The first occurrence of halophyte Oryza coarctata in the mid-southern coast of Bangladesh

Adaptive Phenotypic Plasticity: Target or By-Product of Selection in a Variable Environment?

The ability to express phenotypically plastic responses to environmental cues might be adaptive in changing environments. We studied phenotypic plasticity in mating behaviour as a response to population density and adult sex ratio in a freshwater isopod (Asellus aquaticus). A. aquaticus has recently diverged into two distinct ecotypes, inhabiting different lake habitats (reed Phragmites australis and stonewort Chara tomentosa, respectively). In field surveys, we found that these habitats differ markedly in isopod population densities and adult sex ratios. These spatially and temporally demographic differences are likely to affect mating behaviour. We performed behavioural experiments using animals from both the ancestral ecotype (“reed” isopods) and from the novel ecotype (“stonewort” isopods) population. We found that neither ecotype adjusted their behaviour in response to population density. However, the reed ecotype had a higher intrinsic mating propensity across densities. In contrast to the effects of density, we found ecotype differences in plasticity in response to sex ratio. The stonewort ecotype show pronounced phenotypic plasticity in mating propensity to adult sex ratio, whereas the reed ecotype showed a more canalised behaviour with respect to this demographic factor. We suggest that the lower overall mating propensity and the phenotypic plasticity in response to sex ratio have evolved in the novel stonewort ecotype following invasion of the novel habitat. Plasticity in mating behaviour may in turn have effects on the direction and intensity of sexual selection in the stonewort habitat, which may fuel further ecotype divergence.

Ecological speciation is a consequence of phenotypic and genetic differentiation, which is driven by divergent selection and reproductive isolation between different environments. In Elaeocarpus photiniifolia, a plant species endemic to the Bonin Islands, genetic differentiation between a shrub ecotype in dry habitats and a tree ecotype in mesic habitats occurs in the Chichijima Island Group, while gene flow between the ecotypes and migration between the habitats are feasible. To clarify environmental and genetic effects on traits different between the ecotypes, we examined the soil moisture content, nuclear microsatellite genotypes, plant height, and flowering phenology in dry and mesic habitats in two areas on Chichijima Island. The soil moisture content decreased from June to July in both areas and tended to be lower in dry habitats than in mesic habitats in July. Genetic structure indicated not only genetic differentiation between the ecotypes but also admixture between them and migration between the habitats. Both environmental and genetic effects were detected in plant height and flowering phenology: lower height and earlier flowering of the shrub ecotype in the dry habitats, indicating phenotypic plasticity in response to drought, and genetic variation between ecotypes in both traits. These findings indicate that phenotypic plasticity in response to different environments results in different flowering phenology, which facilitates reproductive isolation and genetic differentiation, leading to genetic variation in adaptive traits associated with the environments.

Phenotypic plasticity and adaptive evolution enable population persistence in response to global change. However, there are few experiments that test how these processes interact within and across generations, especially in marine species with broad distributions experiencing spatially and temporally variable temperature and pCO2. We employed a quantitative genetics experiment with the purple sea urchin, Strongylocentrotus purpuratus, to decompose family-level variation in transgenerational and developmental plastic responses to ecologically relevant temperature and pCO2. Adults were conditioned to controlled non-upwelling (high temperature, low pCO2) or upwelling (low temperature, high pCO2) conditions. Embryos were reared in either the same conditions as their parents or the crossed environment, and morphological aspects of larval body size were quantified. We find evidence of family-level phenotypic plasticity in response to different developmental environments. Among developmental environments, there was substantial additive genetic variance for one body size metric when larvae developed under upwelling conditions, although this differed based on parental environment. Furthermore, cross-environment correlations indicate significant variance for genotype-by-environment interactive effects. Therefore, genetic variation for plasticity is evident in early stages of S. purpuratus, emphasizing the importance of adaptive evolution and phenotypic plasticity in organismal responses to global change.

Fluctuating asymmetry (FA) is widely used to quantify developmental instability (DI) in ecological and evolutionary studies. It has long been recognized that FA may not exclusively originate from DI for sessile organisms such as plants, because phenotypic plasticity in response to heterogeneities in the environment might also produce FA. This study provides the first empirical evidence for this hypothesis. We reasoned that solar irradiance, which is greater on the southern side than on the northern side of plants growing in the temperate zone of the Northern Hemisphere, would cause systematic morphological differences and asymmetry associated with the orientation of plant parts. We used geometric morphometrics to characterize the size and shape of flower parts in Iris pumila grown in a common garden. The size of floral organs was not significantly affected by orientation. Shape and particularly its asymmetric component differed significantly according to orientation for three different floral parts. Orientation accounted for 10.4% of the total shape asymmetry within flowers in the falls, for 11.4% in the standards and for 2.2% in the style branches. This indicates that phenotypic plasticity in response to a directed environmental factor, most likely solar irradiance, contributes to FA of flowers under natural conditions. That FA partly results from phenotypic plasticity and not just from DI needs to be considered by studies of FA in plants and other sessile organisms.

Exploring Cost Constraints on Stem Elongation in Plants Using Phenotypic Manipulation

Seaweeds are widely assumed to be phenotypically plastic across hydrodynamic gradients, yet while many marine macroalgae exhibit intraspecific phenotypic variation that correlates with flow, researchers often fail to test whether such variation is due to plasticity or another mechanism, such as local adaptation. In this minireview, we considered mechanisms for sensing flow in seaweeds that could facilitate adaptive phenotypic plasticity across hydrodynamic gradients. We then reviewed the literature from 1900 to 2024 to see how often phenotypic variation and plasticity across hydrodynamic gradients had been observed and demonstrated in different groups of seaweeds. In the last 124 years, phenotypic variation and plasticity in response to flow have been well documented in brown algae but scarcely documented in red and green algae. This could suggest that brown algae are better able to sense and respond to flow than red and green algae, perhaps due to the intercalary meristem of many brown algae, including most kelps. However, this skewed distribution could also be the result of publication bias, as most studies involving flow have been conducted on brown algae. Only 30% of 141 papers specifically investigated if observations of phenotypic variation along hydrodynamic gradients were due to plasticity. To date, phenotypic plasticity in response to flow has been demonstrated in 20 brown algal species, five red algal species, and two green algal species. Thus, the assumption that phenotypic plasticity to flow is common across seaweeds is not particularly well supported by the literature. Mechanisms underlying plasticity to flow are poorly understood and remain a critical avenue for future research.

Warming climate has led to significant phenological advances in many plant and animal populations. Whether these advances represent evolutionary responses or phenotypic plasticity remain typically unknown. Using a 53-year-long time series of individually marked Great Tits (Parus major) and Willow Tits (Poecile montanus), we investigated whether the significant breeding time advances in these species could be explained as resulting from evolutionary responses, phenotypic plasticity, or both. In the case of both species, we did not find any evidence for changes in breeding values for timing of breeding, suggesting that the observed changes do not have a genetic and, hence, evolutionary basis. In contrast, we found that annually fluctuating environmental effects explained most of the variation in first egg-laying dates, suggesting that advances in breeding time were attributable to phenotypic plasticity. We further inferred that phenotypic plasticity in response to spring temperatures can fully explain the observed advancement of Great Tit phenology over time, whereas Willow Tits have advanced their phenology much beyond what would be expected from phenotypic plasticity in response to spring temperatures. The latter observation suggests that some other yet unidentified environmental factor, uncorrelated with spring temperatures, likely explains about half of the advancement in their breeding time.

Plants show phenotypic plasticity in response to changing or extreme abiotic environments; but over millions of years they also have co-evolved to respond to the presence of soil microbes. Studies on phenotypic plasticity in plants have focused mainly on the effects of the changing environments on plants’ growth and survival. Evidence is now accumulating that the presence of microbes can alter plant phenotypic plasticity in a broad range of traits in response to a changing environment. In this review, we discuss the effects of microbes on plant phenotypic plasticity in response to changing environmental conditions, and how this may affect plant fitness. By using a range of specific plant-microbe interactions as examples, we demonstrate that one way that microbes can alleviate the effect of environmental stress on plants and thus increase plant fitness is to remove the stress, e.g., nutrient limitation, directly. Furthermore, microbes indirectly affect plant phenotypic plasticity and fitness through modulation of plant development and defense responses. In doing so, microbes affect fitness by both increasing or decreasing the degree of phenotypic plasticity, depending on the phenotype and the environmental stress studied, with no clear difference between the effect of prokaryotic and eukaryotic microbes in general. Additionally, plants have the ability to modulate microbial behaviors, suggesting that they manipulate bacteria, enhancing interactions that help them cope with stressful environments. Future challenges remain in the identification of the many microbial signals that modulate phenotypic plasticity, the characterization of plant genes, e.g. receptors, that mediate the microbial effects on plasticity, and the elucidation of the molecular mechanisms that link phenotypic plasticity with fitness. The characterization of plant and microbial mutants defective in signal synthesis or perception, together with carefully designed glasshouse or field experiments that test various environmental stresses will be necessary to understand the link between molecular mechanisms controlling plastic phenotypes with the resulting effects on plant fitness.

Genetic diversity among and within wild populations is important in fluctuating environments. Phenotypic plasticity is also essential under environmental changes, especially those that are shorter than the species lifespan. Primula sieboldii is in danger of extinction in the wild in Japan; understanding how wild populations can respond to environmental fluctuations is important for its long‐term conservation. To examine genetic variation in phenotypic plasticity in response to temperature, we grew 38 genets in 2004 and 43 genets in 2005 derived from five wild P. sieboldii populations at three experimental sites at different altitudes. The response to temperature on the traits related to bud initiation differed most among populations. Mean budding rate was 61% at experimental site 3 (Yatsugatake) and at least 90% at experimental site 1 (Tsukuba) and 2 (Suwa). In particular, that of the Saitama population at experimental site 3 (Yatsugatake) (30.8%) was considerably lower than those of other populations, indicating that experimental site 3 (Yatsugatake) was a severe environmental condition for the Saitama population, with the mean February temperature about 9°C lower than at Saitama. Days to bud initiation of the Saitama population were significantly shorter than those of the other populations at other environmental sites, but were longer than at experimental site 3 (Yatsugatake). Phenotypic plasticity of days to bud initiation differed significantly among populations in both years. Most genets of the Saitama population died at experimental site 3 (Yatsugatake), but some had high phenotypic plasticity that allowed the population to survive in this low‐temperature environment.

Some introduced species spread rapidly beyond their native range and into novel habitats mediated by a high degree of phenotypic plasticity and/or rapid evolutionary responses. In this context, clonality has been described as a significant factor contributing to invasiveness. We studied the abiotic environment and the responses of different tussock architecture traits of the invasive cordgrass Spartina densiflora Brongn. (Poaceae). A common garden experiment and field studies of S. densiflora in salt marshes across a wide latitudinal gradient from California (USA) to British Columbia (Canada) provided a model system for an integrated study of the potential mechanisms underlying the response of invasive S. densiflora populations to changes in environmental conditions. Our results showed that S. densiflora is able to adjust to widely variable climate (specifically, air temperature and the duration of the growing season) and sediment conditions (specifically, texture and hypoxia) through phenotypical plastic key functional tussock traits (e.g. shoot density, height, above- and below-ground biomass allocation patterns). Root biomass increased in coarser sediments in contrast to rhizomes, which were more abundant in finer sediments. Above-ground biomass and leaf area index increased mainly with air temperature during summer, and more robust (taller and wider) shoots were associated with more oxygenated sediments. In view of our results, S. densiflora appears to be a halophyte with a high degree of phenotypic plasticity that would enable it to respond successfully to changes in the abiotic conditions of salt marshes driven by global climate change, such as increasing salinity and temperatures.

Grazing Intensity and Phenotypic Plasticity in the Clonal Grass Leymus chinensis

完全水淹环境中光照和溶氧对喜旱莲子草表型可塑性的影响

A few studies in the past have shown that plant diversity in terms of species richness and functional composition can modify plant defense chemistry. However, it is not yet clear to what extent genetic differentiation of plant chemotypes or phenotypic plasticity in response to diversity-induced variation in growth conditions or a combination of both is responsible for this pattern. We collected seed families of ribwort plantain (Plantago lanceolata) from six-year old experimental grasslands of varying plant diversity (Jena Experiment). The offspring of these seed families was grown under standardized conditions with two levels of light and nutrients. The iridoid glycosides, catalpol and aucubin, and verbascoside, a caffeoyl phenylethanoid glycoside, were measured in roots and shoots. Although offspring of different seed families differed in the tissue concentrations of defensive metabolites, plant diversity in the mothers' environment did not explain the variation in the measured defensive metabolites of P. lanceolata offspring. However secondary metabolite levels in roots and shoots were strongly affected by light and nutrient availability. Highest concentrations of iridoid glycosides and verbascoside were found under high light conditions, and nutrient availability had positive effects on iridoid glycoside concentrations in plants grown under high light conditions. However, verbascoside concentrations decreased under high levels of nutrients irrespective of light. The data from our greenhouse study show that phenotypic plasticity in response to environmental variation rather than genetic differentiation in response to plant community diversity is responsible for variation in secondary metabolite concentrations of P. lanceolata in the six-year old communities of the grassland biodiversity experiment. Due to its large phenotypic plasticity P. lanceolata has the potential for a fast and efficient adjustment to varying environmental conditions in plant communities of different species richness and functional composition.

Phenotypic plasticity is the ability of organisms to modify their phenotype in response to environmental changes. We estimated and compared the amount of phenotypic plasticity in response to drought in seedlings of different accessions of two varieties (var. makarikariense and var. coloratum) of Panicum coloratum, an allogamous warm season perennial grass, introduced and collected in sites in Argentina with different precipitation regimes. Amount of phenotypic plasticity was quantified in shoot/root biomass, blade/sheath biomass, specific leaf area and leaf area ratio (leaf area/total biomass) and mean phenotypic plasticity was estimated. The two genetically distinct varieties differed in the phenotypic plasticity of leaf area ratio (p = 0.008, F‐test), with var. makarikariense showing higher phenotypic plasticity. Accessions within varieties differed in phenotypic plasticity of leaf area ratio, specific leaf area, blade/sheath biomass and mean phenotypic plasticity (p < 0.05, F‐test). A strong relationship (r = 0.82, p < 0.01, F‐test) between mean phenotypic plasticity of each accession and precipitation variability was found. Relationships between phenotypic plasticity of blade/sheath biomass and leaf area ratio with annual mean precipitation were r = 0.86 and r = 0.75, respectively (p < 0.05; p < 0.01, F‐test, respectively). Evidence of a decoupling between phenotypic plasticity of above‐ versus belowground characters was apparent; outcomes on the interpretation of the variability in phenotypic plasticity and the potential applications of this variability are presented.