Frontiers in Metapopulation Biology: The Legacy of Ilkka Hanski

2018 ◽  
Vol 49 (1) ◽  
pp. 231-252 ◽  
Author(s):  
Otso Ovaskainen ◽  
Marjo Saastamoinen
Keyword(s):  
Evolutionary Dynamics ◽  
Molecular Level ◽  
Extinction Risk ◽  
Natural Populations ◽  
Special Focus ◽  
Trait Variation ◽  
Ecological Aspects ◽  
Dispersal Traits ◽  
Selection For ◽  
Natural Laboratory

This review of metapopulation biology has a special focus on Professor Ilkka Hanski's (1953–2016) research. Hanski made seminal contributions to both empirical and theoretical metapopulation biology throughout his scientific career. Hanski's early research focused on ecological aspects of metapopulation biology, in particular how the spatial structure of a landscape influences extinction thresholds and how habitat loss and fragmentation can result in extinction debt. Hanski then used the Glanville fritillary system as a natural laboratory within which he studied genetic and evolutionary processes, such as the influence of inbreeding on extinction risk and variation in selection for dispersal traits generated by landscape variation. During the last years of his career, Hanski's work was in the forefront of the rapidly developing field of eco-evolutionary dynamics. Hanski was a pioneer in showing how molecular-level underpinnings of trait variation can explain why evolutionary change can occur rapidly in natural populations and how these changes can subsequently influence ecological dynamics.

scholarly journals Gene buddies: linked balanced polymorphisms reinforce each other even in the absence of epistasis

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e5110 ◽  
Author(s):  
Jacob A. Tennessen
Keyword(s):  
Genetic Architecture ◽  
Evolutionary Dynamics ◽  
Balancing Selection ◽  
Natural Populations ◽  
Adaptive Variation ◽  
Recombination Rates ◽  
Future Studies ◽  
Close Physical Proximity ◽  
Selection For ◽  
Independent Effects

The fates of genetic polymorphisms maintained by balancing selection depend on evolutionary dynamics at linked sites. While coevolution across linked, epigenetically-interacting loci has been extensively explored, such supergenes may be relatively rare. However, genes harboring adaptive variation can occur in close physical proximity while generating independent effects on fitness. Here, I present a model in which two linked loci without epistasis are both under balancing selection for unrelated reasons. Using forward-time simulations, I show that recombination rate strongly influences the retention of adaptive polymorphism, especially for intermediate selection coefficients. A locus is more likely to retain adaptive variation if it is closely linked to another locus under balancing selection, even if the two loci have no interaction. Thus, two linked polymorphisms can both be retained indefinitely even when they would both be lost to drift if unlinked. While these results may be intuitive, they have important implications for genetic architecture: clusters of mutually reinforcing genes may underlie phenotypic variation in natural populations, and such genes cannot be assumed to be functionally associated. Future studies that measure selection coefficients and recombination rates among closely linked genes will be fruitful for characterizing the extent of this phenomenon.

scholarly journals Gene buddies: Linked balanced polymorphisms reinforce each other even in the absence of epistasis

2017 ◽  
Author(s):  
Jacob A Tennessen
Keyword(s):  
Recombination Rate ◽  
Evolutionary Dynamics ◽  
Balancing Selection ◽  
Natural Populations ◽  
Adaptive Variation ◽  
Recombination Rates ◽  
Future Studies ◽  
Close Physical Proximity ◽  
Selection For ◽  
Independent Effects

The fates of genetic polymorphisms maintained by balancing selection depend on evolutionary dynamics at linked sites. While coevolution across linked, epigenetically-interacting loci has been extensively explored, such supergenes may be relatively rare. However, genes harboring adaptive variation can occur in close physical proximity while generating independent effects on fitness. Here, I present a model in which two linked loci without epistasis are both under balancing selection for unrelated reasons. Using forward-time simulations, I show that recombination rate strongly influences the retention of adaptive polymorphism, especially for intermediate selection coefficients. A locus is more likely to retain adaptive variation if it is closely linked to another locus under balancing selection, even if the two loci have no interaction. Thus, two linked polymorphisms can both be retained indefinitely even when they would both be lost to drift if unlinked. Such clusters of mutually reinforcing genes may underlie phenotypic variation in natural populations. Future studies that measure selection coefficients and recombination rates among closely linked genes will be fruitful for characterizing the extent of this phenomenon.

scholarly journals Ilkka Aulis Hanski. 14 February 1953—10 May 2016

2020 ◽  
Vol 68 ◽  
pp. 231-250
Author(s):  
Daniel Simberloff ◽  
Otso Ovaskainen
Keyword(s):  
Evolutionary Biology ◽  
Evolutionary Dynamics ◽  
Natural Populations ◽  
Empirical Work ◽  
Dung Beetle ◽  
Research Centre ◽  
University Of Oxford ◽  
Evolutionary Changes ◽  
Ecological Aspects ◽  
Research Findings

Professor Ilkka Hanski made seminal contributions to both empirical and theoretical ecology and evolutionary biology, in particular metapopulation biology, throughout his scientific career. He started his career with dung beetle ecology, earning his doctorate at University of Oxford in 1979. He developed the rest of his career at University of Helsinki, where he was appointed professor in ecology in 1993 and academy professor in 2006. Hanski's most influential research was based on empirical work on the Glanville fritillary metapopulation in the Åland Islands, started in 1991, and continued until his death. His early research focused on ecological aspects of metapopulation biology, such as how the spatial structure of a landscape influences extinction thresholds, whereas his later work focused on genetic and evolutionary processes, such as maintenance of genetic variation by selection pressures varying with landscape structure. During the last years of his career, Hanski was a pioneer in the field of eco-evolutionary dynamics, showing how molecular-level underpinnings of trait variation can explain rapid evolutionary changes in natural populations. Hanski actively applied his research findings to conservation biology, involving himself in debates ranging from forest conservation in Finland to the links between human health and biodiversity. He was an exceptionally devoted group leader and mentor of younger researchers. His Metapopulation Research Centre grew gradually from a group consisting of Hanski and a few PhD students into a centre of 70 researchers.

Evidence of local adaptation and stabilizing selection on quantitative traits in populations of the multipurpose American species Acacia aroma (Fabaceae)

2019 ◽  
Vol 191 (1) ◽  
pp. 128-141 ◽  
Author(s):  
Carolina L Pometti ◽  
Cecilia F Bessega ◽  
Ana M Cialdella ◽  
Mauricio Ewens ◽  
Beatriz O Saidman ◽  
...  
Keyword(s):  
Quantitative Traits ◽  
Genetic Basis ◽  
Natural Populations ◽  
Tree Height ◽  
Phenotypic Traits ◽  
Stabilizing Selection ◽  
Trait Variation ◽  
Chaco Region ◽  
Neutral Genetic Variation ◽  
Selection For

Abstract Economically and ecologically important quantitative traits of Acacia aroma are related to life history and the size and shape of fruits and leaves. Substantial variation is observed for these traits in natural populations, suggesting a possible genetic basis that could be useful for selection programmes. Our objective was to detect signals of selection on 12 phenotypic traits in 170 individuals belonging to seven populations of A. aroma in the Chaco Region of Argentina. Phenotypic traits were compared with molecular markers assessed in the same populations. Here, we search for signatures of natural selection by comparing quantitative trait variation to neutral genetic variation through the PST–FST test. We further test for differences among populations for the 12 phenotypic traits, an association of phenotypic variation with environmental variables and geographical distance, and we compare the power of discrimination between the phenotypic and AFLP datasets. The PST–FST test suggested directional selection for tree height and stabilizing selection for the remaining traits. Analyses of variance showed significant differentiation for eight phenotypic traits. These results suggest selecting among provenances as a management strategy to improve tree height (which showed divergent selection), whereas significant genetic gain for the other traits might be obtained by selection within provenances.

Can the Lewis basicity of an isolated solvent molecule be used for characterizing solvent effects?

2020 ◽  
Vol 16 ◽  
Author(s):  
Jean-François Gal ◽  
Pierre-Charles Maria
Keyword(s):  
Solvent Effects ◽  
Molecular Level ◽  
Solvent Molecule ◽  
Lewis Base ◽  
Bulk Liquid ◽  
Donor Number ◽  
Special Focus ◽  
Solution Processes ◽  
Inert Solvent

Background: The ubiquitous Lewis acid/base interactions are important in solution processes. Analytical chemistry may benefit of a better understanding of the role of Lewis basicity, at the molecular level or acting through a bulk solvent effect. Objective: To clearly delineate (i) the basicity at a molecular level, hereafter referred as solute basicity, and (ii) the solvent basicity, which is a bulk-liquid property. Method: The literature that relates Lewis basicity scales and solvent effects is analyzed. A special focus is placed on two extensive scales, the Donor Number, DN, and the BF3 affinity scale, BF3A, which were obtained by calorimetric measurement on molecules as solutes diluted in a quasi-inert solvent, and therefore define a molecular Lewis basicity. We discuss the validity of these solute scales when regarded as solvent scales, in particular when the basicity of strongly associated liquids is discussed. Results: We demonstrate the drawbacks of confusing the Lewis basicity of a solvent molecule, isolated as solute, and that of the bulk liquid solvent itself. Conclusion: Consequently, we recommend a reasoned use of the concept of Lewis basicity taking clearly into account the specificity of the process for which a Lewis basicity effect may be invoked. In particular, the action of the Lewis base, either as an isolated entity, or as a bulk liquid, must be distinguished.

scholarly journals Polygenic and single gene responses to selection for resistance to diazinon in Lucilia cuprina.

Genetics ◽  
1992 ◽  
Vol 130 (3) ◽  
pp. 613-620 ◽  
Author(s):  
J A McKenzie ◽  
A G Parker ◽  
J L Yen
Keyword(s):  
Resistant Strain ◽  
Single Gene ◽  
Natural Populations ◽  
Susceptible Strain ◽  
Selection Line ◽  
Base Population ◽  
Gene Response ◽  
Biochemical Profiles ◽  
Resistant Strains ◽  
Selection For

Abstract Following mutagenesis with ethyl methanesulfonate, selection in a susceptible strain with a concentration of the insecticide diazinon (0.0004%, w/v) above that required to kill 100% of the susceptible strain, the LC100 of that strain, resulted in a single gene response. The resultant four mutant resistant strains have equivalent physiological, genetical and biochemical profiles to a diazinon-resistant strain derived from a natural population and homozygous for the Rop-1 allele. Modification of the microsomal esterase E3 is responsible for resistance in each case. The Rop-1 locus maps approximately 4.4 map units proximal to bu on chromosome IV. Selection within the susceptible distribution, at a concentration of diazinon [0.0001% (w/v)] less than the LC100, resulted in a similar phenotypic response irrespective of whether the base population had been mutagenized. The responses were polygenically based, unique to each selection line and independent of Rop-1. The relevance of the results to selection for insecticide resistance in laboratory and natural populations is discussed.

scholarly journals Evolutionary dynamics of spore killers.

Genetics ◽  
1993 ◽  
Vol 135 (3) ◽  
pp. 923-930 ◽  
Author(s):  
M J Nauta ◽  
R F Hoekstra
Keyword(s):  
Life Cycle ◽  
Segregation Distortion ◽  
Population Genetic ◽  
Field Data ◽  
Evolutionary Dynamics ◽  
Natural Populations ◽  
Additional Advantage ◽  
Genetic Modeling ◽  
Spore Killing ◽  
Ascospore Formation

Abstract Spore killing in ascomycetes is a special form of segregation distortion. When a strain with the Killer genotype is crossed to a Sensitive type, spore killing is expressed by asci with only half the number of ascospores as usual, all surviving ascospores being of the Killer type. Using population genetic modeling, this paper explores conditions for invasion of Spore killers and for polymorphism of Killers, Sensitives and Resistants (which neither kill, nor get killed), as found in natural populations. The models show that a population with only Killers and Sensitives can never be stable. The invasion of Killers and stable polymorphism only occur if Killers have some additional advantage during the process of spore killing. This may be due to the effects of local sib competition or some kind of "heterozygous" advantage in the stage of ascospore formation or in the short diploid stage of the life cycle. This form of segregation distortion appears to be essentially different from other, well-investigated forms, and more field data are needed for a better understanding of spore killing.

scholarly journals The Tomato Interspecific NB-LRR Gene Arsenal and Its Impact on Breeding Strategies

Genes ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 184
Author(s):  
Giuseppe Andolfo ◽  
Nunzio D’Agostino ◽  
Luigi Frusciante ◽  
Maria Raffaella Ercolano
Keyword(s):  
Evolutionary Dynamics ◽  
Special Focus ◽  
Breeding Strategies ◽  
Adaptive Diversification ◽  
Solanum Lycopersicum L ◽  
Solanaceae Species ◽  
Specific Pathogen ◽  
Adaptive Processes ◽  
Species Specific ◽  
R Loci

Tomato (Solanum lycopersicum L.) is a model system for studying the molecular basis of resistance in plants. The investigation of evolutionary dynamics of tomato resistance (R)-loci provides unique opportunities for identifying factors that promote or constrain genome evolution. Nucleotide-binding domain and leucine-rich repeat (NB-LRR) receptors belong to one of the most plastic and diversified families. The vast amount of genomic data available for Solanaceae and wild tomato relatives provides unprecedented insights into the patterns and mechanisms of evolution of NB-LRR genes. Comparative analysis remarked a reshuffling of R-islands on chromosomes and a high degree of adaptive diversification in key R-loci induced by species-specific pathogen pressure. Unveiling NB-LRR natural variation in tomato and in other Solanaceae species offers the opportunity to effectively exploit genetic diversity in genomic-driven breeding programs with the aim of identifying and introducing new resistances in tomato cultivars. Within this motivating context, we reviewed the repertoire of NB-LRR genes available for tomato improvement with a special focus on signatures of adaptive processes. This issue is still relevant and not thoroughly investigated. We believe that the discovery of mechanisms involved in the generation of a gene with new resistance functions will bring great benefits to future breeding strategies.

scholarly journals Different Within-Host Viral Evolution Dynamics in Severely Immunosuppressed Cases with Persistent SARS-CoV-2

Biomedicines ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 808
Author(s):  
Laura Pérez-Lago ◽  
Teresa Aldámiz-Echevarría ◽  
Rita García-Martínez ◽  
Leire Pérez-Latorre ◽  
Marta Herranz ◽  
...  
Keyword(s):  
Single Nucleotide Polymorphisms ◽  
Evolutionary Dynamics ◽  
Viral Evolution ◽  
Special Focus ◽  
Nucleotide Polymorphisms ◽  
Single Nucleotide ◽  
New Variant ◽  
History Of ◽  
Evolution Dynamics ◽  
The Uk

A successful Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) variant, B.1.1.7, has recently been reported in the UK, causing global alarm. Most likely, the new variant emerged in a persistently infected patient, justifying a special focus on these cases. Our aim in this study was to explore certain clinical profiles involving severe immunosuppression that may help explain the prolonged persistence of viable viruses. We present three severely immunosuppressed cases (A, B, and C) with a history of lymphoma and prolonged SARS-CoV-2 shedding (2, 4, and 6 months), two of whom finally died. Whole-genome sequencing of 9 and 10 specimens from Cases A and B revealed extensive within-patient acquisition of diversity, 12 and 28 new single nucleotide polymorphisms, respectively, which suggests ongoing SARS-CoV-2 replication. This diversity was not observed for Case C after analysing 5 sequential nasopharyngeal specimens and one plasma specimen, and was only observed in one bronchoaspirate specimen, although viral viability was still considered based on constant low Ct values throughout the disease and recovery of the virus in cell cultures. The acquired viral diversity in Cases A and B followed different dynamics. For Case A, new single nucleotide polymorphisms were quickly fixed (13–15 days) after emerging as minority variants, while for Case B, higher diversity was observed at a slower emergence: fixation pace (1–2 months). Slower SARS-CoV-2 evolutionary pace was observed for Case A following the administration of hyperimmune plasma. This work adds knowledge on SARS-CoV-2 prolonged shedding in severely immunocompromised patients and demonstrates viral viability, noteworthy acquired intra-patient diversity, and different SARS-CoV-2 evolutionary dynamics in persistent cases.

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