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- Countergradient variation is a type of phenotypic plasticity that occurs when the phenotypic variation determined by a biological population's genetic components opposes the phenotypic variation caused by an environmental gradient. This can cause different populations of the same organism to display similar phenotypes regardless of their underlying genetics and differences in their environments. To illustrate a common example known as countergradient growth rate, consider two populations. The two populations live in different environments that affect growth differently due to many ecological factors, such as the temperature and available food. One population is genetically predisposed to have an increased growth rate but inhabits an environment that reduces growth rate, such as a cool environment, and thereby limits the opportunities to take full advantage of any genetic predisposition. The second population is genetically predisposed to have a decreased growth rate but inhabits an environment that supports an increased growth rate, such as a warm environment, and allows members of the population to grow faster despite their genetic disadvantage. Since the genetic influence directly counteracts the environmental influence in each population, both populations will have a similar intermediate growth rate. Countergradient variation can reduce apparent variability by creating similar phenotypes, but it is still possible for the two populations to show phenotypic diversity if either the genetic gradient or the environmental gradient has a stronger influence. Many examples of countergradient variation have been discovered through the use of transplant experiments. Countergradient variation of growth rate is one of the most common examples. Growth rate and body size have important ecological implications, such as how they impact an organism's survival, life history, and fecundity. Countergradient variation has been described in many ectothermic animals, since ectotherms rely on environmental temperature to regulate their metabolic rates, and thus, their growth rates. Ectotherms grow at a slower rate as latitude increases due to this impact of temperature. However, under countergradient variation, when these same animals are placed in a common environment with their low-latitude relatives, they grow faster relative to the low-latitude population. These studies are useful in predicting how animals can adapt to and will survive in different environmental conditions. (en)
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- Countergradient variation is a type of phenotypic plasticity that occurs when the phenotypic variation determined by a biological population's genetic components opposes the phenotypic variation caused by an environmental gradient. This can cause different populations of the same organism to display similar phenotypes regardless of their underlying genetics and differences in their environments. (en)
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- Countergradient variation (en)
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