The repeated evolution of a particular character
Recurrent evolution is the repeated
mutation. Most evolution is the result of
drift, often interpreted as the random chance of some
alleles being passed down to the next generation and others not. Recurrent evolution is said to occur when patterns emerge from this stochastic process when looking across multiple distinct populations. These patterns are of particular interest to
evolutionary biologists, as they can demonstrate the underlying forces governing evolution.
Recurrent evolution is a broad term, but it is usually used to describe recurring regimes of
Phenotypic vs. genotypic levels
Recurrent changes may be observed at the phenotype level or the genotype level. At the phenotype level, recurrent evolution can be observed across a continuum of levels, which for simplicity can be broken down into molecular phenotype, cellular phenotype, and organismal phenotype. At the genotype level, recurrent evolution can only be detected using DNA sequencing data. The same or similar sequences appearing in the genomes of different lineages indicates recurrent genomic evolution may have taken place. Recurrent genomic evolution can also occur within a lineage; an example of this would include some types of phase variation that involve highly directed changes at the DNA sequence level. The evolution of different forms of phase variation in separate lineages represents convergent and recurrent evolution toward increased evolvability. In organisms with long generation times, any potential recurrent genomic evolution within a lineage would be difficult to detect. Recurrent evolution has been studied most extensively at the organismal level, but with the advent of cheaper and faster sequencing technologies more attention is being paid to recurrent evolution at the genomic level.
Convergent, parallel, and recurrent evolution
The distinction between convergent and parallel evolution is somewhat unresolved in evolutionary biology. Some authors have claimed it is a
phylogenetic relatedness among the organisms being considered. While convergent and parallel evolution can both be interpreted as forms of recurrent evolution, they involve multiple lineages whereas recurrent evolution can also take place within a single lineage.
[1][6]As mentioned before, recurrent evolution within a lineage can be difficult to detect in organisms with long generation times; however, paleontological evidence can be used to show recurrent phenotypic evolution within a lineage.pathogenic bacterium moving between hosts – and represent the other major source of recurrent evolution.
[6]
Examples
At the phenotypic level
On the island of
selection pressure for larger shell size in the snails.
[6]In
eusocial insects, new colonies are usually formed by a solitary queen, though this is not always the case. Dependent colony formation, when new colonies are formed by more than one individual, has evolved recurrently multiple times in ants, bees, and wasps.
[7]Recurrent evolution of polymorphisms in colonial invertebrate bryozoans of the order Cheilostomatida has given rise to zooid polymorphs and certain skeletal structures several times in evolutionary history.[8]
Neotropical tanagers of the genera Diglossa and
Diglossopis, known as flowerpiercers, have undergone recurrent evolution of divergent bill types.
[9]
There is evidence for at least 133 transitions between
bryophytes. Additionally, the transition rate from hermaphroditism to dioecy was approximately twice the rate in the reverse direction, suggesting greater diversification among hermaphrodites and demonstrating the recurrent evolution of dioecy in mosses.
[10]lateral gene transfer has also played a role in optimizing the C4 pathway by providing better adapted C4 genes to the plants.
[11]At the genotypic level
Certain genetic mutations occur with measurable and consistent frequency.purifying selection when it acts to maintain functionally important characters but also results in the loss or diminished size of useless organs as the
functional constraint is lifted. An example of this is the diminished size of the
Y chromosome in mammals, which can be attributed to recurrent mutations and recurrent evolution.
[12]
The existence of mutational "hotspots" within the genome often gives rise to recurrent evolution. Hotspots can arise at certain nucleotide sequences because of interactions between the DNA and DNA repair, replication, and modification enzymes.[13] These sequences can act like fingerprints to help researchers locate mutational hotspots.[13]
Cis-regulatory elements are frequent targets of evolution resulting in varied morphology.
[14] When looking at long-term evolution, mutations in cis-regulatory regions appear to be even more common.
[15] In other words, more interspecific morphological differences are caused by mutations in cis-regulatory regions than intraspecific differences.
[14]Across oligopeptides in the N-terminal tails of CenH3 have also been observed in humans and in mice.
[16]
Many divergent
GC-rich genomes are rarer among eukaryotes, but when they evolve independently in two different species the recurrent evolution of similar preferential
codon usages will usually result.
[1]"Generally,
regulatory genes occupying nodal position in
gene regulatory networks, and which function as morphogenetic switches, can be anticipated to be prime targets for evolutionary changes and therefore repeated evolution."
[17]See also
References
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