An autapomorphy is in biology - especially in cladistics - a derivative ( apomorphes ) feature that characterizes a monophyletic group compared with related taxa. Derived means that the feature in relation to the evolutionary precursors is new. As a feature are both anatomical and physiological or direct genetic traits, such as DNA sequences into account. The loss of a feature can be interpreted as an autapomorphy. Whether a feature is to be regarded as an autapomorphy, is the subject of evolutionary biology and biological systematics.
The term autapomorphy depends on the level of the observed phylogenetic system. An autapomorphy as a derived feature of a taxon appear at the next lower level of the system as a synapomorphy of the two sister groups that make up this taxon. At deeper levels, the agreement, however, a Symplesiomorphie dar.
As an example of the human (Homo sapiens ) and its closest extinct relatives can serve ( the Hominini ). The Hominini include the genera Ardipithecus, Australopithecus, Paranthropus and Homo. Autapomorphies of this family are:
- Extension of the hind limbs and transformation to walking legs
- Redesign of the rear feet by extending the metatarsal bones and shortening of the toes
- Remodeling of the pelvis with expression of pan of the hip joint to accommodate larger loads
- Remodeling of the female pelvis in particular by increasing the ilium and the birth canal
- Transformation of the hands of the forelimbs to grip members (instead of climbing ) by shortening the metacarpal
This anatomically recognizable characteristics are related to the ability to walk upright for a long time and stand by. They can not be found in the other members of the superfamily of human -like ( Hominoidea ). While also Gibbons ( Hylobatidae ) are able to walk upright over shorter distances in them but are the anatomical features listed above are not available. Even older fossils of monkeys that come as close relatives of the forerunners of the Hominini in question, these features do not show.
All tardigrades ( Tardigrada ) possess calcareous stilettos as mouthparts. The structure is very similar in all species of this animal strain, that is, they can be regarded as homologous to each other. Although stilettos come in other animals such as insect larvae or nematodes before ( Nematoda ), but these stilettos differ both in the fine structure as well as in development. Therefore, the purpose-built Stilettapparate the tardigrades can be interpreted as an autapomorphy.
Distinction of analogies
In the evaluation of characteristics must be kept in mind that similar ( analog ) can arise organs by convergent evolution, such as Saumflossen for squid ( Theutida ) and fish ( Pisces) or the four -chambered heart of mammals ( Mammalia) and birds ( Aves). That there is an autapomorphy of a taxon in a characteristic, is likely if it is homologous within a taxon and does not appear at all closely related groups. The probability of homology increases with the complexity of the feature.
However autapomorphy may be the absence of a feature. In case of missing features, the assessment of homology is not logically possible because only existing features can be compared.