilized by several males (78% of the broods were multiply sired) occupying any position within the stack, a result reinforcing the hypothesis of sperm competition. Our study pointed out that mating behaviours and patterns of gender allocation varied in concert across sites suggesting that multiple paternities might enhance sex reversal depending on sperm competition intensity.

Erem Kazancıoğlu - One of the best experts on this subject based on the ideXlab platform.

  • A COMPARATIVE ANALYSIS OF SEX CHANGE IN LABRIDAE SUPPORTS THE SIZE ADVANTAGE HYPOTHESIS
    Evolution; international journal of organic evolution, 2010
    Co-Authors: Erem Kazancıoğlu, Suzanne H. Alonzo
    Abstract:

    The size advantage hypothesis (SAH) predicts that the rate of increase in male and female fitness with size (the size advantage) drives the evolution of Sequential Hermaphroditism or sex change. Despite qualitative agreement between empirical patterns and SAH, only one comparative study tested SAH quantitatively. Here, we perform the first comparative analysis of sex change in Labridae, a group of hermaphroditic and dioecious (non-sex changer) fish with several model sex-changing species. We also estimate, for the first time, rates of evolutionary transitions between sex change and dioecy. Our analyses support SAH and indicate that the evolution of Hermaphroditism is correlated to the size advantage. Furthermore, we find that transitions from sex change to dioecy are less likely under stronger size advantage. We cannot determine, however, how the size advantage affects transitions from dioecy to sex change. Finally, contrary to what is generally expected, we find that transitions from dioecy to sex change are more likely than transitions from sex change to dioecy. The similarity of sexual differentiation in hermaphroditic and dioecious labrids might underlie this pattern. We suggest that elucidating the developmental basis of sex change is critical to predict and explain patterns of the evolutionary history of Sequential Hermaphroditism.

  • eLS - Sex Allocation in Hermaphrodites
    Encyclopedia of Life Sciences, 2009
    Co-Authors: Erem Kazancıoğlu
    Abstract:

    Organisms in which individuals can reproduce both as males and females are called hermaphrodites. Sex allocation in hermaphrodites involves the division of reproductive resources between the male and female function, and presents an interesting contrast to species that alter sex allocation by adjusting offspring sex ratio. Theoretical and empirical research in the past four decades have largely attempted to explain when Hermaphroditism is favoured, and how sex allocation in hermaphrodites is controlled. Furthermore, the application of endocrinological methods has elucidated some of the molecular processes that underlie hermaphroditic sex allocation, especially in Sequential hermaphrodites. Despite significant advances in our understanding of hermaphrodites, some fundamental predictions such as the adaptiveness of changes in sex allocation have not been tested, and some basic questions on Hermaphroditism have not been answered. Key concepts: In hermaphroditic organisms, individuals are capable of reproducing as both males and females. Simultaneous hermaphrodites have male and female reproductive organs that are functional at the same time, and are both involved in a mating event. Simultaneous Hermaphroditism is favoured, when an increase in male and female reproduction yields diminishing fitness returns. Factors such as limited mobility, low density or self-fertilization can result in diminishing fitness returns for males, and favour simultaneous Hermaphroditism. However, local resource competition and physiological limitations could saturate fitness through female function. Simultaneous hermaphrodites can adjust sex allocation according to the social environment (e.g. mating group size), and the amount of resources available for reproduction (e.g. body size). Sequential hermaphrodites, or sex changers, reproduce as one sex for a part of their lifetime, and then switch to reproducing as the opposite sex. Sequential Hermaphroditism is favoured in mating systems where individuals have consistently greater reproductive success as one sex earlier and as the other sex later in life. Sequential hermaphrodites can adjust the optimal timing of sex change according to relative size or social status in a mating group. There are also mixed hermaphroditic systems where individuals can repeatedly switch between sexes, or simultaneous hermaphrodites coexist with pure sexes. Sex change in fishes involves complex behavioural and morphological changes that are regulated by an endocrine gland system conserved across all vertebrates. Keywords: sex allocation; Hermaphroditism; reproduction; life history

  • costs of changing sex do not explain why Sequential Hermaphroditism is rare
    The American Naturalist, 2009
    Co-Authors: Erem Kazancıoğlu, Suzanne H. Alonzo
    Abstract:

    Abstract: Sex change is a relatively rare phenomenon among animals. While classic theory has been successful in assessing the adaptive significance of sex change and predicting within‐species patterns, it does not explain why more animals are not sex changers. A possible explanation for the rarity of sex change is that costs such as decreased reproduction due to gonadal reconstruction favor separate sexes, or dioecy. These costs, however, have not been studied empirically or theoretically. Here, we investigate whether costs of changing sex can favor dioecy. Our analyses suggest that dioecy is favored only when costs of changing sex are large. Moreover, the fitness effect of costs and the strength of male size advantage are not static but change with the population composition, resulting in a dynamic evolutionary game between sex change and dioecy. We conclude that costs of changing sex alone are unlikely to explain the observed rarity of sex changers. Instead, assessing mating systems comparatively and qu...

Ronald G Oldfield - One of the best experts on this subject based on the ideXlab platform.

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