Reproductive Value and Fluctuating Selection in an Age-Structured Population

Engen, Steinar; Lande, Russell; Sæther, Bernt‐Erik

doi:10.1534/genetics.109.105841

Cited by 23 publications

(25 citation statements)

References 48 publications

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“…Fisher claimed in calculating gene frequencies and selection that individuals should be weighted by their reproductive value. Engen et al (2009b) showed how reproductive value weighting filters out transient stochastic fluctuations in allele frequencies generated by fluctuations in the age structure around the stable age distribution.…”

Section: Discussionmentioning

confidence: 99%

Evolution of a Plastic Quantitative Trait in an Age-Structured Population in a Fluctuating Environment

2011

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We analyze weak fluctuating selection on a quantitative character in an age-structured population not subject to density regulation.We assume that early in the first year of life before selection, during a critical state of development, environments exert a plastic effect on the phenotype, which remains constant throughout the life of an individual. Age-specific selection on the character affects survival and fecundity, which have intermediate optima subject to temporal environmental fluctuations with directional selection in some age classes as special cases. Weighting individuals by their reproductive value, as suggested by Fisher, we show that the expected response per year in the weighted mean character has the same form as for models with no age structure. Environmental stochasticity generates stochastic fluctuations in the weighted mean character following a first-order autoregressive model with a temporally autocorrelated noise term and stationary variance depending on the amount of phenotypic plasticity. The parameters of the process are simple weighted averages of parameters used to describe age-specific survival and fecundity. The "age-specific selective weights" are related to the stable distribution of reproductive values among age classes. This allows partitioning of the change in the weighted mean character into age-specific components. K E Y W O R D S :Age structure, evolutionary dynamics, fluctuating selection, life history, plasticity, reproductive value.During the past few decades a large number of empirical estimates of phenotypic selection have appeared, facilitated by Lande and Arnold's (1983) realization that multiple regression of individual fitness (or a component of fitness) on individual characters provides estimates of selection gradients on quantitative characters. This approach has produced considerable general insight into operation of directional and stabilizing selection (Endler 1986;Kingsolver et al. 2001; Siepielski et al. 2009). In combination with estimates of additive genetic variances and covariances based, for example, on the animal model (Kruuk 2004), a mechanistic understanding of factors causing variation in the rate of evolutionary response to selection in fluctuating environments has now started to emerge (Ellegren and Sheldon 2008;Kruuk et al. 2008; Siepielski et al. 2009; Walsh and Blows 2009). However, we still have little knowledge about how variable environments affect selection pressures and rates of evolutionary responses to environmental changes.The method of Lande and Arnold (1983) is still based on several simplifying assumptions, including no age-structure. The step from an evolutionary theory for nonoverlapping generations to populations with age or stage structure is a large one, introducing heterogeneity among individuals of different ages, temporal interactions between age-specific survival and fecundity, and transient fluctuations in age structure (Caswell 2001). Based on earlier ideas of Hamilton (1966), Medawar (1946, 1952), and Fisher (1930, 1958, de...

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Section: Discussionmentioning

confidence: 99%

Evolution of a Plastic Quantitative Trait in an Age-Structured Population in a Fluctuating Environment

2011

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“…Further analysis carried out on the data set after removing this population failed to find any substructure (data not shown). Temporal variations of allelic frequencies in small pelagic fish may result from fluctuations in the dominant age classes in the stock (Mariani et al 2005;Engen et al 2009). Although the samples analysed were not aged, it was possible to retrieve data on size distributions, which can roughly be used as a proxy for the age range.…”

Section: Resultsmentioning

confidence: 99%

Spatio-temporal variability in the population structure in North-east Atlantic stocks of horse mackerel (<em>Trachurus trachurus</em>)

Bozano¹,

Mariani²,

Barratt³

et al. 2015

Biology and Environment: Proceedings of the Royal Irish Academy

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JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. This content downloaded from 170. ABSTRACTThe long-term sustainability of fish stocks is dependent upon the identification of biologically meaningful demographic boundaries and, subsequently, appropriate assessment figures and management strategies. In the case of the horse mackerel, Trachurus trachurus, stock management in the North-east Atlantic area is currently based on stock identities derived from multidisciplinary data integration, but including genetic markers that might lack statistical power, hence potentially misrepresenting the units of assessment. For this reason, and based on multiannual field observations, the boundaries of the vast 'western stock', whose distribution spans from the Bay of Biscay to the Norwegian coast, were reassessed. The preliminary results of a population genetics survey of samples collected over three consecutive years off the western Irish coast (areas VI and VII) and Norway (IVa), and screened by employing a suite of thirteen microsatellite loci are presented. Results indicate that the core of the putative stock in the west of Ireland is temporally stable, but its spatial extent and connection with Norwegian waters varies between years. Interannual variation in nutrient transport and oceanographic regimes may explain unstable patterns of genetic variation west of Norway, where local, smaller, previously unknown populations might exist.

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“…For a complete census N e = N /σ 2 d is the effective population size (Engen et al 2005b), whereas for a sample we may call it the effective sample size determining the uncertainty in the estimated selection differentials including the effect of the genetic drift.…”

Section: Appendix B: Genetic Drift and Estimation Uncertaintymentioning

confidence: 99%

Reversal of response to artificial selection on body size in a wild passerine

et al. 2017

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Preface -If I have seen further, it is by standing on the shoulders of giants.Sir Isaac Newton (1676) I am thankful for the opportunity to become deeply immersed in the fascinating world of biology, it has been challenging, rewarding and periodically exhausting. The work of this thesis build on the effort of several people in study systems spanning two decades. They deserve many thanks for the dedication and careful collection of high quality data. I would also like to thank all the local people at the islands along the coast of Helgeland for the hospitality and friendliness experienced during all my fieldwork, it has been unprecedented.During the days in the office, out in the field and in the lab, I have been lucky to be surrounded by a lot of great colleagues and friends. Thanks for the most welcomed distractions and good laughs, and thanks for the helpful, interesting and inspiring talks and discussions. Special thanks go to all my good colleagues in both the house sparrow and moose project. I have enjoyed working with you all.At last I want to thank my friends, parents and family, your presence and support means a lot to me. Most of all I want to thank my dearest Eva Sofie for being loving, caring and supportive, and our two sons, William and Sebastian, for bringing so much joy into our lives. You three are most important of all.

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Reproductive Value and Fluctuating Selection in an Age-Structured Population

Cited by 23 publications

References 48 publications

Evolution of a Plastic Quantitative Trait in an Age-Structured Population in a Fluctuating Environment

Evolution of a Plastic Quantitative Trait in an Age-Structured Population in a Fluctuating Environment

Spatio-temporal variability in the population structure in North-east Atlantic stocks of horse mackerel (<em>Trachurus trachurus</em>)

Reversal of response to artificial selection on body size in a wild passerine

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