scholarly journals Evolution of dispersal can rescue populations from expansion load

2018 ◽  
Author(s):  
Stephan Peischl ◽  
Kimberly J. Gilbert
Keyword(s):  
Natural Selection ◽  
Genetic Drift ◽  
Evolutionary Biology ◽  
Empirical Work ◽  
Leading Edge ◽  
Slowing Down ◽  
Spatial Sorting ◽  
Mean Fitness ◽  
Expansion Load ◽  
Probability Of Fixation

AbstractUnderstanding the causes and consequences of range expansions or range shifts has a long history in evolutionary biology. Recent theoretical, experimental, and empirical work has identified two particularly interesting phenomena in the context of species range expansions: (i) gene surfing and the relaxation of natural selection, and (ii) spatial sorting. The former can lead to an accumulation of deleterious mutations at range edges, causing an expansion load and slowing down expansion. The latter can create gradients in dispersal-related traits along the expansion axis and cause an acceleration of expansion. We present a theoretical framework that treats spatial sorting and gene surfing as spatial versions of natural selection and genetic drift, respectively. This model allows us to study analytically how gene surfing and spatial sorting interact, and to derive the probability of fixation of pleiotropic mutations at the expansion front. We use our results to predict the co-evolution of mean fitness and dispersal rates, taking into account the effects of random genetic drift, natural selection and spatial sorting, as well as correlations between fitnessand dispersal-related traits. We identify a “rescue effect” of spatial sorting, where the evolution of higher dispersal rates at the leading edge rescues the population from incurring expansion load.

Power and Evolutionary Fitness of Teleosts

1982 ◽  
Vol 39 (1) ◽  
pp. 3-13 ◽  
Author(s):  
D. M. Ware
Keyword(s):  
Life History ◽  
Natural Selection ◽  
Optimal Foraging ◽  
Evolutionary Biology ◽  
Life History Theory ◽  
A Priori ◽  
Empirical Work ◽  
Physiological Basis ◽  
Vital Functions ◽  
Surplus Power

The use of optimization arguments in evolutionary biology has been criticized because the methodology requires an assumption about what is being maximized by natural selection. As optimality arguments are often a priori and always speculative, the critics point out that there is no theoretical basis for any maximization principles in biology. They contend that only empirical work can establish if there are some properties of species that are generally maximized by natural selection. I accept this standard for evaluation, and argue that the concept of surplus power, which provides a physiological basis for optimal foraging and life history theory, is related to fitness. Evidence in the form of specific morphological and behavioral traits in teleost fishes is presented to demonstrate that natural selection has increased surplus power. Life history theory is concerned with how power is allocated by organisms to various vital functions; therefore, the specific problem of stock and recruitment in fisheries can be treated as a special application of life history theory. Some implications about the dynamics and possible survival value of different reproductive strategies exhibited by teleosts are discussed.Key words: surplus power, evolutionary biology, optimal foraging, life history theory, fitness

Inferring natural selection in a fossil threespine stickleback

Paleobiology ◽  
2006 ◽  
Vol 32 (4) ◽  
pp. 562-577 ◽  
Author(s):  
Michael A. Bell ◽  
Matthew P. Travis ◽  
D. Max Blouw
Keyword(s):  
Natural Selection ◽  
Random Process ◽  
Genetic Drift ◽  
Fossil Record ◽  
Evolutionary Biology ◽  
Threespine Stickleback ◽  
Stabilizing Selection ◽  
Persistent Problem ◽  
Selection For ◽  
Lines Of Evidence

Inferring the causes for change in the fossil record has been a persistent problem in evolutionary biology. Three independent lines of evidence indicate that a lineage of the fossil stickleback fish Gasterosteus doryssus experienced directional natural selection for reduction of armor. Nonetheless, application to this lineage of three methods to infer natural selection in the fossil record could not exclude random process as the cause for armor change. Excluding stabilizing selection and genetic drift as the mechanisms for biostratigraphic patterns in the fossil record when directional natural selection was the actual cause is very difficult. Biostratigraphic sequences with extremely fine temporal resolution among samples and other favorable properties must be used to infer directional selection in the fossil record.

Evolutionary Processes in Cancer

2022 ◽  
Keyword(s):  
Immune System ◽  
Natural Selection ◽  
Genetic Drift ◽  
Evolutionary Biology ◽  
Evolutionary Processes ◽  
Medical Interventions ◽  
Selective Pressures ◽  
And Migration ◽  
Multicellular Organisms ◽  
Mutant Cells

Cancer develops through the evolution of somatic cells in multicellular bodies. The familiar dynamics of organismal evolution, including mutations, natural selection, genetic drift, and migration, also occur among the cells of multicellular organisms. In some cases, but not all, these evolutionary processes lead to cancer. This has profound implications for both our understanding of cancer and our treatment of the disease, as well as its prevention. All of our medical interventions impose selective pressures on the heterogeneous populations of billions of cells in tumors, and tend to select for mutant cells that are resistant to the intervention, regardless of whether the intervention is a drug, radiation, the immune system, or anything else that has been tried. We will likely need evolutionary and ecological approaches to cancer to manage its evolution in response to our interventions. The field of the evolutionary biology and ecology of cancer is still young and relatively small. We are in the early stages of translating ideas and tools from evolutionary biology and ecology to study and manage cancers. There is a desperate need for more researchers with expertise in evolutionary biology and ecology to apply their skills and ideas to cancer. Currently, there are far more important questions that need to be addressed than there are people to address them.

Social Selection and the Evolution of Maladaptation

2021 ◽  
Author(s):  
Joel W. McGlothlin ◽  
David N. Fisher
Keyword(s):  
Natural Selection ◽  
Genetic Model ◽  
Inclusive Fitness ◽  
Empirical Work ◽  
General Rule ◽  
Social Selection ◽  
Population Mean ◽  
Individual Level ◽  
Quantitative Genetic ◽  
Mean Fitness

AbstractEvolution by natural selection is often viewed as a process that inevitably leads to adaptation, or an increase in population fitness over time. However, maladaptation, an evolved decrease in fitness, may also occur in response to natural selection under some conditions. Social effects on fitness (or social selection) have been identified as a potential cause of maladaptation, but we lack a general rule identifying when social selection should lead to a decrease in population mean fitness. Here we use a quantitative genetic model to develop such a rule. We show that maladaptation is most likely to occur when social selection is strong relative to the nonsocial component of selection and acts in an opposing direction. In this scenario, evolutionary increases in traits that impose fitness costs on others may outweigh evolved gains in fitness for the individual, leading to a net decrease in population mean fitness. Further, we find maladaptation may also sometimes occur when phenotypes of interacting individuals negatively covary. We outline the biological situations where maladaptation in response to social selection can be expected, provide both quantitative genetic and phenotypic versions of our derived result, and suggest what empirical work would be needed to test it. We also consider the effect of social selection on inclusive fitness and support previous work showing that inclusive fitness cannot suffer an evolutionary decrease. Taken together, our results show that social selection may decrease population mean fitness when it opposes individual-level selection, even as inclusive fitness increases.

scholarly journals Allele Based Inference on Evolution and Extinction; A Genetic Drift Approach

2019 ◽  
Vol 1 (4) ◽  
pp. 1-15
Author(s):  
S. Oluwafemi Oyamakin ◽  
Angela U. Chukwu ◽  
Wale-Orojo Oluwaseun A ◽  
Ogunjobi E. O
Keyword(s):  
Natural Selection ◽  
Genetic Drift ◽  
Selective Advantage ◽  
Random Mutation ◽  
Genetic Changes ◽  
Moran Model ◽  
Fitness Advantage ◽  
Model Probability ◽  
Or Gene ◽  
Probability Of Fixation

In other to present a series of stochastic models from population dynamics capable of describing rudimentary aspects of genetic evolution, we studied two-allele Wright–Fisher and the Moran models for evolution of the relative frequencies of two alleles at a diploid locus under random genetic drift in a population of fixed size “simplest form, selection, and random mutation”. Principal results were presented in qualitative terms, illustrated by Monte Carlo simulations from R and http://www.radford.edu/~rsheehy/Gen_flash/popgen. Moran and the Wright-Fisher Models exhibited the same fixation probabilities, only that the Moran model runs twice as fast as the Wright-Fisher Model. A clue that can help us to understand this result is provided by the variance in reproductive success in the two models. Genetic changes due to drift were neither directional nor predictable in any deterministic way. Nonetheless, genetic drift led to evolutionary change in the absence of mutation (P=0.5), natural selection or gene flow. In general, alleles drift to fixation is significantly faster in smaller populations. Probability of fixation of an allele A was approximately equivalent to the initial frequency of that allele. With the inclusion of selection in our model, probability of fixation of a favoured allele due to natural selection increased with increase in fitness advantage and population size. The time taken to reach fixation is much slower, in case of no selective advantage, than a fixation under mutation with selective advantage.

scholarly journals GENETIC LOAD IN NATURAL POPULATIONS: IS IT COMPATIBLE WITH THE HYPOTHESIS THAT MANY POLYMORPHISMS ARE MAINTAINED BY NATURAL SELECTION?

Genetics ◽  
1974 ◽  
Vol 77 (3) ◽  
pp. 569-589
Author(s):  
Martin L Tracey ◽  
Francisco J Ayala
Keyword(s):  
Drosophila Melanogaster ◽  
Natural Selection ◽  
Natural Population ◽  
Natural Populations ◽  
Genetic Load ◽  
Structural Genes ◽  
Invertebrate Species ◽  
Average Proportion ◽  
Mean Fitness ◽  
The Mean

ABSTRACT Recent studies of genetically controlled enzyme variation lead to an estimation that at least 30 to 60% of the structural genes are polymorphic in natural populations of many vertebrate and invertebrate species. Some authors have argued that a substantial proportion of these polymorphisms cannot be maintained by natural selection because this would result in an unbearable genetic load. If many polymorphisms are maintained by heterotic natural selection, individuals with much greater than average proportion of homozygous loci should have very low fitness. We have measured in Drosophila melanogaster the fitness of flies homozygous for a complete chromosome relative to normal wild flies. A total of 37 chromosomes from a natural population have been tested using 92 experimental populations. The mean fitness of homozygous flies is 0.12 for second chromosomes, and 0.13 for third chromosomes. These estimates are compatible with the hypothesis that many (more than one thousand) loci are maintained by heterotic selection in natural populations of D. melanogaster.

scholarly journals Genome size correlates with reproductive fitness in seed beetles

2015 ◽  
Vol 282 (1815) ◽  
pp. 20151421 ◽  
Author(s):  
Göran Arnqvist ◽  
Ahmed Sayadi ◽  
Elina Immonen ◽  
Cosima Hotzy ◽  
Daniel Rankin ◽  
...  
Keyword(s):  
Life History ◽  
Natural Selection ◽  
Genome Size ◽  
Evolutionary Biology ◽  
Large Scale ◽  
Life History Traits ◽  
Single Species ◽  
Reproductive Fitness ◽  
Correlated Evolution ◽  
Seed Beetles

The ultimate cause of genome size (GS) evolution in eukaryotes remains a major and unresolved puzzle in evolutionary biology. Large-scale comparative studies have failed to find consistent correlations between GS and organismal properties, resulting in the ‘ C -value paradox’. Current hypotheses for the evolution of GS are based either on the balance between mutational events and drift or on natural selection acting upon standing genetic variation in GS. It is, however, currently very difficult to evaluate the role of selection because within-species studies that relate variation in life-history traits to variation in GS are very rare. Here, we report phylogenetic comparative analyses of GS evolution in seed beetles at two distinct taxonomic scales, which combines replicated estimation of GS with experimental assays of life-history traits and reproductive fitness. GS showed rapid and bidirectional evolution across species, but did not show correlated evolution with any of several indices of the relative importance of genetic drift. Within a single species, GS varied by 4–5% across populations and showed positive correlated evolution with independent estimates of male and female reproductive fitness. Collectively, the phylogenetic pattern of GS diversification across and within species in conjunction with the pattern of correlated evolution between GS and fitness provide novel support for the tenet that natural selection plays a key role in shaping GS evolution.

Exploring Genetic Drift & Natural Selection through a Simulation Activity

1998 ◽  
Vol 60 (9) ◽  
pp. 681-683 ◽  
Author(s):  
Timothy J. Maret ◽  
Steven W. Rissing
Keyword(s):  
Natural Selection ◽  
Genetic Drift

The Causal Structure of Natural Selection

2021 ◽  
Author(s):  
Charles H. Pence
Keyword(s):  
Natural Selection ◽  
Case Studies ◽  
Genetic Drift ◽  
Evolutionary Theory ◽  
Causal Structure ◽  
Philosophy Of Biology ◽  
Philosophy Of Physics ◽  
Potential Value ◽  
Multi Level ◽  
Evolutionary Explanations

Recent arguments concerning the nature of causation in evolutionary theory, now often known as the debate between the 'causalist' and 'statisticalist' positions, have involved answers to a variety of independent questions – definitions of key evolutionary concepts like natural selection, fitness, and genetic drift; causation in multi-level systems; or the nature of evolutionary explanations, among others. This Element offers a way to disentangle one set of these questions surrounding the causal structure of natural selection. Doing so allows us to clearly reconstruct the approach that some of these major competing interpretations of evolutionary theory have to this causal structure, highlighting particular features of philosophical interest within each. Further, those features concern problems not exclusive to the philosophy of biology. Connections between them and, in two case studies, contemporary metaphysics and philosophy of physics demonstrate the potential value of broader collaboration in the understanding of evolution.

scholarly journals Evolutionary biology today and the call for an extended synthesis

2017 ◽  
Vol 7 (5) ◽  
pp. 20160145 ◽  
Author(s):  
Douglas J. Futuyma
Keyword(s):  
Natural Selection ◽  
Evolutionary Theory ◽  
Evolutionary Biology ◽  
Epigenetic Inheritance ◽  
Reaction Norm ◽  
Evolutionary Synthesis ◽  
Historical Background ◽  
Extended Evolutionary Synthesis ◽  
Extended Synthesis ◽  
Proximate Causation

Evolutionary theory has been extended almost continually since the evolutionary synthesis (ES), but except for the much greater importance afforded genetic drift, the principal tenets of the ES have been strongly supported. Adaptations are attributable to the sorting of genetic variation by natural selection, which remains the only known cause of increase in fitness. Mutations are not adaptively directed, but as principal authors of the ES recognized, the material (structural) bases of biochemistry and development affect the variety of phenotypic variations that arise by mutation and recombination. Against this historical background, I analyse major propositions in the movement for an ‘extended evolutionary synthesis’. ‘Niche construction' is a new label for a wide variety of well-known phenomena, many of which have been extensively studied, but (as with every topic in evolutionary biology) some aspects may have been understudied. There is no reason to consider it a neglected ‘process’ of evolution. The proposition that phenotypic plasticity may engender new adaptive phenotypes that are later genetically assimilated or accommodated is theoretically plausible; it may be most likely when the new phenotype is not truly novel, but is instead a slight extension of a reaction norm already shaped by natural selection in similar environments. However, evolution in new environments often compensates for maladaptive plastic phenotypic responses. The union of population genetic theory with mechanistic understanding of developmental processes enables more complete understanding by joining ultimate and proximate causation; but the latter does not replace or invalidate the former. Newly discovered molecular phenomena have been easily accommodated in the past by elaborating orthodox evolutionary theory, and it appears that the same holds today for phenomena such as epigenetic inheritance. In several of these areas, empirical evidence is needed to evaluate enthusiastic speculation. Evolutionary theory will continue to be extended, but there is no sign that it requires emendation.

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