Ecotypes

An ecotype is a genetically distinct population within a species that is adapted to a particular local environment. Ecotypes arise when populations experience different selective pressures across their range, leading to heritable differences in traits that improve fitness in the home habitat. They are not a formal taxonomic rank and can coexist with ongoing gene flow, though natural selection maintains divergence in key adaptive traits.

Ecotypes exhibit characteristic phenotypes and genotypes that reflect the environmental conditions they inhabit, such as climate, soil type, salinity, altitude, or biotic interactions. Evidence for ecotypes comes from reciprocal transplant or common garden experiments showing higher fitness of local ecotypes in their home environment compared with nonlocal populations, as well as population genetic analyses revealing differentiation at loci linked to adaptive traits.

Ecotypes can be widespread within a species and may represent a continuum of adaptations rather than discrete subspecies. If divergence in adaptive traits is coupled with reduced gene flow in mating, ecotypes can accumulate further differences and potentially contribute to speciation over time.

Examples are common in plants, where coastal and inland, or desert and temperate ecotypes have been documented, and in species with strong local adaptation such as Arabidopsis thaliana. In microbiology, the term ecotype is also used to describe ecologically distinct lineages within a species that occupy different niches, highlighting ecological rather than taxonomic distinctions.

Ecotype concepts have practical implications for conservation and management, since translocating individuals between environments can reduce fitness when local adaptation is strong.