Tierformen

Tierformen is a German term that translates roughly as "animal forms." In biology, it refers to the phenotypic variants that can occur within a single species or taxonomic group. Tierformen describe differences in appearance or morphology that are not due to different species, but to genetic variation, developmental pathways, or environmental influences. Common examples include color morphs, patterns, body size variation, sexual dimorphism, and the existence of distinct castes in eusocial insects.

In zoological literature, the concept is used to document and compare variants such as the color morphs of amphibians or fish, the different morphs in insects like beetles, or the distinct body plans seen in metamorphic life cycles. Tierformen may be stable across generations or may shift under ecological pressures. They are studied in fields such as ecology, evolution, and conservation biology to understand adaptation, gene flow, and population structure.

Important to note is that Tierformen are not taxonomic ranks; they are descriptive phenotypes. While a population may be described as having several Tierformen, these forms do not constitute separate species. The term is widely used in German-language texts and field guides, and parallels exist in other languages under terms like polymorphism, morph, or caste.

See also: polymorphism, sexual dimorphism, metamorphosis, ecotype, caste.