83 research outputs found
Loss of coral reef growth capacity to track future increases in sea level
Water-depths above coral reefs is predicted to increase due to global sea-level rise (SLR). As ecological degradation inhibits the vertical accretion of coral reefs, it is likely that coastal wave exposure will increase but there currently exists a lack of data in projections concerning local rates of reef growth and local SLR. In this study we have aggregated ecological data of more than 200 tropical western Atlantic and Indian Ocean reefs and calculated their vertical growth which we have then compared with recent and projected rates of SLR across different Representative Concentration Pathway (RCP) scenarios. While many reefs currently show vertical growth that would be sufficient to keep-up with recent historic SLR, future projections under scenario RCP4.5 reveal that without substantial ecological recovery many reefs will not have the capacity to track SLR. Under RCP8.5, we predict that mean water depth will increase by over half a metre by 2100 across the majority of reefs. We found that coral cover strongly predicted whether a reef could track SLR, but that the majority of reefs had coral cover significantly lower than that required to prevent reef submergence. To limit reef submergence, and thus the impacts of waves and storms on adjacent coasts, climate mitigation and local impacts that reduce coral cover (e.g., local pollution and physical damage through development land reclamation) will be necessary
The Evolution of Life Histories : Theory and Analysis
xii,535 hal,;ill,;21 c
The evolution of life histories: theory and analysis
xii+535hlm.;23c
Of flies, fitness and fluctuating environments
Environmental heterogeneity may be important in determining the amount of genetic variation within a population. Previous theoretical studies have analysed the importance of spatio-temporal variablity for ecological genetics within a very general framework. The present study attempts to analyse the consequences of environmental heterogeneity for a particular ecologically important character. The study is concerned with the evolution of body size in an 'r-selected' poikilotherm. Is body size. The measure of fitness, r, is determined by the fecundity of the organism and its development time. These two life history characters are correlated to body size and hence the latter may be used as a measure of changes in life history parameters, whether or not selection acts directly upon body size. A model is presented that relates the effect of spatial and temporal variation on body size. This effect may be due to direct effects on body size as with size selective predation or due to effects upon other characters such as development time. To demonstrate that the behaviour of the model does not result from implausible assumptions or parameter values the model is developed with reference to an organism for which these factors have been reasonably well studied. This group is the Drosophila and most particularly, Drosophila melanogaster. The conclusions drawn from the model are that spatial and temporal variability can determine both the optimum body size and the range in body size and that 'rare' events may have significantly more effect on the evolution of body size than the most frequently occurring conditions.Science, Faculty ofZoology, Department ofGraduat
Data from: The costs of being dark: the genetic basis of melanism and its association with fitness-related traits in the sand cricket
Melanism is an important component of insect cuticle and serves numerous functions that enhance fitness. Despite its importance, there is little information on its genetic basis or its phenotypic and genetic correlation with fitness-related traits. Here, we examine the heritability of melanism in the wing dimorphic sand cricket and determine its phenotypic and genetic correlation with wing morphology, gonad mass and size of the dorso-longitudinal muscles (the principle flight muscles). Previously demonstrated trade-offs among these traits are significant factors in the evolution of life history variation. Using path analysis, we show that melanization is causally related to gonad mass, but not flight muscle mass. Averaged over the sexes, the heritability of melanism was 0.61, the genetic correlation with gonad mass was â0.36 and with wing morph was 0.51. The path model correctly predicted the ranking of melanization score in lines selected for increased ovary mass, increased flight muscle mass, an index that increased both traits and an unselected control. Our results support the general hypothesis that melanization is costly for insects and negatively impacts investment in early reproduction
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Tests for associations between sexual dimorphism and patterns of quantitative genetic variation in the water strider, Aquarius remigis.
The evolution of sexual dimorphisms requires divergence between sexes in the evolutionary trajectories of the traits involved. Discerning how genetic architecture could facilitate such divergence has proven challenging because of the difficulty in estimating non-additive and sex-linked genetic variances using traditional quantitative genetic designs. Here we use a three-generation, double-first-cousin pedigree design to estimate additive, sex-linked and dominance (co)variances for 12 traits in the water strider, Aquarius remigis. Comparisons among these traits, which have size ratios ranging from 1 to 5 (larger/smaller), allow us to ask if sexual dimorphisms are associated with characteristic patterns of quantitative genetic variation. We frame our analysis around three main questions, derived from existing theory and empirical evidence: Are sexual dimorphisms associated with (1) lower additive inter-sex genetic correlations, (2) higher proportions of sex-linked variance, or (3) differences between sexes in autosomal additive and dominance genetic variances? For questions (1) and (2), we find weak and non-significant trends in the expected directions, which preclude definitive conclusions. However, in answer to question (3), we find strong evidence for a positive relationship between sexual dimorphism and differences between sexes in proportions of autosomal dominance variance. We also find strong interactions among the three genetic components indicating that their relative influence differs among traits and between sexes. These results highlight the need to include all three components of genetic (co)variance in both theoretical evolutionary models and empirical estimations of the genetic architecture of dimorphic traits
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