Ecotone, a transitional area of vegetation between two different plant communities, such as forest and grassland. It has some of the characteristics of each bordering biological communityand often contains species not found in the overlapping communities. An ecotone may exist along a broad belt or in a small pocket, such as a forest clearing, where two local communities blend together. The influence of the two bordering communities on each other is known as the edge effect. An ecotonal area often has a higher density of organisms of one species and a greater number of species than are found in either flanking community. Some organisms need a transitional area for activities such as courtship, nesting, or foraging for food.

Ecotype: A locally adapted population of a widespread species. Such populations show minor changes of morphology and/or physiology, which are related to habitat and are genetically induced. Nevertheless they can still reproduce with other ecotypes of the same species. Heavy-metal-tolerant ecotypes of common grasses such as Agrostis tenuis are an example.

Ecological Niche: All of the interactions of a species with the other members of its community, including competition, predation, parasitism, and mutualism. A variety of abiotic factors, such as soil type and climate, also define a species’ niche.

Ecocline (ecological gradient): A gradation from one ecosystem to another when there is no sharp boundary between the two. It is the joint expression of associated community and complex environmental gradients.

Source: Environment by Shankar IAS