Population History and Natural Selection Shape Patterns of Genetic Variation in 132 Genes

Species populations commonly carry a great deal of genetic variation which is not expressed in individual phenotypes. Cryptic variation can be carried in recessive alleles, in cases of heterosis, or where modifier genes inhibit expression of the hidden trait. Other genetic and ecological factors also allow cryptic variation. Stabilizing selection prevents the expression of hidden traits; normalizing selection weeds out the deviants and canalizing selection suppresses their traits. Together the two keep the species near the top of the adaptive peak. Cryptic variation balances a species' need to be well-adapted to its environment and also for it to maintain a reserve of variation for potential environmental change. Expression of cryptic traits is rare and is usually associated with times of greatly reduced natural selection and rapid population growth, when the lower slopes of the adaptive peak are exposed.A possible example of the manifestation of cryptic traits occurs within the lower Trentonian Rafinesquina lineage of New York State. The two most commonly reported species of the genus have been reappraised in terms of cryptic variation. Extensive collections of Rafinesquina “lennoxensis” reveal far more intergrading morphotypes than had hitherto been recognized. The form which Salmon (1942) described is broadly U-shaped with sulcate margins. It grades into very convex forms as well as sharply-defined or convexly geniculate types. Of great importance, all forms grade into the flat, U-shaped, alate R. trentonensis, which is, by far, the most common and widespread lower Trentonian member of the genus. The R. “lennoxensis” assemblage has a very narrow biostratigraphy, being confined to a few locations in the upper Napanee Limestone. This places it in a quiet, protected, low stress, lagoonal setting behind the barrier shoal facies of the Kings Falls Limestone.The R. “lennoxensis” assemblage does not constitute a natural biologic species; it is reinterpreted as an assemblage of phenodeviants occupying a low stress, low natural selection lagoon facies. All such forms should be included within R. trentonensis. Given the evolutionary plasticity of this genus, extensive cryptic variation is not surprising.

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Evolution and evolvability: celebrating Darwin 200

Biology Letters ◽

10.1098/rsbl.2008.0639 ◽

2008 ◽

Vol 5 (1) ◽

pp. 44-46 ◽

Cited By ~ 33

Author(s):

John F.Y Brookfield

Keyword(s):

Genetic Variation ◽

Natural Selection ◽

Time Scales ◽

Evolutionary Change ◽

Adaptive Mutation ◽

Genetic Covariances ◽

The Relationship ◽

The Way

The concept of ‘evolvability’ is increasingly coming to dominate considerations of evolutionary change. There are, however, a number of different interpretations that have been put on the idea of evolvability, differing in the time scales over which the concept is applied. For some, evolvability characterizes the potential for future adaptive mutation and evolution. Others use evolvability to capture the nature of genetic variation as it exists in populations, particularly in terms of the genetic covariances between traits. In the latter use of the term, the applicability of the idea of evolvability as a measure of population's capacity to respond to natural selection rests on one, but not the only, view of the way in which we should envisage the process of natural selection. Perhaps the most potentially confusing aspects of the concept of evolvability are seen in the relationship between evolvability and robustness.

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The genomics of adaptation

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2012.2322 ◽

2012 ◽

Vol 279 (1749) ◽

pp. 5024-5028 ◽

Cited By ~ 35

Author(s):

Jacek Radwan ◽

Wiesław Babik

Keyword(s):

Genetic Variation ◽

Natural Selection ◽

Royal Society ◽

Genetic Basis ◽

Genomic Data ◽

Evolutionary Change ◽

Introductory Article ◽

Technological Advances ◽

A Genome ◽

Genome Level

The amount and nature of genetic variation available to natural selection affect the rate, course and outcome of evolution. Consequently, the study of the genetic basis of adaptive evolutionary change has occupied biologists for decades, but progress has been hampered by the lack of resolution and the absence of a genome-level perspective. Technological advances in recent years should now allow us to answer many long-standing questions about the nature of adaptation. The data gathered so far are beginning to challenge some widespread views of the way in which natural selection operates at the genomic level. Papers in this Special Feature of Proceedings of the Royal Society B illustrate various aspects of the broad field of adaptation genomics. This introductory article sets up a context and, on the basis of a few selected examples, discusses how genomic data can advance our understanding of the process of adaptation.

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Population history and taxonomy of African hares (genus Lepus) inferred from genetic variation

Mammalian Biology ◽

10.1016/j.mambio.2016.07.035 ◽

2016 ◽

Vol 81 ◽

pp. 12

Author(s):

Sara Lado ◽

P.C. Alves ◽

J.C. Brito ◽

J. Melo-Ferreira

Keyword(s):

Genetic Variation ◽

Population History

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Evidence of between-population differences in natural selection on extra-floral nectaries of the shrub Anemopaegma album (Bignoniaceae)

Botany ◽

10.1139/cjb-2015-0201 ◽

2016 ◽

Vol 94 (3) ◽

pp. 201-213

Author(s):

Anselmo Nogueira ◽

Pedro J. Rey ◽

Julio M. Alcántara ◽

Lúcia G. Lohmann

Keyword(s):

Genetic Variation ◽

Natural Selection ◽

Evolutionary Ecology ◽

Common Garden ◽

Phenotypic Selection ◽

Population Differences ◽

Wild Populations ◽

Neotropical Savanna ◽

Foliar Damage ◽

Floral Nectaries

Extra-floral nectaries (EFNs) are thought to represent protective adaptations against herbivory, but studies on the evolutionary ecology of EFNs have seldom been conducted. Here we investigate the patterns of natural selection and genetic variation in EFN traits in two wild populations of Anemopaegma album Mart. ex DC. (Bignoniaceae) that have been previously described as contrasting EFN – ant adapted localities in the Neotropical savanna (Cristália and Grão Mogol). In each population, four EFN descriptors, foliar damage, and reproductive success variables were measured per plant (100–120 plants per population). To estimate the heritability of EFN traits, we crossed reproductive plants in the field, and grew offspring plants in a common garden. The results showed that ant assemblages differed between populations, as did the range of foliar herbivory. Genetic variation and positive phenotypic selection in EFN abundance were only detected in the Cristália population, in which plants with more EFNs were more likely to reproduce. An evaluation of putative causal links conducted by path analysis corroborated the existence of phenotypic selection on EFNs, which was mediated by the herbivory process in the Cristália population. While EFNs could be currently under selection in Cristália, it is possible that past selection may have driven EFN traits to become locally adapted to the local ant assemblage in the Grão Mogol population.

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Experimental evolution reveals natural selection on standing genetic variation

Nature Genetics ◽

10.1038/ng.289 ◽

2009 ◽

Vol 41 (2) ◽

pp. 251-257 ◽

Cited By ~ 111

Author(s):

Henrique Teotónio ◽

Ivo M Chelo ◽

Martina Bradić ◽

Michael R Rose ◽

Anthony D Long

Keyword(s):

Genetic Variation ◽

Natural Selection ◽

Experimental Evolution

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Genetic Variation Explains Changes in Susceptibility in a Naïve Host Against an Invasive Forest Pathogen: The Case of Alder and the Phytophthora alni Complex

Phytopathology ◽

10.1094/phyto-07-19-0272-r ◽

2020 ◽

Vol 110 (2) ◽

pp. 517-525 ◽

Cited By ~ 1

Author(s):

Miguel A. Redondo ◽

Jan Stenlid ◽

Jonàs Oliva

Keyword(s):

Genetic Variation ◽

Natural Selection ◽

Transmission Rate ◽

Alternative Hypothesis ◽

Simulated Data ◽

Alnus Glutinosa ◽

Heritable Variation ◽

Narrow Sense Heritability ◽

Black Alder

Predicting whether naïve tree populations have the potential to adapt to exotic pathogens is necessary owing to the increasing rate of invasions. Adaptation may occur as a result of natural selection when heritable variation in terms of susceptibility exists in the naïve population. We searched for signs of selection on black alder (Alnus glutinosa) stands growing on riverbanks invaded by two pathogens differing in aggressiveness, namely, Phytophthora uniformis (PU) and Phytophthora × alni (PA). We compared the survival and heritability measures from 72 families originating from six invaded and uninvaded (naïve) sites by performing in vitro inoculations. The results from the inoculations were used to assess the relative contribution of host genetic variation on natural selection. We found putative signs of natural selection on alder exerted by PU but not by PA. For PU, we found a higher survival in families originating from invaded sites compared with uninvaded sites. The narrow sense heritability of susceptibility to PU of uninvaded populations was significantly higher than to PA. Simulated data supported the role of heritable genetic variation on natural selection and discarded a high aggressiveness of PA decreasing the transmission rate as an alternative hypothesis for a slow natural selection. Our findings expand on previous attempts of using heritability as a predictor for the likelihood of natural adaptation of naïve tree populations to invasive pathogens. Measures of genetic variation can be useful for risk assessment purposes or when managing Phytophthora invasions.

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Geographical Gradients of Genetic Diversity and Differentiation among the Southernmost Marginal Populations of Abies sachalinensis Revealed by EST-SSR Polymorphism

Forests ◽

10.3390/f11020233 ◽

2020 ◽

Vol 11 (2) ◽

pp. 233 ◽

Cited By ~ 1

Author(s):

Keiko Kitamura ◽

Kentaro Uchiyama ◽

Saneyoshi Ueno ◽

Wataru Ishizuka ◽

Ikutaro Tsuyama ◽

...

Keyword(s):

Genetic Diversity ◽

Genetic Variation ◽

Local Population ◽

Distribution Center ◽

Population History ◽

Peripheral Populations ◽

Abies Sachalinensis ◽

Marginal Populations ◽

Local Populations ◽

Longitudinal Gradients

Research Highlights: We detected the longitudinal gradients of genetic diversity parameters, such as the number of alleles, effective number of alleles, heterozygosity, and inbreeding coefficient, and found that these might be attributable to climatic conditions, such as temperature and snow depth. Background and Objectives: Genetic diversity among local populations of a plant species at its distributional margin has long been of interest in ecological genetics. Populations at the distribution center grow well in favorable conditions, but those at the range margins are exposed to unfavorable environments, and the environmental conditions at establishment sites might reflect the genetic diversity of local populations. This is known as the central-marginal hypothesis in which marginal populations show lower genetic variation and higher differentiation than in central populations. In addition, genetic variation in a local population is influenced by phylogenetic constraints and the population history of selection under environmental constraints. In this study, we investigated this hypothesis in relation to Abies sachalinensis, a major conifer species in Hokkaido. Materials and Methods: A total of 1189 trees from 25 natural populations were analyzed using 19 EST-SSR loci. Results: The eastern populations, namely, those in the species distribution center, showed greater genetic diversity than did the western peripheral populations. Another important finding is that the southwestern marginal populations were genetically differentiated from the other populations. Conclusions: These differences might be due to genetic drift in the small and isolated populations at the range margin. Therefore, our results indicated that the central-marginal hypothesis held true for the southernmost A. sachalinensis populations in Hokkaido.

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