Synapomorphy and apomorphy
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In
phylogenetics In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanisms, ...

phylogenetics
, an apomorphy (or derived trait) is a novel
character Character(s) may refer to: Arts, entertainment, and media Literature * ''Character'' (novel), a 1936 Dutch novel by Ferdinand Bordewijk * ''Characters'' (Theophrastus), a classical Greek set of character sketches attributed to Theophrastus M ...
or character state that has
evolved Evolution is change in the heritable Heredity, also called inheritance or biological inheritance, is the passing on of Phenotypic trait, traits from parents to their offspring; either through asexual reproduction or sexual reproduction, ...

evolved
from its ancestral form (or
plesiomorphy File:Cladogram imaginary birds.jpg, Imaginary cladogram. The yellow mask is a plesiomorphy for each living masked species, because it is ancestral. It is also a symplesiomorphy for them. But for the four living species as a whole, it is an apomorph ...
). A synapomorphy is an apomorphy shared by two or more
taxa In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanism ...
and is therefore
hypothesized A hypothesis (plural hypotheses) is a proposed explanation for a phenomenon. For a hypothesis to be a scientific hypothesis, the scientific method requires that one can testable, test it. Scientists generally base scientific hypotheses on prev ...
to have evolved in their
most recent common ancestor In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanisms ...
. ) In
cladistics Cladistics (; ) is an approach to biological classification In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular ...

cladistics
, synapomorphy is synonymous with homology. An example of an apomorphy or synapomorphy is the presence of derived traits such as an erect
gait Gait is the pattern of movement Movement may refer to: Common uses * Movement (clockwork), the internal mechanism of a timepiece * Motion (physics), commonly referred to as movement Arts, entertainment, and media Literature * Movement ...
,
fur Fur is a thick growth of hair Hair is a protein filament that grows from follicles found in the dermis. Hair is one of the defining characteristics of mammals. The human body, apart from areas of glabrous skin, is covered in follicles ...

fur
, and
mammary gland A mammary gland is an exocrine gland in humans and other mammals that produces milk to feed young offspring. Mammals get their name from the Latin word ''mamma'', "breast". The mammary glands are arranged in organ (anatomy), organs such as the b ...
s in
mammal Mammals (from Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman Republ ...
s but not in other
vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic ma ...
animal Animals (also called Metazoa) are organisms that form the Animalia. With few exceptions, animals , , are , can , and grow from a hollow sphere of , the , during . Over 1.5 million animal have been —of which around 1 million are —b ...

animal
s like
amphibian Amphibians are ectothermic, tetrapod vertebrates of the Class (biology), class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial animal, ter ...
s and
reptile Reptiles, as most commonly defined, are the animals in the Class (biology), class Reptilia , a paraphyletic grouping comprising all amniotes except synapsids (mammals and their extinct relatives) and Aves (birds). Living reptiles comprise turtl ...

reptile
s, which have retained their ancestral traits of a sprawling gait and a lack of fur. Thus, each of these derived traits is an apomorphy of each individual mammalian
species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individu ...

species
and a synapomorphy of mammals in general, not shared by other vertebrates.


Etymology

The word —coined by German entomologist
Willi Hennig Emil Hans Willi Hennig (20 April 1913 – 5 November 1976) was a German German(s) may refer to: Common uses * of or related to Germany * Germans, Germanic ethnic group, citizens of Germany or people of German ancestry * For citizens of German ...

Willi Hennig
—is derived from the
Ancient Greek Ancient Greek includes the forms of the used in and the from around 1500 BC to 300 BC. It is often roughly divided into the following periods: (), Dark Ages (), the period (), and the period (). Ancient Greek was the language of an ...
words (''sún''), meaning "with, together"; (''apó''), meaning "away from"; and (''morphḗ''), meaning "shape, form".


Clade analysis

The concept of synapomorphy depends on a given clade in the tree of life.
Cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics Cladistics (, from Greek language, Greek , ''kládos'', "branch") is an approach to Taxonomy (biology), biological classification in whi ...

Cladogram
s are diagrams that depict evolutionary relationships within groups of taxa. These illustrations are accurate predictive device in modern genetics. They are usually depicted in either tree or ladder form. Synapomorphies then create evidence for historical relationships and their associated hierarchical structure. Evolutionarily, a synapomorphy is the marker for the most recent common ancestor of the monophyletic group consisting of a set of taxa in a cladogram. What counts as a synapomorphy for one clade may well be a primitive character or
plesiomorphy File:Cladogram imaginary birds.jpg, Imaginary cladogram. The yellow mask is a plesiomorphy for each living masked species, because it is ancestral. It is also a symplesiomorphy for them. But for the four living species as a whole, it is an apomorph ...

plesiomorphy
at a less inclusive or nested clade. For example, the presence of
mammary gland A mammary gland is an exocrine gland in humans and other mammals that produces milk to feed young offspring. Mammals get their name from the Latin word ''mamma'', "breast". The mammary glands are arranged in organ (anatomy), organs such as the b ...
s is a synapomorphy for
mammals Mammals (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the R ...
in relation to
tetrapod Tetrapods (; ) are four-limbed animals constituting the superclass Tetrapoda (). It includes Neontology#Extant taxa vs. extinct taxa, extant and extinct amphibians, reptiles (including dinosaurs and therefore birds), and synapsids (including mam ...
s but is a
symplesiomorphy File:Cladogram imaginary birds.jpg, Imaginary cladogram. The yellow mask is a plesiomorphy for each living masked species, because it is ancestral. It is also a symplesiomorphy for them. But for the four living species as a whole, it is an apomorph ...
for mammals in relation to one another—rodents and primates, for example. So the concept can be understood as well in terms of "a character newer than" (
autapomorphy In phylogenetics In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiol ...

autapomorphy
) and "a character older than" (
plesiomorphy File:Cladogram imaginary birds.jpg, Imaginary cladogram. The yellow mask is a plesiomorphy for each living masked species, because it is ancestral. It is also a symplesiomorphy for them. But for the four living species as a whole, it is an apomorph ...
) the apomorphy: mammary glands are evolutionarily newer than vertebral column, so mammary glands are an autapomorphy if vertebral column is an apomorphy, but if mammary glands are the
apomorph Cladistics (, from Greek , ''kládos'', "branch") is an approach to biological classification in which organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual contiguous sys ...
y being considered then vertebral column is a plesiomorphy.


Relations to other terms

These phylogenetic terms are used to describe different patterns of ancestral and derived character or trait states as stated in the above diagram in association with apomorphies and synapomorphies. *
Symplesiomorphy File:Cladogram imaginary birds.jpg, Imaginary cladogram. The yellow mask is a plesiomorphy for each living masked species, because it is ancestral. It is also a symplesiomorphy for them. But for the four living species as a whole, it is an apomorph ...
– an ancestral trait shared by two or more taxa. ** ''Plesiomorphy'' – a symplesiomorphy discussed in reference to a more derived state. ** Pseudoplesiomorphy – is a trait that cannot be identified as neither a plesiomorphy nor an apomorphy that is a reversal. * Reversal – is a loss of derived trait present in ancestor and the reestablishment of a plesiomorphic trait. * Convergence – independent evolution of a similar trait in two or more taxa. * ''Apomorphy'' – a derived trait. Apomorphy shared by two or more taxa and inherited from a common ancestor is synapomorphy. Apomorphy unique to a given taxon is autapomorphy. ** Synapomorphy/ homology – a derived trait that is found in some or all terminal groups of a clade, and inherited from a common ancestor, for which it was an autapomorphy (i.e., not present in ''its'' immediate ancestor). ** ''Underlying synapomorphy'' – a synapomorphy that has been lost again in many members of the clade. If lost in all but one, it can be hard to distinguish from an autapomorphy. **
Autapomorphy In phylogenetics In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiol ...

Autapomorphy
– a distinctive derived trait that is unique to a given taxon or group. * Homoplasy in is when a
trait Trait may refer to: * Phenotypic trait in biology, which involve genes and characteristics of organisms * Trait (computer programming), a model for structuring object-oriented programs (a template class in the C++ programming language) * Trait the ...
has been gained or lost independently in separate lineages during evolution. This
convergent evolution Convergent evolution is the independent evolution Evolution is change in the heritable Heredity, also called inheritance or biological inheritance, is the passing on of Phenotypic trait, traits from parents to their offspring; eithe ...
leads to species independently sharing a trait that is different from the trait inferred to have been present in their common ancestor. ** Parallel
homoplasy Homoplasy, in biology and phylogenetics, is when a Phenotypic trait, trait has been gained or lost independently in separate lineages over the course of evolution. This is different from Homology (biology), homology, which is the similarity of trait ...

homoplasy
– derived trait present in two groups or species without a common ancestor due to
convergent evolution Convergent evolution is the independent evolution Evolution is change in the heritable Heredity, also called inheritance or biological inheritance, is the passing on of Phenotypic trait, traits from parents to their offspring; eithe ...
. ** Reverse
Homoplasy Homoplasy, in biology and phylogenetics, is when a Phenotypic trait, trait has been gained or lost independently in separate lineages over the course of evolution. This is different from Homology (biology), homology, which is the similarity of trait ...

Homoplasy
– trait present in an ancestor but not in direct descendants that reappears in later descendants. * is the case where a character that appears homoplastic given the species tree actually has a single origin on the associated gene tree. Hemiplasy reflects gene tree-species tree discordance due to the Multispecies coalescent process, multispecies coalescent.


References


External links


Cladistics
Berkeley {{Phylogenetics Phylogenetics Evolutionary biology terminology de:Apomorphie#Unterteilung von Apomorphien