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Debate surrounding the integration of phenotypic plasticity within the neo-Darwinian paradigm has recently intensified, but is largely dominated by conceptual abstractions. Advances in our capacities to identify candidate genes, and quantify their levels of expression, now facilitate the study of natural variation in inherently plastic traits, and may lead to a more concrete understanding of plasticity's role in adaptive evolution. We present data from parapatric threespine stickleback ( Gasterosteus aculeatus) demes inhabiting geologically recent, freshwater and saltwater zones of a large estuary. Reaction norms for survival confirm adaptation to local salinity conditions. Analysis of osmoregulatory candidate gene expression within an ecological quantitative genetics framework suggests putative mechanisms underlying adaptive variation, and provides insights into the role of ancestral trait plasticity in this divergence. A sodium–potassium ATPase (ATP1A1) is identified as a candidate gene for freshwater adaptation. In addition to heritable variation for gene expression, we infer significant correlation between measures of expression and individual fitness. Overall results indicate a loss of plasticity in the freshwater deme. We discuss how this is consistent with adaptation facilitated by ancestral plasticity as a heuristic example that may prove useful for future, explicit tests of the genetic assimilation hypothesis. [ABSTRACT FROM AUTHOR]

Small (SK) and large conductance (BK) Ca2+-activated K+ channels contribute to action potential repolarization, shape dendritic Ca2+spikes and postsynaptic responses, modulate the release of hormones and neurotransmitters, and contribute to hippocampal-dependent synaptic plasticity. Over the last decade, SK and BK channels have emerged as important targets for the development of acute ethanol tolerance and for altering neuronal excitability following chronic ethanol consumption. In this mini-review, we discuss new evidence implicating SK and BK channels in ethanol tolerance and ethanol-associated homeostatic plasticity. Findings from recent reports demonstrate that chronic ethanol produces a reduction in the function of SK channels in VTA dopaminergic and CA1 pyramidal neurons. It is hypothesized that the reduction in SK channel function increases the propensity for burst firing in VTA neurons and increases the likelihood for aberrant hyperexcitability during ethanol withdrawal in hippocampus. There is also increasing evidence supporting the idea that ethanol sensitivity of native BK channel results from differences in BK subunit composition, the proteolipid microenvironment, and molecular determinants of the channel-forming subunit itself. Moreover, these molecular entities play a substantial role in controlling the temporal component of ethanol-associated neuroadaptations in BK channels. Taken together, these studies suggest that SK and BK channels contribute to ethanol tolerance and adaptive plasticity. [ABSTRACT FROM AUTHOR]

Behavior has been viewed as a pacemaker of evolutionary change because changes in behavior are thought to expose organisms to novel selection pressures and result in rapid evolution of morphological, life history and physiological traits. However, the idea that behavior primarily drives evolutionary change has been challenged by an alternative view of behavior as an inhibitor of evolution. According to this view, a high level of behavioral plasticity shields organisms from strong directional selection by allowing individuals to exploit new resources or move to a less stressful environment. Here, I suggest that absence of clear mechanisms underlying these hypotheses impedes empirical evaluation of behavior's role in evolution in two ways. First, both hypotheses focus on behavioral shifts as a key step in the evolutionary process but ignore the developmental mechanisms underlying these shifts and this has fostered unwarranted assumptions about the specific types of behavioral shifts that are important for evolutionary change. Second, neither hypothesis provides a means of connecting within-individual changes in behavior to population-level processes that lead to evolutionary diversification or stasis. To resolve these issues, I incorporate developmental and evolutionary mechanisms into a conceptual framework that generates predictions about the types of behavior and types of behavioral shifts that should affect both micro and macroevolutionary processes. [ABSTRACT FROM AUTHOR]

In Mediterranean environments, light and water are clearly dominant ecological drivers of seedling growth and survival, and their interaction could modify productivity and forest composition. We examine the early response of seedlings of four co-occurring Mediterranean tree species (Pinus pinea, Juniperus thurifera, Quercus ilex and Quercus faginea) grown in the nursery to differing light and water availability conditions. Morphological (survival, height, biomass) and physiological (shoot midday water potential, net photosynthesis, transpiration rate, stomatal conductance, Fv/Fm, PSII and ETR) traits were studied, along with biomass allocation traits and drought resistance and plasticity indices. A significant effect of both factors was mainly shown for growth and morphological traits, while survival, physiological traits and allometry were affected by either water availability or light, being more remarkable the effect of water availability over light. Drought severely limited Q. faginea's survival under both light intensities. The high plasticity of J. thurifera and Q. ilex seedlings to different light and water availability environments will confer these two species with an adaptive advantage in the early growth stages in comparison with P. pinea and Q. faginea seedlings. Thus, to maintain the codominance of the four species, silvicultural interventions should focus on the joint management of all of them. [ABSTRACT FROM AUTHOR]

The interacting effects of different environmental cues in determining a plant's phenotype and performance are poorly understood aspects of phenotypic plasticity. We examined the interacting effects of shading and mechanical stress (MS) on growth, reproduction, and mechanical stability. We subjected 10 grassland genotypes and 10 forest genotypes of Impatiens capensis to two levels of spectral shading and two levels of MS. Shade induced the production of taller, thinner internodes, but this response was inhibited by MS. This interactive effect was stronger in the grassland genotypes than in the forest genotypes, indicating that shade avoidance can be suppressed by MS and that the degree of this suppression differs between habitats. Among genotypes, greater plasticity in shade-induced internode elongation resulted in a larger reduction in the ability of plants to carry their own weight. This suggests that the occurrence of mechanical constraints may strongly contribute to the selection against shade-induced elongation responses in forest understory genotypes. Our results show that combined responses to different environmental cues can result in a fine-tuning of phenotypic expression by plants by maintaining the potential to strongly respond to single environmental cues but also by preventing potential future costs resulting from poor adaptation to other stresses. [ABSTRACT FROM AUTHOR]

To examine the evolution of endurance-exercise behaviour, we have selectively bred four replicate lines of laboratory mice (Mus domesticus) for high voluntary wheel running ('high runner' or HR lines), while also maintaining four non-selected control (C) lines. By generation 16, HR mice ran -2.7-fold more than C mice, mainly by running faster (especially in females), a differential maintained through subsequent generations, suggesting an evolutionary limit of unknown origin. We hypothesized that HR mice would have higher glycogen levels before nightly running, show greater depletion of those depots during their more intense wheel running, and have increased glycogen synthase activity and GLUT-4 protein in skeletal muscle. We sampled females from generation 35 at three times (photophase 07:00 h-19:00 h) during days 5-6 of wheel access, as in the routine selection protocol: Group 1, day 5, 16:00h-17:30h, wheels blocked from 13:00h; Group 2, day 6, 02:00h-03:30h (immediately after peak running); and Group 3, day 6, 07:00h-08:30h. An additional Group 4, sampled 16:00h-17:30h, never had wheels. HR individuals with the mini-muscle phenotype (50% reduced hindlimb muscle mass) were distinguished for statistical analyses comparing C, HR normal, and HR mini. HR mini ran more than HR normal, and at higher speeds, which might explain why they have been favored by the selective-breeding protocol. Plasma glucose was higher in Group 1 than in Group 4, indicating a training effect (phenotypic plasticity). Without wheels, no differences in gastrocnemius GLUT-4 were observed. After 5 days with wheels, all mice showed elevated GLUT-4, but HR normal and mini were 2.5-fold higher than C. At all times and irrespective of wheel access, HR mini showed approximately three-fold higher [glycogen] in gastrocnemius and altered glycogen synthase activity. HR mini also showed elevated glycogen in soleus when sampled during peak running. All mice showed some glycogen depletion during nightly wheel running, in muscles and/or liver, but the magnitude of this depletion was not large and hence does not seem to be limiting to the evolution of even-higher wheel running. [ABSTRACT FROM AUTHOR]

Abstract: Paillard [Paillard J. Réflexions sur l’usage du concept de plasticité en Neurobiologie. J Psychol Norm Pathol 1976;1:33–47] defined adaptive plasticity as the capacity of the system to change its own structure and expand its behavioural repertoire. We review the literature on brain damage patients, in whom, adaptive plasticity was observed via neuropsychological and functional neuroimaging examinations. Attentional and memory system alterations and some resulting changes considered as compensatory mechanisms are commented. We have selected a single case presenting with developmental amnesia [Vargha-Khadem F, Gadian DG, Watkins KE, Connelly A, Van Paesschen W, Mishkin M. Differential effects of early hippocampal pathology on episodic and semantic memory. Science 1997;277(5324):376–80; Maguire EA, Vargha-Khadem F, Mishkin M. The effects of bilateral hippocampal damage on fMRI regional activations and interactions during memory retrieval. Brain 2001;124(Pt 6):1156–70] and several groups of multiple sclerosis patients studied recently [e.g. Mainero C, Pantano P, Caramia F, Pozzilli C. Brain reorganization during attention and memory tasks in multiple sclerosis: insights from functional MRI studies. J Neurol Sci 2006;245(1/2):93–8; Morgen K, Sammer G, Courtney SM, Wolters T, Melchior H, Blecker CR, et al. Distinct mechanisms of altered brain activation in patients with multiple sclerosis. Neuroimage 2007;37(3):937–46; Nebel K, Wiese H, Seyfarth J, Gizewski ER, Stude P, Diener HC, et al. Activity of attention related structures in multiple sclerosis patients. Brain Res 2007;1151:150–60]. Convergence evidence via the two approaches – neuropsychological and functional fMRI – was shown as functional and structural brain plasticity was demonstrated in the selected works. Some common characteristics of brain plasticity emerge from this review independently of the neurological conditions we reviewed. [Copyright &y& Elsevier]

Phenotypic plasticity in response to environmental variation occurs at all levels of organization and across temporal scales within plants. However, the magnitude and functional significance of plasticity is largely unexplored in perennial species. We measured the plasticity of leaf- and shoot-level physiological, morphological and developmental traits in nursery-grown Populus deltoides Bartr. ex Marsh. individuals subjected to different nutrient and water availabilities. We also examined the extent to which nutrient and water availability influenced the relationships between these traits and productivity. Populus deltoides responded to changes in resource availability with high plasticity in shoot-level traits and moderate plasticity in leaf-level traits. Although shoot-level traits generally correlated strongly with productivity across fertilization and irrigation treatments, few leaf-level traits correlated with productivity, and the relationships depended on the resource examined. In fertilized plants, leaf nitrogen concentration was negatively correlated with productivity, suggesting that growth, rather than enhanced leaf quality, is an important response to fertilization in this species. With the exception of photosynthetic nitrogen-use efficiency, traits associated with resource conservation (leaf senescence rate, water-use efficiency and leaf mass per area) were uncorrelated with short-term productivity in nutrient- and water-stressed plants. Our results suggest that plasticity in shoot-level growth traits has a greater impact on plant productivity than does plasticity in leaf-level traits and that the relationships between traits and productivity are highly resource dependent. [ABSTRACT FROM AUTHOR]

Abstract: Long-term rotational vestibulo-ocular (VOR) adaptation occurs during systematic dysmetria between visual and vestibular afferents, adjusting eye-rotation angular velocity to re-establish retinal stability of the visual field. Due to translational motion of the eyes during head rotation, VOR gain is higher when fixating near objects. The current study measures VOR in humans before and after 6min of exposure to a foveal near-target during sinusoidal whole-body rotation at 0.45Hz. All of six participants showed post-exposure increases in open-loop VOR gain after fixating near targets, demonstrating a mean modulation increase of open-loop VOR gain from 0.86 before adaptation to 1.2 after adaptation. We discuss a number of theoretical and applied implications. [Copyright &y& Elsevier]

Adaptive evolution of phenotypic plasticity requires that plastic genotypes have the highest global fitness. We studied selection by spatial heterogeneity of interspecific competition and flooding, and by temporal heterogeneity of flooding on morphological plasticity of 52 genotypes of the clonal shore plant Ranunculus reptans. Competition reduced clone size, rosette size, leaf length and stolon internode thickness. Flooding had similar effects and reduced competition. Differences in selection between environments imply potential for either local adaptation or for indirect evolution of phenotypic plasticity. We also detected direct selection for plastic reductions in internode length in response to flooding and for a plastic increase in internode length in response to competition. Plastic responses of some morphological traits to flooding were in line with selection thereon, suggesting that they indeed are adaptive and might have evolved in response to direct selection on plasticity. [ABSTRACT FROM AUTHOR]

The ability to appropriately modify physiological and morphological traits in response to temporal variation should increase fitness. We used recombinant hybrid plants generated by crossing taxa in the Piriqueta caroliniana complex to assess the effects of individual leaf traits and trait plasticities on growth in a temporally variable environment. Recombinant hybrids were used to provide a wide range of trait expression and to allow an assessment of the independent effects of individual traits across a range of genetic backgrounds. Hybrid genotypes were replicated through vegetative propagation and planted in common gardens at Archbold Biological Station in Venus, Florida, where they were monitored for growth, leaf morphological characters, and integrated water use efficiency (WUE) (C isotope ratio; δ13C) for two successive seasons. Under wet conditions only leaf area had significant effects on plant growth, but as conditions became drier, growth rates were greatest in plants with narrow leaves and higher trichome densities. Plants with higher WUE exhibited increased growth during the dry season but not during the wet season. WUE during the dry season was increased for plants with smaller, narrower leaves that had higher trichome densities and increased reflectance. Examination of alternative path models revealed that during the dry season leaf traits had significant effects on plant growth only through their direct effects on WUE, as estimated from δ13C. Over the entire growing season, plants with a greater ability to produce smaller and narrower leaves with higher trichome densities in response to reduced water availability had the greatest growth rate. These findings suggest that plants making appropriate changes to leaf morphology as conditions became dry had increased WUE, and that the ability to adjust leaf phenotypes in response to environmental variation is a mechanism by which plants increase fitness. [ABSTRACT FROM AUTHOR]

Adaptive values of plasticity in Iris pumila leaf traits (morphological: SLA, specific leaf area; anatomical: SD, stomatal density; LT, leaf thickness; VBN, vascular bundle number; SW, sclerenchyma width; CW, cuticle width, and physiological: ChlT, total chlorophyll concentration; ChlA/B, chlorophyll a/b ratio) were tested at three irradiance levels in a growth-room. Siblings from 28 full-sib families from an open dune site and a woodland understory responded similarly to variation in light availability: SLA gradually increased, while anatomical and physiological traits decreased with light reduction. In the Dune population, standardized linear selection gradients were significant for SLA and ChlT at high light, VBN along the entire light gradient, SW at high- and low-, and ChlA/B at low-irradiance. In the Woods population, the significant standardized linear selection gradients were observed for SLA and LT at low- and VBN at both high- and low-irradiance. A significant nonlinear selection gradient was recorded for SD and LT at medium irradiance. Comparisons of the plastic responses to each light quantity with the phenotypes favored by selection in that environments revealed that only an increased SLA value at low light in the Woods population was ecologically significant (adaptive). In the Dune population, SD and VBN entailed plasticity costs at low irradiance, while a cost of homeostasis was recognized for ChlT and ChlA/B at medium light, SD and CW at high- and low-, and SLA at high- and medium-light level. In the shaded population, CW and ChlA/B incurred plasticity costs at high irradiance, while for ChlT plasticity costs appeared under medium- and low-light conditions. In all leaf traits, genetic variation for plasticity was statistically undetectable. Genetic correlations between these traits were mostly insignificant, implying that they possess a capability for relatively independent evolution by natural selection across different light environments. [ABSTRACT FROM AUTHOR]

1 Unlike non-clonal plants, clonal plants can develop a division of labour in which connected ramets specialize to acquire different, locally abundant resources. This occurs as a plastic response to a patchy environment where two resources tend not to occur together and different ramets experience high availabilities of different resources. We hypothesized that if division of labour is an important advantage of clonal growth in such environments in nature, then clones from habitats where resource availabilities are negatively associated should show a greater capacity for division of labour than clones from habitats where resource availabilities are more uniform. 2 To test this, we collected clones of Fragaria chiloensis from sand dune and grassland sites in each of three regions of the central coast of California, grew pairs of connected or severed ramets under low light and high N or under high light and low N, and measured leaf area, chlorophyll content and final dry mass. Given that previous work has indicated that high availabilities of light and N show a stronger tendency not to occur together in the dune than in the grassland sites, we expected that clones from dunes would show greater capacity for division of labour than clones from grasslands. 3 Clones from dunes showed a greater capacity than clones from grasslands to specialize for acquisition of abundant N via high proportional mass of roots. Clones from the two types of habitats showed similar capacity to specialize for acquisition of abundant light via high leaf area and chlorophyll content of leaves. Specialization via leaf area and chlorophyll content took place mainly within the first half of the 60-day experiment. 4 These results provide evidence that division of labour in a clonal plant has been selected for in natural habitats where high levels of different resources tend to be spatially separated. Results also show that division of labour can occur, not just via allocation of mass, but also via physiological traits, and that both morphological and physiological specialization can take place within a few weeks. 5 Clonal plants dominate many habitats and include many highly invasive species. Division of labour is one of the most striking potential advantages of clonal growth, and is a remarkable instance of phenotypic plasticity in plants. This study further suggests that division of labour in clonal plants is an instance of adaptive plasticity and could therefore play a part in their widespread ecological success. [ABSTRACT FROM AUTHOR]

An organism’s investment in different traits to reduce predation is determined by the fitness benefit of the defense relative to the fitness costs associated with the allocation of time and resources to the defense. Inherent tradeoffs in time and resource allocation should result in differential investment in defense along a resource gradient, but competing models predict different patterns of investment. There are currently insufficient empirical data on changes in investment in defensive traits or their costs along resource gradients to differentiate between the competing allocation models. In this study, I exposed tadpoles to caged predators along a resource gradient in order to estimate investment in defense and costs of defense by assessing predator-induced plasticity. Induced defenses included increased tail depth, reduced feeding, and reduced swimming activity; costs associated with these defenses were reduced developmental rate, reduced growth, and reduced survival. At low resource availability, these costs predominately resulted in reduced survival, while at high resource availability the costs yielded a reduced developmental rate. Defensive traits responded strongly to predation risk, but did not respond to resource availability (with the exception of feeding activity), whereas traits construed as costs of defenses showed the opposite pattern. Therefore, defensive traits were highly sensitive to predation risk, while traits construed as costs of defense were highly sensitive to resource allocation tradeoffs. This difference in sensitivity between the two groups of traits may explain why the correlation between the expression of defensive traits and the expression of the associated defense costs was weak. Furthermore, my results indicate that genetic linkages and mechanistic integration of multiple defensive traits and their associated costs may constrain time and resource allocation in ways that are not addressed in existing models. [ABSTRACT FROM AUTHOR]

The ability of plants to make morphological or physiological adjustments in response to environmental cues allows them to survive and reproduce under a wide range of conditions. One stress that plants are often exposed to is soil oxygen depletion due to flooding. Plants can respond to hypoxic soils by producing oxygen-conducting aerenchymous tissue or through induction of enzymes in the ethanolic fermentation pathway. Here we use greenhouse experiments to examine flood responses in plants of the Piriqueta caroliniana (Tumeraceae) complex, which occupy a range of moisture regimes. Morphotypes and hybrids in this complex exhibited contrasting responses to hypoxic conditions. Genotypes from flooded habitats developed aerenchyma and did not substantially elevate levels of alcohol dehydrogenase (ADH) activity, an enzyme associated with anaerobic respiration. Plants from drier sites, on the other hand, did not develop aerenchyma but had much higher levels of ADH activity. Plants with aerenchymous tissue had substantially higher rates of growth under sustained flooding. Results are consistent with the hypothesis that aerenchyma development is an effective strategy in habitats subject to persistent flooding, while elevating activity of enzymes for ethanolic fermentation is effective only under ephemeral flooding. The range of phenotypic responses observed illustrates contrasting adaptive strategies that can lead to habitat isolation and evolutionary divergence. [ABSTRACT FROM AUTHOR]

Excessive, repetitive and altered loading have been implicated in the initiation of a series of soft- and hard-tissue responses or `functional adaptations' of masticatory and locomotor elements. Such adaptive plasticity in tissue types appears designed to maintain a sufficient safety factor, and thus the integrity of given element or system, for a predominant loading environment(s). Employing a mammalian species for which considerable in vivo data on masticatory behaviors are available, genetically similar domestic white rabbits were raised on diets of different mechanical properties so as to develop an experimental model of joint function in a normal range of physiological loads. These integrative experiments are used to unravel the dynamic inter-relationships among mechanical loading, tissue adaptive plasticity, norms of reaction and performance in two cranial joint systems: the mandibular symphysis and temporomandibular joint (TMJ). Here, we argue that a critical component of current and future research on adaptive plasticity in the skull, and especially cranial joints, should employ a multifaceted characterization of a functional system, one that incorporates data on myriad tissues so as to evaluate the role of altered load versus differential tissue response on the anatomical, cellular and molecular processes that contribute to the strength of such composite structures. Our study also suggests that the short-term duration of earlier analyses of cranial joint tissues may offer a limited notion of the complex process of developmental plasticity, especially as it relates to the effects of long-term variation in mechanical loads, when a joint is increasingly characterized by adaptive and degradative changes in tissue structure and composition. Indeed, it is likely that a component of the adaptive increases in rabbit TMJ and symphyseal proportions and biomineralization represent a compensatory mechanism to cartilage degradation that serves to maintain the overall functional integrity of each joint system. Therefore, while variation in cranial joint anatomy and performance among sister taxa is, in part, an epiphenomenon of interspecific differences in diet-induced masticatory stresses characterizing the individual ontogenies of the members of a species, this behavioral signal may be increasingly mitigated in over-loaded and perhaps older organisms by the interplay between adaptive and degradative tissue responses. [ABSTRACT FROM AUTHOR]

Parasitism changes the host environment and may influence resource allocation between reproductive effort and somatic maintenance. We characterized the impact of dose-dependent schistosome exposure and/or infection establishment on intermediate host survival and reproduction. Four matched groups of Biomphalaria glabrata snails were individually exposed to increasing doses of Schistosoma mansoni parasites, with a fifth control group remaining unexposed. Increased mortality was observed amongst both snails infected and also those snails exposed to the parasite but within which infection did not establish, although only exposed but uninfected snails showed a dose-dependent increase in mortality. Snails also facultatively altered their reproductive output in response to parasite exposure: egg mass production decreased with increasing parasite dose in patently infected snails, whilst, in contrast, exposed but uninfected snails demonstrated a positive association between egg mass production and parasite dose in the post-patent period. These results uniquely suggest an exposure-dose-dependent post-patent fecundity compensation occurring in relation to the risk of future parasite-associated mortality. [ABSTRACT FROM AUTHOR]

Examining the phenotypic and genetic underpinnings of life-history variation in long-lived organisms is central to the study of life-history evolution. Juvenile growth and survival are often density dependent in reptiles, and theory predicts the evolution of slow growth in response to low resources (resource-limiting hypothesis), such as under densely populated conditions. However, rapid growth is predicted when exceeding some critical body size reduces the risk of mortality (mortality hypothesis). Here we present results of paired, large-scale, five-year field experiments to identify causes of variation in individual growth and survival rates of an Australian turtle (Emydura macquarii) prior to .maturity. To distinguish between these competing hypotheses, we reduced nest predators in two populations and retained a control population to create variation in juvenile density by altering recruitment levels. We also conducted a complementary split-clutch field-transplant experiment to explore the impact of incubation temperature (25° or 30°C), nest predator level (low or high), and clutch size on juvenile growth and survival. Juveniles in high-recruitment (predator removal) populations were not resource limited, growing more rapidly than young turtles in the control populations. Our experiments also revealed a remarkably long-term impact of the thermal conditions experienced during embryonic development on growth of turtles prior to maturity. Moreover, this thermal effect was manifested in turtles approaching maturity, rather than in turtles closer to hatching, and was dependent on population density in the post-hatching rearing environment. This apparent phenotypic plasticity in growth complements our observation of a strong, positive genetic correlation between individual body size in the experimental and control populations over the first five years of life (rG ∼ +0.77). Thus, these Australian pleurodiran turtles have the impressive capacity to acclimate plastically to major demographic perturbations and enjoy the longer-term potential to evolve adaptively to maintain viability. [ABSTRACT FROM AUTHOR]

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Natural or artificial selection that favors higher values of a particular trait within a given population should engender an evolutionary response that increases the mean value of the trait. For this prediction to hold, the phenotypic variance of the trait must be caused in part by additive effects of alleles segregating in the population, and also the trait must not be too strongly genetically correlated with other traits that are under selection. Another prediction, rarely discussed in the literature, is that directional selection should favor alleles that increase phenotypic plasticity in the direction of selection, where phenotypic plasticity is defined as the ability of one genotype to produce more than one phenotype when exposed to different environments. This prediction has received relatively little empirical attention. Nonetheless, many laboratory experiments impose selection regimes that could allow for the evolution of enhanced plasticity (e.g. desiccation trials with Drosophila that last for several hours or days). We review one example that involved culturing of Drosophila on lemon for multiple generations and then tested for enhanced plasticity of detoxifying enzymes. We also review an example with vertebrates that involves selective breeding for high voluntary activity levels in house mice, targeting wheel-running behavior on days 5+6 of a 6-day wheel exposure. This selection regime allows for the possibility of wheel running itself or subordinate traits that support such running to increase in plasticity over days 1-4 of wheel access. Indeed, some traits, such as the concentration of the glucose transporter GLUT4 in gastrocnemius muscle, do show enhanced plasticity in the selected lines over a 5-6 day period. In several experiments we have housed mice from both the Selected (S) and Control (C) lines with or without wheel access for several weeks to test for differences in plasticity (training effects). A variety of patterns were observed, including no training effects in either S or C mice, similar changes in both the S and C lines, greater changes in the S lines but in the same direction in the C lines, and even opposite directions of change in the S and C lines. For some of the traits that show a greater training effect in the S lines, but in the same direction as in C lines, the greater effect can be explained statistically by the greater wheel running exhibited by S lines (`more pain, more gain'). For others, however, the differences seem to reflect inherently greater plasticity in the S lines (i.e. for a given amount of stimulus, such as wheel running/day, individuals in the S lines show a greater response as compared with individuals in the C lines). We suggest that any selection experiment in which the selective event is more than instantaneous should explore whether plasticity in the appropriate (adaptive) direction has increased as a component of the response to selection. [ABSTRACT FROM AUTHOR]

In outcrossing plants, seed dispersal distance is often less than pollen movement. If the scale of environmental heterogeneity within a population is greater than typical seed dispersal distances but less than pollen movement, an individual's environment will be similar to that of its mother but not necessarily its father. Under these conditions, environmental maternal effects may evolve as a source of adaptive plasticity between generations, enhancing offspring fitness in the environment that they are likely to experience. This idea is illustrated usingCampanula americana, an herb that grows in understory and light-gap habitats. Estimates of seed dispersal suggest that offspring typically experience the same light environment as their mother. In a field experiment testing the effect of open vs understory maternal light environments, maternal light directly influenced offspring germination rate and season, and indirectly affected germination season by altering maternal flowering time. Results to date indicate that these maternal effects are adaptive; further experimental tests are ongoing. Evaluating maternal environmental effects in an ecological context demonstrates that they may provide phenotypic adaptation to local environmental conditions.New Phytologist(2005)doi: 10.1111/j.1469-8137.2004.01314.x© New Phytologist(2005) [ABSTRACT FROM AUTHOR]

1. The significance for whole-plant carbon gain of plasticity in between-leaf and within-leaf partitioning of photosynthetic resources was investigated using an experimental and modelling approach.Lysimachia vulgarisL. was grown at two contrasting stand densities and two levels of nutrient availability in a glasshouse. Whole-plant daily C gain was calculated for the four treatments. The importance of the two forms of plasticity in photosynthetic resource partitioning was investigated by switching distribution patterns of leaf nitrogen and photosynthetic capacity per unit chlorophyll between plants in the two stand densities and recalculating whole-plant C gain, which was used as a measure of fitness.2. The plants had a high photosynthetic capacity per unit leaf area in top leaves in the dense stands, and a low capacity in bottom leaves. The distribution over plant height was more homogeneous in the open stands. This plasticity in between-leaf resource partitioning was not very important for whole-plant C gain, provided the plants had a dense-canopy type of partitioning. It is argued, however, that this result of the model calculations is valid only for low, but not high, nutrient availability.3. Photosynthetic capacity per unit chlorophyll, a parameter representative of within-leaf partitioning of photosynthetic resources between capacity and light harvesting, also showed plasticity in response to stand density. High values were found in open stands and in the top leaves in dense stands, whereas a low capacity per unit chlorophyll was found in shaded bottom leaves in dense stands. Plasticity in this trait was also not very important for C gain of plants in stands of contrasting densities. Here the condition was that plants have a distribution pattern found for open-stand plants. However, in the case of subordinate plants that have all their leaves in the shade cast by their taller neighbours, adjustment of photosynthetic capacity per unit chlorophyll to the level of irradiance is much more important for whole-plant C gain.Functional Ecology(2004)18, 802–811 [ABSTRACT FROM AUTHOR]

On exposure to ultraviolet radiation (UV), many plant species both reduce stem elongation and increase production of phenolic compounds that absorb in the UV region of the spectrum. To demonstrate that such developmental plasticity to UV is adaptive, it is necessary to show that the induced phenotype is both beneficial in inductive environments and maladaptive in non-inductive environments. We measured selection on stem elongation and phenolic content of seedlings of Impatiens capensis transplanted into ambient-UV and UV- removal treatments. We extended the range of phenotypes expressed, and thus the opportunity for selection in each UV treatment, by pretreating seedlings with either a low ratio of red:far-red wavelengths (R:FR), which induced stem elongation and reduced phenolic concentrations, or high R:FR, which had the opposite effect on these two phenotypic traits. Reduced stem length relative to biomass was advantageous for elongated plants under ambient UV, whereas increased elongation was favored in the UV-removal treatment. Selection favored an increase in the level of phenolics induced by UV in the ambient-UV treatment, but a decrease in phenolics in the absence of UV. These results are consistent with the hypotheses that reduced elongation and increased phenolic concentrations serve a UV- protective function and provide the first explicit demonstration in a wild species that plasticity of these traits to UV is adaptive. The observed cost to phenolics in the absence of UV may explain why many species plastically upregulate phenolic production when exposed to UV, rather than evolve constitutively high levels of these compounds. Finally, pretreatment with low R:FR simulating foliar shade did not exacerbate the fitness impact of UV exposure when plants had several weeks to acclimate to UV. This observation suggests that the evolution of adaptive shade avoidance responses to low R:FR in crowded stands will not be constrained by increased sensitivity to UV... [ABSTRACT FROM AUTHOR]

Weakening the ankle extensor muscles of cats by denervation of the synergists of the medial gastrocnemius (MG) muscle results in transient increase in yield at the ankle during early stance. Recovery of ankle function occurs over a period of 1–2 weeks, is use-dependent, and is associated with increases in the strength of reflexes from MG group I muscle afferents and an increase in the magnitude of bursts in the MG muscles during stance. These observations have led to the hypothesis that feedback from large muscle afferents is necessary for functional recovery. In this investigation we have tested this hypothesis by examining functional recovery in animals treated with pyridoxine, a drug known to destroy large muscle afferents. In four adult animals we confirmed that pyridoxine abolished the group I-mediated tendon-tap reflex in the ankle extensor muscle, and subsequently found that group I afferents from MG were either destroyed or non-conducting. Immediately after pyridoxine treatment the animals showed severe locomotor dysfunction but all recovered significantly over a period of 1 or 2 months and showed only minor kinematics deficits at the time of the muscle denervations. In all four pyridoxine-treated animals, weakening of the ankle extensors by denervation of the synergists of the MG muscle resulted in a large increase in yield at the ankle that persisted almost unchanged for a month after the operation. The magnitude of burst activity in the MG muscle during early stance of the pyridoxine-treated animals either did not increase or increased only slightly after the denervation of synergists. These observations are consistent with the hypothesis that feedback from group I afferents is necessary for functional recovery in untreated animals. [ABSTRACT FROM AUTHOR]

The vestibular system is known to participate in cardiovascular regulation during movement and postural alterations. The present study considered whether lesions of two regions of the posterior cerebellar vermis (the nodulus and uvula) that provide inputs to vestibular nucleus regions that affect control of blood pressure would alter cardiovascular responses during changes in posture. Blood pressure and heart rate were monitored in awake cats during nose-up tilts up to 60° in amplitude before and following aspiration lesions of the nodulus or uvula; in most animals, cardiovascular responses were also recorded following the subsequent removal of vestibular inputs. Lesions of the nodulus or uvula did not affect baseline blood pressure or heart rate, although cardiovascular responses during nose-up tilts were altered. Increases in heart rate that typically occurred during 60° nose-up tilt were attenuated in all three animals with lesions affecting both dorsal and ventral portions of the uvula; in contrast, the heart rate responses were augmented in the two animals with lesions mainly confined to the nodulus. Furthermore, following subsequent removal of vestibular inputs, uvulectomized animals, but not those with nodulus lesions, experienced more severe orthostatic hypotension than has previously been reported in cerebellum-intact animals with bilateral labyrinthectomies. These data suggest that the cerebellar nodulus and uvula modulate vestibulo-cardiovascular responses, although the two regions play different roles in cardiovascular regulation. [Copyright &y& Elsevier]

The genetic response of body size to temperature in the laboratory provides an interesting example of phenotypic plasticity. We found that females of Drosophila ananassae reared to adulthood at 18°C showed significant increase in body weight as compared to females reared at 25°C. At a given temperature, early productivity and lifetime productivity were the highest when the rearing and test temperature were the same. The effect of test temperature was highly significant for total productivity and early productivity. The interaction between test temperature and development temperature was also highly significant. Effect of development temperature was not significant. The females reared at 18°C showed greater body weight but their productivity was not significantly higher than smaller females reared at 25°C. Thus, the usually close relationship between size and fecundity is lost when the size change is due to rearing temperature. These findings provide evidence for adaptive plasticity in D. ananassae. We also found a negative correlation (trade-off) between longevity and productivity, the first report of such a trade-off between longevity and productivity in D. ananassae. [ABSTRACT FROM AUTHOR]

The adaptiveness of shade avoidance responses to density was studied in Picea omorika seedlings raised in a growth-room. Siblings of a synthetic population comprising 117 families from six natural populations were exposed to contrasting density conditions in order to score variation in phenotypic expression of several epicotyl and bud traits included in the shade avoidance syndrome. As predicted for the adaptive plasticity to foliage shade, epicotyl elongation traits tended toward higher, while axillary bud traits toward lower values in high-density vs. low-density conditions. Phenotypic selection analysis revealed that the elongated plants had greater relative fitness than the suppressed ones in both density treatments which could be ascribed to the effect of direct selection on epicotyl length. There was no evidence for plasticity costs associated with the expression of the shade avoidance phenotype either under low or under high density, with only a single exception. Estimates of variance component genetic correlations across densities were significantly different from unity for the majority of the seedling traits studied, indicating the existence of heritable variation within reaction norms of these traits. However, since all these correlations were positive in sign and large in magnitude, this conclusively means that the level of the additive genetic variation for plasticity in the shade-avoidance traits of P. omorika is rather low. [ABSTRACT FROM AUTHOR]

Evidence accumulates that dispersal is correlated with individual behavioural phenotype (dispersal syndrome). The evolutionary causes and consequences of such covariation depend on the degree of plasticity versus inheritance of the traits, which requires challenging experiments to implement in mobile organisms. Here, we combine a forced dispersal experiment, natural colonization and longitudinal data to establish if dispersal and aggression levels are integrated and to test their adaptive nature in pied flycatchers ( Ficedula hypoleuca ). We found that (forced) dispersers behaved more aggressively in their first breeding year after dispersal and decreased their aggression in following years. Strength of dispersal syndrome and direction of fecundity selection on aggression in newly colonized areas varied between years. We propose that the net benefits of aggression for dispersers increase under harsh conditions (e.g. low food abundance). This hypothesis now warrants further testing. Overall, this study provides unprecedented experimental evidence that dispersal syndromes can be remodelled via adaptive plasticity depending on the individuals' local breeding experience and/or year-specific ecological conditions. It highlights the importance of individual behavioural variation in population dynamics.

Vegetative traits of plants can respond directly to changes in the environment, such as those occurring under climate change. That phenotypic plasticity could be adaptive, maladaptive, or neutral. We manipulated the timing of spring snowmelt and amount of summer precipitation in factorial combination and examined responses of specific leaf area (SLA), trichome density, leaf water content (LWC), photosynthetic rate, stomatal conductance and intrinsic water-use efficiency (iWUE) in the subalpine herb Ipomopsis aggregata. The experiment was repeated in three years differing in natural timing of snowmelt. To examine natural selection, we used survival, relative growth rate, and flowering as fitness indices. A 50% reduction in summer precipitation reduced stomatal conductance and increased iWUE, and doubled precipitation increased LWC. Combining natural and experimental variation, earlier snowmelt reduced soil moisture, photosynthetic rate and stomatal conductance, and increased trichome density and iWUE. Precipitation reduction reversed the mortality selection favoring high stomatal conductance under normal and doubled precipitation, and higher LWC improved growth. Earlier snowmelt is a strong signal of climate change and can change expression of leaf morphology and gas exchange traits, just as reduced precipitation can. Stomatal conductance and SLA showed adaptive plasticity under some conditions., (© 2022 The Authors. New Phytologist © 2022 New Phytologist Foundation.)

AbstractDistinguishing between genetic, environmental, and genotype × environment effects is central to understanding geographic variation in phenotypic clines. Two of the best-documented phenotypic clines are Bergmann's rule and Allen's rule, which describe larger body sizes and shortened extremities in colder climates, respectively. Although numerous studies have found inter- and intraspecific evidence for both ecogeographic patterns, we still have a poor understanding of the extent to which these patterns are driven by genetics, environment, or both. Here, we measured the genetic and environmental contributions to Bergmann's rule and Allen's rule across introduced populations of house mice ( Mus musculus domesticus ) in the Americas. First, we documented clines for body mass, tail length, and ear length in natural populations and found that these conform to both Bergmann's rule and Allen's rule. We then raised descendants of wild-caught mice in the lab and showed that these differences persisted in a common environment and are heritable, indicating that they have a genetic basis. Finally, using a full-sib design, we reared mice under warm and cold conditions. We found very little plasticity associated with body size, suggesting that Bergmann's rule has been shaped by strong directional selection in house mice. However, extremities showed considerable plasticity, as both tails and ears grew shorter in cold environments. These results indicate that adaptive phenotypic plasticity as well as genetic changes underlie major patterns of clinal variation in house mice and likely facilitated their rapid expansion into new environments across the Americas.

Phenotypic plasticity is predicted to evolve in environmentally variable habitats, or those experiencing a high frequency of strong selection. The evolution of plasticity may however be constrained by costs or physiological limitations. In flowers, UV-absorbing pigmentation ameliorates UV damage to pollen, and is linked with elevated UV exposure. Whether plasticity contributes to this pattern remains unclear. Petals of Argentina anserina have larger UV-absorbing petal areas at high elevations where they experience higher and more variable UV exposure than low elevations. We measured UV-induced pigmentation plasticity in high- and low-elevation populations (hereafter, "high," "low"), and selection on pigmentation via male fitness. We dissected UV pigment biochemistry using metabolomics to explore biochemical mechanisms underlying plasticity. High displayed positive UV-induced pigmentation plasticity but low lacked plasticity. Selection favored elevated pigmentation under UV in high, supporting adaptive plasticity. In high, UV absorption was conferred by flavonoids produced in one flavonoid pathway branch. However, in low, UV absorption was associated with many compounds spanning multiple branches. Elevated plasticity was thus associated with reduced pigment diversity. These results are consistent with adaptive floral pigmentation plasticity in more extreme and variable environments. We discuss how biochemical underpinnings of pigmentation may permit or constrain the evolution of pigmentation plasticity., (© 2022 The Authors. Evolution © 2022 The Society for the Study of Evolution.)

The yeast Saccharomyces cerevisiae has a remarkable ability to adapt its lifestyle to fluctuating or hostile environmental conditions. This adaptation most often involves morphological changes such as pseudofilaments, biofilm formation, or cell aggregation in the form of flocs. A prerequisite for these phenotypic changes is the ability to self-adhere and to adhere to abiotic surfaces. This ability is conferred by specialized surface proteins called flocculins, which are encoded by the FLO genes family in this yeast species. This mini-review focuses on the flocculin encoded by FLO11, which differs significantly from other flocculins in domain sequence and mode of genetic and epigenetic regulation, giving it an impressive plasticity that enables yeast cells to swiftly adapt to hostile environments or into new ecological niches. Furthermore, the common features of Flo11p with those of adhesins from pathogenic yeasts make FLO11 a good model to study the molecular mechanism underlying cell adhesion and biofilm formation, which are part of the initial step leading to fungal infections. [ABSTRACT FROM AUTHOR]

Life in seasonal environments often means facing extreme environmental fluctuations. Many multicellular organisms have evolved strategies to cope with this lifestyle. Single-celled malaria parasites are no different. An elegant experiment reveals that they respond to the availability of mosquitoes to make the most of seasonal transmission opportunities. [ABSTRACT FROM AUTHOR]