scholarly journals Functional trade-offs and environmental variation shaped ancient trajectories in the evolution of dim-light vision

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Gianni M Castiglione ◽  
Belinda SW Chang
Keyword(s):  
Protein Stability ◽  
Visual Pigment ◽  
Environmental Variation ◽  
Epistatic Interactions ◽  
Epistatic Effects ◽  
Trade Offs ◽  
Evolutionary Trajectories ◽  
Dim Light ◽  
Multicellular Organisms ◽  
Dim Light Vision

Trade-offs between protein stability and activity can restrict access to evolutionary trajectories, but widespread epistasis may facilitate indirect routes to adaptation. This may be enhanced by natural environmental variation, but in multicellular organisms this process is poorly understood. We investigated a paradoxical trajectory taken during the evolution of tetrapod dim-light vision, where in the rod visual pigment rhodopsin, E122 was fixed 350 million years ago, a residue associated with increased active-state (MII) stability but greatly diminished rod photosensitivity. Here, we demonstrate that high MII stability could have likely evolved without E122, but instead, selection appears to have entrenched E122 in tetrapods via epistatic interactions with nearby coevolving sites. In fishes by contrast, selection may have exploited these epistatic effects to explore alternative trajectories, but via indirect routes with low MII stability. Our results suggest that within tetrapods, E122 and high MII stability cannot be sacrificed—not even for improvements to rod photosensitivity.

Plasticity and trade-offs in physiological traits of intertidal mussels subjected to freshwater-induced environmental variation

2016 ◽  
Vol 553 ◽  
pp. 93-109 ◽  
Author(s):  
L Ramajo ◽  
L Prado ◽  
AB Rodriguez-Navarro ◽  
MA Lardies ◽  
CM Duarte ◽  
...  
Keyword(s):  
Environmental Variation ◽  
Physiological Traits ◽  
Trade Offs

scholarly journals Effects of intra-gene fitness interactions on the benefit of sexual recombination

2006 ◽  
Vol 34 (4) ◽  
pp. 560-561 ◽  
Author(s):  
R.A. Watson ◽  
D.M. Weinreich ◽  
J. Wakeley
Keyword(s):  
Nucleotide Sequence ◽  
Point Mutation ◽  
Sequence Space ◽  
Fitness Effect ◽  
Epistatic Interactions ◽  
Genetic Sequence ◽  
High Fitness ◽  
Sexual Recombination ◽  
Evolutionary Trajectories ◽  
Asexual Populations

Whereas spontaneous point mutation operates on nucleotides individually, sexual recombination manipulates the set of nucleotides within an allele as an essentially particulate unit. In principle, these two different scales of variation enable selection to follow fitness gradients in two different spaces: in nucleotide sequence space and allele sequence space respectively. Epistasis for fitness at these two scales, between nucleotides and between genes, may be qualitatively different and may significantly influence the advantage of mutation-based and recombination-based evolutionary trajectories respectively. We examine scenarios where the genetic sequence within a gene strongly influences the fitness effect of a mutation in that gene, whereas epistatic interactions between sites in different genes are weak or absent. We find that, in cases where beneficial alleles of a gene differ from one another at several nucleotide sites, sexual populations can exhibit enormous benefit compared with asexual populations: not only discovering fit genotypes faster than asexual populations, but also discovering high-fitness genotypes that are effectively not evolvable in asexual populations.

scholarly journals Breaking through evolutionary constraint by environmental fluctuations

2015 ◽  
Author(s):  
Marjon GJ de Vos ◽  
Alexandre Dawid ◽  
Vanda Sunderlikova ◽  
Sander J Tans
Keyword(s):  
Escherichia Coli ◽  
Environmental Variability ◽  
Model System ◽  
Evolutionary Constraint ◽  
Apparent Paradox ◽  
Epistatic Interactions ◽  
Genetic Constraints ◽  
Trade Offs ◽  
Fluctuating Environments ◽  
Genetic Constraint

Epistatic interactions can frustrate and shape evolutionary change. Indeed, phenotypes may fail to evolve because essential mutations can only be selected positively if fixed simultaneously. How environmental variability affects such constraints is poorly understood. Here we studied genetic constraints in fixed and fluctuating environments, using theEscherichia coli lacoperon as a model system for genotype-environment interactions. The data indicated an apparent paradox: in different fixed environments, mutational trajectories became trapped at sub-optima where no further improvements were possible, while repeated switching between these same environments allowed unconstrained adaptation by continuous improvements. Pervasive cross-environmental trade-offs transformed peaks into valleys upon environmental change, thus enabling escape from entrapment. This study shows that environmental variability can lift genetic constraint, and that trade-offs not only impede but can also facilitate adaptive evolution.

scholarly journals Evolutionary trade-offs between unicellularity and multicellularity in budding yeast

2018 ◽  
Author(s):  
Jennie J. Kuzdzal-Fick ◽  
Lin Chen ◽  
Gábor Balázsi
Keyword(s):  
Mitotic Exit ◽  
Fundamental Question ◽  
Bet Hedging ◽  
Evolutionary Transitions ◽  
Wild Yeast ◽  
Yeast Strains ◽  
Trade Offs ◽  
Mitotic Exit Network ◽  
Multicellular Organisms ◽  
Benefits And Costs

ABSTRACTMulticellular organisms appeared on Earth through several independent major evolutionary transitions. Are such transitions reversible? Addressing this fundamental question entails understanding the benefits and costs of multicellularity versus unicellularity. For example, some wild yeast strains form multicellular clumps, which might be beneficial in stressful conditions, but this has been untested. Here we show that unicellular yeast evolves from clump-forming ancestors by propagating samples from suspension after larger clumps have settled. Unicellular yeast strains differed from their clumping ancestors mainly by mutations in the AMN1 (Antagonist of Mitotic exit Network) gene. Ancestral yeast clumps were more resistant to freeze/thaw, hydrogen peroxide, and ethanol stressors than their unicellular counterparts, while unicellularity was advantageous without stress. These findings inform mathematical models, jointly suggesting a trade-off between the benefits and downsides of multicellularity, causing bet-hedging by regulated phenotype switching as a survival strategy in unexpected stress.

Spectral absorbance, structure, and population density of photoreceptors in the retina of the lake sturgeon (Acipenser fulvescens)

2007 ◽  
Vol 85 (4) ◽  
pp. 584-587 ◽  
Author(s):  
A.J. Sillman ◽  
E.K. Ong ◽  
E.R. Loew
Keyword(s):  
Visual Pigment ◽  
Visual Pigments ◽  
Lake Sturgeon ◽  
Acipenser Fulvescens ◽  
Long Wavelength ◽  
Rods And Cones ◽  
The North ◽  
Spectral Absorbance ◽  
Dim Light ◽  
Scanning Electron

Lake sturgeon ( Acipenser fulvescens Rafinesque, 1817) photoreceptors were studied with scanning electron microscopy and microspectrophotometry. The retina contains both rods and cones, with cones estimated composing about 30% of the photoreceptor population. Only large single cones were identified and they are similar to those found in other species of the order Acipenseriformes. The rods are large, with long, broad outer segments, and are similar to the dominant rod found in other sturgeons and the North American paddlefish ( Polyodon spathula (Walbaum, 1792)). Mean (SD) rod packing density at 22 624 ± 3 509 rods/mm2 is low compared with those of other animals that function primarily in dim light. The visual pigment of the rods has a mean (SD) peak absorbance (λmax) at 541 ± 2 nm. Three different cone populations were identified: a long wavelength sensitive cone containing a visual pigment with λmax at 619 ± 3 nm; middle wavelength sensitive cone with λmax at 538 ± 1 nm; and short wavelength sensitive cone with λmax at 448 ± 1 nm. All the visual pigments are based on the vitamin A2 chromophore.

scholarly journals Antibiotic Resistance Evolution Is Contingent on the Quorum-Sensing Response in Pseudomonas aeruginosa

2019 ◽  
Vol 36 (10) ◽  
pp. 2238-2251 ◽  
Author(s):  
Sara Hernando-Amado ◽  
Fernando Sanz-García ◽  
José Luis Martínez
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Antibiotic Resistance ◽  
Quorum Sensing ◽  
Wild Type ◽  
Resistance Mutations ◽  
Epistatic Interactions ◽  
Adaptive Mutations ◽  
Resistance Evolution ◽  
Evolutionary Trajectories

Abstract Different works have explored independently the evolution toward antibiotic resistance and the role of eco-adaptive mutations in the adaptation to a new habitat (as the infected host) of bacterial pathogens. However, knowledge about the connection between both processes is still limited. We address this issue by comparing the evolutionary trajectories toward antibiotic resistance of a Pseudomonas aeruginosa lasR defective mutant and its parental wild-type strain, when growing in presence of two ribosome-targeting antibiotics. Quorum-sensing lasR defective mutants are selected in P. aeruginosa populations causing chronic infections. Further, we observed they are also selected in vitro as a first adaptation for growing in culture medium. By using experimental evolution and whole-genome sequencing, we found that the evolutionary trajectories of P. aeruginosa in presence of these antibiotics are different in lasR defective and in wild-type backgrounds, both at the phenotypic and the genotypic levels. Recreation of a set of mutants in both genomic backgrounds (either wild type or lasR defective) allowed us to determine the existence of negative epistatic interactions between lasR and antibiotic resistance determinants. These epistatic interactions could lead to mutual contingency in the evolution of antibiotic resistance when P. aeruginosa colonizes a new habitat in presence of antibiotics. If lasR mutants are selected first, this would constraint antibiotic resistance evolution. Conversely, when resistance mutations (at least those studied in the present work) are selected, lasR mutants may not be selected in presence of antibiotics. These results underlie the importance of contingency and epistatic interactions in modulating antibiotic resistance evolution.

scholarly journals Contingent evolution of alternative metabolic network topologies determines whether cross-feeding evolves

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Jeroen Meijer ◽  
Bram van Dijk ◽  
Paulien Hogeweg
Keyword(s):  
Metabolic Networks ◽  
Mechanistic Model ◽  
Building Blocks ◽  
Division Of Labour ◽  
Ecosystem Structure ◽  
Evolutionary Contingency ◽  
Trade Offs ◽  
Evolutionary Trajectories ◽  
Network Topologies ◽  
Metabolic Strategies

AbstractMetabolic exchange is widespread in natural microbial communities and an important driver of ecosystem structure and diversity, yet it remains unclear what determines whether microbes evolve division of labor or maintain metabolic autonomy. Here we use a mechanistic model to study how metabolic strategies evolve in a constant, one resource environment, when metabolic networks are allowed to freely evolve. We find that initially identical ancestral communities of digital organisms follow different evolutionary trajectories, as some communities become dominated by a single, autonomous lineage, while others are formed by stably coexisting lineages that cross-feed on essential building blocks. Our results show how without presupposed cellular trade-offs or external drivers such as temporal niches, diverse metabolic strategies spontaneously emerge from the interplay between ecology, spatial structure, and metabolic constraints that arise during the evolution of metabolic networks. Thus, in the long term, whether microbes remain autonomous or evolve metabolic division of labour is an evolutionary contingency.

Dim light vision of Squilla mantis L

1963 ◽  
Vol 205 (5) ◽  
pp. 927-940 ◽  
Author(s):  
H. Schiff
Keyword(s):  
Light Intensity ◽  
Mediterranean Sea ◽  
Environmental Conditions ◽  
Green Fluorescence ◽  
Fiber Analysis ◽  
Near Ultraviolet ◽  
Intensity Changes ◽  
Dim Light ◽  
Dim Light Vision ◽  
Shape And Size

The anatomy of the eye of Squilla mantis and the geometrical optics derived from it are briefly described. The shape and size of the electroretinogram (ERG) are dependent on a) position where it is picked up, b) the light intensity, and c) the change of intensity. Single-fiber analysis confirms the results obtained by the anatomy and the ERG of the eye. Frequency of response of a single secondary fiber to intensity changes of light is proportional to the derivate dI/dt ( I = intensity; t = time). The Squilla sees a moving object as the sum of the intensity changes caused by that object, varied in time and space. The eyes have a maximum of sensitivity for light of 535–555 mµ wavelength, and a second maximum in the near ultraviolet light, the latter partly seen as green fluorescence due to an eye pigment. Anatomy, physiology, and the environmental conditions have been combined to explain the vision of this animal, adapted to his life in the blue-violet twilight of the deeper Mediterranean sea.

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