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  • reema
    Member
    • Feb 2014
    • 27

    #1

    Testing a force topology in mrBayes

    Hello Everybody,


    I have a question related to "Testing a topological hypothesis". I have
    tried to run the same procedure as mentioned in the tutorial in order to
    check whether two species form monophyletic group or not. As far as i
    understand the manual- - by setting hard constraint we are forcing two
    species to form a monophyletic group every time. And by setting the
    negative constraint we should reproduce the original topology. However, In
    my case , after running the analysis as mentioned in the manual- both hard
    and negative constraint are producing the same tree. After running the
    stepping stone analysis, i am getting some weird output in log file:-

    "24600 -- [nan] (nan) (nan) (nan) * [nan] (nan) (nan) (nan) (...0 remote
    chains"

    Run Marginal likelihood (ln)
    ------------------------------
    1 nan
    2 nan
    ------------------------------
    Mean: nan

    As I am running the entire analysis on the cluster. So, here's the command
    i am using for this analysis:-

    "begin mrbayes;
    set autoclose=yes nowarn=yes;
    execute Set1_Out_Ehist_Concat.nexus;
    lset rates=invgamma;
    constraint subell = Asub Aell;
    constraint nosubell = Asub Aell;
    prset topologypr = constraints(subell);
    mcmc ngen=100000 samplefreq=100 printfreq=100 diagnfreq=1000
    file=PositiveConstraint;
    sump burnin=25000;
    sumt burnin=25000;
    prset topologypr = constraints(nosubell);
    mcmc ngen=100000 samplefreq=100 printfreq=100 diagnfreq=1000
    file=NegativeConstraint;
    sump burnin=25000;
    sumt burnin=25000;
    prset topologypr = constraints(subell);
    ss ngen=250000 diagnfreq=2500 filename=positive;
    prset topologypr = constraints(nosubell);
    ss filename=negative;
    quit;
    end;
    "

    Here the Asub and Aell are the two species name that i want to be force to
    form a monophyletic group in the hard constraint.


    Now I don't understand what is happening here. And my questions are :-

    1) Why i am getting the same tree after setting hard and negative
    constraint?
    2) What does this "*nan"* mean in the stepping stone analysis?
    3) How do i known if the procedure i am running is correct or not?


    As these question making me very confuse now. So I would highly appreciate
    any help and clarification on this questions. I have also posted this question on the mrbayes mailing list[http://sourceforge.net/p/mrbayes/mai...age/34174009/] as well as biostar[https://www.biostars.org/p/145595/], but i didn't get any reply.

    Very much looking forward for the answer

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