Multiple HOGs refer to the same OMAmer Root Hog

[iantsang-ebi]

Hi,

Could you please let me know why multiple orthologGroup ids refer to the same OMAmerRootHOG, and what this represents from a biological perspective?

I have also noticed that when multiple groups refer to the same OMAmerRootHOG, one group contains the majority of nested groups and genes, while the other groups have very few child groups and genes.

Below, HOG:0000011_5 has 154 children groups and 197 genes in total, while HOG:0000012_7 has 3 children groups and 5 genes in total.

Example from the OrthoXML:

$ grep "HOG:F0731889" -B 2 FastOMA_HOGs.orthoxml 
    <orthologGroup id="HOG:0000011_5" taxonId="5">
      <score id="CompletenessScore" value="0.208" />
      <property name="OMAmerRootHOG" value="HOG:F0731889" />
--
    <orthologGroup id="HOG:0000012_7" taxonId="7">
      <score id="CompletenessScore" value="0.0192" />
      <property name="OMAmerRootHOG" value="HOG:F0731889" />