* This allows for linking of internal nodes of the species tree (as opposed
* to just external nodes, as in the method it overrides.
* If TaxonomyComparisonBase is null, it will try to determine it.
* This allows for linking of internal nodes of the species tree (as opposed
* to just external nodes, as in the method it overrides.
* If TaxonomyComparisonBase is null, it will try to determine it.