Phenotypic Evolution: A Reaction Norm Perspective
... But also, variation in trait development is expected according to the estimated bene ts under speci c strategies to cope with environmental variations [8,9]. For plastic bimodal traits, the shifting from one stage to another is accomplished by the existence of reaction norms and thresholds [10,11]. Thresholds of change may affect a suite of physiological and behavioral processes, that can be in uenced by environmental cues causing the modulation of genomic activity. ...
... Focusing on the most abundant isoform, TH 10 (Table 3). See also summarized results in Figure 4 (below). ...
... See summarized results in Figure 4 (below). The two pairs of TH primers speci cally ampli ed their target sequence (Figure 3) generating unique amplicons of 166 bp (TH [10][11] ) and 173 bp (TH 2-3 ) ...
Mate competition encourages individuals to modulate characters involved in mating success. Adult Iberian red deer ( Cervus elaphus hispanicus ) males show a dark ventral patch (DVP) that plays a central role in mating rivalry, whose size and chemical compounds varied according to the level of male-male competition within the population. In the pigmentation of the DVP appears, after urinary excretion, a molecule called DOPEG originating from the metabolism of norepinephrine, leading us to investigate whether differential expression mechanisms of key genes (DBH and TH) encoding enzymes catalyzing the process can be sensitive to different competitive population situations and responsible for the plastic development of the DVP in red deer. We found that social environment with higher intrasexual competition, where male invest more in sexual traits, was associated with increased levels of DBH and TH transcripts, while Dopamine showed reversed values. We found alternative splicing for the TH gene, although differences between social environments appeared just related to expression levels. Our results support the internal cause of trait modulation based on differential gene expression in relation to the conditions of intrasexual competition in social environment. We propose the quantification of DBH transcripts as a molecular biomarker of male red deer reproductive activity.
... Plasticity of a phenotypic trait is often depicted as a reaction norm across varying environmental conditions (Schlichting, 1986;Schlichting & Pigliucci, 1998;Sultan, 1987). While plasticity can be studied as reaction norms across multiple environments, here we focus on plastic responses across two environments (Figure 1). ...
... Plasticity can evolve when there is significant G × E interaction (Schlichting & Pigliucci, 1998). Yet, environment-specific expression F I G U R E 6 Heritably plastic transcripts in Indica can be clustered in modules of co-expressed transcripts using k-means clustering (a). ...
... While plasticity may be beneficial and under selection for many traits in many contexts, as we found with many GPTs, there are also cases in which plasticity is costly, harmful and selected against, with selection for canalization (reduction in plasticity) instead (Schlichting & Pigliucci, 1998). We found that the majority of DPTs in our analysis showed selection against expression plasticity. ...
Gene expression can be highly plastic in response to environmental variation. However, we know little about how expression plasticity is shaped by natural selection and evolves in wild and domesticated species. We used genotypic selection analysis to characterize selection on drought‐induced plasticity of over 7,500 leaf transcripts of 118 rice accessions (genotypes) from different environmental conditions grown in a field experiment. Gene expression plasticity was neutral for most gradually plastic transcripts, but transcripts with discrete patterns of expression showed stronger selection on expression plasticity. Whether plasticity was adaptive and co‐gradient or maladaptive and counter‐gradient varied among varietal groups. No transcripts that experienced selection for plasticity across environments showed selection against plasticity within environments, indicating a lack of evidence for costs of adaptive plasticity that may constrain its evolution. Selection on expression plasticity was influenced by degree of plasticity, transcript length and gene body methylation. We observed positive selection on plasticity of co‐expression modules containing transcripts involved in photosynthesis, translation and responsiveness to abiotic stress. Taken together, these results indicate that patterns of selection on expression plasticity were context‐dependent and likely associated with environmental conditions of varietal groups, but that the evolution of adaptive plasticity would likely not be constrained by opposing patterns of selection on plasticity within compared to across environments. These results offer a genome‐wide view of patterns of selection and ecological constraints on gene expression plasticity and provide insights into the interplay between plastic and evolutionary responses to drought at the molecular level.
... Phenotypic plasticity, the ability of a single genotype to manifest different phenotypes in response to environmental cues, is widespread across taxa (Schlichting & Pigliucci, 1998). During adaptation, plasticity can influence the strength of selective pressures and shift population responses to such pressures (Muschick et al., 2011;Rohner & Moczek, 2020;Yeh et al., 2004). ...
... Plasticity in novel environments may be especially critical for mediating rapid adaptation because plasticity can change the expression of traits and, consequently individual fitness in the new habitat. Therefore, the evolution of plasticity of key adaptive traits is hypothesized to facilitate population survival and persistence in novel environments (Axelrod et al., 2023;Levis & Pfennig, 2016;Robinson & Dukas, 1999;West-Eberhard, 2003), as well as increase population performance in highly variable environments (Schlichting & Pigliucci, 1998;West-Eberhard, 2003). As such, it is critical to study not only the evolution of trait values under ecological variation but also the impact of trait flexibility on local adaptation. ...
... We propose that along with larger brains, more plastic brains may similarly facilitate performance when adapting to different environmental conditions. The evolution of phenotypic plasticity is hypothesized as a major contributor to phenotypic diversity (Schlichting & Pigliucci, 1998;Via & Lande, 1985), and empirical studies in bird breeding season length (Yeh et al., 2004) and fruit fly heat temperature tolerance (Mallard et al., 2020) demonstrate that such evolution is possible. Though rarely studied, brain morphology plasticity can evolve (Axelrod et al., 2022;Crispo & Chapman, 2010;Gonda et al., 2012). ...
Phenotypic plasticity is critical for organismal performance and can evolve in response to natural selection. Brain morphology is often developmentally plastic, affecting animal performance in a variety of contexts. However, the degree to which plasticity of brain morphology evolves has rarely been explored. Here we use Trinidadian guppies (Poecilia reticulata), which are known for their repeated adaptation to high-predation (HP) and low-predation (LP) environments, to examine the evolution and plasticity of brain morphology. We exposed second-generation offspring of individuals from HP and LP sites to two different treatments: predation cues and conspecific social environment. Results show that LP guppies had greater plasticity in brain morphology compared to their ancestral HP population, suggesting that plasticity can evolve in response to environmentally divergent habitats. We also show sexual dimorphism in the plasticity of brain morphology, highlighting the importance of considering sex-specific variation in adaptive diversification. Overall, these results may suggest the evolution of brain morphology plasticity as an important mechanism that allows for ecological diversification and adaptation to divergent habitats.
... Phenotypic plasticity, a genotype's ability to produce a different phenotype in response to some nongenetic perturbation that may result from environmental disturbances or from developmental noise, is an important property of developmental mechanisms. Plasticity's prevalence in all taxa and in all kinds of traits is not surprising since all organisms build phenotypes through interactions among multiple components, including genes, external factors, and random events within the organism (Gilbert and Epel 2009;Laland et al. 2015;Lewontin 2000;Schlichting and Pigliucci 1998). Indeed, as Moczek (2015) writes: "To develop is to be plastic." ...
... For example, adaptive plasticity may delay a population's extinction, "buying time" for the appearance of new beneficial mutations (Diamond and Martin 2021;Levis and Pfennig 2021). Plasticity may also play a role that could be important for setting the course of evolution (e.g., Gilbert and Epel 2009;Schlichting and Pigliucci 1998;Waddington 1942;West-Eberhard 2003). In this perspective, evolution of new genetically determined traits occurs through plastic intermediates (Waddington 1942;West-Eberhard 2003). ...
Phenotypic plasticity is an organism's ability to produce a different phenotype in response to nongenetic perturbations such as environmental disturbances. Beneficial phenotypic plasticity can be important in evolution. After an environmental disturbance, it can delay extinction giving opportunity to the appearance of beneficial mutations. In addition, plasticity may also be one of the factors that define the course that evolution takes, for example, through genetic assimilation. This is a process in which a phenotype that initially appears as a plastic response becomes under genetic control. In the end, development of such a phenotype does not require the factor that originally induced it. Here, I use a model of the evolution of gene regulatory networks to study the range of conditions that allow the association between plasticity and the course of evolution. I assayed conditions like the difference between ancestral and optimum phenotypes, the difficulty to build the optimum phenotype, the complexity of the developmental system, mutation rate, strength of plasticity limitations, fitness advantage of the optima, and the similarity between the initially induced phenotype and the optimum. I found that populations that yield a beneficial phenotype through plasticity most often evolve a similar genetically determined phenotype under all the conditions that I assayed. I also identified conditions that facilitate evolution through genetic assimilation. Notwithstanding, even under less favorable circumstances, this form of evolution still confers easier access to a new genetically determined optimum.
... Additionally, variation in trait expression is expected to reflect the benefits associated with specific strategies for adapting to environmental fluctuations [8,9]. Plastic bimodal traits exhibit distinct phenotypes depending on the environmental context, a phenomenon often described using reaction norms and thresholds [10,11]. These thresholds can influence a range of physiological and behavioral processes, which are modulated by environmental cues that Background Sexual selection drives the evolution of traits associated with intrasexual competition or mate choice [1]. ...
... Small arrows aside the main route depict compound's changes for HC compared to LC individuals. For statistical significance of the differences between HC and LC animals, p values are indicated as resulting from the linear models for TH [10][11] and DBH, otherwise significance is after unpaired Student t-tests exhibited a mean of 482 ± 89 transcripts/pg tRNA (Supplementary Table S4). ...
Mate competition encourages individuals to modulate characters involved in mating success. Adult Iberian red deer (Cervus elaphus hispanicus) males show a dark ventral patch (DVP) that plays a central role in mating rivalry, whose size and chemical compounds varied according to the level of male-male competition within the population. In the pigmentation of the DVP appears, after urinary excretion, a molecule called DOPEG originating from the metabolism of norepinephrine, leading us to investigate whether differential expression mechanisms of key genes dopamine B-hydroxylase (DBH) and tyrosine hydroxylase (TH), encoding enzymes catalyzing the process can be sensitive to different competitive population situations and responsible for the plastic development of the DVP in red deer. We found that social environment with higher intrasexual competition, where male invest more in sexual traits, was associated with increased levels of DBH and TH transcripts, while Dopamine showed reversed values. We found alternative splicing for the TH gene, although differences between social environments appeared just related to expression levels. Our results support the internal cause of trait modulation based on differential gene expression in relation to the conditions of intrasexual competition in social environment. We propose the quantification of DBH transcripts as a molecular biomarker of male red deer reproductive activity.
... The phenotype of a given genotype can vary in response to its environment of development or expression, through a phenomenon broadly described as phenotypic plasticity (Bradshaw 1965;Schlichting and Pigliucci 1998). Phenotypic plasticity is currently attracting considerable interest in the context of rapidly changing natural environments (Chevin et al. 2010;Gienapp et al. 2008;Merilä and Hendry 2014). ...
... The relationship between the phenotype and the environment is captured by the reaction norm (or norm of reaction), which is defined at the level of genotypes (Schlichting and Pigliucci 1998;Woltereck 1909). Reaction norms encompass phenotypic responses to both continuous environments (such as temperature, salinity, etc.) and categorical/discrete ones (such as host plant for a phytophagous insect). ...
... Females from both populations showed a greater degree of active thermoregulation compared to males. In INTRODUCTION Species with wide distributions and/or populations of the same species that inhabit contrasting environments express phenotypic differences according to their genotype and the environmental pressures (biotic and abiotic) they experience, which is known as plastic reaction norms (Stearns 1992;Schlichting & Pigliucci 1998). Additionally, spatial and temporal changes in environments promote adaptive divergence in the morphology, coloration, physiology, and behavior of organisms (Schlichting & Pigliucci 1998;Sultan & Stearns 2005;Corl et al. 2018). ...
... In INTRODUCTION Species with wide distributions and/or populations of the same species that inhabit contrasting environments express phenotypic differences according to their genotype and the environmental pressures (biotic and abiotic) they experience, which is known as plastic reaction norms (Stearns 1992;Schlichting & Pigliucci 1998). Additionally, spatial and temporal changes in environments promote adaptive divergence in the morphology, coloration, physiology, and behavior of organisms (Schlichting & Pigliucci 1998;Sultan & Stearns 2005;Corl et al. 2018). In this context, greater intraspecific divergence may arise the more separated the populations are from each other and/or the more contrasting the environments are (Roitberg et al. 2013;García-Rosales et al. 2017). ...
Populations of the same species that inhabit contrasting environments
may be subject to different selection pressures, promoted by the local environment.
Therefore, the individuals of the different populations respond to these
pressures with adaptations to local environments; however, not all species or
populations respond in the same way. We compared some morphological and
ecological traits of the lizard Sceloporus mucronatus that inhabits contrasting
environments in central Mexico. The results show male-biased sexual size
dimorphism in Tecocomulco, but no differences in size between sexes in
Parque Nacional El Chico (PNCH). Significant differences were observed in
morphometric traits and in body mass between sexes and populations, but not
in the interaction between these two factors. In general, females were heavier
than males, while males had larger head structures, jaws, and hind limbs than
females. In addition, differences were recorded in the volume of the abdomen,
which was female-biased in the PNCH, and male-biased in Tecocomulco.
Between populations, it was recorded that the organisms from the PNCH were
heavier and had larger heads than those from Tecocomulco. Thermal traits
showed differences among populations, but not between sexes nor in the interaction among these factors. Individuals from the locality with lower temperature
and higher precipitation (PNCH) reached higher body temperatures and
used warmer microhabitats than those individuals from the locality with higher
temperature and lower precipitation (Tecocomulco). Females from both populations
showed a greater degree of active thermoregulation compared to males. In addition, in both sexes and populations, average values of behavioral thermo
regulation were different from zero. Significant differences were recorded in microhabitat use between populations. In agreement with previous studies of morphology and thermal ecology carried out in this species from this and other localities, and in different years, we suggest that its populations present a wide phenotypic plasticity.
... Since behavioral responses are controlled by neurological processes in the brain, the development of brains and behaviors occurs in coordination (Shumway 2010;Triki et al. 2022aTriki et al. , 2023. Adaptive behavioral and neural plasticity allows animals to cope with spatial and temporal environmental variation by adjusting their phenotypes to the given conditions (Schlichting and Pigliucci 1998;West-Eberhard 2003). If there is no constraint, animals should exhibit unlimited plasticity, expressing the best trait value in every environment. ...
... Environmental enrichment can alter brain structure and function, and such changes are associated with improved cognitive abilities, including learning and memory (Kotrschal and Taborsky 2010;Ebbesson and Braithwaite 2012). Such neurological and behavioral responses to environmental changes can depend on the current condition of the individual (Houston and McNamara 1992;Schlichting and Pigliucci 1998) or even the condition of the mother at reproduction (Mousseau and Fox 1998;Taborsky 2006). Offspring of old mothers may have a limited ability to produce adaptive behavioral plasticity due to the negative effects of maternal effect senescence (Monaghan 2008;. ...
It is well known that maternal age at reproduction affects offspring lifespan and some other fitness-related traits, but it remains understudied whether maternal senescence affects how offspring respond to their environments. Early environment often plays a significant role in the development of an animal’s behavioral phenotype. For example, complex environments can promote changes in cognitive ability and brain morphology in young animals. Here, we study whether and how maternal effect senescence influences offspring plasticity in cognition, group behavior, and brain morphology in response to environmental complexity. For this, juvenile 3-spined sticklebacks from young and old mothers (i.e. 1-yr and 2-yr-old) were exposed to different levels of environmental enrichment and complexity (i.e. none, simple, and complex), and their behavior, cognitive ability, and brain size were measured. Exposing fish to enriched conditions improved individual learning ability assessed by a repeated detour-reaching task, increased the size of the whole brain, and decreased aggressive interactions in the shoal. Maternal age did not influence the inhibitory control, learning ability, and group behavioral responses of offspring to the experimental environmental change. However, maternal age affected how some brain regions of offspring changed in response to environmental complexity. In offspring from old mothers, those exposed to the complex environment had larger telencephalons and cerebellums than those who experienced simpler environments. Our results suggest that maternal effect senescence may influence how offspring invest in brain functions related to cognition in response to environmental complexity.
... Most organisms possess a certain degree of developmental plasticity that allows them to persist over varying conditions by adjusting their morphology, physiology, and behavior (Kingsolver and Huey, 1998;West-Eberhard, 2003). When environmental cues are reliable and phenotypic responses are not limited by costs or constraints, adaptive plasticity is expected to evolve so that the expressed phenotypes will predictably depend on environmental conditions (Schlichting and Pigliucci, 1998;Snell-Rood and Ehlman, 2021). In contrast, less predictable environments or less reliable environmental cues are likely to result in bet-hedging strategies (Schlichting and Pigliucci, 1998). ...
... When environmental cues are reliable and phenotypic responses are not limited by costs or constraints, adaptive plasticity is expected to evolve so that the expressed phenotypes will predictably depend on environmental conditions (Schlichting and Pigliucci, 1998;Snell-Rood and Ehlman, 2021). In contrast, less predictable environments or less reliable environmental cues are likely to result in bet-hedging strategies (Schlichting and Pigliucci, 1998). In that case, phenotypic variation will be found within a single environment and associated rather to variation in genotypes, independently of environmental input (Seger and Brockmann, 1987;DeWitt and Langerhans, 2004). ...
Developmental plasticity evolves in heterogeneous environmental conditions as long as individuals can accurately perceive them. A paradigmatic example of developmental plasticity is the ability of amphibian larvae to alter growth and development in response to the risk of pond drying. Such responses are often found in amphibian species breeding in highly dynamic water bodies with high desiccation risk. The inselbergs of the Guianan Shield are rocky outcrops with extremely high and fluctuating temperatures and a marked seasonality in precipitation. During the rainy season, eroded depressions form precipitation-dependent pools with a high and variable risk of desiccation within the timeframe of a few days. The frog Leptodactylus lithonaetes specializes in breeding in this extreme environment, and its tadpoles are thus forced to cope with desiccation risk by adjusting their developmental trajectories and physiological performance. We experimentally assessed the effect of different levels of desiccation risk, under controlled temperature conditions, on developmental rate, growth, and temperature-dependent locomotor performance in tadpoles of Leptodactylus lithonaetes. We did not find an effect of desiccation risk on developmental rate, but under simulated drying conditions, tadpoles showed larger body size, greater body mass, and enhanced locomotor performance compared to constant (high or low) water levels. These results suggest that drying pools offer cues that trigger developmental and behavioral changes in these tadpoles, enabling them to enhance growth over a short time span without accelerating development. We discuss the potential compensatory mechanisms behind these responses and highlight the need for further investigations in species with semiterrestrial life histories in extreme environments.
... Small arrows aside the main route depict compound's changes for HC compared to LC individuals. For statistical signi cance, p values are indicated as resulting from the linear models for TH [10][11] and DBH, otherwise signi cance is after unpaired Student t-tests. ...
... of the amplicons obtained with each TH primer pair in cDNA and gDNA; in both cases one band of the expected size, without or with the corresponding intron, was obtained. (c) Ampli cation and melting curves obtained with each TH primer pair; only one sequence was generated in each case, with Tm values of 88 °C and 91 °C, respectively, for TH[10][11] (166 bp) and TH 2-3 (173 bp). ...
Mates competition encourages individuals to modulate characters involved in mating success. Adult Iberian red deer ( Cervus elaphus hispanicus ) males show a dark ventral patch (DVP) that plays a central role in mating rivalry, whose size and chemical compounds varied according to the level of male-male competition within the population. In the pigmentation of the DVP appears, after urinary excretion, a molecule called DOPEG originating from the metabolism of norepinephrine, leading us to investigate whether differential expression mechanisms of key genes (DBH and TH) encoding enzymes catalyzing the process can be sensitive to different competitive population situations and responsible for the plastic development of the DVP in red deer. We found that social environment with higher intrasexual competition, where male invest more in sexual traits, was associated with increased levels of DBH and TH transcripts, while Dopamine showed reversed values. We found alternative splicing for the TH gene, although differences between social environments appeared just related to expression levels. Our results support the internal cause of trait modulation based on differential gene expression in relation to the conditions of intrasexual competition in social environment. We propose the quantification of DBH transcripts as a molecular biomarker of male red deer reproductive activity.
... correlation of plasticities), which may be of ecological significance when they include plasticity to key environmental factors. The correlation of plasticities has been deemed important for the production of coordinated phenotypes in response to changing environments (Schlichting 1986, 1989, Schlichting and Pigliucci 1998, Pigliucci 2001. Although the correlation of plasticities has received attention from studies on evolutionary ecology or behavioural ecology (Schlichting and Pigliucci 1998, Stamps 2016, Parsons et al. 2020), its implications for understanding niche differences among co-occurring plant species remain unexplored. ...
... The correlation of plasticities has been deemed important for the production of coordinated phenotypes in response to changing environments (Schlichting 1986, 1989, Schlichting and Pigliucci 1998, Pigliucci 2001. Although the correlation of plasticities has received attention from studies on evolutionary ecology or behavioural ecology (Schlichting and Pigliucci 1998, Stamps 2016, Parsons et al. 2020), its implications for understanding niche differences among co-occurring plant species remain unexplored. We describe below a conceptual framework that links correlations of plasticities to relevant environmental gradients and niche overlap patterns. ...
Phenotypic plasticity can increase the extent of the environmental gradient occupied by a species (niche breadth) and modify the portion of niche space shared among co‐occurring species (niche overlap). Thus, phenotypic plasticity may play a role in community assembly processes. Given that plants deal with a multivariate environment, and that functional traits are often correlated, plastic responses to different environmental factors are likely correlated. However, the implications of correlations of plasticities for niche overlap remain unexplored. Here, we present and evaluate a conceptual framework that links correlations of plasticities and niche overlap patterns among co‐occurring plant species. We specifically tested in an arid shrubland whether positive, negative, or null correlations between plasticity to light and water availability would be associated with patterns of high, low, or random niche overlap, respectively. Field data identified light and water availability as key factors shaping herbaceous plant community structure. We estimated species' niche breadth and niche overlap using two‐dimensional kernel–density estimations (NO K ) and standardised effect sizes of Pianka's niche overlap index ( O SES ). We measured phenotypic plasticity to light and water availability in the six most abundant species in a greenhouse experiment. We used the plasticity index (PI) to test 1) the relationship between plasticity to light and water availability, and 2) the association between overall plasticity (average PI across traits) and niche breadth. We found a positive relationship between plasticity to light and water availability. Increased overall plasticity was associated with a broader niche breadth. Both NO K and O SES estimations indicated a significant niche overlap pattern. Results supported one of the predictions of our conceptual framework: that a positive correlation of plasticities would lead to increased niche overlap. The verified conceptual framework broadens our understanding of the role of phenotypic plasticity in plant community coexistence.
... As a result, it is suggested that phenotypic integration (i.e. the pattern of coordination and covariation among traits reflected by the amount of significant correlations between traits, Schlichting & Pigliucci, 1998;Gianoli & Palacio-López, 2009;Armbruster et al., 2014) could play a role in constraining trait variation Matesanz et al., 2021). This assumption is also based on the impossibility of the evolution of organisms that can reach an optimal value for every trait simultaneously (Rees, 1993;Laughlin & Messier, 2015). ...
Phenotypic differences addressed from functional traits are widely used to study forest functioning. However, while ecological studies have traditionally focused on species-level trait differences, recent research emphasizes the need of considering intraspecific and intraindividual trait variation. Using leaf-level data collected in two large-scale forest biodiversity experiments in subtropical China and in Germany, I studied leaf trait variation along diversity gradients. The results show that trees change their leaf strategy and the leaf variability within the crown in response to diversity. Further, intraspecific trait variation is higher in monocultures to alleviate intraspecific competitive interactions and decreases with increasing tree species richness. Last, the results show how the organization of intraspecific and intraindividual trait variation lead to higher functional diversity of forest stands, which highlights their importance for understanding forest functioning.
... The results presented here show that, even with relatively small sample sizes, single species can display network variation. Variability in natural populations is a crucial property for evolution by natural selection to be possible (Huxley, 1942;Schlichting & Pigliucci, 1998;West-Eberhard, 2003). The omission of within-species variation in the conceptual framework of AnNA thus seems out of place. ...
Modularity and integration are key developmental properties and have remained central in evo‐devo research because of how they relate to evolvability. While modularity and integration have commonly been assessed with landmark‐based geometric morphometrics (GMM), other methods such as anatomical network analysis (AnNA) are increasingly being explored. Nonetheless, AnNA has seldom been used to assess variability within taxa, and there have been no attempts to verify whether its results are commensurate with GMM. We used the pectoral girdle of members of the Chrosomus eos‐neogaeus hybridization complex as a case study system to assess differences between AnNA and GMM‐based approaches and discuss how they should be best used. The general anatomy and composition of the pectoral girdle do not vary much within the complex; however, bones within the pectoral girdle show significant diversity in morphology and in the presence of sutures. Indeed, C. neogaeus displays characteristically enlarged coracoids and radials, and bone fusion between the cleithra, coracoids, and radials, while C. eos displays a gracile and unfused pectoral girdle. Hybrids display morphologies that are distinct from both parental species. AnNA detected multiple potential patterns of modularity, and GMM supported similar patterns of modularity across the complex but suggested different trajectories of morphological variation. Altogether, AnNA can be a valuable tool to formulate novel hypotheses in understudied taxa, which may then be tested using GMM, but careful morphological descriptions of skeletal systems are a valuable addition to the interpretation of both AnNA and GMM approaches.
... The same photoperiodic conditions sometimes have oppositely directed effects at high and low temperatures, namely acceleration of development at certain temperature conditions and its retardation at others (Geispits et al., 1971;Goryshin and Akhmedov, 1971;Lopatina et al., 2007). In light of better understanding of the significance of reaction norms in adaptive evolution (Groeters, 1992;Stearns, 1992;Nylin, 1994;Nylin and Gotthard, 1998;Schlichting and Pigliucci, 1998;Roff, 2002;Kingsolver et al., 2004;Murren et al., 2014;Kivelä et al., 2015), these interactions of photoperiod and temperature are now interpreted as photoperiodic plasticity of the thermal reaction norms for growth and development (Gotthard et al., 1999;Lopatina et al., 2007;Kutcherov et al., 2011Kutcherov et al., , 2015Lopatina, 2022a, 2022b). ...
... The evolution of behavioural plasticity is still elusive (Snell-Rood, 2013). In heterogeneous environments, behavioural plasticity that allows individuals to adjust behaviour across varying conditions may be advantageous (Pigliucci, 2001;Schlichting & Pigliucci, 1998). In contrast, in stable environmental conditions, this advantage may diminish and less behavioural plasticity may be expected. ...
A longstanding question in evolutionary biology is how within‐population phenotypic variation is maintained under natural selection. The fluctuating selection hypothesis suggests that genetic and phenotypic variation scales with fluctuations in selection over space and time. This implies that phenotypic variation might be greater in populations with fluctuating than stable environmental conditions. However, this aspect has rarely been investigated, likely because habitats with minimal fluctuations are rare.
We addressed this hypothesis by comparing surface and cave populations of the freshwater isopod Asellus aquaticus species complex. Surface environments are spatiotemporally more variable than cave environments, grounding the prediction that the surface ecotype is phenotypically more variable than the cave ecotype. We conducted a longitudinal behavioural study on individuals from four surface and four cave populations, measuring their movement activity and risk‐taking in two light conditions. To account for differences in the natural light regimes between surface and cave populations, half of the individuals were first acclimated under a diurnal light regime and the other half in complete darkness. Initially (acclimation tests), their behaviour was recorded in bright and dark light conditions, respectively. Next, each individual was evaluated six times in alternating light conditions—three times in each light condition.
In addition to assessing average differences, we estimated among‐ and within‐individual variation, as well as repeatability and light‐induced plasticity in behaviours, enabling a comparison of these parameters between the two ecotypes.
In the dark, surface individuals were on average more active and less risk‐taking than cave individuals. As predicted, the surface compared with the cave ecotype displayed greater among‐ and within‐individual variance in movement activity, but not in risk‐taking. Repeatability was not significantly different between ecotypes. Both ecotypes showed significant among‐individual variation for light‐induced plasticity in both behaviours, however, plasticity did not differ between ecotypes. Our results also suggest that more active or risk‐taking individuals exhibited greater plasticity.
Our findings support the hypothesis that fluctuating selection plays a role in maintaining variation for movement activity but not for risk‐taking.
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... A key component of plasticity theory is that plastic traits are often accompanied by trade-o s that are also molded by selection (33,43,44). e tissue mass trade-o emerges in L. obtusata because thick shells have less internal habitable volume available for tissue growth than thin shells of similar length (8,30). ...
The impact of invasive predators during the early stages of invasion is often variable in space and time. Such variation is expected to initially favor plasticity in prey defenses, but fixed defenses as invaders become established. Coincident with the range expansion of an invasive predatory crab in the Gulf of Maine, we document rapid changes in shell thickness—a key defense against shell crushing predators—of an intertidal snail. Field experiments, conducted 20 years apart, revealed that temporal shifts in shell thickness were driven by the evolution of increased trait means and erosion of thickness plasticity. The virtual elimination of the trade-off in tissue mass that often accompanies thicker shells is consistent with the evolution of fixed defenses under increasingly certain predation risk.
... Organisms have evolved different strategies to track such change in the optimal phenotype with the evolved strategy being expected to depend on the timescale of environmental change (relative to the generation time) and on the degree of predictability in the environment (Botero et al. 2015). When environmental change is relatively rapid but also predictable, phenotypic plasticity is expected to be the primary mode of response because it can facilitate an adaptive match between the organism phenotype and the phenotype that is optimal in the current environment (Padilla and Adolph 1996;Gabriel 2005;Gabriel et al. 2005;Siljestam and change in the environment (or reaction norm slope, Schlichting and Pigliucci 1998). The deviation between capacity and the change in the optimal phenotype across environments determines the extent of matching between the expressed phenotype and environment once the plastic response has been established. ...
Phenotypic plasticity enables organisms to express a phenotype that is optimal in their current environment. The ability of organisms to obtain the optimum phenotype is determined by their (i) capacity for plasticity, which facilitates phenotypic adjustment corresponding to the amplitude of environmental change but also their (ii) rate of plasticity, because this determines if the expressed phenotype lags behind changes in the optimum. How the rate of‐ and capacity for plasticity have co‐evolved will thus be critical for the resilience of organisms under different patterns of environmental change. To evaluate the direction of the evolved relationship between plasticity rate and capacity, we reanalysed experiments documenting the time course of thermal tolerance acclimation to temperature change across species of ectothermic animals. We found that the rate and capacity with which thermal tolerance responds plastically to temperature change are negatively correlated, a pattern inconsistent with current theory regarding the evolution of phenotypic plasticity.
... Growth is further constrained by the two-dimensional character of the test in which the oral and aboral plates are linked by buttressing. Variation can be described in terms of developmental reaction norms (Schlichting & Pigliucci, 1998). ...
Using a holistic morphometric method based on Geographic Information System technology, recurring themes (developmental reaction norms) in phenotypic expression of skeletal architectures are demonstrated for a group of scutelliform sand dollar echinoids. In particular, similarities in the expression of timing of imago to post-imago stage transitions, juvenile through adult plate growth, aboral-oral plate dependencies, translocation of ambulacral and interambulacral plates, and asymmetric radial expansion can be shown for the extinct Protoscutellidae and extant Echinarachniidae. Distinct morphotypes in a single population of Echinarachnius parma, defined using information from all the plates in the skeleton and complete ontogenetic trajectories, are compared with similarly examined morphospecies of protoscutellids. This information is critical to unraveling both the taxonomy and the phylogeny of the Protoscutellidae
... The plasticity for each trait (i.e., MxRD, RAindex, grain yield, grain number and grain weight) was calculated as the slope of the reaction norm, which is the phenotypic response to the environment (Schlichting and Pigliucci 1998;Stelzer 2002;Sadras et al. 2009). A slope ≅ 1 indicates average plasticity, > 1 indicates above-average plasticity, and < 1 indicates belowaverage plasticity (Sadras et al. 2009). ...
Context
Phenotypic plasticity can be a valuable adaptation strategy for coping with environmental heterogeneity. There is limited information on the plasticity of root traits and their effect on yield and yield stability.
Objectives
With a perspective of phenotypic plasticity, we focus on functional root traits associated to water uptake in field-grown sorghum to answer: (i) How do genetic (G), environmental (E) and management (M) factors and their interactions, affect the root traits? and (ii) How do root traits and their plasticity affect yield and yield stability?
Methods
A new high-throughput functional root phenotyping approach was used in G × E × M trials to quantify two root traits, maximum rooting depth (MxRD) and a root activity index (RAindex). Crop phenotypic plasticities were determined using the reaction norm method.
Results
The applied G × E × M treatments created plastic responses between the tested hybrids. There was a hierarchy of plasticities for the different traits studied i.e., grain number traits > root traits > grain weight traits. The plasticity of root traits was associated with the stability of grain yield traits. Hybrids with high root plasticity tend to have more stable grain numbers and grain weights.
Conclusions
There is valuable genetic diversity in the mean value and plasticity of root traits that could be used to match root phenotypes to target production environments. Our root phenotyping approach can be a valuable tool for understanding the dynamic interactions between root function, root architecture and yield traits in the field under variable environments.
... To address the topic, we developed tadpoles of the three aforementioned OTUs in two different temperatures and quantified phenotypic traits functionally relevant to the persistence of true frogs in different environments. Plastic responses may differ among OTUs in magnitude and direction, and we also admit the possibility of canalization (i.e., absence of plasticity, see Figure 1) in specific traits or OTUs (see Schlichting and Pigliucci 1998;West-Eberhard 2003;Schlichting 2008). If phenotypic similarity between OTUs that represent different species is established in specific developmental conditions, we have evidence of plastic responses surpassing phenotypic boundaries between taxa, a result that empirically reinforces the plasticity-led evolutionary diversification hypothesis Pfennig 2016, 2021). ...
Developmental plasticity can affect traits directly related to survival, and some changes may promote or impair population persistence in changing environments. At the same time, it can also originate new complex phenotypes, surpassing species-specific boundaries. Therefore, plastic responses have the potential to participate in processes of micro and macroevolution. In this study, we evaluate plastic responses to different thermal regimes during development in traits related to survival and also used for taxonomic classification of two true-toad species, Rhinella icterica and Rhinella ornata. We raised tadpoles representing distinct operational taxonomic units (OTUs) at different temperatures, and the resulting phenotypic patterns suggest canali-zation in R. icterica and complex variation revealed by plasticity among R. ornata OTUs. Plastic responses to thermal regimes produced differences among the OTUs in traits associated with specific survival strategies of Rhinella species. Some changes surpassed taxonomic boundaries and rescued lineage-specific phenotypic patterns, establishing unusual phenotypic combinations for these species. Our results illustrate the contribution of developmental plasticity for processes involving phenotypic differentiation among species in traits directly related to survival.
... Genetic robustness can be characterized in terms of the variation of phenotype distribution induced by genotypic change (1,2,3) and concerns the insensitivity of a phenotype to genetic changes. Mutational robustness has been studied in the context of noncoding RNA (ncRNA) (4,5). ...
Genetic robustness, the preservation of evolved phenotypes against genotypic mutations, is one of the central concepts in evolution. In recent years a large body of work has focused on the origins, mechanisms, and consequences of robustness in a wide range of biological systems. In particular, research on ncRNAs studied the ability of sequences to maintain folded structures against single-point mutations. In these studies, the structure is merely a reference. However, recent work revealed evidence that structure itself contributes to the genetic robustness of ncRNAs. We follow this line of thought and consider sequence-structure pairs as the unit of evolution and introduce the spectrum of inverse folding rates (IFR-spectrum) as a measurement of genetic robustness. Our analysis of the miRNA let-7 family captures key features of structure-modulated evolution and facilitates the study of robustness against multiple-point mutations.
... The genetic variable is fixed, and phenotypic outcomes are analyzed in different environments. Importantly, although NoR plays a central role in the study of phenotypic plasticity, NoR is not necessarily associated with plastic responses (Schlichting and Pigliucci, 1998). While some phenotypic outcomes change under different environmental conditions, in other cases the outcome remains robust under changing environmental conditions. ...
In this paper, I will conduct three interrelated analyses. First, I will develop an analysis of various concepts in the history of biology that used to refer to individual-level phenomena but were then reinterpreted by the Modern Synthesis in terms of populations. Second, a similar situation can be found in contemporary evolutionary theory. While different approaches reflect on the causal role of developing organisms in evolution, proponents of the Modern Synthesis refrain from any substantial change by reinterpreting and explaining individual-level phenomena from a population perspective. Finally, I will approach these historical and contemporary debates by arguing for the statistical reading of natural selection, which holds that explanations by natural selection are statistical. My main conclusion is that the historical conceptual reinterpretations belong to a new explanatory strategy developed by the Modern Synthesis based on population thinking. Adopting the statistical point of view has three advantages for the issues discussed in this paper. First, understanding historical conceptual change as part of an explanatory shift fits with the emergence of population biology as a discipline that employs statistical methods. Second, concerning current debates in evolutionary biology, the statisticalist reading can validate the goal of both sides of the dispute. It ascribes an invaluable role to the population statistical explanation of the MS and also commends the study of developmental and organismal causes of adaptive evolution. Finally, the division of explanatory roles in evolutionary biology, embarrassed by statisticalism, can be related to the different interpretations that important biological concepts have undergone throughout history and contemporary biology, i.e., that the division of explanatory roles allows for a division of conceptual interpretations.
... While phenotypic evolution is an important component of speciation (Schlichting and Pigliucci 1998), morphological variation in sand flies could play a pivotal role in their dispersion, fitness and consequently in the transmission of parasites (Dujardin 2011;Prudhomme et al., 2016). ...
Lutzomyia cruciata is a sand fly species of medical importance with a wide distribution in America. In Mexico its distribution includes nine heterogeneous biogeographic provinces in ecological and biodiversity terms. The latter could represent a strong ecological pressure on the species, giving rise to phenotypic variation mainly in those functional traits that are determining for the species. In this study, we used a broad geographic sampling of Lu. cruciata and geometric morphometric techniques to assess variation in head shape in populations from two environmentally heterogeneous biogeographic provinces, Veracruz and the Yucatán Peninsula. We also tested whether morphological variation could be related to the climatic conditions across the two biogeographical provinces. We found that head shape revealed more differences among populations within provinces than between them. Such morphological head shape variation was not associated with bioclimatic or geographical variables in either province. This pattern of morphological variation in head shape is congruent with previous evidence on the wing shape of Lu. cruciata populations. Further studies of these and other populations using genetic markers are clearly needed to allow a more precise estimate of variation or differentiation in this sand fly vector.
... Classic ecogeographical rules, such as Bergmann's rule, Gloger's rule, and Allen's rule, provide frameworks to explain how morphological traits in both warm-blooded and cold-blooded animals adapt to external environmental factors [1,2,7]. These morphological changes can also result from phenotypic plasticity, where a single genotype exhibits multiple phenotypes in response to different environments [8][9][10]. Adaptive responses are shaped by directional selection, which favors plastic responses that optimize fitness in changing Insects 2024, 15, 719 2 of 15 environments [11]. ...
Simple Summary
Ants are highly adaptable insects that thrive in a variety of climates and habitats worldwide. This study examines how climate and habitat influence the morphological traits of the ant species Camponotus japonicus across 22 sites in mainland China. These sites represent three climate zones and three habitat types. Our analysis shows that both climate and habitat significantly shape the ants’ morphological traits. Specifically, ants in mid-temperate farmlands exhibit more constrained morphological traits, while those in sparse woodlands show greater variation. Urban parks present a stable environment with less morphological variation. Temperature, precipitation, humidity, and altitude were found to be closely linked to these morphological traits. This research enhances our understanding of how ants adapt to environmental changes through morphological variation and underscores their critical ecological roles in various ecosystems.
Abstract
Ants are a highly adaptable group of insects that have globally established themselves in diverse climates and habitats. This study investigates the influence of climate and habitat on the morphological traits of Camponotus japonicus across 22 sites in mainland China. These sites span three climate zones (mid-temperate, warm temperate, and subtropical) and three habitat types (urban parks, farmlands, and sparse woodlands). Principal component analysis (PCA) was used to determine the principal axis of morphological variation, while hypervolume analysis and centroid distance calculation were used to verify the environmental filtering hypothesis and the optimal transfer hypothesis. The results support both hypotheses showing that climate and habitat significantly affect the morphological space of C. japonicus workers. In particular, the morphological space is more constrained in mid-temperate farmlands, while workers in sparse woodlands exhibit greater morphological variation. In contrast, urban parks are characterized by higher stability and reduced morphological differences. Additionally, robust regression analysis reveals that environmental factors such as temperature, precipitation, humidity, and altitude are closely linked to the morphological traits of the workers. Understanding how ant morphology responds to external environmental changes enhances our understanding of their adaptability and their essential ecological roles across various ecosystems.
... This may reflect different levels of transcriptomic plasticity, and it has been proposed that genotypes that exhibit high level of plasticity in response to novel environmental conditions may be more likely to survive compared with less-plastic genotypes (Lohman, Stutz, and Bolnick 2017). Indeed, genetic variation for plasticity may provide the raw material for further selection and adaptation (Schlichting and Pigliucci 1998). It is also worth noting that high-latitude populations were numerous and situated far from the margins of the species' geographic range, minimising the effects of genetic drift, or preventing steeper selection gradients that are expected at range margins, as shown in previous studies (Eckert, Samis, and Lougheed 2008;Sniegula et al. 2016). ...
The impact of global changes on populations may not be necessarily uniform across a species' range. Here, we aim at comparing the phenotypic and transcriptomic response to warming and an invasive predator cue in populations across different geographic scales in the damselfly Ischnura elegans. We collected adult females in two ponds in southern Poland (central latitude) and two ponds in southern Sweden (high latitude). We raised their larvae in growth chambers and exposed them to combination of temperature and a predator cue released by the crayfish Orconectes limosus. When larvae reached the prefinal larval stage, they were phenotyped for traits related to growth and size and collected for a gene expression analysis. High‐latitude populations exhibited greater phenotypic and transcriptomic variation than central‐latitude populations. Across latitudes and ponds, temperature generally increased growth rate and the predator cue decreased mass, but the effects of temperature were also pond‐specific. Comparison of the transcriptomic profiles revealed a greater overlap in the response to temperature across latitudes and ponds, especially for pathway‐related oxidative stress and sugar and lipid metabolism. The transcriptomic response to a predator cue and to the interaction temperature × predator cue was more pond‐specific and overlapped only for few genes and pathways related to cuticle, development and signal transduction. We demonstrated that central‐ and high‐latitude populations may partially respond through similar mechanisms to warming and, to a lower extent to a predator cue and to the interaction temperature × predator cue. For the predator cue and the interaction, the large fraction of ponds‐specific genes suggests local adaptation. We show that high‐latitude populations were generally more plastic at the phenotypic and transcriptomic level and may be more capable to cope with environmental changes than their central‐latitude counterparts.
... These responses manifest through a variety of biological processes (or adaptations), including acclimatization, evolution, range shifts, and ecological reorganization, occurring across different scales of organization (Webster et al., 2017(Webster et al., , 2023. Phenotypic plasticity plays a crucial role in facilitating many of these adaptations, allowing a single genotype to generate multiple phenotypes in response to environmental stimuli (Scheiner, 1993;Schlichting and Pigliucci, 1998;West-Eberhard, 2003) or to other external stressors, such as fishing pressure (Rouyer et al., 2014;Hollins et al., 2018;Morrongiello et al., 2019). The resulting phenotypes can be classified as adaptative (positive or negative), non-adaptative (or maladaptive) or neutral concerning an individual's fitness (Ghalambor et al., 2007;Chevin et al., 2010;Storz and Scott, 2021). ...
During the last decades, there has been a growing interest in the Atlantic chub mackerel, Scomber colias, owing to its northward expansion across the East Atlantic Ocean. This trend has been observed from regions of higher abundance off northwest Africa to the waters of the Atlantic Iberian and the Mediterranean Sea. Changes in abundance and spatial distribution of Atlantic chub mackerel have been previously studied and various theoretical models have been proposed to elucidate the changes in its abundance and biomass. However, within this fishing context, only a limited number of studies have attempted to understand how this species has responded at both the individual and population levels to the changing environmental conditions. The phenotypic variability of 1660 individuals of S. colias collected from the Canary Islands, Madeira, the Cantabrian Sea and the Central-Northern Mediterranean Sea was examined, with a specific focus on otolith shape. We identified six morphotypes classified into two groups and associated to the four analyzed regions. Despite of the occurrence of shared phenotypes in varying proportions among the different fishing grounds, this classification might be explained by the adaptation of certain morphotypes to specific environmental conditions and the migratory behavior of this species. The morphotypes M1-M5 were more abundant in the warmer waters of Madeira-Canary Islands region and M6 in the colder waters of Ligurian-Cantabrian. It is plausible that the former set may represent resident contingents, while morphotypes M2-M3 and M4 are likely to exhibit migratory behavior. Therefore, we suggest a complex metapopulation structure, where different contingents coexist.
... On the other hand, environmental conditions influence organismal phenotype expression, through the phenomenon of phenotypic plasticity. This environmental dependence of phenotype expression is represented graphically by reaction norms (Schlichting & Pigliucci, 1998), which display phenotype as a function of environmental conditions. Developmental plasticity, in particular, refers to the phenomenon by which the phenotype is influenced by the environmental conditions during development (Beldade et al., 2011;West-Eberhard, 2003). ...
Phenotypic variation in natural populations results from complex interactions between organisms and their changing environments. The environment shapes both phenotypic frequencies (during adaptation) and organismal phenotypes (through phenotypic plasticity). Developmental plasticity, in particular, refers to the phenomenon whereby an organism's phenotype depends on the environmental conditions during development. It can match phenotype to ecological conditions and help organisms to cope with environmental heterogeneity, including differences between alternating seasons.
Experimental studies of developmental plasticity often focus on the impact of individual environmental cues and do not take explicit account of genetic variation. In contrast, natural environments are complex, comprising multiple variables with combined effects that are poorly understood and may vary among genotypes. We investigated the effects of multifactorial environments on the development of the seasonally plastic eyespots of Bicyclus anynana butterflies. Eyespot size depends on developmental temperature and is involved in alternative seasonal strategies for predator avoidance.
In nature, both temperature and food availability undergo seasonal fluctuations. However, our understanding of how thermal plasticity in eyespot size varies in response to food availability and across genotypes remains limited. To address this, we investigated the combined effects of temperature (T; two levels: 20°C and 27°C) and food availability (N; two levels: control and limited) during development. We examined their impact on wing and eyespot size in adult males and females from multiple genotypes (G; 28 families).
We found evidence of thermal and nutritional plasticity and temperature‐by‐nutrition interactions (significant T × N) on the size of eyespots in both sexes. Food limitation resulted in relatively smaller eyespots and tempered the effects of temperature. Additionally, we found differences among families for thermal plasticity (significant G × T effects), but not for nutritional plasticity (non‐significant G × N effects) nor for the combined effects of temperature and food limitation (non‐significant G × T × N effects).
Our results reveal the context dependence of thermal plasticity, with the slope of thermal reaction norms varying across genotypes and across nutritional environments. We discuss these results in the light of the ecological significance of pigmentation and the value of considering thermal plasticity in studies of the biological impact of climate change.
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... Developmental plasticity and flexibility should instead evolve at moderate levels of environmental variability with reliable cues about impending environmental changes. In such cases, developmental plasticity is more likely to evolve when the environment varies across generations or at large spatial scales relative to the dispersal capabilities of the species, making it unlikely that a single individual will encounter an environment that differs from the one in which it developed (Schlichting & Pigliucci, 1998). In contrast, phenotypic flexibility should evolve when an individual is likely to experience multiple predictable environmental changes over the course of its life or can readily disperse between different environments, favouring the ability to alter a phenotype repeatedly (Gabriel et al., 2005). ...
Phenotypic plasticity has long played a central role in eco‐evolutionary theory, but it was not until 20 years ago that it was proposed that the term encompasses two distinct phenomena—developmental plasticity and phenotypic flexibility. While this terminology has since been adopted by some, the question of whether they are distinct phenomena remains contentious and they are both frequently lumped under the umbrella of ‘plasticity.’
Here, we treat the dichotomy between developmental plasticity and phenotypic flexibility as a hypothesis, put forth a set of predictions that follow from this hypothesis, and review the support for this hypothesis in the literature. We predict that, if they result from separate phenomena, developmentally plastic and phenotypically flexible traits should differ in: (1) the environmental context under which they evolve, (2) their mechanisms of regulation, (3) their costs of production, (4) how selection acts on them and (5) their influence on a population's evolutionary trajectory.
In general, most evidence supports treating developmental plasticity and phenotypic flexibility as separate phenomena, but much remains to be learned, and few studies have specifically investigated their potential differences. In particular, explorations of their regulation, as well as the costs of trait production and reversal are needed.
Given the hypothesized link between developmental plasticity, phenotypic flexibility and resiliency in the face of rapid environmental change, this is an urgent topic that will further our understanding of phenotypic evolution across environmental contexts.
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... This is termed phenotypic plasticity (Garland & Kelly, 2006;Losos & Mahler, 2010;Pigliucci, 2001;Pigliucci et al., 2006). Understanding the underlying reasons for phenotypic plasticity and the resulting morphological disparity is one of the key topics of evolutionary biological and paleobiological research (Dewitt & Scheiner, 2004;Fusco & Minelli, 2010;Gilbert & Epel, 2009;Greene, 1999;Jablonka & Lamb, 2005;Lewontin, 2000;Minelli & Fusco, 2008;Schlichting & Pigliucci, 1998;West-Eberhard, 2003, 2005. It is especially important in the conservation of spatially restricted refugial habitats harboring long-existing endemic biota, where the sudden or gradual transformation of environmental conditions may result in differential responses to habitat segmentation. ...
Understanding the underlying reasons for phenotypic plasticity and resulting morphological disparity is one of the key topics of evolutionary research. The phenotypic plasticity of extant and fossil melanopsids has been widely documented. Yet millennial‐resolution, well‐dated records from small aquatic habitats harboring endemics are scarce. The thermal spring‐fed Lake Pețea is an ice age refugia harboring a unique endemic warm‐water fauna. Subfossil melanopsids display incredible morphological variability from smooth to keeled, elongated to ribbed, shouldered forms. Numerous morphotypes have been considered as individual taxa with a fluent succession from the smooth elongated to the ribbed, shouldered types. This study presents an extensive morphometric analysis of subfossil melanopsids (ca. 3500 specimens) derived from stratified samples with an independent chronology. The aim was to separate morphotypes for investigations of temporal morphological disparity. Our results challenge the widely accepted hypothesis that proposes the evolution of shouldered, compressed, ribbed shells through a two‐step process from smooth elongated spindle‐shaped shells. Instead, it suggests that the subfossil shells belong to two distinct taxa present throughout the available stratigraphic data. The main components of shape variation, shape globularity, and shell coiling seem allometry‐related. Ribs, striation, and keels appear randomly. High‐spired spindle‐shaped forms were considered to represent specimens of Microcolpia daudebartii hazayi . Bulkier low‐spired and shouldered specimens represent phenotypes of Mi. parreyssii parreyssii . The collective and random distribution of morphotypes from the early stages of the lake's history also refutes the idea of a continuous transformation of the elongated forms into compressed, shouldered ones. Rather points to multiple events and environmental stimuli triggering development. Melanopsids appear in Late Glacial horizons, with Theodoxus prevostianus preferring temperatures above 23°C which may indicate the subordinate presence of hot water microhabitats in cooler waters.
... Polyploidy, or the duplication of the whole genome, results in a large influx of genetic redundancy which has been variously recognised as a diversifying force, potentially promoting an increased capacity to express different gene copies under varying environmental conditions (de Jong & Adams, 2023). An elevated genetic redundancy is expected to result in phenotypic plasticity (Mattingly & Hovick, 2023), or the ability for an individual to adjust to environmental fluctuations and thus track a dynamically changing trait optimum beyond that allowed by its fixed genotype (Schlichting & Pigliucci, 1998). However, increased levels of phenotypic plasticity are regarded as inherently costly in relatively stable or extreme environments. ...
Phenotypic plasticity, the dynamic adjustment of traits to environmental variations, is crucial for enabling species to exploit broader niches and withstand suboptimal conditions. This adaptability is particularly relevant for newly formed allopolyploids, which possess redundant gene copies and must become established in diverse environments distinct from their parents and other relatives. By evaluating gene expression and root mycobiome among two ecologically divergent sibling allopolyploid marsh orchids ( Dactylorhiza majalis and D. traunsteineri ) in reciprocal transplants at localities where both species are native, we aimed to understand the drivers of species persistence in the face of interspecific gene flow. Despite consistent abiotic differences characterising the alternative environments at each locality, the majority of gene expression differences between the allopolyploids appears to be plastic. Ecologically relevant processes, such as photosynthesis and transmembrane transport, include some genes that are differentially expressed between the two orchids regardless of the environment, while others change their activity plastically in one species or the other. This suggests that although plasticity helps define the specific ecological range of each sibling allopolyploid, it also mediates gene flow between them, thereby preventing differentiation. Extending our investigations to the root mycobiome, we uncover more diverse fungal communities for either species when grown in the environment with nutrient-poor soils, indicating that both abiotic and biotic factors drive the distribution of sibling marsh orchids. Altogether, our results indicate that plasticity can simultaneously promote diversification and homogenization of lineages, influencing the establishment and persistence of recurrently formed allopolyploid species.
Significance statement
This study highlights the role of phenotypic plasticity in the persistence and distribution of sibling allopolyploid marsh orchids ( Dactylorhiza majalis s.l.). By examining gene expression and the diversity of root mycobiome across reciprocal transplantations in native environments, we uncover high plasticity that facilitates adaptation and gene flow, thereby promoting both diversification and homogenization. These findings underscore the importance of plasticity in the establishment and long-term survival of allopolyploid species across the landscape.
... How organisms adapt to changing environments is a central question in ecology and evolution (Levins, 1968;Pfennig, 2021). Phenotypic plasticity, the ability of a genotype to produce alternative phenotypes when exposed to different environments, is a pervasive response of most organisms when facing varying conditions (Nylin & Gotthard, 1998;Schlichting & Pigliucci, 1998). Although the plastic response of certain phenotypic traits may only be the consequence of environmentally induced passive effects on those traits (Brooker et al., 2022;Schneider, 2022;Van Kleunen & Fischer, 2005), organisms often respond actively to environmental variations to avoid any reduction in fitness (Brooker et al., 2022;Ghalambor et al., 2007). ...
Adaptive phenotypic plasticity evolves in response to the contrasting selection pressures that arise when organisms face environmental heterogeneity. Despite its importance for understanding how organisms successfully cope with environmental change, adaptive plasticity is often assumed but rarely demonstrated. We study here the adaptive nature of the extreme seasonal within-individual floral polyphenism exhibited by the crucifer Moricandia arvensis, a Mediterranean species that produces two different types of flowers depending on the season of the year. During spring, this species has large, cross-shaped, lilac flowers, while during summer, it develops small, rounded, white flowers. Although floral polyphenism was associated with increased plant fitness, selection moved floral traits away from their local optimum values during the harsh summer. This result strongly suggests that floral polyphenism is not adaptive in M. arvensis. The main factor selecting against floral polyphenism was pollinators, as they select for the same floral morph in all environments. Despite not being adaptive, floral polyphenism occurs throughout the entire distribution range of M. arvensis and has probably been present since the origin of the species. To solve this paradox, we explored the factors causing floral polyphenism, finding that floral polyphenism was triggered by summer flowering. Summer flowering was beneficial because it led to extra seed production and was favored by adaptive plasticity in leaf functional traits. Taken together, our study reveals a complex scenario in which nonadaptive floral polyphenism has been indirectly maintained over M. arvensis evolutionary history by selection operating to favor summer flowering. Our study provides thus strong evidence that nonadaptive plasticity may evolve as a byproduct of colonizing stressful environments.
... Исследования в эволюционной биологии развития ведутся в следующих основных направлениях: выявление связи между гомеозисными генами и планом строения (Bauplan), оценка устойчивости и пластичности фенотипа, выявление ограничений (constraints, запретов) на выражение тех или иных признаков и их комбинаций, описание паттернов фенотипической вариации, а также описание модульной организации особи на разных структурных уровнях, оценка влияний условий среды, происхождение эволюционных новшеств (Schlichting, Pigliucci 1998;Newman, Müller 2000;West-Eberhard 2003;Minelli 2009Minelli , 2018Bateson, Gluckman 2011). ...
Эпигенетические идеи на западе и в России (представления М.А. Шишкина и его последователей) основываются на двух разных структурах мышления: индивидуалистической (на западе) и холистической (российская ЭТЭ).
В западной эпигенетике акцент делается на молекулярных механизмах, которые, как считается, лежат в основе физиологических, эмбриологических и эволюционных явлений, то есть полагается, что все явления в организме исходно обуславливаются генной активностью, которую регулируют эпигенетические механизмы. Наследование таких механизмов представляется как дополнительное наследованию, осуществляемому при посредстве ядерной ДНК у эвкариот. Эпигенетические механизмы легко модифицируются в течение индивидуального развития, и в определённых случаях эти модификации передаются следующему поколению, что позволяет говорить о наследовании приобретаемых признаков. Отсюда интерес к Ж.Б. Ламарку и молекулярному ламаркизму. Однако западные эпигенетические идеи рассматриваются в русле дальнейшего развития неодарвинизма, то есть никто не интерпретирует их как идеи, альтернативные мейнстримной концепции.
Сторонники ЭТЭ свою теорию возводят к идеям Ч. Дарвина, а предшественником считают И.И. Шмальгаузена. В основу ЭТЭ полагается концепция целостности организма, хотя она несовместима с представлениями Ч. Дарвина. Акцент делается на морфогенезе, то есть базовым считается организменный, а не молекулярный или клеточный уровень. Для российских сторонников ЭТЭ характерно неприятие неоламаркизма, а также претензия на альтернативность по отношению к неодарвинизму и синтетической теории эволюции.
... Phenotypic plasticity, the ability of organisms to alter their phenotype in response to the environment, allows individuals to incorporate information and optimize their fitness to fine-scale environmental change (Schlichting & Pigliucci, 1998). Because plasticity can respond to selective pressures faster than evolution, it has been hypothesized to facilitate adaptation and promote diversification (Pfennig, 2021;West-Eberhard, 2003). ...
Behavioural plasticity is a major driver in the early stages of adaptation, but its effects in mediating evolution remain elusive because behavioural plasticity itself can evolve.
In this study, we investigated how male Trinidadian guppies (Poecilia reticulata) adapted to different predation regimes diverged in behavioural plasticity of their mating tactic. We reared F2 juveniles of high‐ or low‐predation population origins with different combinations of social and predator cues and assayed their mating behaviour upon sexual maturity.
High‐predation males learned their mating tactic from conspecific adults as juveniles, while low‐predation males did not. High‐predation males increased courtship when exposed to chemical predator cues during development; low‐predation males decreased courtship in response to immediate chemical predator cues, but only when they were not exposed to such cues during development.
Behavioural changes induced by predator cues were associated with developmental plasticity in brain morphology, but changes acquired through social learning were not.
We thus show that guppy populations diverged in their response to social and ecological cues during development, and correlational evidence suggests that different cues can shape the same behaviour via different neural mechanisms. Our study demonstrates that behavioural plasticity, both environmentally induced and socially learnt, evolves rapidly and shapes adaptation when organisms colonize ecologically divergent habitats.
... high degree of plasticity in growth and development (Kulkarni et al. 2017; Ruthsatz 409 et al. 2018; Burraco et al. 2021; Sinai et al. 2022), providing a means for increasing fitness 410(Schlichting & Pigliucci 1998). Therefore, plasticity in timing of metamorphosis appears to be 411 more important than that in thermal tolerance to reduce mortality risk(Rudolf & Rödel 2007) 412 due to desiccation or temperature extremes (Burraco et al. 2022; Albecker et al. 2023).413 ...
Amphibians and fishes play a central role in shaping the structure and function of freshwater environments. These organisms have a limited capacity to disperse across different habitats and the thermal buffer offered by freshwater systems is small. Understanding determinants and patterns of their physiological sensitivity across life history is, therefore, imperative to predicting the impacts of climate change in freshwater systems. Based on a systematic literature review including 345 studies with 998 estimates on 96 amphibian and 93 freshwater fish species, we conducted a meta-analysis to explore phylogenetic, ontogenetic, and biogeographic (i.e. thermal adaptation) patterns in upper thermal tolerance (CT max ) and thermal acclimation capacity (Acclimation Response Ratio, ARR) as well as the influence of the methodology used to assess these thermal traits using a conditional inference tree analysis. We found CT max and ARR differed between taxa, pre- and post-metamorphic life stages as well as with thermal adaptation. The ARR of freshwater fishes exceeded that of amphibians by more than twice across life stages. In amphibians, CT max decreased throughout early development, with juveniles exhibiting the lowest heat tolerance, potentially representing a life history bottleneck if other strategies to reach thermal refugia, e.g. through behavioral thermoregulation, would also be constrained. In contrast to the broader literature, CT max was not generally higher in low latitude populations but also varied with ontogeny, emphasizing the importance of assessing life stage-specific sensitivity to thermal stress. Importantly, the application of different methods (e.g. acclimation duration, ramping rates) changed life stage, phylogeny, and thermal adaptation patterns in CT max and ARR. Our analyses highlight biases and data limitations with respect to coverage in taxonomy, biogeographic distribution of species, life stage, and study design. We propose methods to improve robustness and comparability of thermal sensitivity knowledge needed to adopt interventions to safeguard freshwater biodiversity in a future climate.
Natural selection is not the only mechanism that promotes adaptation of an organism to its environment. Another mechanism is matching habitat choice, in which individuals sense and disperse toward habitat best suited to their phenotype. This can in principle facilitate rapid adaptation, enhance range expansion, and promote genetic differentiation, reproductive isolation, and speciation. However, empirical evidence that confirms the evolution of matching habitat choice in nature is limited. Here we obtain theoretical evidence that phenotype-optimal dispersal, a particular form of matching habitat choice, is likely to evolve only in the presence of a steep environmental gradient. Such a gradient may be steeper than the gradient the majority of species typically experience in nature, adding to the collection of possible explanations for the scarcity of evidence for matching habitat choice. We draw this conclusion from numerical solutions of a system of deterministic partial differential equations for a population’s density along with the mean and variance of a fitness-related quantitative phenotypic trait such as body size. In steep gradients, we find that phenotype-optimal dispersal facilitates rapid adaptation on single-generation time scales, reduces within-population trait variation, increases range expansion speed, and enhances the chance of survival in rapidly changing environments. Moreover, it creates a directed gene flow that compensates for the maladaptive core-to-edge effects of random gene flow caused by random movements. These results suggest that adaptive gene flow to range margins, together with substantially reduced trait variation at central populations, may be hallmarks of phenotype-optimal dispersal in natural populations. Further, slowly-growing species under strong natural selection may particularly benefit from evolving phenotype-optimal dispersal.
Understanding how morphology evolves requires identifying the types of mutations that contribute to changes in development. We integrated comparative genomics and transcriptomics to reconstruct the evolution and regulation of follistatin paralogs in relation to the evolution of aphid winged and wingless morphs. We find that different pea aphid follistatin duplicates play an essential molecular role in both the male and female wing dimorphisms, linking the genetic and environmental control of morph determination in each sex, respectively. We also find that an ancestral follistatin gene likely had multiple promoters and that the follistatin duplicates that evolved wingless-specific expression retained only the ancestral wingless-specific promoter. Our work provides a roadmap for how alternative promoter usage and subsequent gene duplication can enable the evolution of animal form.
“We have probably already found the genotype that, in a statistical sense, predicts violent crime better than any gene to be discovered in the future. This is simply an XY genotype. Women are, of course, perpetrators of some violence, but from both self-report and official records, men tend to commit many more acts of assault, robbery, and homicide than women. At this point the skeptical reader may react with considerable incredulity. How is this genetic? Surely, one might protest, the socialization process that gives us male linebackers but female cheerleaders cannot be overlooked in its contribution to violent crime.
The local persistence of long-lived organisms is at risk as climate change drives a rapid shift in selection regimes world-wide. Although adaptive evolution is one of the main mechanisms by which populations persist in changing environments, we have little information regarding how selection regimes will shift in response to continued climate change, nor on the potential for trees to evolve adaptively under novel selection pressures. To address these gaps, here we assessed the changes in selection in three sites along a spatial climate gradient which mimics expected temporal changes in climate and determined whether trait covariance might accelerate or impede the rate of adaptive evolution of seven P. mariana populations in the warmer and drier environment. In three common garden sites established 50 years ago, we measured an array of traits which represent water use, response to temperature, structural investment, and metabolic efficiency. Our findings reveal that all 10 traits measured in this study were under selection in at least one site. We also find different traits are under selection in each site, with four instances where the shift in selection gradient is consistent with shifts in climate: water use efficiency (WUE); needle carbon to nitrogen ratio (CN); the interaction between WUE and CN; and the interaction between CN and huber value. In the warm and dry site, traits under selection were largely uncorrelated, with only four of the 49 trait combinations under selection exhibiting intrapopulation trait covariances. The shifts in selection gradient suggest that climate change may select for needles with higher WUE, higher structural carbon and higher hydraulic supply to the needles. The few trait-trait correlations indicate that phenotypic integration should neither impede nor facilitate adaptive evolution, leaving P. mariana provenances with the evolutionary flexibility to respond to climate change regardless of the direction to selection.
Simple Summary
Polyphenisms, the most extreme form of phenotypic plasticity, translate continuous environmental variation into discrete phenotypes in both animals and plants. While deeply embedded in the development of the individual organism, the mode of developmental regulation of polyphenisms has not been intensively studied for decades. Similarly, few attempts were made to search for conceptual similarities of polyphenisms across organismal groups. This situation is currently changing with the establishment of new model systems and advanced technological platforms. Here, we review mouth-form polyphenism in the nematode Pristionchus pacificus and compare associated molecular mechanisms to polyphenisms in insects and plants. These comparisons identify epigenetic switches as central features in the regulation of polyphenisms, with conserved system properties found in diverse organisms, including nematodes, insects, plants and human cancer progression. Thus, polyphenisms might provide important insight into the Nature vs. Nurture debate and help towards a better integration of genetic and environmental influences in health and disease.
High-altitude human populations are a classic example of adaptation to extremely stressful environments through thrifty phenotypes, where individuals adapt plastically by reducing specific organ size, like limbs, while maintaining overall size. However, it remains unknown, whether other organisms exhibit thrifty phenotypes, and which external factors may shape them. Here, we address these questions in ant colonies, considered superorganisms. The thrifty phenotype hypothesis applied to eusocial organisms predicts that colonies experiencing food shortage should reduce investment in costly individuals. In polymorphic colonies, the largest workers known as majors are costly to produce and should therefore be less abundant in colonies experiencing food shortage. Alternatively, the starvation resistance hypothesis posits that colonies in stressful environments should maintain larger colonies, which provide a nutritional buffer in times of food shortage. We show that the proportion of majors in colonies of the Hercules ant, Camponotus herculeanus, decreases plastically with increasing latitude across the temperate and boreal forest biomes of eastern Canada, independently of their average body size, or colony size, resulting in a thrifty superorganism phenotype. Furthermore, we find that the low number of days, annually, when workers can nurse the brood, best predicts these phenotypes. Our study reinforces claims that eusocial organisms may adapt plastically to fluctuating environments, and that extreme environments favour thrifty phenotypes in both humans and ants.
Global warming threatens the productivity of forest plantations. We propose here the integration of environmental information into a genomic evaluation scheme using individual reaction norms, to enable the quantification of resilience in forest tree improvement and conservation strategies in the coming decades. Random regression models were used to fit wood ring series, reflecting the longitudinal phenotypic plasticity of tree growth, according to various environmental gradients. The predictive ability of the models was considered to select the most relevant environmental gradient, namely a gradient derived from an ecophysiological model and combining trunk water potential and temperature. Even if the individual ranking was preserved over most of the environmental gradient, strong genotype x environment interactions were detected in the extreme unfavorable part of the gradient, which includes environmental conditions that are very likely to be more frequent in the future. Combining genomic information and longitudinal data allowed to predict the growth of individuals in environments where they have not been observed. Phenotyping of 50% of the individuals in all the environments studied allowed to predict the growth of the remaining 50% of individuals in all these environments with a predictive ability of 0.25. Without changing the total number of observations, adding observations in a reduced number of environments for the individuals to be predicted, while decreasing the number of individuals phenotyped in all environments, increased the predictive ability to 0.59, highlighting the importance of phenotypic data allocation. We found that genomic reaction norms are useful for the characterization and prediction of the function of genetic parameters and facilitate breeding in a climate change context.
In biological societies, complex interactions between the behavior and morphology of evolving organisms and their environment have given rise to a wide range of complex and diverse social structures. Similarly, in artificial counterparts such as swarm-robotics systems, collective behaviors emerge via the interconnected dynamics of robot morphology (sensory-motor configuration), behavior (controller), and environment (task). Various studies have demonstrated morphological and behavioral diversity enables biological groups to exhibit adaptive, robust, and resilient collective behavior across changing environments. However, in artificial (swarm robotic) systems there is little research on the impact of changing environments on morphological and behavioral (body-brain) diversity in emergent collective behavior, and the benefits of such diversity. This study uses evolutionary collective robotics as an experimental platform to investigate the impact of increasing task environment complexity (collective behavior task difficulty) on the evolution and benefits of morphological and behavioral diversity in robotic swarms. Results indicate that body-brain evolution using coupled behavior and morphology diversity maintenance yields higher behavioral and morphological diversity, which is beneficial for collective behavior task performance across task environments. Results also indicate that such behavioral and morphological diversity maintenance coupled with body-brain evolution produces neuro-morpho complexity that does not increase concomitantly with task complexity.
The thermal spring-fed Lake Pețea located in NW Romania southeast of the city of Oradea harbors a unique endemic warm water biota. It is the only location in Europe where thermal water endemic melanopsid Microcolpia parreyssii (Philippi, 1847) lived along with the highly endangered warm-water relict neritid Theodoxus prevostianus. Lake Petea’s evolution was mainly controlled by major climate-driven hydrological changes also seen in regional records. The hydrological changes were mainly controlled by varying input of thermal water due to recurring increased/decreased recharge of the underground karst water system. The driving factor was warming connected to the interstadial GI 1 increasing recharge by melting of regional ice sheets in the Late Glacial. Conversely, during the Younger Dryas (H0) and the Holocene increasing/decreasing moisture availability was in control. Low stands created multiple bottlenecks reducing genetic variability seen in the appearance of extreme morphologies during next rapid climate melioration. The studied gastropods responded mostly similarly to changes controlling the availability of elements in shell construction and habitat reduction leading to changes in shape, density, size. Periods of lower lake levels and reduced warm water input are characterized by the emergence of elongated tightly coiled shells while globular, compressed loosely coiled shells develop at times of warmer water provision and increased Mg availability. In size there is a contrasting trend. Namely globose Th. prevostianus shells are larger than the elongated ones. Conversely globose, compressed Microcolpia are generally smaller than their elongated spindle-shaped counterparts. In this sense the development of dwarf morphotypes in warmer water habitats is characteristic of Lake Pețea melanopsids. This type of dwarfism i.e. the reduction of shell size is lacking though in Lake Pețea neritids. Our findings also confirm the presence of various ecophenotypes of Microcolpia in the pond degrading our endemic species Mi. parreyssii to a variety of Mi. daudebartii.
Background
Nutrient availability is among the most widespread means by which environmental variability affects developmental outcomes. Because almost all cells within an individual organism share the same genome, structure-specific growth responses must result from changes in gene regulation. Earlier work suggested that histone deacetylases (HDACs) may serve as epigenetic regulators linking nutritional conditions to trait-specific development. Here we expand on this work by assessing the function of diverse HDACs in the structure-specific growth of both sex-shared and sex-specific traits including evolutionarily novel structures in the horned dung beetle Onthophagus taurus.
Results
We identified five HDAC members whose downregulation yielded highly variable mortality depending on which HDAC member was targeted. We then show that HDAC1, 3, and 4 operate in both a gene- and trait-specific manner in the regulation of nutrition-responsiveness of appendage size and shape. Specifically, HDAC 1, 3, or 4 knockdown diminished wing size similarly while leg development was differentially affected by RNAi targeting HDAC3 and HDAC4. In addition, depletion of HDAC3 transcript resulted in a more rounded shape of genitalia at the pupal stage and decreased the length of adult aedeagus across all body sizes. Most importantly, we find that HDAC3 and HDAC4 pattern the morphology and regulate the scaling of evolutionarily novel head and thoracic horns as a function of nutritional variation.
Conclusion
Collectively, our results suggest that both functional overlap and division of labor among HDAC members contribute to morphological diversification of both conventional and recently evolved appendages. More generally, our work raises the possibility that HDAC-mediated scaling relationships and their evolution may underpin morphological diversification within and across insect species broadly.
Developmental plasticity refers to the phenomenon whereby an organism's phenotype depends on the environmental conditions experienced during development. This plasticity can match phenotype to ecological conditions and help organisms to cope with environmental heterogeneity, including differences between alternating seasons. Experimental studies of developmental plasticity often focus on the impact of individual environmental cues and do not take explicit account of genetic variation. In contrast, natural environments are complex, comprising multiple variables with combined effects that are poorly understood and may vary among genotypes. We investigated the effects of multifactorial environments on the development of the seasonally plastic eyespots of Bicyclus anynana butterflies. Eyespot size is known to depend on developmental temperature and to be involved in alternative seasonal strategies for predator avoidance. In nature, both temperature and food availability undergo seasonal fluctuations. However, our understanding of whether thermal plasticity in eyespot size varies in relation to food availability and across genotypes remains limited. To address this, we investigated the combined effects of temperature (T; two levels: 20°C and 27°C) and food availability (N; two levels: control and limited) during development. We examined their impact on wing and eyespot size in adult males and females from multiple genotypes (G; 28 families). We found evidence of thermal and nutritional plasticity, and of temperature-by-nutrition interactions (significant TxN) on the size of eyespots in both sexes. Food limitation resulted in relatively smaller eyespots and tempered the effects of temperature. Additionally, we found differences among families for thermal plasticity (significant GxT effects), but not for nutritional plasticity (non-significant GxN effects) nor for the combined effects of temperature and food limitation (non-significant GxTxN effects). Our results reveal the context dependence of thermal plasticity, with the slope of thermal reaction norms varying across genotypes and across nutritional environments. We discuss these results in light of the ecological significance of pigmentation and the value of considering thermal plasticity in studies of the biological impact of climate change.
In this paper, I will conduct three interrelated analyses. First, I will develop an analysis of various concepts in the history of biology that used to refer to individual-level phenomena but were then reinterpreted by the Modern Synthesis in terms of populations. Second, I argue that a similar situation can be found in contemporary biological theory. While different approaches reflect on the causal role of developing organisms in evolution, proponents of the Modern Synthesis avoid any substantial change by reinterpreting and explaining individual-level phenomena from a population perspective. Finally, I will approach this debate by advocating the statistical reading of natural selection, which holds that explanations by natural selection are statistical. I will argue that the above historical conceptual reinterpretations belong to a new explanatory strategy developed by the Modern Synthesis based on population thinking. The reinterpretation of concepts at the individual level is part of the explanatory framework of the Modern Synthesis and the empty role of development within this framework. Moreover, the statistical perspective adopted here allows for the integration of two explanatory models: population-statistical and individual-causal. Finally, I will argue that this pluralistic framework can help to define the explanatory scope of the different biological approaches in order to achieve a coherent integration of development into evolution without rejecting population thinking.
