Explanation:

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 (coenocline) and
complex environmental gradients.
Ecotone: An ecotone is a transition area between two biomes. It is where two communities meet and integrate. It may be narrow or wide, and it may be local (the zone between a field and forest) or regional (the transition between forest and grassland ecosystems).
Ecotype: In evolutionary ecology, an ecotype, sometimes called ecospecies, describes a genetically distinct geographic variety, population or race within a species, which is adapted to specific environmental conditions. They typically show morphological differences.
An ecological niche is the role and position a species has in its environment; how it meets its needs for food and shelter, how it survives, and how it reproduces. A species' niche includes all of its interactions with the biotic and abiotic factors of its environment. No two species have identical niches