Homoplasy

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Not to be confused with Homoplasmy.

Homoplasy, in biology and phylogenetics, is the term used to describe a feature that has been gained or lost independently in separate lineages over the course of evolution. This is different from homology, which is the term used to characterize the similarity of features that can be parsimoniously explained by common ancestry.[1] Homoplasy can arise from both similar selection pressures acting on adapting species, and the effects of genetic drift.[2][3]

Homoplasy is the similarity in a feature that is not parsimoniously explained by descent from a common ancestor.

Most often, homoplasy is viewed as a similarity in morphological characters. However, homoplasy may also appear in other character types, such as similarity in the genetic sequence,[4][5] life cycle types[6] or even behavioral traits.[7][5]

Etymology

The term homoplasy was first used by Ray Lankester in 1870.[8] The corresponding adjective is either homoplasic or homoplastic. It is derived from the two Ancient Greek words ὁμός (homós), meaning "similar, alike, the same", and πλάσσω (plássō), meaning "to shape, to mold".[9][10][11][4]

Parallelism and convergence

Chrysochloridae) and northern moles (Talpidae). These are mammals from different geographical regions and lineages, and have all independently evolved very similar burrowing characteristics (such as cone-shaped heads and flat frontal claws) to live in a subterranean ecological niche.[15]

Reversion

In contrast,

reversal (a.k.a. vestigialization) leads to homoplasy through the disappearance of previously gained features.[16] This process may result from changes in the environment in which certain gained characteristics are no longer relevant, or have even become costly.[17][3] This can be observed in subterranean and cave-dwelling animals by their loss of sight,[15][18] in cave-dwelling animals through their loss of pigmentation,[18] and in both snakes and legless lizards through their loss of limbs.[19][20]

Distinguishing homology from homoplasy

Homoplasy, especially the type that occurs in more closely related phylogenetic groups, can make phylogenetic analysis more challenging.

likelihood analysis
, where the most likely tree, given a particular model of evolution, is selected, and branch lengths are inferred.

According to the cladistic interpretation, homoplasy is invoked when the distribution of a character state cannot be explained parsimoniously (without extra inferred character state transformations between the terminals and their ancestral node) on a preferred phylogenetic hypothesis - that is, the feature in question arises (or disappears) at more than one point on the tree.[16]

In the case of DNA sequences, homoplasy is very common due to the redundancy of the genetic code. An observed homoplasy may simply be the result of

adaptationist evolutionary explanation.[5]

Examples and applications of homoplasy

There are numerous documented examples of homoplasy within the following taxa:

The occurrence of homoplasy can also be used to make predictions about evolution. Recent studies have used homoplasy to predict the possibility and the path of extraterrestrial evolution. For example, Levin et al. (2017) suggest that the development of eye-like structures is highly likely, due to its numerous, independently evolved incidences on earth.[16][32]

Homoplasy vs. evolutionary contingency

In his book Wonderful Life, Stephen Jay Gould claims that repeating the evolutionary process, from any point in time onward, would not produce the same results.[33] The occurrence of homoplasy is viewed by some biologists as an argument against Gould's theory of evolutionary contingency. Powell & Mariscal (2015) argue that this disagreement is caused by an equivocation and that both the theory of contingency and homoplastic occurrence can be true at the same time.[34]

See also

References

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  11. ^ Holt JR, Judica CA (February 4, 2014). "Systematic Biology - Dictionary of Terms: Homoplasy". Archived from the original on July 1, 2017. Retrieved September 21, 2018.
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