Merge tables from different sources (APA citation)
If a student of mine asked me this I would say to write a brief introduction sentence (or paragraph) just before the table and indicate (verbally, as some say) as follows:


  The following table is based on work from Smith (2012) but does
  include additional rows. Those additional rows are marked with an asterisk (*).


Then I would simple mark the new rows with an asterisk.

The point is to make it very clear what originated with you and what originated with someone else. This does that clearly.