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Phenotypic Plasticity (phenotypic + plasticity)
Kinds of Phenotypic Plasticity Selected AbstractsCOSTS AND LIMITS OF PHENOTYPIC PLASTICITY IN ISLAND POPULATIONS OF THE COMMON FROG RANA TEMPORARIA UNDER DIVERGENT SELECTION PRESSURESEVOLUTION, Issue 6 2009Martin I. Lind Costs and limits are assumed to be the major constraints on the evolution of phenotypic plasticity. However, despite their expected importance, they have been surprisingly hard to find in natural populations. It has therefore been argued that natural selection might have removed high-cost genotypes in all populations. However, if costs of plasticity are linked to the degree of plasticity expressed, then high costs of plasticity would only be present in populations where increased plasticity is under selection. We tested this hypothesis by investigating costs and limits of adaptive phenotypic plasticity in development time in a common garden study of island populations of the common frog Rana temporaria, which have varying levels of development time and phenotypic plasticity. Costs of plasticity were only found in populations with high-plastic genotypes, whereas the populations with the most canalized genotypes instead had a cost of canalization. Moreover, individuals displaying the most extreme phenotypes also were the most plastic ones, which mean we found no limits of plasticity. This suggests that costs of plasticity increase with increased level of plasticity in the populations, and therefore costs of plasticity might be more commonly found in high-plastic populations. [source] PHENOTYPIC PLASTICITY OF HERMAPHRODITE SEX ALLOCATION PROMOTES THE EVOLUTION OF SEPARATE SEXES: AN EXPERIMENTAL TEST OF THE SEX-DIFFERENTIAL PLASTICITY HYPOTHESIS USING SAGITTARIA LATIFOLIA (ALISMATACEAE)EVOLUTION, Issue 4 2008Marcel E. Dorken Separate sexes can evolve under nuclear inheritance when unisexuals have more than twice the reproductive fitness of hermaphrodites through one sex function (e.g., when females have more than twice the seed fertility of hermaphrodites). Because separate sexes are thought to evolve most commonly via a gynodioecious intermediate (i.e., populations in which females and hermaphrodites cooccur), the conditions under which females can become established in populations of hermaphrodites are of considerable interest. It has been proposed that resource-poor conditions could promote the establishment of females if hermaphrodites are plastic in their sex allocation and allocate fewer resources to seed production under these conditions. If this occurs, the seed fertility of females could exceed the doubling required for the evolution of unisexuality under low-, but not high-resource conditions (the sex-differential plasticity hypothesis). We tested this hypothesis using replicate experimental arrays of the aquatic herb Sagittaria latifolia grown under two fertilizer treatments. The results supported the sex-differential plasticity hypothesis, with females having more than twice the seed fertility of hermaphrodites under low-, but not high-fertilizer conditions. Our findings are consistent with the idea that separate sexes are more likely to evolve under unfavorable conditions. [source] PRELIMINARY ANALYSIS OF QUANTITATIVE GENETICS AND PHENOTYPIC PLASTICITY IN AULACOSEIRA SUBARCTICA (BACILLAR-IOPHYTA)JOURNAL OF PHYCOLOGY, Issue 2000S. M. Edgar Several clones of Aulacoseira subarctica were isolated from Yellowstone, Lewis, and East Rosebud Lakes (Montana, Wyoming). Two to four clones from each lake were grown in batch cultures under three light intensities, 2, 11.4 and 115 ,E m,2 s,1. Clones were conditioned to their light environment for a three-week period. Inoculants from the conditioned clones taken during log phase of growth, were grown until in log phase, then samples were collected. Five randomly chosen valves for 2 replicates of each clone were examined using a scanning electron microscope and captured on film at a magnification of 20,000x. Each image was digitized and quantitative morphometric characters were measured. A preliminary quantitative genetic analysis was performed on selected characters within each light environment. Plasticity of characters within clones across the three light regimes were also examined. The amount of variability found within characters in A. subarctica will be discussed in terms of environmental, genetic, and microenvironmental sources. [source] Phenotypic Plasticity of Life History Characteristics: Quantitative Analysis of Delayed Reproduction of Green Foxtail (Setaria viridis) in the Songnen Plain of ChinaJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 6 2008Hai-Yan Li Abstract Green foxtail (Setaria viridis L.) is a common weed species in temperate regions. Research on the effect of delayed reproduction on the phenotypic plasticity and regularity of the vegetative and reproductive growth is of vital significance for understanding population regulation and control of the weed in the growing season. Green foxtail seeds were sown every 10 days from 25 June to 24 August of 2004. The growth and production metrics were measured via harvesting tufts and statistical analysis was carried out. The results showed that the reproductive tillers, seed number, seed biomass and one thousand-seed weight of plants at the first sowing (25 June) approximately increased 28.8, 7 827.0, 1 104.0 and 12.3 times compared with that at the last sowing (24 August), respectively. Total tillers, reproductive tillers and height increased linearly as the reproductive period delayed, however, biomass increased exponentially. Quadratic equations best explained the relationships between the delayed reproductive period and seed number, inflorescence length, one thousand-seed weight, seed biomass. Based on the quantity and quality of seed production, weeding young seedlings emerging before July can be the most effective weed-control strategy in the Songnen Plain. [source] Implications of Genotypic Diversity and Phenotypic Plasticity in the Ecophysiological Success of CAM Plants, Examined by Studies on the Vegetation of Madagascar,PLANT BIOLOGY, Issue 3 2001M. Kluge Abstract: On the basis of ,13C-values, genotypic diversity and phenotypic plasticity of CAM behaviour in plants of the Malagasy vegetation is surveyed. The study compares CAM patterns performed in the wild on the levels of genera (Kalanchoë [Crassulaceae], Angraecum [Orchidaceae], Lissochilus [Orchidaceae] and Rhipsalis [Cactaceae]), on the level of a family (Didiereaceae) and finally on the level of a common growth form, namely in leafless orchids. For Rhipsalis, also non-Malagasy species were included in the comparison. The genus Kalanchoë was found to be dominated by species representing the CAM-physiotype with CO2 fixation taking place only during the night, whereas the CAM/C3- and the C3-physiotypes (with limited intrinsic CAM potential) were less frequent. The opposite holds true for Angraecum. In the genus Rhipsalis, in the Didiereacean family and in the leafless orchids only the CAM-physiotype is represented. The photosynthetic physiotypes of CAM plants were found to be related to the environmental conditions of the habitat. That is, strong CAM performers are typically abundant in the dry climatic zones or at otherwise dry niches, species of the C3-physiotype (possibly with weak intrinsic capability of CAM performance) are distributed at humid sites and those of the CAM/C3-physiotype occupy sites with medium and changing exposure to stress. Phenotypic plasticity of CAM, as indicated by the intraspecific variability of the ,13C-values, was lower in the CAM-physiotype compared with the CAM/C3-physiotype. Our data support the view that strong stress leads to the dominance of highly adapted specialists among the CAM plants, with low phenotypic plasticity of the photosynthetic behaviour, whereas medium stress advances the unfolding of plastic CAM behaviour. Moreover, the data suggest that genera comprising all three physiotypes (Kalanchoë, Angraecum) are dispersed all over Madagascar, whilst groups comprising only strong CAM performers are restricted to limited areas or special types of habitats. This suggests that both genotypic diversity and phenotypic plasticity are important factors for the ecophysiological success of CAM. [source] Phenotypic plasticity in number of glomeruli and sensory innervation of the antennal lobe in leaf-cutting ant workers (A. vollenweideri)DEVELOPMENTAL NEUROBIOLOGY, Issue 4 2010Christina Kelber Abstract In the leaf-cutting ant Atta vollenweideri, the worker caste exhibits a pronounced size-polymorphism, and division of labor is dependent on worker size (alloethism). Behavior is largely guided by olfaction, and the olfactory system is highly developed. In a recent study, two different phenotypes of the antennal lobe of Atta vollenweideri workers were found: MG- and RG-phenotype (with/without a macroglomerulus). Here we ask whether the glomerular numbers are related to worker size. We found that the antennal lobes of small workers contain ,390 glomeruli (low-number; LN-phenotype), and in large workers we found a substantially higher number of ,440 glomeruli (high-number; HN-phenotype). All LN-phenotype workers and some small HN-phenotype workers do not possess an MG (LN-RG-phenotype and HN-RG-phenotype), and the remaining majority of HN-phenotype workers do possess an MG (HN-MG-phenotype). Using mass-staining of antennal olfactory receptor neurons we found that the sensory tracts divide the antennal lobe into six clusters of glomeruli (T1,T6). In LN-phenotype workers, ,50 glomeruli are missing in the T4-cluster. Selective staining of single sensilla and their associated receptor neurons revealed that T4-glomeruli are innervated by receptor neurons from the main type of olfactory sensilla, the Sensilla trichodea curvata. The other type of olfactory sensilla (Sensilla basiconica) exclusively innervates T6-glomeruli. Quantitative analyses of differently sized workers revealed that the volume of T6 glomeruli scales with the power of 2.54 to the number of Sensilla basiconica. The results suggest that developmental plasticity leading to antennal-lobe phenotypes promotes differences in olfactory-guided behavior and may underlie task specialization within ant colonies. © 2009 Wiley Periodicals, Inc. Develop Neurobiol 70: 222,234, 2010. [source] Phenotypic plasticity, polymorphism and phylogeny within placodermsACTA ZOOLOGICA, Issue 2009K. Trinajstic Abstract Intraspecies variation, polymorphism and asymmetric traits are observed within two families of Arthrodira, the Incisoscutidae and Camuropiscidae, from the Gogo Formation in northern Western Australia. Individual plates of the head and trunk shield show considerable variation between individuals. Plates that show the greatest degree polymorphic traits are the rostral (R), marginal (M), submarginal (SM), preorbital (PrO), anterior dorsolateral, anterior median ventral (AMV) and posterior ventrolateral (PVL) plates. The paths of the sensory line canals are the most variable feature and the dermal plates of the cheek show the greatest asymmetry. It is apparent that if anatomical data in arthrodires are to be interpreted with greater precision, detailed knowledge of intraspecies variation, polymorphic and asymmetric traits is essential. How these variables are treated in cladistic analysis is also critical. Here multistate characters were coded differently in five discrete analyses, each analysis yielding a different number of trees and relationships. It was concluded that including and coding for multistate characters gave the most robust tree. In addition, further morphological characters from a new specimen of Gogosteus sarahae Long (1994) indicates many of the characters used to separate this genus from Incisoscutum are inconsistent and so it is here considered that the genus Gogosteus is a junior synonym of Incisoscutum. [source] Achieving high sexual size dimorphism in insects: females add instarsECOLOGICAL ENTOMOLOGY, Issue 3 2007TOOMAS ESPERK Abstract 1.,In arthropods, the evolution of sexual size dimorphism (SSD) may be constrained by a physiological limit on growth within each particular larval instar. A high SSD could, however, be attained if the larvae of the larger sex pass through a higher number of larval instars. 2.,Based on a survey of published case studies, the present review shows that sex-related difference in the number of instars is a widespread phenomenon among insects. In the great majority of species with a sexually dimorphic instar number, females develop through a higher number of instars than males. 3.,Female-biased sexual dimorphism in final sizes in species with sexually dimorphic instar number was found to considerably exceed a previously estimated median value of SSD for insects in general. This suggests a causal connection between high female-biased SSD, and additional instars in females. Adding an extra instar to larval development allows an insect to increase its adult size at the expense of prolonged larval development. 4.,As in the case of additional instars, SSD is fully formed late in ontogeny, larval growth schedules and imaginal sizes can be optimised independently. No conflict between selective pressures operating in juvenile and adult stages is therefore expected. 5.,In most species considered, the number of instars also varied within the sexes. Phenotypic plasticity in instar number may thus be a precondition for a sexual difference in instar number to evolve. [source] Conspicuous extra-floral nectaries are inducible in Vicia fabaECOLOGY LETTERS, Issue 6 2003Edward B. Mondor Abstract Mutualistic interactions are dynamic associations that vary depending on the costs and benefits to each of the interacting parties. Phenotypic plasticity in mutualistic interactions allows organisms to produce rewards to attract mutualists when the benefits of their presence outweigh the costs of producing the rewards. In ant,plant defensive mutualisms, defences are indirect as plants produce extra-floral nectaries (EFN) to attract predatory ants to deter herbivores. Here we demonstrate that in broad bean, Vicia faba, the overall number of EFNs on a plant increases dramatically following leaf damage. In two damage treatments, removal of: (1) one-third of one leaf in a single leaf pair or (2) one-third of both halves of a single leaf pair, resulted in a 59 and 106% increase in the number of EFNs on the plants, respectively, over 1 week. We suggest that the increased production of visually conspicuous EFNs is an adaptive inducible response, to attract predatory arthropods when risk of herbivory increases. [source] PATTERNS OF PHENOTYPIC AND GENETIC VARIATION FOR THE PLASTICITY OF DIAPAUSE INCIDENCEEVOLUTION, Issue 7 2007Wade E. Winterhalter Phenotypic plasticity describes an organism's ability to produce multiple phenotypes in direct response to its environmental conditions. Over the past 15 years empiricists have found that this plasticity frequently exhibits geographic variation and often possesses a significant heritable genetic basis. However, few studies have examined both of these aspects of plasticity simultaneously. Here, we examined both the geographic and genetic variations of the plasticity for diapause incidence (the proportion of eggs that enter an arrested state of development capable of surviving over the winter) relative to temperatures and photoperiods associated with long and short season environments across six populations of the striped ground cricket, Allonemobius socius, using a half-sibling split brood quantitative genetic design. We found that plasticity, as measured by the slope of the reaction norm, was greater in the southern-low altitude region (where populations are bivoltine) relative to the southern-high and northern-low altitude regions (where populations are univoltine). However, the heritability of plasticity was only significantly different from zero in univoltine populations that experienced "intermediate" natal season lengths. These patterns suggest that selection may favor the plasticity of diapause incidence in bivoltine regions, but act against plasticity in regions in which populations are univoltine. Furthermore, our data suggest that under "intermediate" natal season length conditions, the interplay between local adaptation and gene flow may keep the plasticity of diapause incidence low (but still significant) while maintaining its genetic variation. As such, this study not only provides a novel observation into the geographic variation of phenotypic plasticity, but also provides much needed groundwork for tests of its adaptive significance. [source] Phenotypic plasticity in insects: the effects of substrate color on the coloration of two ground-hopper speciesEVOLUTION AND DEVELOPMENT, Issue 3 2008Axel Hochkirch SUMMARY The question of how phenotypic variation is maintained within populations has long been a central issue in evolutionary biology. Most of these studies focused on the maintenance of genetic variability, but the phenotype of organisms may also be influenced by environmental cues experienced during ontogeny. Color polymorphism has received particular attention in evolutionary studies as it has strong fitness consequences. However, if body coloration is influenced by the environment, any conclusions on evolutionary consequences of fitness trade-offs can be misleading. Here we present data from a laboratory experiment on the influence of substrate color on three aspects of the coloration of two ground-hopper species, Tetrix subulata and Tetrix ceperoi. We reared hatchlings either on dark or on light substrates, using a split-brood design. Although the type of pronotal pattern changed mainly in response to nymphal development, the basic color was strongly influenced by the substrate color. In both species, black and dark olive color morphs were found more frequently on the dark substrate, whereas the gray color morph dominated on the light substrate. These findings have considerable implications for our understanding of color morph evolution as they show that color polymorphism may not only be maintained by natural selection acting on discrete color morphs, but also by phenotypic plasticity, which enables organisms to adjust to the environmental conditions experienced during ontogeny. This facultative morphology is opposing to the prevailing view of color morph adaptation, which assumes a purely genetic determination and co-evolution of discrete color morphs with life history traits. [source] Development and evolution of adaptive polyphenismsEVOLUTION AND DEVELOPMENT, Issue 1 2003H. Frederik Nijhout SUMMARY Phenotypic plasticity is the primitive character state for most if not all traits. Insofar as developmental and physiological processes obey the laws of chemistry and physics, they will be sensitive to such environmental variables as temperature, nutrient supply, ionic environment, and the availability of various macro- and micronutrients. Depending on the effect this phenotypic plasticity has on fitness, evolution may proceed to select either for mechanisms that buffer or canalize the phenotype against relevant environmental variation or for a modified plastic response in which some ranges of the phenotypic variation are adaptive to particular environments. Phenotypic plasticity can be continuous, in which case it is called a reaction norm, or discontinuous, in which case it is called a polyphenism. Although the morphological discontinuity of some polyphenisms is produced by discrete developmental switches, most polyphenisms are due to discontinuities in the environment that induce only portions of what is in reality a continuous reaction norm. In insect polyphenisms, the environmental variable that induces the alternative phenotype is a token stimulus that serves as a predictor of, but is not itself, the environment to which the polyphenism is an adaptation. In all cases studied so far, the environmental stimulus alters the endocrine mechanism of metamorphosis by altering either the pattern of hormone secretion or the pattern of hormone sensitivity in different tissues. Such changes in the patterns of endocrine interactions result in the execution of alternative developmental pathways. The spatial and temporal compartmentalization of endocrine interactions has produced a developmental mechanism that enables substantial localized changes in morphology that remain well integrated into the structure and function of the organism. [source] Phenotypic plasticity in pigmentation in Daphnia induced by UV radiation and fish kairomonesFUNCTIONAL ECOLOGY, Issue 4 2004R. TOLLRIAN Summary 1Planktonic organisms are exposed to harmful ultraviolet (UV) radiation. Pigmentation offers protection but at the same time increases visibility, and therefore vulnerability, to visually orienting predators such as fish. As an adaptation against fish predation, zooplankton should be transparent, though this would leave them less protected against UV radiation. Thus both adaptations would appear to be mutually exclusive. However, phenotypic plasticity in pigmentation could allow flexible adaptation to both environmental situations. 2We tested the hypothesis that Daphnia should be able to change their level of pigmentation in response to fish kairomone and/or UV radiation using four species of Daphnia. 3Daphnia hyalina Leydig increased pigmentation under UV radiation and D. pulex Leydig reduced pigmentation in the fish kairomone treatment. Both species live in habitats with variable UV and fish impact. 4Daphnia cucullata Sars and D. middendorffiana Fischer showed no reaction, probably because of their extreme adaptations: D. middendorffiana is strongly pigmented and seems to be adapted to high UV-B impact and an absence of fish in its arctic habitat. In contrast, D. cucullata has evolved in coexistence with fish. It can afford being nearly transparent because it lives in eutrophic lakes where UV-B is not relevant. 5Our data on four species suggest that plasticity in pigmentation might be common in Daphnia adapted to environments with contrasting or variable selection pressures. [source] Phenotypic plasticity of body size at different temperatures in a planktonic rotifer: mechanisms and adaptive significanceFUNCTIONAL ECOLOGY, Issue 6 2002C. P. Stelzer Summary 1Larger body size at low temperatures is a commonly observed phenomenon in ectothermic organisms. The mechanisms that lead to this pattern and its possible adaptive significance were studied in laboratory experiments using the parthenogenetically reproducing rotifer Synchaeta pectinata. 2At low temperatures of 4 °C mean body volume was 46% larger than in individuals cultured at 12 °C. Egg volume was 35% larger in low vs high temperatures. 3Larger body size at low temperatures was caused by two mechanisms. First, when exposed to low temperatures, mothers laid larger eggs and the hatchlings of these eggs developed into larger adults (irrespective of temperature). Second, individuals cultured at low temperatures grew to a larger body size during their juvenile phase. The former mechanism had a greater influence on adult size than the latter. 4The production of larger eggs at low temperatures seemed to be due to a higher reproductive investment into individual offspring as it occurred independently of differences in maternal size. 5Life table experiments showed that offspring from small eggs (produced at high temperatures) had a significantly higher population growth rate than offspring from large eggs, when cultured at high temperatures. This was mainly due to an increase in fertility during the first days of adult life. [source] Phenotypic plasticity in a maternal trait in red deerJOURNAL OF ANIMAL ECOLOGY, Issue 2 2005DANIEL H. NUSSEY Summary 1Phenotypic plasticity and microevolution represent the two processes by which phenotypic traits in a population can track environmental change. While there is a growing literature documenting microevolution in reproductive traits in naturally occurring animal populations, few studies to date have examined either between-individual variation in levels of plasticity or how selection acts on plasticity. 2We present here mixed-effect linear models analysing changes in calving date in relation to autumn rainfall observed over a 30-year study of 2147 red deer on the Isle of Rum, Scotland. The study period is characterized by a phase of low and rising population density (up to and including 1980), followed by a phase of high and fluctuating population density (1981 to present). 3Variation within individual females explained a population-level trend of delayed calving dates following years of high autumn rainfall. There was significant variation between females both in their average calving dates and in their individual plastic responses of calving date to autumn rainfall. 4Females born in the low population density phase were, on average, phenotypically plastic for the calving date,autumn rainfall relationship, and showed significant variation in plasticity. Selection favoured individuals with early average calving dates among these females. 5Among females born at high population density, there was on average no significant plasticity for calving date, but variation in plastic responses was still present. Selection favoured females with increasingly positive plastic responses of calving date to autumn rainfall. 6We argue that early experience of high population density affects the physiological condition of females, making an environmental response (calving early following dry autumns) in later life physiologically untenable for all but a few high quality individuals. These same few individuals also tend to be fitter and have higher reproductive success. [source] Mechanism of a plastic phenotypic response: predator-induced shell thickening in the intertidal gastropod Littorina obtusataJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 3 2007J. I. BROOKES Abstract Phenotypic plasticity has been the object of considerable interest over the past several decades, but in few cases are mechanisms underlying plastic responses well understood. For example, it is unclear whether predator-induced changes in gastropod shell morphology represent an active physiological response or a by-product of reduced feeding. We address this question by manipulating feeding and growth of intertidal snails, Littorina obtusata, using two approaches: (i) exposure to predation cues from green crabs Carcinus maenas and (ii) reduced food availability, and quantifying growth in shell length, shell mass, and body mass, as well as production of faecal material and shell micro-structural characteristics (mineralogy and organic fraction) after 96 days. We demonstrate that L. obtusata actively increases calcification rate in response to predation threat, and that this response entails energetic and developmental costs. That this induced response is not strictly tied to the animal's behaviour should enhance its evolutionary potential. [source] Variation in Reproductive Behaviour within a Sex:Neural Systems and Endocrine ActivationJOURNAL OF NEUROENDOCRINOLOGY, Issue 7 2002T. Rhen Abstract Intrasexual variation in reproductive behaviour, morphology and physiology is taxonomically widespread in vertebrates, and is as biologically and ecologically significant as the differences between the sexes. In this review, we examine the diverse patterns of intrasexual variation in reproductive behaviours within vertebrates. By illustrating the genetic, cellular, hormonal and/or neural mechanisms underlying behavioural variation in a number of species, another level of complexity is added to studies of brain organization and function. Such information increases our understanding of the unique and conserved mechanisms underlying sex and individual differences in behaviour in vertebrates as a whole. Here, we show that intrasexual variation in behaviour may be discrete or continuous in nature. Moreover, this variation may be due to polymorphism at a single genetic locus or many loci, or may even be the result of phenotypic plasticity. Phenotypic plasticity simply refers to cases where a single genotype (or individual) can produce (or display) different phenotypes. Defined in this way, plasticity subsumes many different types of behavioural variation. For example, some behavioural phenotypes are established by environmental factors during early ontogeny, others are the result of developmental transitions from one phenotype early in life to another later in life, and still other strategies are facultative with different behaviours displayed in different social contexts. [source] Phenotypic plasticity of anuran larvae: environmental variables influence body shape and oral morphology in Rana temporaria tadpolesJOURNAL OF ZOOLOGY, Issue 2 2002Miguel Vences Abstract Environmental variables shaped the morphology of tadpoles of the common frog, Rana temporaria, in various ways at the Pyrenean locality Circo de Piedrafita. Examining only specimens in similar developmental stages, those from small ponds (with higher temperature and higher tadpole density) had lower growth rates, lower relative tail height, lower relative body width and fewer labial keratodonts and keratodont rows. The variation in keratodonts may have been caused by heterochrony related to the slower growth rate. The number of lingual papillae also differed between ponds but was not related to pond size. Higher predator densities caused a higher percentage of damaged tails and a lower relative tail length in specimens with apparently intact tails, probably as a result of incomplete regeneration after mutilations earlier in development. [source] Phenotypic plasticity , contrasting species-specific traits induced by identical environmental constraintsNEW PHYTOLOGIST, Issue 3 2004John A. Strand No abstract is available for this article. [source] Phenotypic plasticity in seedling defense strategies: compensatory growth and chemical inductionOIKOS, Issue 6 2008Kasey E. Barton Phenotypic plasticity in growth (leading to compensation) and secondary chemical production (leading to induction) in response to herbivory are key defense strategies in adult plants, but their role in seedling defense remains unclear. A pair of greenhouse studies was conducted to investigate compensation and induction in seedlings and juvenile plants, using Plantago lanceolata (Plantaginaceae) and the specialist buckeye caterpillar Junonia coenia (Nymphalidae) as a model system. Plants received 50% defoliation at two and four weeks of age, and groups of plants were harvested one week after herbivory and six to eight weeks after herbivory to investigate the duration of the responses. Plants damaged at two weeks showed no chemical induction and fully compensated for the lost leaf tissue by ten weeks of age. Plants damaged at four weeks showed a significant reduction in iridoid glycosides one week after herbivory and achieved full shoot compensation by ten weeks of age at the expense of root biomass. These results indicate that P. lanceolata seedlings use compensation, but not chemical induction, as a defense strategy. This research highlights the importance of considering ontogeny in studies of plant,herbivore interactions and suggests that seedling defense may differ markedly from adult plant defense. [source] Phenotypic plasticity: Functional and conceptual approachesAMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 1 2005David P. Crews No abstract is available for this article. [source] Implications of Genotypic Diversity and Phenotypic Plasticity in the Ecophysiological Success of CAM Plants, Examined by Studies on the Vegetation of Madagascar,PLANT BIOLOGY, Issue 3 2001M. Kluge Abstract: On the basis of ,13C-values, genotypic diversity and phenotypic plasticity of CAM behaviour in plants of the Malagasy vegetation is surveyed. The study compares CAM patterns performed in the wild on the levels of genera (Kalanchoë [Crassulaceae], Angraecum [Orchidaceae], Lissochilus [Orchidaceae] and Rhipsalis [Cactaceae]), on the level of a family (Didiereaceae) and finally on the level of a common growth form, namely in leafless orchids. For Rhipsalis, also non-Malagasy species were included in the comparison. The genus Kalanchoë was found to be dominated by species representing the CAM-physiotype with CO2 fixation taking place only during the night, whereas the CAM/C3- and the C3-physiotypes (with limited intrinsic CAM potential) were less frequent. The opposite holds true for Angraecum. In the genus Rhipsalis, in the Didiereacean family and in the leafless orchids only the CAM-physiotype is represented. The photosynthetic physiotypes of CAM plants were found to be related to the environmental conditions of the habitat. That is, strong CAM performers are typically abundant in the dry climatic zones or at otherwise dry niches, species of the C3-physiotype (possibly with weak intrinsic capability of CAM performance) are distributed at humid sites and those of the CAM/C3-physiotype occupy sites with medium and changing exposure to stress. Phenotypic plasticity of CAM, as indicated by the intraspecific variability of the ,13C-values, was lower in the CAM-physiotype compared with the CAM/C3-physiotype. Our data support the view that strong stress leads to the dominance of highly adapted specialists among the CAM plants, with low phenotypic plasticity of the photosynthetic behaviour, whereas medium stress advances the unfolding of plastic CAM behaviour. Moreover, the data suggest that genera comprising all three physiotypes (Kalanchoë, Angraecum) are dispersed all over Madagascar, whilst groups comprising only strong CAM performers are restricted to limited areas or special types of habitats. This suggests that both genotypic diversity and phenotypic plasticity are important factors for the ecophysiological success of CAM. [source] Performance benefits of growth-form plasticity in a clonal red seaweedBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2009KEYNE MONRO Phenotypic plasticity may be adaptive if the phenotype expressed in a focal environment performs better there relative to alternative phenotypes. Plasticity in morphology may particularly benefit modular organisms that must tolerate environmental change with limited mobility, yet this hypothesis has rarely been evaluated for the modular inhabitants of subtidal marine environments. We test the hypothesis for Asparagopsis armata, a clonal red seaweed whose growth-form plasticity across light environments is consistent with the concept of foraging behaviour in clonal plants. We manipulated the light intensity to obtain clonal replicates of compact, densely branched (,phalanx') phenotypes and elongate, sparsely branched (,guerrilla') phenotypes, which we reciprocally transplanted between inductive light environments to explore the performance consequences of a poor phenotype,environment match. Consistent with the hypothesis of adaptive plasticity, we found that performance (as relative growth rate) depended significantly on the interaction between growth form and environment. Each growth form performed better in its inductive environment than the alternative form, implying that this type of plasticity, thought to be adaptive for clonal plants, may also benefit photoautotrophs in marine environments. Given the prevalence and diversity of modular phyla in such systems, they offer a relatively unexplored opportunity to broaden our understanding of the evolutionary ecology of phenotypic plasticity. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 97, 80,89. [source] Latitudinal variation in axial patterning of the medaka (Actinopterygii: Adrianichthyidae): Jordan's rule is substantiated by genetic variation in abdominal vertebral numberBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 4 2009KAZUNORI YAMAHIRA Because the body axes of fish consist of two anatomically distinct vertebrae, abdominal and caudal, one type may be more variable in number than the other and thus contribute more to morphological diversification. Jordan's rule, a geographical tendency for fish from higher latitudes to have more vertebrae, has not been examined in terms of numbers of abdominal and/or caudal vertebrae, despite its prevalence. Vertebral observations of wild populations of the medaka (Oryzias latipes) revealed that the latitudinal increase in vertebral number is caused by an increase in abdominal vertebrae; caudal vertebrae did not vary systematically across latitudes. Laboratory experiments revealed that this latitudinal cline in abdominal vertebral number persists in a range of common environments, demonstrating a genetic basis. Phenotypic plasticity was also evident: lower developmental temperatures resulted in more abdominal vertebrae. This indicates that greater numbers of abdominal vertebrae in higher latitude individuals in the wild may be caused not only by genetic factors but by lower habitat temperatures, although the contribution of the former to Jordan's rule is assessed to be much greater. The genetic basis of the latitudinal variation in abdominal vertebral number suggests that selection on functions associated with abdominal regions is the probable explanation for Jordan's rule in this fish. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 96, 856,866. [source] Growth potential of adult hepatocytes in mammals: Highly replicative small hepatocytes with liver progenitor-like traitsDEVELOPMENT GROWTH & DIFFERENTIATION, Issue 2 2007Katsutoshi Yoshizato The liver is one of the few organs that is capable of completely regenerating itself without using a stem cell population. When damaged, growth factors and cytokines are released, stimulating terminally differentiated adult hepatocytes and making them re-enter the cell cycle. We have been developing a series of studies on the growth potential of rat and human hepatocytes to identify a population of hepatocytes that is responsible for the regeneration of the injured liver. For this purpose, we established an appropriate culture method for hepatocytes by which growth and differentiation capacities are practically examined under various experimental conditions. This in vitro assay system allows us to identify small hepatocytes that are prominently replicative compared to large hepatocytes. Non-parenchymal cells play critical roles in the proliferation of small hepatocytes. These hepatocytes are present in both rat and human liver and are located in portal regions there. Phenotypic features were examined at morphological and gene/protein levels in detail, which showed the phenotypic plasticity in vitro. Mammalian liver includes a population of small hepatocytes in normal adults with a minute occupancy rate. We speculate that small hepatocytes play a role in regenerating the injured liver and in compensating for apoptotic hepatocytes in the physiological turnover of hepatocytes. [source] Ecological fitting by phenotypically flexible genotypes: implications for species associations, community assembly and evolutionECOLOGY LETTERS, Issue 11 2008Salvatore J. Agosta Abstract Ecological fitting is the process whereby organisms colonize and persist in novel environments, use novel resources or form novel associations with other species as a result of the suites of traits that they carry at the time they encounter the novel condition. This paper has four major aims. First, we review the original concept of ecological fitting and relate it to the concept of exaptation and current ideas on the positive role of phenotypic plasticity in evolution. Second, we propose phenotypic plasticity, correlated trait evolution and phylogenetic conservatism as specific mechanisms behind ecological fitting. Third, we attempt to operationalize the concept of ecological fitting by providing explicit definitions for terms. From these definitions, we propose a simple conceptual model of ecological fitting. Using this model, we demonstrate the differences and similarities between ecological fitting and ecological resource tracking and illustrate the process in the context of species colonizing new areas and forming novel associations with other species. Finally, we discuss how ecological fitting can be both a precursor to evolutionary diversity or maintainer of evolutionary stasis, depending on conditions. We conclude that ecological fitting is an important concept for understanding topics ranging from the assembly of ecological communities and species associations, to biological invasions, to the evolution of biodiversity. [source] Invasive aliens and sampling biasECOLOGY LETTERS, Issue 4 2003Andrew M. Simons Abstract Two hypotheses have been proposed to explain the observation of increased vigour of invasive alien plants in their nonindigenous ranges: phenotypic plasticity, and the post-invasion evolution of increased competitive ability (EICA). Here I specify how a general pattern of increased vigour may result from sampling bias. Ignoring failed invasions can account for the illusion of increased vigour over a broad range of assumptions. Plasticity and EICA need not be viewed as explanations for a general pattern of increased vigour even if they are the mechanisms underlying every occurrence. [source] Contemporary egg size divergence among sympatric grayling demes with common ancestorsECOLOGY OF FRESHWATER FISH, Issue 1 2008F. Gregersen Abstract, This study documents divergence in egg size that has occurred over less than 25 generations among sympatric demes of European grayling (Thymallus thymallus) from Lake Lesjaskogsvatnet in Norway. A cluster analysis identified two clusters of tributaries: one of small, warm tributaries (SW) and the other of large, cold tributaries (LC). Spawning occurs more regularly and up to 4 weeks earlier in SW tributaries compared with that in LC ones. We explored numerous mixed models predicting egg size from year (random effect), basin and tributary (fixed effects), and female length. The most supported model estimated length-adjusted egg size to be larger in SW tributaries compared with that in LC tributaries. Combinations of density-dependent (competition for food/space) and density-independent (temperature) factors along with phenotypic plasticity and maternal effects are discussed as potential differentiation sources. We suggest high temperatures (increased metabolism) to reinforce the selective advantage of large eggs under conditions with highly density-dependent fry interactions. [source] Diet-induced phenotypic plasticity in the skull morphology of hatchery-reared Florida largemouth bass, Micropterus salmoides floridanusECOLOGY OF FRESHWATER FISH, Issue 4 2005A. P. Wintzer Abstract , Hatchery-reared Florida largemouth bass, Micropterus salmoides floridanus, feed on inert pellet food while their wild counterparts capture elusive prey. Differences in levels of prey elusivity often mandate the use of alternate methods of prey capture. This study examines whether elusivity-based variation in prey capture translates to a phenotypic change during skull development, and if this change results in a functional difference in the feeding mechanism. The developmental pattern of the skull was conserved between hatchery and wild bass until 80,99 mm TL. At this point, wild bass quickly developed morphological changes of the jaw apparatus including a more fusiform head and elongated jaw structures. Natural development in hatchery bass, however, was retarded at this size. Post-release, the skulls of hatchery fish converged towards those of wild bass by 135 mm TL. Despite variation in skull development, no theoretical advantage in food capture was found between these two groups. Resumen 1. Los individuos de Micropterus salmoides floridanus criados en cautividad se alimentan de cápsulas inertes de comida mientras que sus congéneres salvajes capturan presas elusivas. A menudo diferencias en los niveles de elusividad de las presas permiten la utilización de métodos alternativos para capturar presas. Este estudio examina si la variación basada en la elusividad de la captura de presas se traduce en un cambio fenotípico durante el desarrollo del cráneo y si este cambio resulta en una diferencia funcional en el mecanismo de alimentación. 2. El patrón de desarrollo del cráneo se mantuvo entre individuos criados en cautividad y en individuos salvajes hasta los 80,99 mm longitud total. En este punto, los individuos salvajes desarrollaron rápidamente cambios en el aparato mandibular incluyendo una cabeza más fusiforme y estructuras mandibulares mas alargadas. Sin embargo, en individuos de cautiverio, el desarrollo natural se retrasó en este tamaño. 3. Tras una suelta, los cráneos de individuos procedentes de cautiverio convergieron hacia los individuos salvajes en los 135 mm longitud total. A pesar de la variación en el desarrollo del cráneo, no encontramos ninguna ventaja teórica en la captura de alimento entre estos dos grupos. [source] Atlantic salmon Salmo salar L., brown trout Salmo trutta L. and Arctic charr Salvelinus alpinus (L.): a review of aspects of their life historiesECOLOGY OF FRESHWATER FISH, Issue 1 2003A. Klemetsen Abstract ,,,Among the species in the family Salmonidae, those represented by the genera Salmo, Salvelinus, and Oncorhynchus (subfamily Salmoninae) are the most studied. Here, various aspects of phenotypic and life-history variation of Atlantic salmon Salmo salar L., brown trout Salmo trutta L., and Arctic charr Salvelinus alpinus (L.) are reviewed. While many strategies and tactics are commonly used by these species, there are also differences in their ecology and population dynamics that result in a variety of interesting and diverse topics that are challenging for future research. Atlantic salmon display considerable phenotypic plasticity and variability in life-history characters ranging from fully freshwater resident forms, where females can mature at approximately 10 cm in length, to anadromous populations characterised by 3,5 sea-winter (5SW) salmon. Even within simple 1SW populations, 20 or more spawning life-history types can be identified. Juveniles in freshwater can use both fluvial and lacustrine habitats for rearing, and while most smolts migrate to sea during the spring, fall migrations occur in some populations. At sea, some salmon undertake extensive oceanic migrations while other populations stay within the geographical confines of areas such as the Baltic Sea. At the other extreme are those that reside in estuaries and return to freshwater to spawn after spending only a few months at sea. The review of information on the diversity of life-history forms is related to conservation aspects associated with Atlantic salmon populations and current trends in abundance and survival. Brown trout is indigenous to Europe, North Africa and western Asia, but was introduced into at least 24 countries outside Europe and now has a world-wide distribution. It exploits both fresh and salt waters for feeding and spawning (brackish), and populations are often partially migratory. One part of the population leaves and feeds elsewhere, while another part stays as residents. In large, complex systems, the species is polymorphic with different size morphs in the various parts of the habitat. Brown trout feed close to the surface and near shore, but large individuals may move far offshore. The species exhibits ontogenetic niche shifts partly related to size and partly to developmental rate. They switch when the amount of surplus energy available for growth becomes small with fast growers being younger and smaller fish than slow growers. Brown trout is an opportunistic carnivore, but individuals specialise at least temporarily on particular food items; insect larvae are important for the young in streams, while littoral epibenthos in lakes and fish are most important for large trout. The sexes differ in resource use and size. Females are more inclined than males to become migratory and feed in pelagic waters. Males exploit running water, near-shore and surface waters more than females. Therefore, females feed more on zooplankton and exhibit a more uniform phenotype than males. The Arctic charr is the northernmost freshwater fish on earth, with a circumpolar distribution in the Holarctic that matches the last glaciation. Recent mtDNA studies indicate that there are five phylogeographic lineages (Atlantic, Arctic, Bering, Siberian and Acadian) that may be of Pleistocene origin. Phenotypic expression and ecology are more variable in charr than in most fish. Weights at maturation range from 3 g to 12 kg. Population differences in morphology and coloration are large and can have some genetic basis. Charr live in streams, at sea and in all habitats of oligotrophic lakes, including very deep areas. Ontogenetic habitat shifts between lacustrine habitats are common. The charr feed on all major prey types of streams, lakes and near-shore marine habitats, but has high niche flexibility in competition. Cannibalism is expressed in several cases, and can be important for developing and maintaining bimodal size distributions. Anadromy is found in the northern part of its range and involves about 40, but sometimes more days in the sea. All charr overwinter in freshwater. Partial migration is common, but the degree of anadromy varies greatly among populations. The food at sea includes zooplankton and pelagic fish, but also epibenthos. Polymorphism and sympatric morphs are much studied. As a prominent fish of glaciated lakes, charr is an important species for studying ecological speciation by the combination of field studies and experiments, particularly in the fields of morphometric heterochrony and comparative behaviour. [source] | |||||||||||||||||||||||||||||||||||||||||||