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R. A. Seigel - One of the best experts on this subject based on the ideXlab platform.

  • a neglected Life History Trait clutch size variance in snakes
    Journal of Zoology, 1996
    Co-Authors: Richard Shine, R. A. Seigel
    Abstract:

    Most analyses of Life-History Traits have focused on mean values rather than their associated variance. We review published and original data on snakes, including records gathered over many years on single populations, to examine patterns in clutch-size variability in these animals. Within single populations, the coefficient of variation of clutch size did not vary significantly with maternal body size, or among years. The stability of clutch-size variance through time is consistent with experimental studies showing no significant influence of food intake rates on this characteristic. Clutch-size variances did not differ between viviparous and oviparous snakes, but were dependent upon allometric relationships involving maternal body size and the relationship between clutch size and body size. Clutch-size variability was highest in species with relatively variable female sizes, and with a high rate of increase in clutch size with increasing body size. These two factors acted to magnify the extent of clutch-size variability engendered by variability in maternal body sizes. The relationships among these variables were similar in the two squamate Suborders, but the larger body sizes and mean clutch sizes of snakes resulted in clutch-size variances being higher in snakes than in lizards.

  • A neglected Life‐History Trait: clutch‐size variance in snakes
    Journal of Zoology, 1996
    Co-Authors: Richard Shine, R. A. Seigel
    Abstract:

    Most analyses of Life-History Traits have focused on mean values rather than their associated variance. We review published and original data on snakes, including records gathered over many years on single populations, to examine patterns in clutch-size variability in these animals. Within single populations, the coefficient of variation of clutch size did not vary significantly with maternal body size, or among years. The stability of clutch-size variance through time is consistent with experimental studies showing no significant influence of food intake rates on this characteristic. Clutch-size variances did not differ between viviparous and oviparous snakes, but were dependent upon allometric relationships involving maternal body size and the relationship between clutch size and body size. Clutch-size variability was highest in species with relatively variable female sizes, and with a high rate of increase in clutch size with increasing body size. These two factors acted to magnify the extent of clutch-size variability engendered by variability in maternal body sizes. The relationships among these variables were similar in the two squamate Suborders, but the larger body sizes and mean clutch sizes of snakes resulted in clutch-size variances being higher in snakes than in lizards.

Richard Shine - One of the best experts on this subject based on the ideXlab platform.

  • a neglected Life History Trait clutch size variance in snakes
    Journal of Zoology, 1996
    Co-Authors: Richard Shine, R. A. Seigel
    Abstract:

    Most analyses of Life-History Traits have focused on mean values rather than their associated variance. We review published and original data on snakes, including records gathered over many years on single populations, to examine patterns in clutch-size variability in these animals. Within single populations, the coefficient of variation of clutch size did not vary significantly with maternal body size, or among years. The stability of clutch-size variance through time is consistent with experimental studies showing no significant influence of food intake rates on this characteristic. Clutch-size variances did not differ between viviparous and oviparous snakes, but were dependent upon allometric relationships involving maternal body size and the relationship between clutch size and body size. Clutch-size variability was highest in species with relatively variable female sizes, and with a high rate of increase in clutch size with increasing body size. These two factors acted to magnify the extent of clutch-size variability engendered by variability in maternal body sizes. The relationships among these variables were similar in the two squamate Suborders, but the larger body sizes and mean clutch sizes of snakes resulted in clutch-size variances being higher in snakes than in lizards.

  • A neglected Life‐History Trait: clutch‐size variance in snakes
    Journal of Zoology, 1996
    Co-Authors: Richard Shine, R. A. Seigel
    Abstract:

    Most analyses of Life-History Traits have focused on mean values rather than their associated variance. We review published and original data on snakes, including records gathered over many years on single populations, to examine patterns in clutch-size variability in these animals. Within single populations, the coefficient of variation of clutch size did not vary significantly with maternal body size, or among years. The stability of clutch-size variance through time is consistent with experimental studies showing no significant influence of food intake rates on this characteristic. Clutch-size variances did not differ between viviparous and oviparous snakes, but were dependent upon allometric relationships involving maternal body size and the relationship between clutch size and body size. Clutch-size variability was highest in species with relatively variable female sizes, and with a high rate of increase in clutch size with increasing body size. These two factors acted to magnify the extent of clutch-size variability engendered by variability in maternal body sizes. The relationships among these variables were similar in the two squamate Suborders, but the larger body sizes and mean clutch sizes of snakes resulted in clutch-size variances being higher in snakes than in lizards.

Jouni Laakso - One of the best experts on this subject based on the ideXlab platform.

  • Life History trade offs and relaxed selection can decrease bacterial virulence in environmental reservoirs
    PLOS ONE, 2012
    Co-Authors: Lauri Mikonranta, Villepetri Friman, Jouni Laakso
    Abstract:

    Pathogen virulence is usually thought to evolve in reciprocal selection with the host. While this might be true for obligate pathogens, the Life histories of opportunistic pathogens typically alternate between within-host and outside-host environments during the infection-transmission cycle. As a result, opportunistic pathogens are likely to experience conflicting selection pressures across different environments, and this could affect their virulence through Life-History Trait correlations. We studied these correlations experimentally by exposing an opportunistic bacterial pathogen Serratia marcescens to its natural protist predator Tetrahymena thermophila for 13 weeks, after which we measured changes in bacterial Traits related to both anti-predator defence and virulence. We found that anti-predator adaptation (producing predator-resistant biofilm) caused a correlative attenuation in virulence. Even though the direct mechanism was not found, reduction in virulence was most clearly connected to a predator-driven loss of a red bacterial pigment, prodigiosin. Moreover, Life-History Trait evolution was more divergent among replicate populations in the absence of predation, leading also to lowered virulence in some of the ‘predator absent’ selection lines. Together these findings suggest that the virulence of non-obligatory, opportunistic bacterial pathogens can decrease in environmental reservoirs through Life History trade-offs, or random accumulation of mutations that impair virulence Traits under relaxed selection.

Deguang Liu - One of the best experts on this subject based on the ideXlab platform.

  • Life History Trait plasticity and its relationships with plant adaptation and insect fitness a case study on the aphid sitobion avenae
    Scientific Reports, 2016
    Co-Authors: Peng Dai, Xinjia Dai, Deguang Liu, Xiaoqin Shi, Da Wang, Xiuxiang Meng
    Abstract:

    Phenotypic plasticity has recently been considered a powerful means of adaptation, but its relationships with corresponding Life-History characters and plant specialization levels of insects have been controversial. To address the issues, Sitobion avenae clones from three plants in two areas were compared. Varying amounts of Life-History Trait plasticity were found among S. avenae clones on barley, oat and wheat. In most cases, developmental durations and their corresponding plasticities were found to be independent, and fecundities and their plasticities were correlated characters instead. The developmental time of first instar nymphs for oat and wheat clones, but not for barley clones, was found to be independent from its plasticity, showing environment-specific effects. All correlations between environments were found to be positive, which could contribute to low plasticity in S. avenae. Negative correlations between Trait plasticities and fitness of test clones suggest that lower plasticity could have higher adaptive value. Correlations between plasticity and specialization indices were identified for all clones, suggesting that plasticity might evolve as a by-product of adaptation to certain environments. The divergence patterns of Life-History plasticities in S. avenae, as well as the relationships among plasticity, specialization and fitness, could have significant implications for evolutionary ecology of this aphid.

  • genetic basis and selection for Life History Trait plasticity on alternative host plants for the cereal aphid sitobion avenae
    PLOS ONE, 2014
    Co-Authors: Xinjia Dai, Suxia Gao, Deguang Liu
    Abstract:

    Sitobion avenae (F.) can survive on various plants in the Poaceae, which may select for highly plastic genotypes. But phenotypic plasticity was often thought to be non-genetic, and of little evolutionary significance historically, and many problems related to adaptive plasticity, its genetic basis and natural selection for plasticity have not been well documented. To address these questions, clones of S. avenae were collected from three plants, and their phenotypic plasticity under alternative environments was evaluated. Our results demonstrated that nearly all tested Life-History Traits showed significant plastic changes for certain S. avenae clones with the total developmental time of nymphs and fecundity tending to have relatively higher plasticity for most clones. Overall, the level of plasticity for S. avenae clones’ Life-History Traits was unexpectedly low. The factor ‘clone’ alone explained 27.7–62.3% of the total variance for Trait plasticities. The heritability of plasticity was shown to be significant in nearly all the cases. Many significant genetic correlations were found between Trait plasticities with a majority of them being positive. Therefore, it is evident that Life-History Trait plasticity involved was genetically based. There was a high degree of variation in selection coefficients for Life-History Trait plasticity of different S. avenae clones. Phenotypic plasticity for barley clones, but not for oat or wheat clones, was frequently found to be under significant selection. The directional selection of alternative environments appeared to act to decrease the plasticity of S. avenae clones in most cases. G-matrix comparisons showed significant differences between S. avenae clones, as well as quite a few negative covariances (i.e., trade-offs) between Trait plasticities. Genetic basis and evolutionary significance of Life-History Trait plasticity were discussed.

Paul Schmidhempel - One of the best experts on this subject based on the ideXlab platform.