Definition and examples
In nature, there are a variety of animal and plant species. Each species is better or worse adapted to abiotic and biotic environmental conditions. The area in which a living creature can survive and reproduce is also called tolerance.
Within this tolerance range, the environmental factors for an individual or species are tolerable, so that within this habitat, there is the possibility to live. In this context one speaks also of the ecological power (Latin potentia = force). And, in fact, we are dealing here with a force or fitness of the living being, because it has to assert itself in its habitat against competing creatures.
In comparison, there is the concept of physiological potencythat excludes the influence of competition to other species. Example:
Ecological potency of a tree: Actual tolerance for one factor (e.g., salinity of the soil) and in direct competition with other trees. As a rule, the species of a tree will never be found within the entire tolerance range of its ecological potency, because the ecological potency of other species is higher for certain environmental factors (e.g., low salinity). The ecological potency therefore corresponds to a natural / actual potency under real conditions.
Physiological potency of a tree: tolerance in relation to a factor (again salinity of the soil) and this time without competition. The tree species will be found in the total (and maximum) tolerance range because there are no types of competition. In this scenario, one can probably speak of optimal laboratory conditions that can not be found under real conditions.
An exemplary tolerance curve
minimum: The minimum indicates the area where a life is just possible. Growth and reproduction are impaired or no longer possible.
maximum: The maximum denotes the area where a life is just possible. Growth and reproduction are impaired or no longer possible.
optimum: In the optimum of existence, living beings living there find the best conditions. Growth and reproduction reach their absolute highest value here.
Prдferendum: The Prädferendum covers the area to the left and right of the optimum and represents the most preferred habitat. Growth and reproduction are within the normal range.
existence range: = ecological potency
tolerance: = physiological potency
Physiological optimum: corresponds to the optimal habitat of a species without influence of competition.
Ecological optimum: corresponds to the optimal habitat of a species under the influence of competition. It may well happen that the physiological optimum deviates significantly from the ecological optimum, because species are pushed to the limit of their ecological optimum.
Euryches and the most species
In population ecology, species with a relatively broad range and species that have a narrow tolerance range are distinguished from one another. The comparison between euryocs and the most basic creatures has its own article.