scholarly journals Adaptive topography of fluctuating selection in a Mendelian population

2008 ◽  
Vol 21 (4) ◽  
pp. 1096-1105 ◽  
Author(s):  
R. LANDE
Keyword(s):  
Fluctuating Selection ◽  
Mendelian Population

scholarly journals When does parasitism maintain sex in the absence of Red Queen Dynamics?

2020 ◽  
Author(s):  
Ben Ashby
Keyword(s):  
Population Density ◽  
Sexual Reproduction ◽  
Evolutionary Model ◽  
Niche Overlap ◽  
Disease Prevalence ◽  
Heterozygote Advantage ◽  
Red Queen ◽  
Fluctuating Selection ◽  
Antagonistic Coevolution ◽  
Maintenance Of Sex

AbstractParasites can select for sexual reproduction in host populations, preventing replacement by faster growing asexual lineages. This is usually attributed to so-called “Red Queen Dynamics” (RQD), where antagonistic coevolution causes fluctuating selection in allele frequencies, which provides sex with an advantage over asex. However, parasitism may also maintain sex in the absence of RQD when sexual populations are more genetically diverse – and hence more resistant, on average – than clonal populations, allowing sex and asex to stably coexist. While the maintenance of sex due to RQD has been studied extensively, the conditions that allow sex and asex to stably coexist have yet to be explored in detail. In particular, we lack an understanding of how host demography and parasite epidemiology affect the maintenance of sex in the absence of RQD. Here, I use an eco-evolutionary model to show that both population density and the type and strength of virulence are important for maintaining sex, which can be understood in terms of their effects on disease prevalence and severity. In addition, I show that even in the absence of heterozygote advantage, asexual heterozygosity affects coexistence with sex due to variation in niche overlap. These results reveal which host and parasite characteristics are most important for the maintenance of sex in the absence of RQD, and provide empirically testable predictions for how demography and epidemiology mediate competition between sex and asex.

scholarly journals Negative frequency-dependent selection maintains coexisting genotypes during fluctuating selection

2019 ◽  
Author(s):  
Caroline B. Turner ◽  
Sean W. Buskirk ◽  
Katrina B. Harris ◽  
Vaughn S. Cooper
Keyword(s):  
Evolutionary Dynamics ◽  
Burkholderia Cenocepacia ◽  
Natural Environments ◽  
Fluctuating Selection ◽  
Frequency Dependent ◽  
Frequency Dependent Selection ◽  
Fluctuating Environment ◽  
Fluctuating Environments ◽  
Negative Frequency Dependent Selection ◽  
Selection For

AbstractNatural environments are rarely static; rather selection can fluctuate on time scales ranging from hours to centuries. However, it is unclear how adaptation to fluctuating environments differs from adaptation to constant environments at the genetic level. For bacteria, one key axis of environmental variation is selection for planktonic or biofilm modes of growth. We conducted an evolution experiment with Burkholderia cenocepacia, comparing the evolutionary dynamics of populations evolving under constant selection for either biofilm formation or planktonic growth with populations in which selection fluctuated between the two environments on a weekly basis. Populations evolved in the fluctuating environment shared many of the same genetic targets of selection as those evolved in constant biofilm selection, but were genetically distinct from the constant planktonic populations. In the fluctuating environment, mutations in the biofilm-regulating genes wspA and rpfR rose to high frequency in all replicate populations. A mutation in wspA first rose rapidly and nearly fixed during the initial biofilm phase but was subsequently displaced by a collection of rpfR mutants upon the shift to the planktonic phase. The wspA and rpfR genotypes coexisted via negative frequency-dependent selection around an equilibrium frequency that shifted between the environments. The maintenance of coexisting genotypes in the fluctuating environment was unexpected. Under temporally fluctuating environments coexistence of two genotypes is only predicted under a narrow range of conditions, but the frequency-dependent interactions we observed provide a mechanism that can increase the likelihood of coexistence in fluctuating environments.

scholarly journals Fluctuating selection: the perpetual renewal of adaptation in variable environments

2010 ◽  
Vol 365 (1537) ◽  
pp. 87-97 ◽  
Author(s):  
Graham Bell
Keyword(s):  
Natural Selection ◽  
Evolutionary Biology ◽  
Natural Populations ◽  
Phenotypic Variance ◽  
Weak Selection ◽  
Fluctuating Selection ◽  
Environmental Variance ◽  
Strong Selection ◽  
Genomic Studies ◽  
Over Time

Darwin insisted that evolutionary change occurs very slowly over long periods of time, and this gradualist view was accepted by his supporters and incorporated into the infinitesimal model of quantitative genetics developed by R. A. Fisher and others. It dominated the first century of evolutionary biology, but has been challenged in more recent years both by field surveys demonstrating strong selection in natural populations and by quantitative trait loci and genomic studies, indicating that adaptation is often attributable to mutations in a few genes. The prevalence of strong selection seems inconsistent, however, with the high heritability often observed in natural populations, and with the claim that the amount of morphological change in contemporary and fossil lineages is independent of elapsed time. I argue that these discrepancies are resolved by realistic accounts of environmental and evolutionary changes. First, the physical and biotic environment varies on all time-scales, leading to an indefinite increase in environmental variance over time. Secondly, the intensity and direction of natural selection are also likely to fluctuate over time, leading to an indefinite increase in phenotypic variance in any given evolving lineage. Finally, detailed long-term studies of selection in natural populations demonstrate that selection often changes in direction. I conclude that the traditional gradualist scheme of weak selection acting on polygenic variation should be supplemented by the view that adaptation is often based on oligogenic variation exposed to commonplace, strong, fluctuating natural selection.

scholarly journals Inbreeding in a stable simple Mendelian population with special reference to cousin marriage

1911 ◽  
Vol 84 (568) ◽  
pp. 23-42 ◽  
Keyword(s):  
Special Reference ◽  
Close Agreement ◽  
Simple Explanation ◽  
Cousin Marriage ◽  
Precise Data ◽  
Mendelian Population

The Mendelian theory of the segregation of unit characters, though it is far, as yet, from being completely demonstrated, offers a simple explanation of some striking features of inheritance. In particular, Mr. E. C. Snow has recently shown that the gametic correlations for collaterals deducible from the Mendelian hypothesis are in close agreement with the actually observed somatic correlations for man and certain other animals; or, in other words, that a Mendelian theory of segregation without dominance gives values for collateral resemblance not greatly differing from those found from observation. It seems, therefore, possible that the same theory will throw some light on the problem of inbreeding, or, at any rate, will indicate to what points, on which precise data are at present lacking, statistical enquiry should be directed. Without these data the Mendelian theory cannot be corroborated or negatived by the methods of the present paper. So far as they go, however, the statistics at present obtainable with regard to consanguinity in the parentage of albinos and deaf mutes are in approximate agreement with the calculated results, although the accuracy of the figures is too uncertain for the application of anything more than a rough criterion.

scholarly journals Eco-evolutionary feedbacks promote fluctuating selection and long-term stability of antagonistic networks

2018 ◽  
Vol 285 (1874) ◽  
pp. 20172596 ◽  
Author(s):  
Cecilia Siliansky de Andreazzi ◽  
Paulo R. Guimarães ◽  
Carlos J. Melián
Keyword(s):  
Temporal Variation ◽  
Evolutionary Dynamics ◽  
Species Interaction ◽  
Fluctuating Selection ◽  
Term Stability ◽  
Long Term Stability ◽  
Interacting Species ◽  
Species Abundances ◽  
Antagonistic Interactions

Studies have shown the potential for rapid adaptation in coevolving populations and that the structure of species interaction networks can modulate the vulnerability of ecological systems to perturbations. Although the feedback loop between population dynamics and coevolution of traits is crucial for understanding long-term stability in ecological assemblages, modelling eco-evolutionary dynamics in species-rich assemblages is still a challenge. We explore how eco-evolutionary feedbacks influence trait evolution and species abundances in 23 empirical antagonistic networks. We show that, if selection due to antagonistic interactions is stronger than other selective pressures, eco-evolutionary feedbacks lead to higher mean species abundances and lower temporal variation in abundances. By contrast, strong selection of antagonistic interactions leads to higher temporal variation of traits and on interaction strengths. Our results present a theoretical link between the study of the species persistence and coevolution in networks of interacting species, pointing out the ways by which coevolution may decrease the vulnerability of species within antagonistic networks to demographic fluctuation.

scholarly journals Transitional genomes and nutritional role reversals identified for dual symbionts of adelgids (Aphidoidea: Adelgidae)

2021 ◽  
Author(s):  
Dustin T. Dial ◽  
Kathryn M. Weglarz ◽  
Akintunde O. Aremu ◽  
Nathan P. Havill ◽  
Taylor A. Pearson ◽  
...  
Keyword(s):  
Evolutionary History ◽  
Life Cycles ◽  
Fluctuating Selection ◽  
Complex Life Cycles ◽  
History Of ◽  
Sap Feeding ◽  
Selection For ◽  
Gains And Losses ◽  
Conifer Trees ◽  
Plant Sap

AbstractMany plant-sap-feeding insects have maintained a single, obligate, nutritional symbiont over the long history of their lineage. This senior symbiont may be joined by one or more junior symbionts that compensate for gaps in function incurred through genome-degradative forces. Adelgids are sap-sucking insects that feed solely on conifer trees and follow complex life cycles in which the diet fluctuates in nutrient levels. Adelgids are unusual in that both senior and junior symbionts appear to have been replaced repeatedly over their evolutionary history. Genomes can provide clues to understanding symbiont replacements, but only the dual symbionts of hemlock adelgids have been examined thus far. Here, we sequence and compare genomes of four additional dual-symbiont pairs in adelgids. We show that these symbionts are nutritional partners originating from diverse bacterial lineages and exhibiting wide variation in general genome characteristics. Although dual symbionts cooperate to produce nutrients, the balance of contributions varies widely across pairs, and total genome contents reflect a range of ages and degrees of degradation. Most symbionts appear to be in transitional states of genome reduction. Our findings support a hypothesis of periodic symbiont turnover driven by fluctuating selection for nutritional provisioning related to gains and losses of complex life cycles in their hosts.

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