The intraspecific response of the plant species to the habitat. ( review Article)
Shahgolzari Mehdi and Afagh Yavari<br>
Department of Biology, Faculty of Science, Payame Noor university, Tuyserkan, Hamadn, Iran<br>
Abstract<br>
Understanding the sources of intraspecific variation in organisms is central to the understanding of natural variation and the responses of organisms to their environment. One of the most important reserves that led to biodiversity is intraspecific variation. Creation of intraspecific variation is the main origin and storage of speciation. In this order, invention intraspecific variation in different levels of each taxon cause to richness in an area. Individuals of a species that is able to give appropriate response to a tremendous variety of different conditions, have wide distribution in different stations with various ecological conditions. These changes individuals of a species, regarding genotypically, phenotypically and physiologically, led to intraspecific diversity and tend to appear new ecotypes, ecophenes, chemotypes, cytotypes and even subspecies.<br>
Keyword: intraspecific variation, ecotypes, ecophenes, chemotypes, cytotypes<br>
Introduction<br>
We are becoming increasingly aware that an individual cannot be considered out of the context of its environment. Therefore, at the present time there is a great deal of interest in the way in which an individual maintains its stability in the face of varying environmental situations (Bradshw, 1965). The study of natural variation in ecologically important traits has a long history in evolutionary biology (Turesson, 1922: Clausen, Keck and Hiesey, 1948). The primary motivation for studies of this nature is to further our understanding of the roles of natural selection, gene flow, and genetic drift in shaping levels of adaptation and in affecting the distribution and abundance of species (Christine, and Monica, 1999). Population studies on the pattern of variation in many plant species have revealed the existence of localized populations each adapted to the particular environmental conditions of their habitat (e.g. Tureon, 1922: Bradshaw,1960,1991: McNeilly, 1968: Kiket al, 1990: Geberet et al, 1992). habitat conditions reflect the characteristics of a individual because they are pertinent to environment (Schimd, 1992).because all individual in a population are similar enough to be considered one species, it is expected that the total variation in morphology, behavior, genetic material, and physiology among those individuals is therefore much lower than in a sample of the same number of individuals in a different species. Despite this, considerable variation can exist among or within populations of the same species. This variation could be the result of phenotypic, genotypic and physiologic response to a particular environment. The environmental factors and its influence in plant variation (plant diversity) have been extensively studies. Plants show their response as different changing that some of them is illustrated following forms: the genotypic response of the plant species to the habitat (Turesson, 1922), formation of new ecotypes of Potentilla glandulosa and their appearance in each of the transplant gardens  (Turesson, 1922), ecophysiological variation in ecotypes of Oxyria digyana (Mooney & Billng, 1959), morphological, biochemical and phonological difference between the arctic and alpine populations of Oxyria digyana (Mooney & Billng, 1959). Rejmanek (1996) found major difference in the amount of nuclear DNA in different pine species. Some researchers were studied comparative biogeography of the cyotypes of Microthalaspi perfolatum in Europe using isozymes and cpDNA data (Koch and Bernhardt, 2005). The study were taken on chemical diversification trend in Astragalus caprinus (Semmar, 2005) and Astragalus gossypinus (Atri et al, 2007) based on the flavonoid pathway that introduce several chemotypes between studies populations of Astragalus caprinus and Astragalus gossypinus according geographic sites.<br>
Intraspecific response to habitat<br>
Species populations occurring in different habitat can exhibit physiological, morphological and genetically difference in response to contrasting environmental conditions. Development of different Intraspecific response to habitat is a remarkable property of plants conferring their broad adaptive capability (Evolutionary (phylogenetic)), acclimation (Physiology (reversible adjustment)) and accommodation (Development (ontogeny)) to spatially and temporally environment.<br>
Acclimatization, the morphological and physiological response of the plant to the environmental conditions that is reversible (this changes are not origin genetic) as short and unstable. <br>
Accommodation, the morphologic response of the plant to the environmental conditions that is toward adaptation with environment, these phenotypic changes are reversible and not heritable.<br>
Adaptation, the genetic response of the plant to the environmental conditions that these responses can expression in morphologic and physiologic these changes are genetically and irreversible.
Thus, result of changes ecological factors in diversity, expression as epigenetic and genetic variation. Epigenic mechanisms regular expression of gene without creates change in genetic codes. Epigenetic factors are environment factors that effect on behaviors of an organism, without affect on DNA. Epigenetic changes include, change in structure of chromatin strain (Metilation), transcription of chromosome, active and inactive gene. But genetic changes include, change in stricture of chromosome (dilation, duplication, inversion, translocation, crossing over), and number of chromosome (Anopoloyd, Eupoloyd).thus, genetic and epigenetic responses of the plant species to the environment conditions can to be revealed as cytotype, ecophene and ecogene variations. Ecogen variatios include ecotype, ecocline and topocline.<br>
Cytotype, A portion of the type, prepared to exhibit identical cytological feature (i.e. chromosome) as those originally described for the taxon. cytotype variations are change in structure and number chromosome that can to be revealed in morphology and physiology.<br>
Ecophene (ecad or a habitat form and/or environmental form),The variety of phenotypes (visible physical characteristics or behaviors), from a single genotype, that can be observed in a population within a particular habitat.<br>
Ecotype (ecological race), A subspecies, or breed, that has adapted to its local environment and as a result is distinctive from other members of the species, but can still successfully interbreed with other members of the species.<br>
Ecocline, the gradient between adjacent biomass, gradient of Environmental conditions. The simultaneous gradient in species composition and environmental variation. Thus ecocline, is genotypic variation under effect gradient of Environmental conditions. This variation carries out in limited scales.<br>
Topocline, is genotypic variation under effect gradient of Environmental conditions. This variation carries out in wide scales.<br>
Figure 1:  Intraspecific response kinds in a population of a species in particular habitat.<br>
Morphological variation<br>
Understanding the sources of Morphological variation in organisms is central to the understanding of natural variation and the responses of organisms to their environment. The variability of morphological character expression can indicate differentiation of plant populations in a particular habitat. The ability of plant to alter its morphology in response to changes in environments can be regarded as phenotypic plasticity (Bradshaw, 1965: Schlichting, 1986). Populations resistance to a changing environment is usually achieved by plastic phenotypic respond (Levines, 1968) because it has been agreed that plastic response are necessary for species for the occupancy of disturbed habitats (Thompson, 1991). Therefore, disturbance seems to play a major role in the generation of variation. Describe the natural phenotypic variation that occurs under controlled environmental conditions in one plant species for traits such as height, internodes, length, stem color and flowering Thus, the morphological response of the plant species to the habitat expressed to two forms, ecophene (plasticity response) that plant achieved accommodation and ecophenogene that plant achieved adaptation.<br>
Physiological variation<br>
The physiological variation in plant species both qualitative and quantitative has been found to be considerable among populations and even among genotypes of plant species. This might be due to differences in abiotic and biotic factors: e.g., fertilization, defoliation, elevated CO2, ozone, UV-light are all know to affect the physiological response of individual populations within same species. chemotype (sometimes chemovar) is a chemically distinct entity in aplantormicroorganism, with differences in the composition of thesecondary metabolites. Minorgeneticandepigeneticchanges with little or no effect on morphology may produce large changes in the chemicalphenotype. A good example of a plant with many chemotypes is Thymus vulgaris. While largely indistinguishable in appearance, specimens of T. vulgaris may be assigned to one of six different chemotypes, depending on whether the primary component of theessential oilisthymol,carvacrol,linalool,geraniol, thujanol-4 orterpineol. Such chemotypes may be indicated as Thymus vulgaris ct. thymol (red thyme), or Thymus vulgaris ct. geraniol (sweet thyme), etc. Such an indication has no taxonomic standing, also seeecotype. <br>
Genetic variation <br>
Biodiversity defined as the genetic variation among individuals, populations, species, communities, ecosystems and landscapes. Genetic diversity is essential for both short-term adaptations to environmental changes and long-term impacts on species and communities. However the foundation for biodiversity and organic evolution is genetic variation within species. This intraspecific variation provides the materials for long term evolutionary adaptation and short term adaptation to seasonal and rapid fluctuations in environmental factors (Claes Ramel, 1998). Clines and ecotypes are variants of a particular species adapted to specific locale or set of environmental conditions. An ecotype is defined as a genetic subdivision of a species in response to variation in the environment of that species over its range.<br>
Discussion<br>
Common plant species with wide distributions, my perform well in a wide range of environmental conditions. However, the costs of carrying adaptations to all possible environments could make it impossible for individual genotypes to perform well across the full range of conditions. Instead, common plant species are often characterized by both phenotypic plasticity (Accommodation ecophene) and large genetic variation and the successful occupation of many sites. The finding of persistent differences between subpopulations independent of environment conditions suggests that genetic variation underlies observed phenotypic variation. For example, a species of yarrow, Achillea millefolium, grow at a wide variety of habitats in California ranging form sea level to more than 3000m elevation. Plants at a given altitude have different height and biomass compared to plants form other when even seeds of plants from different sites are gown under the same conditions at sea level (Clausen, Keck, and Hiesey, 1948). This result indicates that the observation phenotypic variation among the California Achillea is ecotype, caused by genotypic differences between populations. In this case, we suggest ecophenogen word for these populations. The environmental factors and its influence in plant variation (plant diversity) have been extensively studied. Some of these studies include: (Turesson, 1922: Mooney and Billing, 1959: Rejmanek, 1996: Koch and Brnhart, 2004: Semmar et al., 2005: Telascrea et al., 2006: Atri et al., 2007). We suggested that the development of different types is a remarkable property of plants conferring their broad adaptive capability and accommodation to spatially and temporally environment. Accommodation is plant response to different ecological conditions, this response, occur in the morphologic characters and is epigenetic, namely, changes carries out in gene expression. But adaptation is plant response to different ecological conditions that occur in genetic materials, this response can expression as morphologic and physiologic variations in species populations. On the other hand, continuance in accommodation and acclimatization in length of time can to cause adaptation. Turesson (1922) is believed that ecophene is genetic chenges, but we suggest that ecophene is epigenetic and genetic changes and seen to two forms, accommodation ecophene (phenotypic plasticity) and adaptational ecophene (ecophenogene).    Thus, one of the most important reserves that led to biodiversity is intraspecific variation. Creation of intraspecific variation is the main origin and storage of speciation. In this order, invention intraspecific variation in different levels of each taxon cause to richness in an area. Individuals of a species that is able to give appropriate response to a tremendous variety of different conditions, have wide distribution in different stations with various ecological conditions. These changes individuals of a species, regarding genotypically, phenotypically and physiologically, led to intraspecific diversity and tend to appear new ecotypes, ecophenes, chemotypes, cytotypes and even subspecies. For determinding kind and level of intraspecific variations can used other studies such as: morphological, anatomical, phytochemical and cytological and ect. intraspecific variations have been related to ecological specialization and closely related taxa constitute ecotypes. <br>
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Emaile: mehdi.shahgolzari@gmail.com or <a href="mailto:afagh77@yahoocom">afagh77@yahoocom</a><br>