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Chrístõ
chris@cjsquire.plus.com


On Fri Aug 25, Bob Bridges wrote
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. . forgetting until just now that the famous moths didn't adapt.  We were told at the time that they did, but I gather the later conclusion is that light-winged moths started to die off, and dark-winged moths correspondingly prospered.

There’s adapt at the organism level (e.g. sheltering from a shower under a tree to keep dry) and at the species level as the moths did. The OED lists 7 distinct meanings for ‘adapt; the three from biology are relevant:

'ada t, v. Middle French . .
. . 6. trans. Biol. To modify (an organism, or part of one) through evolutionary change so that it better suits its environment or function. Usually with to, for.
1859 C. Darwin Origin of Species iv. 87 In social animals it [sc. natural selection] will adapt the structure of each individual for the benefit of the community . .

. . 7. intr. Biol.
a. Of an organism: to become acclimatized to environmental conditions, esp. new or changing conditions, through physiological or behavioural change.
. . 2008 N. Draper & C. Hodgson Adventure Sport Physiol. x. 388/1 As you adapt to altitude, catecholamine secretion is reduced.

. . b. Of a variety or species of organism: to become modified through evolution to better fit the environment or an ecological niche. Frequently with to.
1956 Sci. News-let. 12 May 302/2 Through evolution, living creatures adapt closely to their environment . . ‘

The moths are 7.b. 6.a is equivalent.
…………………
From the linked NYT and scientific paper:

. . In a study published in Nature, researchers have pinpointed the precise genetic mutation that led to the darker moth and determined just when this mutation occurred. The same gene, called cortex, was also found to control color patterns on the wings of tropical butterflies in a separate study.

The once rare black peppered moth became commonplace in the United Kingdom during the Industrial Revolution, when its original light speckled wings became a clear target for predators against tree trunks darkened by coal soot. A black version of the same species appeared around 1819, according to the new study. By blending in with the coal-darkened trees, it avoided becoming lunch for birds, passed down its genes and outnumbered the original moth in urban areas for a time.

After searching through a large area of this moth’s genome, Ilik Saccheri, an evolutionary ecologist, and his colleagues at the University of Liverpool found that a single mutation on a gene called cortex was responsible for the wings’ black coloring. The mutation is on a “jumping gene,” or a transposable element, which can hop between locations on the genome . .

[www.nytimes.com/2016/06/02/science/moths-butterflies-dna-cortex-genes.html]

‘The industrial melanism mutation in British peppered moths is a transposable element’

‘Discovering the mutational events that fuel adaptation to environmental change remains an important challenge for evolutionary biology. The classroom example of a visible evolutionary response is industrial melanism in the peppered moth (Biston betularia): the replacement, during the Industrial Revolution, of the common pale typica form by a previously unknown black (carbonaria) form, driven by the interaction between bird predation and coal pollution1. The carbonaria locus has been coarsely localized to a 200-kilobase region, but the specific identity and nature of the sequence difference controlling the carbonaria–typica polymorphism, and the gene it influences, are unknown.

Here we show that the mutation event giving rise to industrial melanism in Britain was the insertion of a large, tandemly repeated, transposable element into the first intron of the gene cortex. Statistical inference based on the distribution of recombined carbonaria haplotypes indicates that this transposition event occurred around 1819, consistent with the historical record. We have begun to dissect the mode of action of the carbonaria transposable element by showing that it increases the abundance of a cortex transcript, the protein product of which plays an important role in cell-cycle regulation, during early wing disc development.

Our findings fill a substantial knowledge gap in the iconic example of microevolutionary change, adding a further layer of insight into the mechanism of adaptation in response to natural selection. The discovery that the mutation itself is a transposable element will stimulate further debate about the importance of ‘jumping genes’ as a source of major phenotypic novelty3.’

Arjen E. van’t Hof et al. Nature 534, 102–105 (02 June 2016)
[www.nature.com/nature/journal/v534/n7605/full/nature17951.html]


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