| 1. |
- Berger, David, et al.
(författare)
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Quantitative genetic divergence and standing genetic (CO)variance in thermal reaction norms along latitude
- 2013
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Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 67:8, s. 2385-2399
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Tidskriftsartikel (refereegranskat)abstract
- Although the potential to adapt to warmer climate is constrained by genetic trade-offs, our understanding of how selection and mutation shape genetic (co)variances in thermal reaction norms is poor. Using 71 isofemale lines of the fly Sepsis punctum, originating from northern, central, and southern European climates, we tested for divergence in juvenile development rate across latitude at five experimental temperatures. To investigate effects of evolutionary history in different climates on standing genetic variation in reaction norms, we further compared genetic (co) variances between regions. Flies were reared on either high or low food resources to explore the role of energy acquisition in determining genetic trade-offs between different temperatures. Although the latter had only weak effects on the strength and sign of genetic correlations, genetic architecture differed significantly between climatic regions, implying that evolution of reaction norms proceeds via different trajectories at high latitude versus low latitude in this system. Accordingly, regional genetic architecture was correlated to region-specific differentiation. Moreover, hot development temperatures were associated with low genetic variance and stronger genetic correlations compared to cooler temperatures. We discuss the evolutionary potential of thermal reaction norms in light of their underlying genetic architectures, evolutionary histories, and the materialization of trade-offs in natural environments.
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| 2. |
- Schaefer, Martin A., et al.
(författare)
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The developmental plasticity and functional significance of an additional sperm storage compartment in female yellow dung flies
- 2013
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Ingår i: Functional Ecology. - : Wiley. - 0269-8463 .- 1365-2435. ; 27:6, s. 1392-1402
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Tidskriftsartikel (refereegranskat)abstract
- 1. The mechanistic basis for and adaptive significance of variation in female sperm storage organs are important for a range of questions concerning sexual selection and speciation, as such variation influences the evolutionary trajectories of male fertilization related traits and may facilitate speciation through its effects on gamete recognition. 2. Female yellow dung flies (Scathophaga stercoraria) usually develop three sperm storage compartments, and this subdivision may be an adaptation for sorting sperm during postcopulatory choice. 3. Using lines artificially selected to express four spermathecae (4s), we explored the fitness consequences of the novel phenotype relative to the naturally prevalent three-spermatheca (3s) phenotype by manipulating the opportunity for postcopulatory sexual selection (females mated either with three or only one male prior to oviposition). In addition, we examined the developmental plasticity of spermathecal number in response to different larval food environments and estimated its genetic correlation with growth rate. 4. Mating treatments with and without the opportunity for postcopulatory sexual selection revealed no significant fitness differences between alternative spermathecal phenotypes within selection lines despite overall benefits associated with multiple mating, and moderate egg-to-adult survival costs in response to artificial selection for 4s. Manipulations of the larval food environment revealed that the expression of 4s is highly plastic and tightly linked to environmental conditions promoting fast somatic growth and development. Likewise, siblings with fast intrinsic (genetic) growth were more likely to express 4s within and across food environments. 5. The present results highlight a great potential for rapid evolutionary change in female sperm storage morphology through indirect selection on life-history traits, and further suggest genetic assimilation as a potential mechanism facilitating phylogenetic transitions in spermatheca number as frequently observed within the Dipterans.
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| 3. |
- Walters, Richard J., et al.
(författare)
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Forecasting extinction risk of ectotherms under climate warming : an evolutionary perspective
- 2012
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Ingår i: Functional Ecology. - : Wiley. - 0269-8463 .- 1365-2435. ; 26:6, s. 1324-1338
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Forskningsöversikt (refereegranskat)abstract
- 1. It has been postulated that climate warming may pose the greatest threat species in the tropics, where ectotherms have evolved more thermal specialist physiologies. Although species could rapidly respond to environmental change through adaptation, little is known about the potential for thermal adaptation, especially in tropical species. 2. In the light of the limited empirical evidence available and predictions from mutation-selection theory, we might expect tropical ectotherms to have limited genetic variance to enable adaptation. However, as a consequence of thermodynamic constraints, we might expect this disadvantage to be at least partially offset by a fitness advantage, that is, the hotter-is-better hypothesis. 3. Using an established quantitative genetics model and metabolic scaling relationships, we integrate the consequences of the opposing forces of thermal specialization and thermodynamic constraints on adaptive potential by evaluating extinction risk under climate warming. We conclude that the potential advantage of a higher maximal development rate can in theory more than offset the potential disadvantage of lower genetic variance associated with a thermal specialist strategy. 4.Quantitative estimates of extinction risk are fundamentally very sensitive to estimates of generation time and genetic variance. However, our qualitative conclusion that the relative risk of extinction is likely to be lower for tropical species than for temperate species is robust to assumptions regarding the effects of effective population size, mutation rate and birth rate per capita. 5. With a view to improving ecological forecasts, we use this modelling framework to review the sensitivity of our predictions to the model's underpinning theoretical assumptions and the empirical basis of macroecological patterns that suggest thermal specialization and fitness increase towards the tropics. We conclude by suggesting priority areas for further empirical research.
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