Adaptation from Leaps in the Dark

Woodruff, R. C.; Zhang, Mingcai

doi:10.1093/jhered/esn058

Cited by 7 publications

(7 citation statements)

References 39 publications

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“…TE expression at these pre-meiotic stages can also yield clusters of progeny carrying identical transposition-induced mutations. (55) Such pre-meiotic clusters have major implications for transposon-mediated host evolution because they increase the fixation probability of a new mutant allele and the likelihood that the new mutation will precipitate reproductive isolation. (56) TEs as a source of new genes and genetic regulatory networks…”

Section: Transposable Elements Drive the Evolution Of Epigenetic Silementioning

confidence: 99%

Transposable elements and an epigenetic basis for punctuated equilibria

2009

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Evolution is frequently concentrated in bursts of rapid morphological change and speciation followed by longterm stasis. We propose that this pattern of punctuated equilibria results from an evolutionary tug-of-war between host genomes and transposable elements (TEs) mediated through the epigenome. According to this hypothesis, epigenetic regulatory mechanisms (RNA interference, DNA methylation and histone modifications) maintain stasis by suppressing TE mobilization. However, physiological stress, induced by climate change or invasion of new habitats, disrupts epigenetic regulation and unleashes TEs. With their capacity to drive non-adaptive host evolution, mobilized TEs can restructure the genome and displace populations from adaptive peaks, thus providing an escape from stasis and generating genetic innovations required for rapid diversification. This ''epi-transposon hypothesis'' can not only explain macroevolutionary tempo and mode, but may also resolve other long-standing controversies, such as Wright's shifting balance theory, Mayr's peripheral isolates model, and McClintock's view of genome restructuring as an adaptive response to challenge.

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Section: Transposable Elements Drive the Evolution Of Epigenetic Silementioning

confidence: 99%

Transposable elements and an epigenetic basis for punctuated equilibria

2009

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“…Because of the low frequency of favorable, large-step mutations we can assume that two will not occur in the same individual, nor even in the same population at a given time (but note that Woodruff and Zhang, 2009, suggest that premeiotic mutation could produce several identical mutant alleles within the same population). This allows focus on mutant individuals bearing this sort of mutation, and their expectation of survival to a first reproduction.…”

Section: Lsa Approachmentioning

confidence: 99%

Flatfishes, Turtles, and Bolyerine Snakes: Evolution by Small Steps or Large, or Both?

Frazzetta

2011

Evol Biol

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Step size in evolution is rapidly becoming a major subject of interest to biologists. Traditionally, small changes alone were seen as significant in evolution, and any large differences between an ancestor and its descendant could be explained entirely by the accumulation of many small steps. Whether the evolution of major adaptations is mainly a matter of amassing such small increments of change, or if a significant proportion occurs through the inclusion of one or more large steps, is vital to the understanding of how evolution works. This paper begins by examining four ''classic'' examples of animalsflatfishes, turtles, bolyerine snakes, and gastropod molluscs-each of which has seemed difficult to interpret as resulting from a continuous series of tiny increments. Recently, however, arguments have appeared to contradict those views, and to propose instead that each of these animal groups arose through continuous adaptive modifications. While some of these arguments are more plausible than others, the view of the present author is that in none of them is there convincing evidence to conclude that the groups arose solely through gradual changes. More specifically, there is no basis to reject an evolutionary origin of the major traits in each group that included at least one principal inovation, occurring in a large, discontinuous step, preceded and followed by relatively small, more gradual changes. The broader question of how discontinuous evolution may occur is addressed through several means. These include considerations of epigenetic (sensu Waddington) development, comparative embryology, population genetics, and other approaches. Overall the phenomenon of adaptive accommodation is seen as of major importance, and its implications for ameliorating possible deleterious attributes of novel phenotypes are discussed. In the course of these analyses the doctrine that all adaptive evolution is driven by external environmental change is reviewed. It is suggested that while small adaptive changes are often closely related to shifts in specific environmental facets, the modifications associated with more major adaptations may be less so.

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“…Selection acting on standing genetic variation and on new mutations is responsible for adaptations to new environments. Yet, the magnitude of the role of preexisting variation vs. new mutations is unknown (Haldane 1932;Fisher 1930;Maynard Smith 1976;Hill 1982;Nei 2007;Gillespie 1991Gillespie , 2006Hartl and Taubes 1998;Orr 1998Orr , 2005aOrr , b, 2009Orr , 2010Orr and Betancourt 2001;Yedid and Bell 2002;Bull and Otto 2005;Rokyta et al 2005;Houle and Kondrashov 2006; Barrett and Schluter 2007;Lynch 2007;Brookfield 2009;Stoltzfus and Yampolsky 2009;Woodruff and Zhang 2009;Azad et al 2010;Lynch and Abegg 2010;Pritchard et al 2010 and references therein). To estimate the effect of mutation on adaptations, genetic variation in the founding populations should be eliminated by using homozygous isogenic stocks so that fitness changes and selection responses over generations can be attributed to new beneficial mutations (Knight and Robertson 1957;Hollingdale and Baker 1971;Caballero et al 1991;Hill and Caballero 1992;Mackay et al 1994;Bataillon 2000;Azad et al 2010).…”

Section: Introductionmentioning

confidence: 99%

Adaptation of Drosophila melanogaster to increased NaCl concentration due to dominant beneficial mutations

2010

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New beneficial mutations, combined with selection, were responsible for quick adaptation of Drosophila melanogaster to a novel environment. Using a highly inbred homozygous stock of D. melanogaster, we observed that in thirty generations the original stock had evolved to resist a previously toxic level of dietary salt (NaCl) and to produce a significantly higher number of progeny when reared in elevated salt concentrations. Survival in higher salt-stressed environments was due to new dominant genetic changes on the second and third chromosomes.

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Adaptation from Leaps in the Dark

Cited by 7 publications

References 39 publications

Transposable elements and an epigenetic basis for punctuated equilibria

Transposable elements and an epigenetic basis for punctuated equilibria

Flatfishes, Turtles, and Bolyerine Snakes: Evolution by Small Steps or Large, or Both?

Adaptation of Drosophila melanogaster to increased NaCl concentration due to dominant beneficial mutations

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