Terminology
Ecotypes have no main taxonomic rank in modern biological classification. However some scientists consider them "taxonomically equivalent to subspecies". This is true in the sense that ecotypes can be sometimes classified as subspecies and the opposite.
Ecotypes are closely related to morphs. In the context of evolutionary biology, genetic polymorphism is the occurrence in equilibrium of two or more distinctly different phenotypes within a population of a species, in other words, the occurrence of more than one form or morph. The frequency of these discontinuous forms (even that of the rarest) is too high to be explained by mutation. In order to be classified as such, morphs must occupy the same habitat at the same time and belong to a panmictic population (whose all members can potentially interbreed). Polymorphism is actively and steadily maintained in populations of species by natural selection (most famously sexual dimorphism in humans) in contrast to transient polymorphisms where conditions in a habitat change in such a way that a "form" is being replaced completely by another.
In fact, Begon, Townsend and Harper assert that
| “ | There is not always clear distinction between local ecotypes and genetic polymorphisms. | ” |
The notions "form" and "ecotype" may appear to correspond to a static phenomenon, however this is not always the case. Evolution occurs continuously both in time and space, so that two ecotypes or forms may qualify as distinct species in only a few generations. Begon, Townsend and Harper use an illuminating analogy on this:
| “ | ...the origin of a species, whether allopatric or sympatric, is a process, not an event. For the formation of a new species, like the boiling of an egg, there is some freedom to argue about when it is completed. | ” |
Thus ecotypes and morphs can be thought of as precursory steps of potential speciation.
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