In the strict sense, intraspecific comparison has a focus on the responding relationship between condition alteration and stress resistance (strategy) variations, which is one of the relations between environmental stress and stress resistance that exist within a species and occur in an individual's life history. Its standard comparison only compares an individual's (not a species') internal physiological (or physioecological strategy) variation, which occurs within the living individual's life history (from cradle to grave) in response to the external ecological changes (e.g., change in stressors). However, this comparison sometimes may extend to include comparisons of an individual's intergenerational physioecological (strategy) variation, or comparisons of physioecological (strategy) variations among different offspring of an ancestor.
For example, a comparative study of leaf morphology relevant to physioecological differences in plant A may involve the following four aspects.
1) A comparative study of leaf morphology relevant to physioecological differences between plant A and other plant species, under the same ecological conditions and at the same space and time. For example, plant A and plant B are both in high-humidity conditions: what is the difference in their leaf morphology (or in their microphysioecological process)? Plant B could be a sibling species, too.
2) The comparative study of intergenerational conspecies plants. For example, under the same high humidity conditions, does the leaf morphology (or their microphysioecological process) change after one hundred generations? If plant A is under diversified conditions with different humidity, sunlight, temperature, and insect conditions, what changes will occur in the leaf shape (or microphysioecological process) of its latter generations?
3) Comparative study between progenies of an ancestor. When comparing among progenies of a maternal plant under the same (or different) ecological conditions, what is the difference in their leaf shape (or in their microphysioecological process)?
4) A comparative study of leaf morphology relevant to physioecological difference within an individual's life history, for example, a comparison of changes in leaf shape (or microphysioecological process) under different moisture conditions, or under different solar radiations, or at different stages of life history, or under the menace of different insects etc.
These four aspects are mixed up in the current study of plant physioecology. Among them, the first aspect belongs to interspecific adaptation comparison, and the other aspects have shifted to study the intraspecific adaptation, especially the fourth aspect, which is a comparative study of stress resistance (strategy) variation in response to condition alterations, one of the relations between stress resistance and environmental stress that exists in an individual's life process. That is the area covered by the comparison of adaptive strategy variation in the intraspecific comparative system. It initially was a marginal direction of biology and now has turned into a mainstream direction.