It appears that Ash trees are evolving resistance to the dieback that has swept Europe.

Ash trees are fighting back against a disease that has ravaged the British countryside, new scientific evidence shows.

When ash dieback arrived in 2012, predictions suggested up to 85% of ash trees could be lost.

But now scientists have discovered that ash woodlands are naturally evolving greater resistance to the infection.

The discovery offers renewed hope that the much-loved trees will survive in the British landscape.

BBC News

Shoots of hope for Britain's cherished ash trees

Scientific evidence suggests ash trees are ‘fighting back’ against a deadly disease.

28 minutes ago, studiot said:

It appears that Ash trees are evolving resistance to the dieback that has swept Europe.

BBC News

Shoots of hope for Britain's cherished ash trees

Scientific evidence suggests ash trees are ‘fighting back’ against a deadly disease.

Why not also post the report about N Sea cod evolving to be smaller, so they escape through the trawl nets of fishing boats?

Just now, exchemist said:

Why not also post the report about N Sea cod evolving to be smaller, so they escape through the trawl nets of fishing boats?

Had I seen that report I could have said I left that for you.

Does this not mean the dieback-resistant phenotypes are the ones that are left and not that they've evolved i.e. mutations have since occurred? An existing phenotype has been selected by the environment to perpetuate. Or am I mincing words? Same idea with the small cod in exchemist's post. @CharonY

Still a type of evolution, usually called directional selection. Mutation is but one of several mechanisms of evolution.

4 hours ago, StringJunky said:

Does this not mean the dieback-resistant phenotypes are the ones that are left and not that they've evolved i.e. mutations have since occurred? An existing phenotype has been selected by the environment to perpetuate. Or am I mincing words? Same idea with the small cod in exchemist's post. @CharonY

Darwin’s principle, as I recall it, was variation plus natural selection. That seems a good description of both the cod case and the ash case. And also that of the peppered moth, too, which is often held up as the classic example.

In terms of the modern definition of evolution, all signify changes in the allele frequency within a population, which I think (?) is how they define it now.

6 hours ago, studiot said:

Had I seen that report I could have said I left that for you.

Fair enough. Here you go: https://www.science.org/content/article/incredible-shrinking-cod

Edited June 27Jun 27 by exchemist

Good to hear! Thanks @studiot +1

Does anyone remember the eastern tree frogs from Chernobyl and how they became increasingly melanated when you GRT closer and closer to the exclusion zone?

4 hours ago, StringJunky said:

and not that they've evolved i.e. mutations have since occurred?

I think that is down to a bit of a difference in language use between common and scientific usage. In biology an evolved trait does not mean that a trait emerges that was not there in the population. Rather it refers to some threshold increase in frequency (often in comparison to other traits or to some other baseline).

The study in question is a bit more interesting than that, though they looked at multiple things. First, it is not a study looking a single allele which is under strong selection. Examples of these are fairly common, and there are a lot of models (say antibiotic resistance genes) where one can look at those.

Rather, the folks look at many loci and found that there was a large shift in many loci between adult trees before the fungal outbreak and juvenile trees. In their simulations they estimated about a third of the juvenile population was selected against and in the surviving population there are many genomic shifts which could not explained by random selection. Thus it is an example of polygenic adaptive change in the population over a short time frame. And again change is meant in terms of frequency change and not necessarily change due to something new popping up, though some might be new.

4 hours ago, StringJunky said:

Does this not mean the dieback-resistant phenotypes are the ones that are left and not that they've evolved i.e. mutations have since occurred? An existing phenotype has been selected by the environment to perpetuate. Or am I mincing words? Same idea with the small cod in exchemist's post. @CharonY

As VAT said, that phenotype could have been here already in small numbers as a variation, and now that variant and off spring of that variant are able to survive.

It is a shame the same thing did not happen with Dutch Elm in the 1960s/70s.

Also fungal disease like dieback, that was spread by beetles which devastated the UK population and elsewhere.

Just now, pinball1970 said:

As VAT said, that phenotype could have been here already in small numbers as a variation, and now that variant and off spring of that variant are able to survive.

Yes pretty much, though again the interesting thing here is that we are looking multi-loci changes which will have a range of phenotypes. And among those they somehow confer protection, but is a bit different to the textbook one (or few) gene and a specific phenotype situation.

And to be clear, this is likely what happens much more common overall compared to the highly specific examples we find in textbooks. But the main reason we usually talk about the simple cases is because the others are technically difficult to assess and in many cases we don't really understand the underlying mechanism. Just that somehow the new genotype in this specific situation seems to be beneficial.

It is the biology equivalent to physic's spherical cow in a vacuum model.

7 minutes ago, Sohan Lalwani said:

Good to hear! Thanks @studiot +1

Does anyone remember the eastern tree frogs from Chernobyl and how they became increasingly melanated when you GRT closer and closer to the exclusion zone?

+1 I certainly do!

I posted on another site as there was a physics angle to it.

https://onlinelibrary.wiley.com/doi/full/10.1111/eva.13476

Just now, pinball1970 said:

+1 I certainly do!

I posted on another site as there was a physics angle to it.

https://onlinelibrary.wiley.com/doi/full/10.1111/eva.13476

IIRC that study did not do genetic work. I.e. while it was speculated that there was adaptation, I don't recall that they e.g. bred the frogs to see whether the coloration persisted.

27 minutes ago, pinball1970 said:

+1 I certainly do!

I posted on another site as there was a physics angle to it.

https://onlinelibrary.wiley.com/doi/full/10.1111/eva.13476

Very interesting, thanks!

18 minutes ago, pinball1970 said:

+1 I certainly do!

I posted on another site as there was a physics angle to it.

https://onlinelibrary.wiley.com/doi/full/10.1111/eva.13476

I remember that one. Melanin seems to act as a radical scavenger as well as absorbing UV. So it is apparently capable of mitigating the effects on the body - at least on the skin - of ionising radiation, by mopping up some of the free radicals generated.

21 minutes ago, CharonY said:

IIRC that study did not do genetic work. I.e. while it was speculated that there was adaptation, I don't recall that they e.g. bred the frogs to see whether the coloration persisted.

A quick glance yes that's right. They found a positive correlation wrt to pigmentation and distance to the plant, measured colour and screened the liver for oxidative stress/markers but no mention of genetics.

4 hours ago, pinball1970 said:

As VAT said, that phenotype could have been here already in small numbers as a variation, and now that variant and off spring of that variant are able to survive.

It is a shame the same thing did not happen with Dutch Elm in the 1960s/70s.

Also fungal disease like dieback, that was spread by beetles which devastated the UK population and elsewhere.

Yes. it is sad. It's a nice wood. I lived in part of an old Georgian rectory and all the doors and most of the structural wood was local elm.

Not meant as a criticism, but thinking about the title, obviously the score would be far higher in favour of evolution, even if we limited ourselves to studies to a topic like e.g. "rapid evolution of novel trait".

I think most studies are just not sexy enough (though some the traits are sexual) to make it to newspapers.

I am supposing those new saplings with the resistance are descendants of specific parent(s) that already had that different genetics - selection amongst existing variations seems more likely than specific, recent mutation, ie more likely that some already had that but for other reasons they were not shared universally (not homologous) within the species. Seems possible it IS very recent mutation and rare within the overall population but pinning that down could take wide ranging sampling and genetic testing, although if it a rare and localised phenomena that might be indicative.

Not sure it is can be assumed it is all good. Any widespread loss of all those without that resistance - the trait becomes homologous - will reduce the genetic diversity, which may include losing some of the traits that made the larger population so successful. It is not like climate and other environmental factors are stable anymore - less diversity can be a longer term problem.

27 minutes ago, Ken Fabian said:

but for other reasons they were not shared universally (not homologous) within the species.

I am not entirely sure what you mean or at least the use of the term homologous seems a bit odd to me. Do you mean present in all members of a species, such as in a fixed allele?

28 minutes ago, Ken Fabian said:

Seems possible it IS very recent mutation and rare within the overall population but pinning that down could take wide ranging sampling and genetic testing, although if it a rare and localised phenomena that might be indicative.

That is unlikely as they looked at many loci. The likelihood of many variants arising and being beneficial within a short time frame is rather slim. And that also somewhat addresses your comment regarding diversity- we are not looking one specific allele that is getting fixed.

Edit: perhaps to reduce some confusion regarding terms, we mostly use homologous to refer to e.g. genes between taxa that share a common ancestry. Depending on the genes are separated we also distinguish between orthologs (separation via speciation) or paralaogs (separation via duplication). I am not familiar with the use of homology in that context of sharing within a species.

I could be wrong about the term - my understanding is that a morphology shared by all members of a clade would be considered homologous - thereby showing ancestry in common - and that this would apply within a species. It may be a different term within a species - a fixed trait maybe - versus sub-species variants. I may need to re-read and refresh.

@CharonY PS - It may not be correct usage but I think 'species' is an arbitrary concept, versus shared traits as evidence of ancestry - homology that applies to clades - that looks sound.

Clade - a grouping of organisms with a common ancestor and all of its lineal descendants.

3 hours ago, Ken Fabian said:

@CharonY PS - It may not be correct usage but I think 'species' is an arbitrary concept, versus shared traits as evidence of ancestry - homology that applies to clades - that looks sound.

Clade - a grouping of organisms with a common ancestor and all of its lineal descendants.

In a way they are, but within that the usage tends to be fairly specific. I think you have been thinking about homologous traits, which refers to similar basic structures that are found in different taxonomic units. Within a population this, to my knowledge is not referred to as that.

How we define taxa is a somewhat different issue. But generally speaking, if we have free gene flow I don't we would refer it as those. Mind you, I am mostly coming from a molecular perspective so I am not sure whether there is another usage (I suspect that I would have come across that by accident, though).