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Classification and differences between homologous, homoplastic, analogous, derived and ancestral traits?
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Larry King
Classification and differences between homologous, homoplastic, analogous, derived and ancestral traits?
This vocabulary is common in textbook but not in the peer-reviewed literature
First please note that while those terms are often used in intro class to evolutionary biology, they are actually rarely used in the peer-reviewed literature.
No trait value is fundamentally derived / ancestral
Note also that any given set of shared trait could be called ancestral or derived depending on the size of the tree that you consider. A trait is therefore not fundamentally ancestral / derived, it depends upon what other trait value you compare it to. Per consequence, it would easier to have a tree under our eyes to discuss these terms.
Note that there is one exception to that. Traits that are shared with LUCA are fundamentally ancestral!
Two states in different lineages can be fundamentally homologous / homoplastic
In general, when we are interest in a given trait, we display a tree so that all homologous trait states appear ancestral. While it is true that homoplastic trait state are necessarily derived when shown, homologous trait state can be shown as derived from a yet more ancestral trait state.
Analogy vs homoplasy
Many think of an analogy as a synonym of homoplasy. However, have a look at @GerardoFurtado's answer for the subtle difference between the two.
This vocabulary is common in textbook but not in the peer-reviewed literature
First please note that while those terms are often used in intro class to evolutionary biology, they are actually rarely used in the peer-reviewed literature.
No trait value is fundamentally derived / ancestral
Note also that any given set of shared trait could be called ancestral or derived depending on the size of the tree that you consider. A trait is therefore not fundamentally ancestral / derived, it depends upon what other trait value you compare it to. Per consequence, it would easier to have a tree under our eyes to discuss these terms.
Note that there is one exception to that. Traits that are shared with LUCA are fundamentally ancestral!
Two states in different lineages can be fundamentally homologous / homoplastic
In general, when we are interest in a given trait, we display a tree so that all homologous trait states appear ancestral. While it is true that homoplastic trait state are necessarily derived when shown, homologous trait state can be shown as derived from a yet more ancestral trait state.
Analogy vs homoplasy
Many think of an analogy as a synonym of homoplasy. However, have a look at @GerardoFurtado's answer for the subtle difference between the two.
As a complement to the other answer: homoplasy and analogy are not synonyms, but not for the reason described in your question.
According to Ridley (2011):
Analogy: A term mainly not used in this edition of the text, but close in meaning to homoplasy. That is, a character shared by a set of species but not present in their common ancestor — a convergently evolved character. Some biologists distinguish between homoplasies and analogies. (emphases mine)
Most of books on phylogenetic systematics treat analogy as a special case of homoplasy. A good explanation can be found, surprisingly (because he was not a systematicist), in Stephen J. Gould's last book (2002):
We now encounter the logical dilemma that underlies nearly all our extensive and lamentable confusion on this issue. Homoplasy and analogy might strike us, at first, as fully synonymous, for both invoke natural selection as the source of separate evolution for similar structures in two lineages. This synonymy certainly applies for convergence. But homoplasy comes in two flavors: parallelism and convergence — with parallelism as the historical root (in Lankester's original definition of homoplasy), but only convergence carrying the full flavor of synonymy [...] Unfortunately, a common error of human thinking leads us to define broad and variable categories by their clearest extreme cases. Thus, many scientists have assumed that all homoplasy, whether by parallelism or by convergence, must originate entirely for functional reasons, and not at all by constraint.
Therefore, all analogies are homoplasies, but not all homoplasies are analogies. As suggested by @Remi.b in the comments:
In short, an analogy is a homoplasy caused by convergent evolution. However, a homoplasy not caused by convergent evolution is not an analogy.
Sources:
Gould, S. (2002). The structure of evolutionary theory. Cambridge (Mass.): Harvard University Press.
Ridley, M. (2011). Evolution. Malden, Mass. [u.a.]: Blackwell.
As a complement to the other answer: homoplasy and analogy are not synonyms, but not for the reason described in your question.
According to Ridley (2011):
Analogy: A term mainly not used in this edition of the text, but close in meaning to homoplasy. That is, a character shared by a set of species but not present in their common ancestor — a convergently evolved character. Some biologists distinguish between homoplasies and analogies. (emphases mine)
Most of books on phylogenetic systematics treat analogy as a special case of homoplasy. A good explanation can be found, surprisingly (because he was not a systematicist), in Stephen J. Gould's last book (2002):
We now encounter the logical dilemma that underlies nearly all our extensive and lamentable confusion on this issue. Homoplasy and analogy might strike us, at first, as fully synonymous, for both invoke natural selection as the source of separate evolution for similar structures in two lineages. This synonymy certainly applies for convergence. But homoplasy comes in two flavors: parallelism and convergence — with parallelism as the historical root (in Lankester's original definition of homoplasy), but only convergence carrying the full flavor of synonymy [...] Unfortunately, a common error of human thinking leads us to define broad and variable categories by their clearest extreme cases. Thus, many scientists have assumed that all homoplasy, whether by parallelism or by convergence, must originate entirely for functional reasons, and not at all by constraint.
Therefore, all analogies are homoplasies, but not all homoplasies are analogies. As suggested by @Remi.b in the comments:
In short, an analogy is a homoplasy caused by convergent evolution. However, a homoplasy not caused by convergent evolution is not an analogy.
Sources:
Gould, S. (2002). The structure of evolutionary theory. Cambridge (Mass.): Harvard University Press.
Ridley, M. (2011). Evolution. Malden, Mass. [u.a.]: Blackwell.
This vocabulary is common in textbook but not in the peer-reviewed literature
First please note that while those terms are often used in intro class to evolutionary biology, they are actually rarely used in the peer-reviewed literature.
No trait value is fundamentally derived / ancestral
Note also that any given set of shared trait could be called ancestral or derived depending on the size of the tree that you consider. A trait is therefore not fundamentally ancestral / derived, it depends upon what other trait value you compare it to. Per consequence, it would easier to have a tree under our eyes to discuss these terms.
Note that there is one exception to that. Traits that are shared with LUCA are fundamentally ancestral!
Two states in different lineages can be fundamentally homologous / homoplastic
In general, when we are interest in a given trait, we display a tree so that all homologous trait states appear ancestral. While it is true that homoplastic trait state are necessarily derived when shown, homologous trait state can be shown as derived from a yet more ancestral trait state.
Analogy vs homoplasy
Many think of an analogy as a synonym of homoplasy. However, have a look at @GerardoFurtado's answer for the subtle difference between the two.
This vocabulary is common in textbook but not in the peer-reviewed literature
First please note that while those terms are often used in intro class to evolutionary biology, they are actually rarely used in the peer-reviewed literature.
No trait value is fundamentally derived / ancestral
Note also that any given set of shared trait could be called ancestral or derived depending on the size of the tree that you consider. A trait is therefore not fundamentally ancestral / derived, it depends upon what other trait value you compare it to. Per consequence, it would easier to have a tree under our eyes to discuss these terms.
Note that there is one exception to that. Traits that are shared with LUCA are fundamentally ancestral!
Two states in different lineages can be fundamentally homologous / homoplastic
In general, when we are interest in a given trait, we display a tree so that all homologous trait states appear ancestral. While it is true that homoplastic trait state are necessarily derived when shown, homologous trait state can be shown as derived from a yet more ancestral trait state.
Analogy vs homoplasy
Many think of an analogy as a synonym of homoplasy. However, have a look at @GerardoFurtado's answer for the subtle difference between the two.
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As a complement to the other answer: homoplasy and analogy are not synonyms, but not for the reason described in your question.
According to Ridley (2011):
Most of books on phylogenetic systematics treat analogy as a special case of homoplasy. A good explanation can be found, surprisingly (because he was not a systematicist), in Stephen J. Gould's last book (2002):
Therefore, all analogies are homoplasies, but not all homoplasies are analogies. As suggested by @Remi.b in the comments:
Sources:
As a complement to the other answer: homoplasy and analogy are not synonyms, but not for the reason described in your question.
According to Ridley (2011):
Most of books on phylogenetic systematics treat analogy as a special case of homoplasy. A good explanation can be found, surprisingly (because he was not a systematicist), in Stephen J. Gould's last book (2002):
Therefore, all analogies are homoplasies, but not all homoplasies are analogies. As suggested by @Remi.b in the comments:
Sources:
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