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Praise and questions

Posted by braney on 10 Jan 2010 at 21:09 GMT

First of all, let me say that I enjoyed this article and am encouraged that folks are still out there trying to understand the diversity of possible life forms.

Secondly, I have a flurry of comments/questions in no particular order or orientation.

I was surprised to see that evidence for being a clone was based on allozyme electrophoresis? Isn't this the sequencing age? There's an awful lot of evolution that doesn't take place at the amino acid level. How much sequence difference between samples could be considered variation within a single clone-population/individual? Within trees potentially connected below ground, how does one distinguish between an individual and a clonal population?

Also, the lack of evidence of viable acorns is not the same as evidence for the lack of viable acorns. Scrub jays are awfully good at collecting acorns, better than grad students I'd bet.

Determining age seems sort of pointless other than establishing a lower bound which would be based entirely on existing living tissue plus any evidence provided by dead wood (which it sounds like there wasn't much of). How do we know that Johnny Oak Seed/Acorn didn't plant saplings across this whole valley at one time? I see scrub jays planting/burying acorns all the time. If I place pots of soil outside my house in the fall, a good number of them have oak saplings in them in the spring.

On the other hand, how do we know the clone didn't exist for 100K years before it was established in this valley? Is there a maximum age of clonal population? What does it mean to be a clonal population if sequence variation due to random mutation exists across members of the population, especially if that sequence variation would be invisible at the protein level?

Thanks again for the article. I suspect there are quite a lot of ancient clonal populations dug in across the planet. I wonder how much of our biomass is in these "sub-optimal" situations?

No competing interests declared.

RE: Praise and questions

rilab replied to braney on 13 Jan 2010 at 16:43 GMT

Glad you enjoyed it.

We used allozymes because they were cheap and available. We were not so much interested in quantifying any kind of molecular evolution as we were simply testing whether stems were genetically identical. It is difficulty to believe that they are not clones given the observation of fixed heterozygosity.

Certainly we can't prove there are no viable acorns. But in at least annual visits to the clone over 9 years we have seen only a handful of mature acorns and have never seen a seedling. The mature-looking acorns we tried to germinate failed to do so, while similar looking acorns from another population of Palmer's oak germinated just fine.

While it is possible that all of the stems were planted at one time as you say, it is extremely unlikely that they would all share the same genotype, even if they were all full siblings.

There is no way or knowing the maximum. We discuss some of the reasons why it may be older than our estimate (of course there are reasons it may be younger, too!). I very much doubt it's 100K years old, but we can't know for sure.

No competing interests declared.