Deviation of split frequencies simply measures the similarity of topologies across the two runs. With twelve taxa and lots of data you are likely to converge on identical/nearly identical trees rapidly and to remain at that optimum. This tells you little or nothing about convergence in other parameters.
On 6/16/10 4:52 AM, "Omar Rota Stabelli" <omar42@...> wrote:
I think it is because you have a reduced taxon sampling (12 taxa). I
work with a similar alignments but >50 taxa, and your kind of
convergence is just a mirage!
best
Omar
2010/6/15 Beatrice Parker <beatrice.d.parker@...>:
> Hi MrBayes users,
>
> I am running MrBayes on long aligmnents (nchar = 16955) of few (12) taxa,
> and I find the program behaving differently than with my usual datasets of
> more (3x to 6x) taxa and shorter (1/10 to 1/30) alignments. In particular,
> with my long alignments, I find the average standard deviation of split
> frequencies converges VERY quickly to below 0.01, and on these short runs
> (maybe inevitable with very short runs?), the plot generated by sump of the
> generation versus the log probability of the data shows values not evenly
> distributed (points have an obvious trend). (BTW- These runs are amino
> acid, using "mixed" model, always resulting in heavy use of Wag matrix.)
>
> Do long alignments result in really low values for average standard
> deviation of split frequencies, just because of their length? (I frequently
> get convergence to below 0.000000 in 10,000 generations.)
>
> If I continue runs long after convergence to below 0.01, or lower, is the
> data generated more or less meaningful than data generated on a run which is
> more slowly converging towards 0.01?
>
> Thanks for any advice.
> Beatrice
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--
Omar Rota Stabelli
Pisani Evolutionary Biology Lab, Department of Biology,
National University of Ireland, Maynooth, Co. Kildare, Ireland
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