Plasticity

2003 ◽  
Author(s):  
Mary Jane West-Eberhard
Keyword(s):  
Genetic Variation ◽  
Phenotypic Plasticity ◽  
Division Of Labor ◽  
Universal Property ◽  
Developmental Pathways ◽  
Living Things ◽  
Universal Properties ◽  
Variation And Selection ◽  
Development And Evolution ◽  
Mechanisms Of Plasticity

A phenotype-centered view of evolution needs to start with a solid idea about the nature of the phenotype. This chapter and the next are devoted to two universal properties of phenotypes, plasticity, or responsiveness to environmental inputs; and modularity, or subdivision into semi-independent and dissociable parts (chapter 4). Of these two properties, plasticity is probably the more fundamental, for the ability to replicate, which distinguishes organic from inorganic nature, requires molecules which are interactive and precisely responsive— adaptively plastic. So plasticity must have been an early universal property of living things. The universality of modularity is a secondary, or “emergent” result of the universality of plasticity (see Wilczek, 2002, on emergent universality in physics). Any organism whose size, whether due to accretion or growth, is large enough to create internal environmental differences, such as those between the inner and the outer regions of a clump of material, has the potential for regional internal differentiation. As differentiation evolves to produce specialized parts and an internal division of labor, internal heterogeneity gives rise to conditional switches between developmental pathways. The result is a stucture characterized by somewhat discrete parts—modularity. Thus, given plasticity as a universal property of living matter, modularity follows. The present chapter describes some of the remarkable mechanisms of phenotypic plasticity. One reason to focus on mechanisms is to indicate the material basis for the evolution of plasticity, which is a product of concrete devices that are subject to genetic variation and selection. A cursory look at these mechanisms, however incomplete, by itself suggests the importance of plasticity in development and evolution, for the mechanisms of plasticity include some of the most ingenious and widely conserved creations of nature. Mechanisms of plasticity are further discussed in chapter 23, which describes how organisms assess environmental conditions when they adaptively switch between alternative developmental pathways. Phenotypic plasticity has already been defined as the ability of an organism to react to an environmental input with a change in form, state, movement, or rate of activity.

Modularity

2003 ◽  
Author(s):  
Mary Jane West-Eberhard
Keyword(s):  
Universal Property ◽  
Biochemical Pathways ◽  
Behavior Development ◽  
Decision Points ◽  
Living Things ◽  
Organ Systems ◽  
Subunit Organization ◽  
Insight Into ◽  
Development And Evolution ◽  
Selection Of

Modularity, like the responsiveness that gives rise to it during development and evolution, is a universal property of living things and a fundamental determinant of how they evolve. Modularity refers to the properties of discreteness and dissociability among parts and integration within parts. There are many other words for the same thing, such as atomization (Wagner, 1995), individualization (Larson and Losos, 1996), autonomy (Nijhout, 1991b), dislocation (Schwanwitsch, 1924), decomposability (Wimsatt, 1981), discontinuity (Alberch, 1982), gene nets (Bonner, 1988), subunit organization (West-Eberhard, 1992a, 1996), compartments or compartmentation (Garcia-Bellido et al., 1979; Zuckerkandl, 1994; Maynard-Smith and Szathmary, 1995; Kirschner and Gerhart, 1998), and compartmentalization (Gerhart and Kirschner, 1997). One purpose of this chapter is to give consistent operational meaning to the concept of modularity in organisms. Seger and Stubblefield (1996, p. 118) note that organisms show “natural planes of cleavage” among organ systems, biochemical pathways, life stages, and behaviors that allow independent selection of different ones. They ask, “What determines where these planes of cleavage are located” and suggest that a “theory of organic articulations” may give insight into the laws of correlation, without specifying what the laws of articulation may be. Wagner (1995, p. 282) recognizes the importance of modularity and proposes a “building block” concept of homology where structural units often correspond to units of function, but concludes (after Rosenberg, 1985) that “there exists no way to distinguish an adequate from an inadequate atomization of the organisms.” Here I propose that modularity has a specific developmental basis (see also West-Eberhard, 1989, 1992a, 1996; see also Larson and Losos, 1996). Modular traits are subunits of the phenotype that are determined by the switches or decision points that organize development, whether of morphology, physiology, or behavior. Development can be seen as a branching series of decision points, including those caused by physical borders such as membranes or contact zones of growing or diffusing parts (e.g., see Meinhardt, 1982; see also chapter 5, on development). Each decision point demarcates the expression or use of a trait—a modular set—and subordinate branches demarcate lower level modular subunits, producing modular sets within modular sets.

scholarly journals Adaptive Alignment of Plasticity With Genetic Variation and Selection

2019 ◽  
Vol 110 (4) ◽  
pp. 514-521 ◽  
Author(s):  
Monica Anderson Berdal ◽  
Ned A Dochtermann
Keyword(s):  
Genetic Variation ◽  
Phenotypic Plasticity ◽  
Matrix Form ◽  
Theoretical Research ◽  
Adaptive Plasticity ◽  
Genetic Variances ◽  
Theoretical Foundations ◽  
Variation And Selection ◽  
Trait Space ◽  
General Prediction

AbstractTheoretical research has outlined how selection may shape both genetic variation and the expression of phenotypic plasticity in multivariate trait space. Specifically, research regarding the evolution of patterns of additive genetic variances and covariances (summarized in matrix form as G) and complementary research into how selection may shape adaptive plasticity lead to the general prediction that G, plasticity, and selection surfaces are all expected to align with each other. However, less well discussed is how this prediction might be assessed and how the modeled theoretical processes are expected to manifest in actual populations. Here, we discuss the theoretical foundations of the overarching prediction of alignment, what alignment mathematically means, how researchers might test for alignment and important caveats to this testing. The most important caveat concerns the fact that, for plasticity, the prediction of alignment only applies to cases where plasticity is adaptive, whereas organisms express considerable plasticity that may be neutral or even maladaptive. We detail the ramifications of these alternative expressions of plasticity vis-à-vis predictions of alignment. Finally, we briefly highlight some important interpretations of deviations from the prediction of alignment and what alignment might mean for populations experiencing environmental and selective changes.

scholarly journals High differentiation in functional traits but similar phenotypic plasticity in populations of a soil specialist along a climatic gradient

2020 ◽  
Vol 125 (6) ◽  
pp. 969-980 ◽  
Author(s):  
Silvia Matesanz ◽  
Marina Ramos-Muñoz ◽  
Mario Blanco-Sánchez ◽  
Adrián Escudero
Keyword(s):  
Genetic Variation ◽  
Phenotypic Plasticity ◽  
Functional Traits ◽  
Common Garden ◽  
Population Level ◽  
General Purpose ◽  
Climatic Conditions ◽  
Environment Interaction ◽  
Moisture Variation ◽  
Neutral Genetic Variation

Abstract Background and Aims Plants experiencing contrasting environmental conditions may accommodate such heterogeneity by expressing phenotypic plasticity, evolving local adaptation or a combination of both. We investigated patterns of genetic differentiation and plasticity in response to drought in populations of the gypsum specialist Lepidium subulatum. Methods We created an outdoor common garden with rain exclusion structures using 60 maternal progenies from four distinct populations that substantially differ in climatic conditions. We characterized fitness, life history and functional plasticity in response to two contrasting treatments that realistically reflect soil moisture variation in gypsum habitats. We also assessed neutral genetic variation and population structure using microsatellite markers. Key Results In response to water stress, plants from all populations flowered earlier, increased allocation to root tissues and advanced leaf senescence, consistent with a drought escape strategy. Remarkably, these probably adaptive responses were common to all populations, as shown by the lack of population × environment interaction for almost all functional traits. This generally common pattern of response was consistent with substantial neutral genetic variation and large differences in population trait means. However, such population-level trait variation was not related to climatic conditions at the sites of origin. Conclusions Our results show that, rather than ecotypes specialized to local climatic conditions, these populations are composed of highly plastic, general-purpose genotypes in relation to climatic heterogeneity. The strikingly similar patterns of plasticity among populations, despite substantial site of origin differences in climate, suggest past selection on a common norm of reaction due to similarly high levels of variation within sites. It is thus likely that plasticity will have a prevalent role in the response of this soil specialist to further environmental change.

New Horizons for Dissecting Epistasis in Crop Quantitative Trait Variation

2020 ◽  
Vol 54 (1) ◽  
pp. 287-307
Author(s):  
Sebastian Soyk ◽  
Matthias Benoit ◽  
Zachary B. Lippman
Keyword(s):  
Genetic Variation ◽  
Quantitative Trait ◽  
Gene Dosage ◽  
Gene Mutations ◽  
Cumulative Effect ◽  
Developmental Pathways ◽  
Trait Variation ◽  
Individual Gene ◽  
New Horizons ◽  
New Strategies

Uncovering the genes, variants, and interactions underlying crop diversity is a frontier in plant genetics. Phenotypic variation often does not reflect the cumulative effect of individual gene mutations. This deviation is due to epistasis, in which interactions between alleles are often unpredictable and quantitative in effect. Recent advances in genomics and genome-editing technologies are elevating the study of epistasis in crops. Using the traits and developmental pathways that were major targets in domestication and breeding, we highlight how epistasis is central in guiding the behavior of the genetic variation that shapes quantitative trait variation. We outline new strategies that illuminate how quantitative epistasis from modified gene dosage defines background dependencies. Advancing our understanding of epistasis in crops can reveal new principles and approaches to engineering targeted improvements in agriculture.

scholarly journals Universal properties for universal types in bifibrational parametricity

2019 ◽  
Vol 29 (06) ◽  
pp. 810-827
Author(s):  
Neil Ghani ◽  
Fredrik Nordvall Forsberg ◽  
Federico Orsanigo
Keyword(s):  
Ad Hoc ◽  
Universal Property ◽  
Axiomatic Treatment ◽  
Model Independent ◽  
Universal Properties ◽  
Extension Lemma ◽  
Uniformity Principle

AbstractIn the 1980s, John Reynolds postulated that a parametrically polymorphic function is an ad-hoc polymorphic function satisfying a uniformity principle. This allowed him to prove that his set-theoretic semantics has a relational lifting which satisfies the Identity Extension Lemma and the Abstraction Theorem. However, his definition (and subsequent variants) has only been given for specific models. In contrast, we give a model-independent axiomatic treatment by characterising Reynolds’ definition via a universal property, and show that the above results follow from this universal property in the axiomatic setting.

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