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Dear knowledgeable bioinformaticians, I'm currently pursuing an undergraduate degree and as a result I do not have so much knowledge in this topic. I'm having some troubles understanding my phylogenetic three construction.

For the construction of a phylogenetic tree UGENE was used. 11 homologous proteins from different species in the same genus/phyla were aligned. For the tree construction PHYLYP Neighbour Joining (NJ) with the distance matrix model “Jones-Taylor-Thornton” was used. Two trees were constructed, one without bootstrapping and one with bootstrapping (1000 pseudoreplicates).

How do I interpret my values? Are they unusable since I have low bootstrap-values in a lot of my nodes? All guidance is appreciated, thank you.Without Bootstrap With Bootstrap

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  • $\begingroup$ Welcome to the site. Could you please clarify which one is without bootstrapping? It seems to be the one on the top, but I might be wrong $\endgroup$
    – llrs
    Nov 6, 2018 at 13:17
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    $\begingroup$ Thank you! The upper one is not bootstrapped, the lower one is the bootstrapped one. $\endgroup$
    – nazub
    Nov 6, 2018 at 13:51
  • $\begingroup$ Bootstrap values above 750 in the lower tree represent robust clades. Bootstraps above 800 are preferred and anything above 900 is strongly supported. $\endgroup$
    – M__ ♦
    Dec 28, 2018 at 21:05

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Bootstrap values usually give you useful information, be they low or high. Usually, a "high" bootstrap value is something >= 70%. That means a clade is strongly supported; lower values are telling you the clade is not clearly separated from others. This could be for several reasons, e.g.:

1) A subpopulation is not really separated from others, e.g. the viral sequences in town "A" and town "B" are completely admixed, meaning the population is panmictic and there is continuous gene flow between the two of them;

2) the populations diverged not long ago, it's too soon to have any phylogenetic signal, at least using the marker you are using (different genes evolve at different rates). Usually, housekeeping genes (which are usually very conserved) are used for populations that supposedly diverged long time ago.

The interpretation of your tree should take into account the biology and epidemiology of your target organism. If you really want to learn more, I suggest a lot of reading, and definitely a class dedicated to molecular phylogenetics.

This might be a good start: https://www.amazon.com/Phylogenetic-Handbook-Practical-Approach-Hypothesis/dp/0521730716

Also, the NJ algorithm should allow for uneven branch lengths, maybe the tree you are showing is the consensus tree?

Hope it helps

Max

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    $\begingroup$ The branch lengths are defaulted, however, they do allow different lengths based on how one would like them to look like. It's just a display function in UGENE. Thank you a lot for your comment, extremely helpful! $\endgroup$
    – nazub
    Nov 6, 2018 at 19:26
  • $\begingroup$ You're welcome, and good luck. If you found the comment useful, please consider upvoting it or accepting it as answer. $\endgroup$
    – Max_IT
    Nov 7, 2018 at 15:22
  • $\begingroup$ "the epidemiology" infers the bacteria are pathogenic. $\endgroup$
    – M__ ♦
    Dec 28, 2018 at 21:03

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