Natural selection by predators on the defensive apparatus of the three-spined stickleback, Gasterosteus aculeatus L.

Three-spined sticklebacks (Gasterosteus aculeatus L.) can receive considerable protection against predators from characteristic dorsal and pelvic spines. The size and structure of this defensive apparatus were examined in marine and freshwater populations located throughout the European distribution of this species and exposed to differing predatory species and levels of predation pressure. Marine populations appear to experience the greatest predation pressure and have the largest defensive apparatus. Predation in freshwater appears to decline towards both the northern and southern distributional extremes of Gasterosteus, a result attributable to the differential distributions of major piscine predators, especially pike and perch; and this pattern produces arched clines in the morphometrics of defensive structures. Local differences in central latitudes can also be attributed to site-specific differences in predation pressure. Evidence is given for both hereditary and environmental determination of variation in dorsal spine number.

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Phenotypic, genetic, and environmental integration of morphology in a stream population of the threespine stickleback, Gasterosteus aculeatus

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f95-127 ◽

1995 ◽

Vol 52 (6) ◽

pp. 1307-1317 ◽

Cited By ~ 26

Author(s):

Jeffrey V. Baumgartner

Keyword(s):

Natural Selection ◽

Gasterosteus Aculeatus ◽

Genetic Factors ◽

Threespine Stickleback ◽

Morphometric Traits ◽

Genetic Determination ◽

Functional Phenotype ◽

Pleiotropic Mutation

Phenotypic, genetic, and environmental variances and covariances for 33 morphometric traits were estimated for a population of threespine stickleback, Gasterosteus aculeatus, from the Brush Creek drainage, California, by sib analysis of laboratory-bred families. Heritabilities of the morphometric traits ranged from −0.28 to 0.78, and were moderately low (mean h2 = 0.26); the mean and range of heritabilities for five phenotypic eigenvectors were similar. The average coefficient of genetic determination of the traits and eigenvectors was high (0.57 and 0.63, respectively), indicating a substantial genotypic contribution to variation in body morphology. The defensive complex, a functional set of bony armor structures, was genetically and environmentally integrated: genetic factors (e.g., pleiotropy) are reinforced by environmental factors to produce a functional phenotype. Other components of morphology, including body form, were environmentally, but not genetically, integrated. Given the importance of genetic factors to evolutionary change under natural selection, these results implicate natural selection in the evolution of the defensive complex; the role of natural selection in the evolution of other components of morphology is equivocal. Genetic integration of functionally (phenotypically) independent traits suggests that stochastic processes or pleiotropic mutation also have played a role in the evolution of morphology in this population of sticklebacks.

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Postautotomy tail movement differs between colour morphs of the red-backed salamander (Plethodon cinereus)

Amphibia-Reptilia ◽

10.1163/15685381-00003107 ◽

2017 ◽

Vol 38 (3) ◽

pp. 395-399 ◽

Cited By ~ 2

Author(s):

Banan W. Otaibi ◽

Quincey K. Johnson ◽

Bradley J. Cosentino

Keyword(s):

Natural Selection ◽

Genetic Correlation ◽

Behavioural Response ◽

Plethodon Cinereus ◽

Predation Pressure ◽

Tail Autotomy ◽

Tail Movement ◽

Colour Morphs ◽

Defensive Mechanism

Striped and unstriped colour morphs of the eastern red-backed salamander,Plethodon cinereus, vary in their pre-attack behavioural response to predators, but it is unknown whether the morphs vary in post-attack strategies. Both morphs employ tail autotomy, a post-attack defensive mechanism enabling an individual to release a portion of their tail to facilitate escape from predation. Postautotomy tail movement diverts attention of a predator away from the individual’s body, so natural selection should favor vigorous tail movement in both colour morphs ofP. cinereus. We compared the degree of postautotomy tail movement between morphs following simulated predation. Striped individuals exhibited substantially longer and faster tail movement than unstriped individuals. Divergence in postautotomy tail movement may be a direct evolved response to variable predation pressure between colour morphs. Alternatively, tail movement may be constrained in the unstriped morph due to a genetic correlation with colouration (e.g., pleiotropy).

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Steps toward Determination of the Size and Structure of the Broad‐Line Region in Active Galactic Nuclei. X. Variability of Fairall 9 from Optical Data

The Astrophysical Journal Supplement Series ◽

10.1086/313046 ◽

1997 ◽

Vol 112 (2) ◽

pp. 271-283 ◽

Cited By ~ 41

Author(s):

M. Santos‐Lleo ◽

E. Chatzichristou ◽

C. Mendes de Oliveira ◽

C. Winge ◽

D. Alloin ◽

...

Keyword(s):

Active Galactic Nuclei ◽

Galactic Nuclei ◽

Optical Data ◽

Broad Line ◽

Broad Line Region ◽

Line Region ◽

Size And Structure

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Two different epigenetic pathways detected in wild three-spined sticklebacks are involved in salinity adaptation

10.1101/649574 ◽

2019 ◽

Cited By ~ 2

Author(s):

Melanie J. Heckwolf ◽

Britta S. Meyer ◽

Robert Häsler ◽

Marc P. Höppner ◽

Christophe Eizaguirre ◽

...

Keyword(s):

Natural Selection ◽

Gasterosteus Aculeatus ◽

Natural Populations ◽

Wild Populations ◽

Epigenetic Marks ◽

Transgenerational Plasticity ◽

The Face ◽

Adaptation Processes ◽

Methylation Patterns ◽

Rapid Emergence

AbstractWhile environmentally inducible epigenetic marks are discussed as one mechanism of transgenerational plasticity, environmentally stable epigenetic marks emerge randomly. When resulting in variable phenotypes, stable marks can be targets of natural selection analogous to DNA sequence-based adaptation processes. We studied both postulated pathways in natural populations of three-spined sticklebacks (Gasterosteus aculeatus) and sequenced their methylomes and genomes across a salinity cline. Consistent with local adaptation, populations showed differential methylation (pop-DMS) at genes enriched for osmoregulatory processes. In a two-generation experiment, 62% of these pop-DMS were insensitive to salinity manipulation, suggesting that they could be stable targets for natural selection. Two-thirds of the remaining inducible pop-DMS became more similar to patterns detected in wild populations from the corresponding salinity, and this pattern accentuated over consecutive generations, indicating a mechanism of adaptive transgenerational plasticity. Natural DNA methylation patterns can thus be attributed to two epigenetic pathways underlying the rapid emergence of adaptive phenotypes in the face of environmental change.

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Using seasonal genomic changes to understand historical adaptation: parallel selection on stickleback in highly-variable estuaries

10.1101/2020.11.24.396291 ◽

2020 ◽

Author(s):

Alan Garcia-Elfring ◽

Antoine Paccard ◽

Timothy J. Thurman ◽

Ben A. Wasserman ◽

Eric P. Palkovacs ◽

...

Keyword(s):

Natural Selection ◽

Allele Frequency ◽

Calcium Binding ◽

Gasterosteus Aculeatus ◽

Environmental Changes ◽

Threespine Stickleback ◽

Functional Enrichment ◽

Genomic Changes ◽

Parallel Selection ◽

Frequency Changes

AbstractParallel evolution is considered strong evidence for natural selection. However, few studies have investigated the process of parallel selection as it plays out in real time. The common approach is to study historical signatures of selection in populations already well adapted to different environments. Here, to document selection in action under natural conditions, we study six populations of threespine stickleback (Gasterosteus aculeatus) inhabiting bar-built estuaries that undergo seasonal cycles of environmental changes. Estuaries are periodically isolated from the ocean due to sandbar formation during dry summer months, with concurrent environmental shifts that resemble the long-term changes associated with postglacial colonization of freshwater habitats by marine populations. We used pooled whole-genome sequencing (Pool-WGS) to track seasonal allele frequency changes in these populations and search for signatures of natural selection. We found consistent changes in allele frequency across estuaries, suggesting a potential role for parallel selection. Functional enrichment among candidate genes included transmembrane ion transport and calcium binding, which are important for osmoregulation and ion balance. The genomic changes that occur in threespine stickleback from bar-built estuaries could provide a glimpse into the early stages of adaptation that have occurred in many historical marine to freshwater transitions.

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