They depend on the survival ability of a complex and resilient individual which is able to cope with all but the worst of natural catastrophes (Robinson 1987). In the nature, r strategist are controlled by density independent control. Study on the population of Puppetry’s edited, shows that interspecies competition and predation play relatively small roles of humid tropics such as Helicon titillate, which said to be K selected, (Earlier and Gilbert 1973) is not subject to catastrophic weather-related mortality, but it faces heavy loses in the larval stage from predatory ants (Daly 1978). The best studied of legible r-K strategy are Trillium castanets and Trillium confuse (King and Dawson 1972).
These beetles have intrinsic density-regulating mechanism, including egg and papal cannibalism by larvae and adult, reduced fecundity and fertility in aged population, and the secretion of an inhibitory quinine gas in crowded situation (Matthew 1976). Cannibalism is not only a regulatory mechanism but also improves the fitness of surviving individuals (Merit and Robert 1970). References Daly, H. V. 1978. Introduction to insect biology and diversity. London: McGraw-Hill. ( Matthews, E. G. 1976. Insect ecology. SST Lucia: University of Queensland Press. ( Matthews, E. G. And R. L. Catching. 1987. Insect ecology 2nd edition. SST Lucia: University of Queensland Press. ( Robinson, R. A. 1987. Host management in crop photometers. New York: MacMillan Publishing Company. ( Spotlight, M. R. , M. D. Hunter, and A. D. Watt. 1999.
Ecology of insect: concept and application. Oxford: Blackwell Science. ( r/K Strategists concept r/k strategist is a life history theory proposed by Mac Arthur and Wilson (1967) for classifying species based on their population growth which has correlation with their fife strategies to survive in the environment (Denny and Dingle, 1981; Robinson, 1987). In this concept, species are classified as r-strategists and K-strategists (Kudos and Scheme, 1979; Pedigree, 1989). Insects (species) which have high reproductive rates but with low survival rates are called r-strategists, named after the statistical parameter “r”; the symbol for the growth rate coefficient (Pedigree, 1989).
Many pests of crops are r-strategists, they are small in size, have high reproductive rate, have short-lived individuals in a relatively brief period of time, have high level of dispersal ( Robinson, 1987; Matthews ND Catching, 1984), have low investment in defense and other interspecies competitive mechanisms (Matthews and Catching, 1984), and they have capacity to escape from severe enemy impact through the interaction of excellent colonizing ability and a high population growth (Metcalf and Lackawanna, 1982). For instance, their colonizing ability can be seen from the explosion of the pest population in early season (after germination of the host plant) or after the application of insecticides, where the big number of new resistant population will be present for replacing the susceptible population (Metcalf and Lackawanna, 1982). Migratory locust is an example of r-strategists. It was so difficult to control this pest which has ability to reproduce new generation rapidly (Matthews and Catching, 1984) and has ability to disperse or migrate in a great distances (Metcalf and Lackawanna, 1982).
Water beetle (Rates Australia’s), ghost moths (Trichina argental) and some of dragonflies are other examples of r-strategists species (Matthews and Catching, 1984) called K-strategists, named after the symbol for flattened portion of a population growth curve “K”, the abbreviation means the carrying capacity of the environment (Pedigree, 1989; Robinson, 1987). K-strategists has characteristics such as large in size, low level of dispersal organisms, long-lived individuals over relative long periods of time (Robinson, 1987). K-strategists live in harsh environment by producing few offspring which have ability to defense from predation (Metcalf and Lackawanna, 1982; Kudos and Scheme). Moraines grasshopper is an example of K- strategists. A Population of this species may contain only a few of individuals (low reproduction rate) but with the ability to survive in the environment by using mimicry/ camouflage on the plants where they are life (Matthews and Catching, 1984).
Tsetse flies, carpenter bees, and some forest lepidopterist are examples of K- strategists species (Spotlight et. Al, 1999). We may find many intermediate species (between r and K strategists) in the real world, and some species may show traits of both r- and K-strategists at different times or in different locations (Spotlight et. Al, 1999). A single species may exhibit r- or K-strategists depending on its population density. Low population densities of the bean weevil (Consolidated obtuse) showed r -strategists characteristics when compared with high-density populations, which appeared to be more K-strategists Allelic et al, 1993 in Spotlight et. Al, 1999). REFERENCES Denny, R. F and Dingle, H. 1981.
Insect Life History Patterns: Habitat and Geographic Variation. Springer-Average: New York. Matthews, E. G and Catching, R. L. 1984. Insect Ecology. Second Edition. University of Queensland Press: Australia. Metcalf, R. L and Lackawanna, W. H. 1982. Introduction to Insect Pest Management. Second Edition. John Wiley and Sons: New York. Pedigree, L. P. 1989. Entomology and Pest Management. MacMillan Publishing Company: New York Robinson, R. A. 1987. Host Management in Crop Photometers. MacMillan Publishing Company: New York Spotlight, M. R; Hunter, M. D; Watt, A. D. 1999. Ecology of Insects. Blackwell Science: London. Kudos, J. C. And Scheme, R. D. 1979.
Epidemiology and Plant Disease Management. Oxford University Press: New York. By Harris changes. Response to environment change and environmental changes produced the dynamical of insect it’s self. The dynamical population of insect known as r-/K- selection (another scientist called r-/K- strategist). r is symbol of rate of population growth and K is symbol population density. The number of individuals of species per nit area of space is referred to as population density, and growth of population is the number of individuals added minus the number lost during a unit of time CLC (Lazing, 1981). Generally insect population had two distinctive characteristic.
First many populations were extremely stable in size, generation after generation, second others could be extremely variable in size, with number rising rapidly in one or two generation to extremely high levels and then falling Just as rapidly to very low numbers. D (Ross, et. Al. 1982). The two principal tactic of the r-strategy, nomadic ND rapid population build up, clearly seen in plague locust, which are associated with areas all over the world D (Matthews, 1984). K-strategic depend on many factor like availability of food and extent of predation D ( Remorse, 1981), it’s happened in Moraine grasshopper in arid and semi-arid region of Australia.
Basically the r-/K- strategic based on assumption, that r- strategic have exponential population growth, stable age distributions, repeated colonization or fluctuations in population density and K- strategy had logistic population growth environmental stable, population near equilibrium density, competition important A ( Stearns, 1977) Kind of insect which belongs to r- and K-strategy can be characterized below: r- strategy-strategically Uncertain variable, unpredictable Fairly consistent, predictable, reasonably certain. Life cycle Short, a few weeks Rapid development and growth rate Early reproduction and single reproduction Small body size Potentially many offspring Mortality catastrophic, usually density interdependently, usually several months Slower development and growth rate Delayed or extended reproduction period Large body size Fewer and large offspring
Mortality more evenly distributed, density differentiations severable in time, non equilibrium, usually significantly below carrying capacity periodic irreconcilability constant, equilibrium, at or near carrying capacity, no need for recolonizationcompetition Variable commonly loquaciously high. D (Ross, et. Al,1982 and Horn, 1976) References : Ross, Herbert et. Al. 1982. A textbook of entomology. John Wiley and Sons, Inc. USA. Horn , David J. 1976. Biology of insect. W. B. Saunders Company. Philadelphia, USA. Matthews, E. G. 1984. Insect ecology. University of Queensland Press. Australia Lazing, Richard J. 1978. Fundamentals of Entomology. Prentice Hall Inc. New Jersey. Remorse, William S. 1981 . Science of Entomology, second De. Macmillan Publishing Co. NC. New York Stearns, Stephen c. Iii. Ann.. Rev. Cell. Sys. MM 45-71 r-selection operates to maximize reproductive rate in harsh, unstable environments where population remain well below the carrying capacity of the environment are resources are not limiting except for time to reproduce successfully ( Peter, 1984). At the other extreme of the continuum, in predictable, stable environment populations ill frequently reach the carrying capacity of the environment and selection will operate by improving adaptations for living in these crowded, competitive condition, where enemies such as predators and parasites will be very effective – k selection.
The bare essentials of this theory of r- and k- selection therefore involve five characteristics that must be integrated there are: Relative stability of environmental conditions and population size Reproductive rate of species Carrying capacity of the environment relative to mean population size. The frequency of introspecting and interspecies competition The importance of enemy attack. In here can be explained the concept of r and k strategist and their development during the evolution of organism is certainly not new, although these particular terms to describe the process have been used for only a short period of time. There is presently a great deal of uncertainty as to how important these stratagems are in the functioning of organism within ecological communities. Diaphanous, 1950 in Peter, 1974.
He described that the differences between temperate or arctic environments and those of tropical regions. In tropical environment, organism are ore constantly crowded and selection is influenced more by biotic factor. Competition then become a primary selective force because the populations are more constantly at or near the carrying capacity of the environment. MacArthur and Wesson, (1967 in peter 1974) they said that the stage of the population there are two possible situations: (1) An environment in which a population is expanding, and (2) an environment in which a population is crowded. They assumed relatively stable condition in both cases, no great physical changes occurring to radically change the environment.
Under this condition, organisms should evolve toward productivity and large families since there is no shortage of resources-/K- Strategy of insect Insects as another animals, has behavior to response the habitat or environment changes. Response to environment change and environmental changes produced the numbers. C] (Ross, et. Al. 1982). The two principal tactic of the r-strategy, nomadic This kind of evolution is called r- selection. On the other hand, under condition of crowding, selection should evolve toward feeding efficiency since resources are in short supply. The organism that can replace itself with the least waste of resources in the most fit in this environment, evolution here is called k selection. Piano, (1970 in peter 1974) thoroughly treated the subject listed some of the correlates of both r and k selection.
He propos that terrestrial vertebrates and perennial plants are predominately k- selected. Whereas terrestrial invertebrates and annual plants are more r- selected. Gail and Solaris, (1972 in peter 1974) discussed r and k selection, objected to the assumption that increased or decreased birth berate by itself is evidence of increased r or k selection respectively. Harmonistic of r and k strategists is: R STRATEGISTS Stratification’s most petulantly where density independent factors predominate: – temperate and arctic climate – edges population range – disturbed situation Have a high fecundity and short generation time Usually reproduce early and rapidly, and died early. To be small in size Dependent upon butane food resources.
Poor competitors- opportunists May have greater tolerances to harsh environment conditions. Found most petulantly where density dependent factors predominate: – tropical climate – center population range – undisturbed situation Have a low fecundity and long generation time To be large in size good competitors- specialists May have restricted tolerances to harsh environment conditions. The concept of r and K strategies can act only as a mechanism for relative comparisons of biotic components of a community since there are no absolute criteria by which an organism can be designated as an r or K strategist. These comparisons may vary, depending on the species In www. Sprinkling. Mom r- strategist and k strategist can be classified according to their population growth curves ( MacArthur and Wilson, 1967 in Robinson). At one are the opportunists, the quantity breeders, that reproduce very large numbers of small-sized, biologically cheap, short-lived in individual. Each population explosion is followed by a population extinction in which all active individuals normally perish and the species survives only in a dormant push as seeds, eggs, pupae, or spores. These quantity breeders is called r-strategist. Plant parasites, such as aphids are typical r-strategists. K-strategists depend on the survival ability of a complex individual.
As the species subjected to r selection build up its numbers, and competitors and redactors, the environment become crowded with species and the condition of r selection no longer prevail. These are the short of selectiveness’s that operate in environment of the second kind, those that are predictably favorable and stable, the k environment( k represents carrying capacity). Southwest, AAA in Martin et all, elaborates on this set of evolutionary interactions with the environment. He associates the r-k spectrum with so called ;durational stability’. Daly and Howell, 1978 can describe the two principal tactic of the r-strategy, nomadic and rapid population build up, on the locusts.
The locust need condition favorable. These favorable condition are largely dependent on soil type. REFERENCE Daly. , Howell. V. 1978. Introduction to Insect and Diversity. America. Martin, R. S. , Mark, D. H, Allan, D. W. 1999. Ecology of insects concepts and applications. Department of zoology, university of Oxford. Oxford. Matthews, E. G. , R. L. Catching. 1976. Insect ecology. University of Queensland Press. Queensland. Peter, W. P. 1974. Evolutionary Strategies of Parasitic Insect. Department of Entomology University of Illinois Urbana, Illinois. Robinson, R. A. Host Management in Crop Pathologist. University of California. Berkeley. Www. Sprinkling. Com