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  • Book
    edited by Janet L. Leonard.
    Summary: This book focuses on explaining the distribution of sexual systems (simultaneous hermaphroditism, sequential hermaphroditism, environmental sex determination, dioecy, androdioecy, etc.) among taxa, which remains a major challenge in evolutionary biology. Although significant advances have been made for angiosperms, there is not yet a theory that predicts the sexual system for the majority of animal taxa, and other taxa of plants also remain poorly understood. The problem, particularly for animals, is that sexual systems can be very conservative, with whole phyla and classes being characterized by a single sexual system; for example essentially the whole phylum Platyhelminthes is simultaneously hermaphroditic, whereas the Insecta (Hexapoda) and the Tetrapoda among the vertebrates, are exclusively dioecious. Sex allocation theory on the other hand, suggests that sexual systems should be highly responsive to evolution, changing with population density, life span, patterns of resource availability, etc. The book provides an overview of the topic and then presents a series of chapters, each dealing with a taxon with substantial lability in sexual system in order to identify the factors associated with changes in sexual system in each case. By doing so, the authors reveal factors that have not been considered in formal theory but seem to have a major impact on transitions between sexual systems. This book appeals to a wide readership in fields from zoology and evolutionary biology to botany.

    Contents:
    1. The Evolution of Sexual Systems in Animals
    2. The Evolution of Sexual Systems in Animals
    3. Evolutionary Transitions Between Combined and Separate Sexes
    4. The Evolution of Uniparental Reproduction in Rhabditina Nematodes: Phylogenetic patterns, Developmental Causes, and Surprising Consequences
    5. Polychaete Worms on the Brink Between Hermaphroditism and Separate Sexes
    6. Sex Determining Mechanisms in Bivalves
    7. Transitions in Sexual and Reproductive Strategies Among the Caenogastropoda
    8. Hermaphrodites, Dwarf Males, and Females: Evolutionary Transitions of Sexual Systems in Barnacles
    9. Life History Constraints Facilitate the Evolution of Androdiocy and Male Dwarfing
    10. Sexual Systems in Shrimps (infraorder Caridea Dana, 1852), with Special Reference to the Historical Origin and Adaptive Value of Protandric Simultaneous Hermaphroditism
    11. Environmental and Genetic Sex Determining Mechanisms in Fishes
    12. Causes and Consequences of Evolutionary Transitions in the Level of Phenotypic Plasticity of Reptilian Sex Determination.
    Digital Access Springer 2018
  • Article
    Fehrenbacher G, Perry K, Thorner J.
    J Bacteriol. 1978 Jun;134(3):893-901.
    Mating-specific adhesion between haploid yeast cells of opposite mating type (a and alpha) was studied by using a quantitative agar plate assay. Washed a and alpha cells that had not previously been exposed to their respective opposite mating type ("naive" cells) adhered relatively weakly. In water, only 5 to 10% of the a cells stuck tightly enough to alpha cells to give rise subsequently to diploid clones on the assay plates. Under optimum conditions (pH 6 to 7, at least 0.1 M Nacl or 0.01 M Mg(2+)), there was about 20% adhesion. Nevertheless, this weak binding defined a mating type-specific interaction because, even under optimum conditions, the homologous interactions (a with a and alpha with alpha) yielded only 3 to 5% cohesion. In contrast to these results, washed cells that had been preincubated in the cell-free culture medium of their opposite mating type ("preconditioned" cells) adhered quite strongly. The degree of adhesion between preconditioned cells (40 to 50%) was essentially unaffected by extremes of ionic strength, pH, and temperature and by the absence of divalent cation. This strong interaction was also mating type specific since cohesion between preconditioned cells of like mating type was only about 5%. The increase in agglutinability was obtained if only the a cells were preconditioned and could be induced by highly purified preparations of natural or synthetically prepared alpha-factor, an oligopeptide pheromone released by the alpha cells. The appearance of increased adhesiveness was blocked by an inhibitor of RNA synthesis and by an inhibitor of protein synthesis, but not by an inhibitor of polysaccharide synthesis. Adhesion between preconditioned cells could be inhibited by pretreatment with functionally univalent succinylated concanavalin A or with extracts from preconditioned cells of the opposite mating type. These results confirm in a quantitative manner that the recognition between conjugating cells of S. cerevisiae is a developmentally regulated event that is under the control of the mating type locus.
    Digital Access Access Options