Variation In Phenotypic Plasticity Research Articles

Genome-wide association mapping for phenotypic plasticity in rice.

Phenotypic plasticity of plants in response to environmental changes is important for adapting to changing climate. Less attention has been paid to exploring the advantages of phenotypic plasticity in resource-rich environments to enhance the productivity of agricultural crops. Here, we examined genetic variation for phenotypic plasticity in indica rice (Oryza sativa L.) across two diverse panels: (1) a Phenomics of Rice Adaptation and Yield (PRAY) population comprising 301 accessions; and (2) a Multi-parent Advanced Generation Inter-Cross (MAGIC) indica population comprising 151 accessions. Altered planting density was used as a proxy for elevated atmospheric CO2 response. Low planting density significantly increased panicle weight per plant compared with normal density, and the magnitude of the increase ranged from 1.10 to 2.78 times among accessions for the PRAY population and from 1.05 to 2.45 times for the MAGIC population. Genome-wide-association studies validate three Environmental Responsiveness (ER) candidate alleles (qER1-3) that were associated with relative response of panicle weight to low density. Two of these alleles were tested in 13 genotypes to clarify their biomass responses during vegetative growth under elevated CO2 in Japan. Our study provides evidence for polymorphisms that control rice phenotypic plasticity in environments that are rich in resources such as light and CO2 .

Growth Pattern of Body Size in Baduy People

Understanding body size growth pattern is one of the best ways to find out biological variation in phenotypic plasticity, health and nutritional statuses, and quality of life. Optimum environment and better nutrition are associated with rapid growth, tall stature, and early puberty. However, poor living condition impacts every stage of development, which results in variation in growth rates, growth periods, and body sizes across populations. Baduy is one of traditional populations who inhabit mountainous area in Kanekes Village, Lebak Regency, Banten Province, Indonesia. The traditional obligatory duties and taboos resulted in genetic, geographic, and cultural isolations. This leads to question whether the biocultural condition affects the growth pattern of their body size. We measured the body height, weight, and mass index of 340 girls and 239 boys aged 4–30 years sampled from 39 of 61 hamlets using cross-sectional method. We found that Baduy people had prolonged growth resulting in small body size because of slow rate and low spurt. This might be a selection to save body maintenance costs in biocultural condition with poor nutrition and high physical activity.

Can individual variation in phenotypic plasticity enhance population viability?

In response to climatic and other sources of environmental variation, individuals within a population may adjust their behavioral, morphological or physiological responses to varying environmental conditions through phenotypic plasticity. In seasonal environments, time constraints related to seasonality, as well as variation in climatic factors, may affect body mass growth rates. To cope with the consequences of a harsh period, individuals may, for example, compensate for lost body mass by accelerating their growth rate in the following period. Phenotypically plastic responses like this can, therefore, directly affect body mass, which may affect individual fitness and, ultimately, population dynamics. Here, we use a well-studied population of yellow-bellied marmots, Marmota flaviventris, in Colorado to parametrize and develop an individual-based model (IBM) to investigate how phenotypically plastic responses in body mass growth rate may compensate for an individual’s bad start after a harsh period (compensatory growth), and to explore whether individual variation in compensatory growth favors population persistence under less favorable climatic scenarios. A simulation model that allowed marmots with a body mass less than the population’s average body mass to compensate their growth provided the best match with observed population sizes, suggesting the importance of trade-offs in population dynamics. We also found that compensatory growth plays an important role in decreasing the probability of extinction under both less favorable colder and random climate scenarios. Our results lead to a deeper understanding of the mechanisms that govern population fluctuations and highlight the importance of quantifying the fitness cost of phenotypically plastic responses.

Linear reaction norms of thermal limits in Drosophila: predictable plasticity in cold but not in heat tolerance

Summary Thermal limits of ectotherms have been studied extensively and are believed to be evolutionarily constrained, leaving ectotherms at risk under future climate change. Phenotypic plasticity may extend the thermal limits, but we lack detailed characterizations of thermal limit reaction norms as well as an understanding of the interspecific variation in these reaction norms. Here, we investigated the interspecific variation in phenotypic plasticity of thermal limits in 13 Drosophila species. We obtained high‐resolution reaction norms for upper and lower thermal limits across the permissive developmental thermal range (12·5–30 °C). The estimated phenotypes were then associated (while accounting for phylogeny) with climatic parameters from the species’ distributional range. All species showed linear reaction norms for cold tolerance (CTmin) and heat tolerance (CTmax) across developmental acclimation temperatures. We observed strong beneficial cold acclimation to lower temperatures in all species. Conversely, the heat acclimation response was non‐existent in some species, and decreasing or increasing with increasing developmental acclimation temperatures in other species. The degree of phenotypic plasticity of CTmin and CTmax was related neither to the basal thermal limits (trade‐off hypothesis) nor to climatic parameters connected to latitudinal distributions (latitudinal hypothesis). A substantial and linear developmental plasticity of lower thermal limits is a general characteristic of Drosophila species, which allows for straightforward application in species distribution models. In general, upper thermal limits also show linear norms of reaction, but their adaptive significance is limited and highly variable among species, making general predictions across species rather impossible. High‐resolution estimates of norms of reaction of thermal limits can considerably increase our understanding of the capacity of ectotherms to acclimate to different thermal environments. However, our understanding of the environmental drivers of the evolution of phenotypic plasticity and thus of the interspecific differences remains ambiguous, potentially constrained by limited microclimate information. A lay summary is available for this article.

Genetic Regulation of Phenotypic Plasticity and Canalisation in Yeast Growth.

The ability of a genotype to show diverse phenotypes in different environments is called phenotypic plasticity. Phenotypic plasticity helps populations to evade extinctions in novel environments, facilitates adaptation and fuels evolution. However, most studies focus on understanding the genetic basis of phenotypic regulation in specific environments. As a result, while it’s evolutionary relevance is well established, genetic mechanisms regulating phenotypic plasticity and their overlap with the environment specific regulators is not well understood. Saccharomyces cerevisiae is highly sensitive to the environment, which acts as not just external stimulus but also as signalling cue for this unicellular, sessile organism. We used a previously published dataset of a biparental yeast population grown in 34 diverse environments and mapped genetic loci regulating variation in phenotypic plasticity, plasticity QTL, and compared them with environment-specific QTL. Plasticity QTL is one whose one allele exhibits high plasticity whereas the other shows a relatively canalised behaviour. We mapped phenotypic plasticity using two parameters–environmental variance, an environmental order-independent parameter and reaction norm (slope), an environmental order-dependent parameter. Our results show a partial overlap between pleiotropic QTL and plasticity QTL such that while some plasticity QTL are also pleiotropic, others have a significant effect on phenotypic plasticity without being significant in any environment independently. Furthermore, while some plasticity QTL are revealed only in specific environmental orders, we identify large effect plasticity QTL, which are order-independent such that whatever the order of the environments, one allele is always plastic and the other is canalised. Finally, we show that the environments can be divided into two categories based on the phenotypic diversity of the population within them and the two categories have differential regulators of phenotypic plasticity. Our results highlight the importance of identifying genetic regulators of phenotypic plasticity to comprehensively understand the genotype-phenotype map.

Loss of heterophylly in aquatic plants: not ABA-mediated stress but exogenous ABA treatment induces stomatal leaves in Potamogeton perfoliatus.

Heterophyllous aquatic plants produce aerial (i.e., floating and terrestrial) and submerged leaves—the latter lack stomata—while homophyllous plants contain only submerged leaves, and cannot survive on land. To identify whether differences in morphogenetic potential and/or physiological stress responses are responsible for variation in phenotypic plasticity between two plants types, responses to abscisic acid (ABA) and salinity stress were compared between the closely related, but ecologically diverse pondweeds, Potamogeton wrightii (heterophyllous) and P. perfoliatus (homophyllous). The ABA-treated (1 or 10 μM) P. wrightii plants exhibited heterophylly and produced leaves with stomata. The obligate submerged P. perfoliatus plants were able to produce stomata on their leaves, but there were no changes to leaf shape, and stomatal production occurred only at a high ABA concentration (10 μM). Under salinity stress conditions, only P. wrightii leaves formed stomata. Additionally, the expression of stress-responsive NCED genes, which encode a key enzyme in ABA biosynthesis, was consistently up-regulated in P. wrightii, but only temporarily in P. perfoliatus. The observed species-specific gene expression patterns may be responsible for the induction or suppression of stomatal production during exposure to salinity stress. These results suggest that the two Potamogeton species have an innate morphogenetic ability to form stomata, but the actual production of stomata depends on ABA-mediated stress responses specific to each species and habitat.Electronic supplementary materialThe online version of this article (doi:10.1007/s10265-016-0844-x) contains supplementary material, which is available to authorized users.

Contrasting Plasticity in Ovariole Number Induced by A Dietary Effect of the Host Plants between Cactophilic Drosophila Species.

Under the preference-performance hypothesis, natural selection will favor females that choose oviposition sites that optimize the fitness of their offspring. Such a preference-performance relationship may entail important consequences mainly on fitness-related traits. We used the well-characterized cactus-Drosophila system to investigate the reproductive capacity in the pair of sibling species D. buzzatii and D. koepferae reared in two alternative host plants. According to our hypothesis, ovariole number (as a proxy of reproductive capacity) depends on host plant selection. Our results indicate that the capacity of D. buzzatii showed to be mild, only increasing the number of ovarioles by as much as 10% when reared in its preferred host. In contrast, D. koepferae exhibited a similar reproductive capacity across host cacti, even though it showed a preference for its primary host cactus. Our study also revealed that D. buzzatii has a larger genetic variation for phenotypic plasticity than its sibling, although ovariole number did not show clear-cut differences between species. We will discuss the weak preference-performance pattern observed in these cactophilic species in the light of nutritional and toxicological differences found between the natural host plants.

How much do phenotypic plasticity and local genetic variation contribute to phenotypic divergences along environmental gradients in widespread invasive plants? A meta‐analysis

For introduced species that have spread across a wide distributional range, phenotypic plasticity (PLA) has often been proposed as an important contributor to invasion success, because it increases the survival rate during initial colonization. In contrast, local genetic variation (LOC) has also been proposed to be important, because it could allow invaders to evolve high performance in a new habitat. While evolutionary ecologists have long been interested in understanding genetic mechanisms that allow rapid colonization and spread of species, until recently experimental tests of these concepts have been limited. As a step towards generalization in our understanding of the importance of PLA and LOC, we review the current state of the literature on this topic using meta‐analysis. Here, we focused on three fundamental questions: 1) which strategy, PLA or LOC, better explains the phenotypic divergences during invader range expansion across different environmental gradients? 2) Which species characteristics correlate with the occurrence of these different phenomena? And 3) does the detection of PLA versus LOC depend on the trait studied? Using meta‐analysis we found that plasticity explained a higher proportion of phenotypic variation regardless of the environmental gradients studied or plant growth forms. PLA predominated in clonal, self‐compatible and perennial species, while LOC predominated in annual species. The patterns were trait‐dependent: LOC was significantly more important than PLA in phenology, while opposite patterns were found in fecundity and biomass allocation. The frequent simultaneous detection of PLA and genotypic variation in PLA among invasive populations suggested that PLA might benefit from LOC to some extent. Our results also indicate that the contribution of plasticity to the competitive advantages of invasive plants may be more informative than the level of plasticity itself.SynthesisFor invasive plants that spread across a wide distributional range, understanding the mechanisms that allow rapid colonization and spread is crucial. Phenotypic plasticity (PLA) and local genetic variation (LOC) are both believed to play important roles in promoting range expansion. However, it is not clear which mechanism, PLA or LOC, contributes more to this process. According to our meta–analysis, PLA explained a higher proportion of adaptive phenotypic variation in most cases. Nevertheless, the predominance of an expansion mechanism depends on species characteristics and the trait studied. PLA may benefit from LOC to some extent. We suggest that the contribution of PLA to range expansion may better explain plant invasion success than the level of PLA itself.

Pre-adaptation or genetic shift after introduction in the invasive species Impatiens glandulifera?

Invasive exotic plants often grow fast, reproduce rapidly and display considerable phenotypic plasticity in their invasive range, which may be essential characteristics for successful invasion. However, it remains unclear whether these characteristics are already present in native populations (pre-adaptation hypothesis) or evolve after introduction (genetic shift hypothesis).To test these hypotheses we compared means and phenotypic plasticity of vegetative and reproductive traits between populations of Impatiens glandulifera collected from either the invasive (Norway) or native range (India). Seeds were sown and the resulting plants were exposed to different experimental environments in a glasshouse. We also tested whether trait means and reaction norms harbored genetic variation, as this may promote fitness in the novel environment.We did not find evidence that invasive populations of I. glandulifera grew more vigorously or produced more seeds than native populations. Phenotypic plasticity did not differ between the native and invasive range, except for the number of nodes which was more plastic in the invasive range. Genetic variation in the slope of reaction norms was absent, suggesting that the lack of change in phenotypic plasticity between native and invasive populations resulted from low genetic variation in phenotypic plasticity initially harbored by this species. Post-introduction evolution of traits thus probably did not boost the invasiveness of I. glandulifera. Instead, the species seems to be pre-adapted for invasion.We suggest that differences in habitat between the native and invasive range, more specifically the higher nutrient availability observed in the new environment, are the main factor driving the invasion of this species. Indeed, plants in the more nutrient-rich invasive range had greater seed mass, likely conferring a competitive advantage, while seed mass also responded strongly to nutrients in the glasshouse. Interactions between habitat productivity and herbivore defense may explain the lack of more vigorous growth in the new range.

Differential Expression of Ecdysone Receptor Leads to Variation in Phenotypic Plasticity across Serial Homologs.

Bodies are often made of repeated units, or serial homologs, that develop using the same core gene regulatory network. Local inputs and modifications to this network allow serial homologs to evolve different morphologies, but currently we do not understand which modifications allow these repeated traits to evolve different levels of phenotypic plasticity. Here we describe variation in phenotypic plasticity across serial homologous eyespots of the butterfly Bicyclus anynana, hypothesized to be under selection for similar or different functions in the wet and dry seasonal forms. Specifically, we document the presence of eyespot size and scale brightness plasticity in hindwing eyespots hypothesized to vary in function across seasons, and reduced size plasticity and absence of brightness plasticity in forewing eyespots hypothesized to have the same function across seasons. By exploring the molecular and physiological causes of this variation in plasticity across fore and hindwing serial homologs we discover that: 1) temperature experienced during the wandering stages of larval development alters titers of an ecdysteroid hormone, 20-hydroxyecdysone (20E), in the hemolymph of wet and dry seasonal forms at that stage; 2) the 20E receptor (EcR) is differentially expressed in the forewing and hindwing eyespot centers of both seasonal forms during this critical developmental stage; and 3) manipulations of EcR signaling disproportionately affected hindwing eyespots relative to forewing eyespots. We propose that differential EcR expression across forewing and hindwing eyespots at a critical stage of development explains the variation in levels of phenotypic plasticity across these serial homologues. This finding provides a novel signaling pathway, 20E, and a novel molecular candidate, EcR, for the regulation of levels of phenotypic plasticity across body parts or serial homologs.

An approach to estimate short‐term, long‐term and reaction norm repeatability

Summary Evolutionary ecologists increasingly study reaction norms that are expressed repeatedly within the same individual's lifetime. For example, foragers continuously alter anti‐predator vigilance in response to moment‐to‐moment changes in predation risk. Variation in this form of plasticity occurs both among and within individuals. Among‐individual variation in plasticity (individual by environment interaction or I × E) is commonly studied; by contrast, despite increasing interest in its evolution and ecology, within‐individual variation in phenotypic plasticity is not. We outline a study design based on repeated measures and a multilevel extension of random regression models that enables quantification of variation in reaction norms at different hierarchical levels (such as among and within individuals). The approach enables the calculation of repeatability of reaction norm intercepts (average phenotype) and slopes (level of phenotypic plasticity); these indices are not specific to measurement or scaling and are readily comparable across data sets. The proposed study design also enables calculation of repeatability at different temporal scales (such as short‐ and long‐term repeatability), thereby answering calls for the development of approaches enabling scale‐dependent repeatability calculations. We introduce a simulation package in the R statistical language to assess power, imprecision and bias for multilevel random regression that may be utilised for realistic data sets (unequal sample sizes across individuals, missing data, etc). We apply the idea to a worked example to illustrate its utility. We conclude that consideration of multilevel variation in reaction norms deepens our understanding of the hierarchical structuring of labile characters and helps reveal the biology in heterogeneous patterns of within‐individual variance that would otherwise remain ‘unexplained’ residual variance.

Elevated temperature is more effective than elevated [CO2 ] in exposing genotypic variation in Telopea speciosissima growth plasticity: implications for woody plant populations under climate change.

Intraspecific variation in phenotypic plasticity is a critical determinant of plant species capacity to cope with climate change. A long-standing hypothesis states that greater levels of environmental variability will select for genotypes with greater phenotypic plasticity. However, few studies have examined how genotypes of woody species originating from contrasting environments respond to multiple climate change factors. Here, we investigated the main and interactive effects of elevated [CO2 ] (CE ) and elevated temperature (TE ) on growth and physiology of Coastal (warmer, less variable temperature environment) and Upland (cooler, more variable temperature environment) genotypes of an Australian woody species Telopea speciosissima. Both genotypes were positively responsive to CE (35% and 29% increase in whole-plant dry mass and leaf area, respectively), but only the Coastal genotype exhibited positive growth responses to TE . We found that the Coastal genotype exhibited greater growth response to TE (47% and 85% increase in whole-plant dry mass and leaf area, respectively) when compared with the Upland genotype (no change in dry mass or leaf area). No intraspecific variation in physiological plasticity was detected under CE or TE , and the interactive effects of CE and TE on intraspecific variation in phenotypic plasticity were also largely absent. Overall, TE was a more effective climate factor than CE in exposing genotypic variation in our woody species. Our results contradict the paradigm that genotypes from more variable climates will exhibit greater phenotypic plasticity in future climate regimes.

Transcriptome analysis of predator- and prey-induced phenotypic plasticity in the Hokkaido salamander (Hynobius retardatus).

Predator- and prey-induced phenotypic plasticity is widely observed among amphibian species. Although ecological factors inducing diverse phenotypic responses have been extensively characterized, we know little about the molecular bases of variation in phenotypic plasticity. Larvae of the Hokkaido salamander, Hynobius retardatus, exhibit two distinct morphs: the presence of their prey, Rana pirica tadpoles, induces a broad-headed attack morph, and the presence of predatory dragonfly nymphs (Aeshna nigroflava) induces a defence morph with enlarged external gills and a high tail. To compare the genes involved in predator- and prey-induced phenotypic plasticity, we carried out a de novo transcriptome analysis of Hokkaido salamander larvae exposed to either prey or predator individuals. First, we found that the number of genes involved in the expression of the defence morph was approximately five times the number involved in the expression of the attack morph. This result is consistent with the fact that the predator-induced plasticity involves more drastic morphological changes than the prey-induced plasticity. Second, we found that particular sets of genes were upregulated during the induction of both the attack and defence morphs, but others were specific to the expression of one or the other morph. Because both shared and unique molecular mechanisms were used in the expression of each morph, the evolution of a new plastic phenotype might involve both the co-option of pre-existing molecular mechanisms and the acquisition of novel regulatory mechanisms.

Utilizing intraspecific variation in phenotypic plasticity to bolster agricultural and forest productivity under climate change.

Climate change threatens the ability of agriculture and forestry to meet growing global demands for food, fibre and wood products. Information gathered from genotype-by-environment interactions (G × E), which demonstrate intraspecific variation in phenotypic plasticity (the ability of a genotype to alter its phenotype in response to environmental change), may prove important for bolstering agricultural and forest productivity under climate change. Nonetheless, very few studies have explicitly quantified genotype plasticity-productivity relationships in agriculture or forestry. Here, we conceptualize the importance of intraspecific variation in agricultural and forest species plasticity, and discuss the physiological and genetic factors contributing to intraspecific variation in phenotypic plasticity. Our discussion highlights the need for an integrated understanding of the mechanisms of G × E, more extensive assessments of genotypic responses to climate change under field conditions, and explicit testing of genotype plasticity-productivity relationships. Ultimately, further investigation of intraspecific variation in phenotypic plasticity in agriculture and forestry may prove important for identifying genotypes capable of increasing or sustaining productivity under more extreme climatic conditions.

Can facilitation influence the spatial genetics of the beneficiary plant population?

Summary Plant facilitation is a positive interaction where a nurse or nurse plant community alters the local conditions, improving the lifetime fitness of other beneficiary plants. In stressful environments, a common consequence is the formation of discrete vegetation patches under nurse plants, surrounded by open space. The consequences of such spatial patterns have been studied mostly at the community level. At the population level, facilitation causes a distribution of beneficiary individuals that could have intraspecific genetic consequences. The spatial patchiness and the increase in local aggregation can potentially affect the population fine‐scale genetic structure. In addition, marked microenvironmental differences under nurses versus outside could lead to plastic phenotypic variation between facilitated and non‐facilitated individuals, as for example reproductive asynchrony, potentially producing assortative mating. This study tests the hypothesis that plant facilitation can have genetic consequences for the population of a beneficiary plant (Euphorbia nicaeensis) by affecting its spatial genetic structure and mating patterns between subpopulations of facilitated and non‐facilitated individuals. Facilitation in this system creates an aggregated distribution of beneficiary individuals compared to a minority of non‐facilitated individuals that grow on the open ground. Facilitation also leads to slight phenological differences mediated by strong microenvironmental differences created by nurses compared to the open ground. Yet a molecular analysis showed that, although there is fine‐scale spatial genetic structure in this system, there is no evidence that it is caused by facilitation. Numerical simulations further showed that spatial genetic patterns in the population are little influenced by the phenological mismatch observed in the field. Synthesis. Facilitation leads to the strong spatial aggregation of beneficiary plants and desynchronizes their flowering phenology, but the magnitude of these effects is not enough to have local genetic consequences in our study system. Facilitation seems thus to have a homogenizing role by allowing the persistence of a diverse gene pool in populations in harsh environments, rather than promoting genetic differentiation. Further information on other systems where facilitation produces stronger spatial or phenological effects on facilitated plants is needed to fill our large knowledge gap on the genetic effects of facilitation.

Variation in phenotypic plasticity for native and invasive populations of Bromus tectorum

Phenotypic plasticity is often considered important for invasive plant success, yet relatively few studies have assessed plasticity in both native and invasive populations of the same species. We examined the plastic response to temperature for Bromus tectorum populations collected from similar shrub-steppe environments in the Republics of Armenia and Georgia, where it is native, and along an invasive front in California and Nevada. Plants were grown in growth chambers in either ‘warm’ (30/20 °C, day/night) or ‘cold’ (10/5 °C) conditions. Invasive populations exhibited greater adaptive plasticity than natives for freezing tolerance (as measured by chlorophyll a fluorescence), such that invasive populations grown in the cold treatment exhibited the highest tolerance. Invasive populations also exhibited more rapid seedling emergence in response to warm temperatures compared to native populations. The climatic conditions of population source locations were related to emergence timing for invasive populations and to freezing tolerance across all populations combined. Plasticity in growth-related traits such as biomass, allocation, leaf length, and photosynthesis did not differ between native and invasive populations. Rather, some growth-related traits were very plastic across all populations, which may help to dampen differences in biomass in contrasting environments. Thus, invasive populations were found to be particularly plastic for some important traits such as seedling emergence and freezing tolerance, but plasticity at the species level may also be an important factor in the invasive ability of B. tectorum.

Genotype-environment interactions affecting preflowering physiological and morphological traits of Brassica rapa grown in two watering regimes.

Plant growth and productivity are greatly affected by drought, which is likely to become more threatening with the predicted global temperature increase. Understanding the genetic architecture of complex quantitative traits and their interaction with water availability may lead to improved crop adaptation to a wide range of environments. Here, the genetic basis of 20 physiological and morphological traits is explored by describing plant performance and growth in a Brassica rapa recombinant inbred line (RIL) population grown on a sandy substrate supplemented with nutrient solution, under control and drought conditions. Altogether, 54 quantitative trait loci (QTL) were identified, of which many colocated in 11 QTL clusters. Seventeen QTL showed significant QTL–environment interaction (Q×E), indicating genetic variation for phenotypic plasticity. Of the measured traits, only hypocotyl length did not show significant genotype–environment interaction (G×E) in both environments in all experiments. Correlation analysis showed that, in the control environment, stomatal conductance was positively correlated with total leaf dry weight (DW) and aboveground DW, whereas in the drought environment, stomatal conductance showed a significant negative correlation with total leaf DW and aboveground DW. This correlation was explained by antagonistic fitness effects in the drought environment, controlled by a QTL cluster on chromosome A7. These results demonstrate that Q×E is an important component of the genetic variance and can play a great role in improving drought tolerance in future breeding programmes.

A synthetic framework for modeling the genetic basis of phenotypic plasticity and its costs

The phenotype of an individual is controlled not only by its genes, but also by the environment in which it grows. A growing body of evidence shows that the extent to which phenotypic changes are driven by the environment, known as phenotypic plasticity, is also under genetic control, but an overall picture of genetic variation for phenotypic plasticity remains elusive. Here, we develop a model for mapping quantitative trait loci (QTLs) that regulate environment-induced plastic response. This model enables geneticists to test whether there exist actual QTLs that determine phenotypic plasticity and, if there are, further test how plasticity QTLs control the costs of plastic response by dissecting the genetic correlation of phenotypic plasticity and trait value. The model was used to analyze real data for grain yield of winter wheat (Triticum aestivum), leading to the detection of pleiotropic QTLs and epistatic QTLs that affect phenotypic plasticity and its cost in this crop.

Clonal Variation in Growth Plasticity within a Bosmina longirostris Population: The Potential for Resistance to Toxic Cyanobacteria

Many aquatic organisms respond phenotypically, through morphological, behavioral, and physiological plasticity, to environmental changes. The small-size cladoceran Bosmina longirostris , a dominant zooplankter in eutrophic waters, displayed reduced growth rates in response to the presence of a toxic cyanobacterium, Microcystis aeruginosa , in their diets. The magnitude of growth reduction differed among 15 clones recently isolated from a single population. A significant interaction between clone and food type indicated a genetic basis for the difference in growth plasticity. The variation in phenotypic plasticity was visualized by plotting reaction norms with two diets. The resistance of each clone to dietary cyanobacteria was measured as the relative change in growth rates on the “poor” diet compared with the “good” diet. The enhanced resistance to M . aeruginosa in B . longirostris was derived from both the reduced slope of reaction norms and the increased mean growth rates with two diets. The large clonal variation within a B . longirostris population may contribute to local adaptation to toxic cyanobacteria and influence ecosystem function via clonal succession.

Conspecific Plasticity and Invasion: Invasive Populations of Chinese Tallow (Triadica sebifera) Have Performance Advantage over Native Populations Only in Low Soil Salinity

Global climate change may increase biological invasions in part because invasive species may have greater phenotypic plasticity than native species. This may be especially important for abiotic stresses such as salt inundation related to increased hurricane activity or sea level rise. If invasive species indeed have greater plasticity, this may reflect genetic differences between populations in the native and introduced ranges. Here, we examined plasticity of functional and fitness-related traits of Chinese tallow (Triadica sebifera) populations from the introduced and native ranges that were grown along a gradient of soil salinity (control: 0 ppt; Low: 5 ppt; Medium: 10 ppt; High: 15 ppt) in a greenhouse. We used both norm reaction and plasticity index (PIv) to estimate the conspecific phenotypic plasticity variation between invasive and native populations. Overall, invasive populations had higher phenotypic plasticity of height growth rate (HGR), aboveground biomass, stem biomass and specific leaf area (SLA). The plasticity Index (PIv) of height growth rate (HGR) and SLA each were higher for plants from invasive populations. Absolute performance was always comparable or greater for plants from invasive populations versus native populations with the greatest differences at low stress levels. Our results were consistent with the “Master-of-some” pattern for invasive plants in which the fitness of introduced populations was greater in more benign conditions. This suggests that the greater conspecific phenotypic plasticity of invasive populations compared to native populations may increase invasion success in benign conditions but would not provide a potential interspecific competitive advantage in higher salinity soils that may occur with global climate change in coastal areas.