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Sexual Strategies (sexual + strategy)

Distribution by Scientific Domains
Life Sciences66%

Selected Abstracts

Virtually Virgins: Sexual Strategies and Cervical Cancer in Recife, Brazil

AMERICAN ANTHROPOLOGIST, Issue 3 2005
TELMA CAMARGO DA SILVA
No abstract is available for this article. [source]

THE EVOLUTION OF DIOECY, HETERODICHOGAMY, AND LABILE SEX EXPRESSION IN ACER

EVOLUTION, Issue 11 2007
S. S. Renner
The northern hemisphere tree genus Acer comprises 124 species, most of them monoecious, but 13 dioecious. The monoecious species flower dichogamously, duodichogamously (male, female, male), or in some species heterodichogamously (two morphs that each produce male and female flowers but at reciprocal times). Dioecious species cannot engage in these temporal strategies. Using a phylogeny for 66 species and subspecies obtained from 6600 nucleotides of chloroplast introns, spacers, and a protein-coding gene, we address the hypothesis (Pannell and Verdú, Evolution 60: 660,673. 2006) that dioecy evolved from heterodichogamy. This hypothesis was based on phylogenetic analyses (Gleiser and Verdú, New Phytol. 165: 633,640. 2005) that included 29,39 species of Acer coded for five sexual strategies (duodichogamous monoecy, heterodichogamous androdioecy, heterodichogamous trioecy, dichogamous subdioecy, and dioecy) treated as ordered states or as a single continuous variable. When reviewing the basis for these scorings, we found errors that together with the small taxon sample, cast doubt on the earlier inferences. Based on published studies, we coded 56 species of Acer for four sexual strategies, dioecy, monoecy with dichogamous or duodichogamous flowering, monoecy with heterodichogamous flowering, or labile sex expression, in which individuals reverse their sex allocation depending on environment,phenotype interactions. Using Bayesian character mapping, we infer an average of 15 transformations, a third of them involving changes from monoecy-cum-duodichogamy to dioecy; less frequent were changes from this strategy to heterodichogamy; dioecy rarely reverts to other sexual systems. Contra the earlier inferences, we found no switches between heterodichogamy and dioecy. Unexpectedly, most of the species with labile sex expression are grouped together, suggesting that phenotypic plasticity in Acer may be a heritable sexual strategy. Because of the complex flowering phenologies, however, a concern remains that monoecy in Acer might not always be distinguishable from labile sex expression, which needs to be addressed by long-term monitoring of monoecious trees. The 13 dioecious species occur in phylogenetically disparate clades that date back to the Late Eocene and Oligocene, judging from a fossil-calibrated relaxed molecular clock. [source]

Sexual vs. asexual reproduction in an ecosystem engineer: the massive coral Montastraea annularis

JOURNAL OF ANIMAL ECOLOGY, Issue 2 2007
NICOLA L. FOSTER
Summary 1Long-lived sedentary organisms with a massive morphology are often assumed to utilize a storage effect whereby the persistence of a small group of adults can maintain the population when sexual recruitment fails. However, employing storage effects could prove catastrophic if, under changing climatic conditions, the time period between favourable conditions becomes so prolonged that the population cannot be sustained solely be sexual recruitment. When a species has multiple reproductive options, a rapidly changing environment may favour alternative asexual means of propagation. 2Here, we revisit the importance of asexual dispersal in a massive coral subject to severe climate-induced disturbance. Montastraea annularis is a major framework-builder of Caribbean coral reefs but its survival is threatened by the increasing cover of macroalgae that prevents settlement of coral larvae. 3To estimate levels of asexual recruitment within populations of M. annularis, samples from three sites in Honduras were genotyped using four, polymorphic microsatellite loci. 4A total of 114 unique genets were identified with 8% consisting of two or more colonies and an exceptionally large genet at the third site comprising 14 colonies. 5At least 70% of multicolony genets observed were formed by physical breakage, consistent with storm damage. 6Our results reveal that long-lived massive corals can propagate using asexual methods even though sexual strategies predominate. [source]

Sexual development and reproductive seasonality of hogfish (Labridae: Lachnolaimus maximus), an hermaphroditic reef fish

JOURNAL OF FISH BIOLOGY, Issue 5 2007
R. S. McBride
The seasonality, size, age, colour phases and sexual dimorphism of 13 reproductive classes of hogfish Lachnolaimus maximus are described. Analysis of histological sections of gonads (n = 1662) confirmed earlier conclusions that L. maximus is a monandric, protogynous hermaphrodite. Sex change was initiated at the end of the spawning season and over a broad range of sizes and ages. It occurred after a functional female phase (postmaturation) and proceeded more slowly (months) than previously believed. Eventually all individuals changed sex to a terminal male phase. Females were batch spawners, spawning as often as every day during winter and spring. There was no evidence of precocious sperm crypts in active females, sperm competition or other alternative male sexual strategies. Mating has been reported elsewhere to be haremic. The sexual development of L. maximus appears to be adaptive in terms of Ghiselin's size-advantage model, which links monandric protogyny and polygyny. The slow rate of sex change, however, poses problems when fishing pressure is high because harvest of a single male has the potential to reduce the reproductive output of an entire harem. [source]

THE EVOLUTION OF DIOECY, HETERODICHOGAMY, AND LABILE SEX EXPRESSION IN ACER

EVOLUTION, Issue 11 2007
S. S. Renner
The northern hemisphere tree genus Acer comprises 124 species, most of them monoecious, but 13 dioecious. The monoecious species flower dichogamously, duodichogamously (male, female, male), or in some species heterodichogamously (two morphs that each produce male and female flowers but at reciprocal times). Dioecious species cannot engage in these temporal strategies. Using a phylogeny for 66 species and subspecies obtained from 6600 nucleotides of chloroplast introns, spacers, and a protein-coding gene, we address the hypothesis (Pannell and Verdú, Evolution 60: 660,673. 2006) that dioecy evolved from heterodichogamy. This hypothesis was based on phylogenetic analyses (Gleiser and Verdú, New Phytol. 165: 633,640. 2005) that included 29,39 species of Acer coded for five sexual strategies (duodichogamous monoecy, heterodichogamous androdioecy, heterodichogamous trioecy, dichogamous subdioecy, and dioecy) treated as ordered states or as a single continuous variable. When reviewing the basis for these scorings, we found errors that together with the small taxon sample, cast doubt on the earlier inferences. Based on published studies, we coded 56 species of Acer for four sexual strategies, dioecy, monoecy with dichogamous or duodichogamous flowering, monoecy with heterodichogamous flowering, or labile sex expression, in which individuals reverse their sex allocation depending on environment,phenotype interactions. Using Bayesian character mapping, we infer an average of 15 transformations, a third of them involving changes from monoecy-cum-duodichogamy to dioecy; less frequent were changes from this strategy to heterodichogamy; dioecy rarely reverts to other sexual systems. Contra the earlier inferences, we found no switches between heterodichogamy and dioecy. Unexpectedly, most of the species with labile sex expression are grouped together, suggesting that phenotypic plasticity in Acer may be a heritable sexual strategy. Because of the complex flowering phenologies, however, a concern remains that monoecy in Acer might not always be distinguishable from labile sex expression, which needs to be addressed by long-term monitoring of monoecious trees. The 13 dioecious species occur in phylogenetically disparate clades that date back to the Late Eocene and Oligocene, judging from a fossil-calibrated relaxed molecular clock. [source]

A polyploid population of Saccharomyces cerevisiae with separate sexes (dioecy)

FEMS YEAST RESEARCH, Issue 6 2010
Rim Al Safadi
Abstract Saccharomyces cerevisiae has proved to be an interesting model for studies of evolution, with whole-genome duplication shown to have played an important role in the evolution of this species. This phenomenon depends on the formation of a transient stable polyploid state. Previous studies have reported polyploidy to be an unstable state in yeast, but here, we describe a polyploid population of S. cerevisiae. The evolution of higher eukaryotes has also involved the development of different systems of sexual reproduction, the choice between self-fertilization and out-crossing becoming a key issue. Saccharomyces cerevisiae is a hermaphrodite eukaryote, despite the theoretical genetic disadvantages of this strategy, in which self-fertilization occurs. We describe, for the first time, a near-dioecious (with separate sexes) population in this species. Mating type and the MAT locus display complex segregations. Essentially, each strain produces, by meiosis, spores of only one mating type: mata or mat,. Moreover, strains are heterothallic, and diploid nonmating clones generated from a single spore do not sporulate. These three properties limit self-fertilization and strongly favour out-crossing. We suggest that the shift in sexual strategy, from hermaphroditism to dioecy, is specific to the brewing process, which overcomes the sexual isolation probably found in natural biotopes. [source]