EDIT

For PalmWeb (and may be others) the updated by/when logging doesn't work. Probably this is due to the update listener doesn't work correctly.

Example: Aiphanes acaulis Galeano & R.Bernal

It has been audited 7 times (though only the last two changes did really change something

SELECT * FROM TaxonNameBase_AUD
WHERE id = 3653
ORDER BY created DESC, id DESC

The created by has been correctly recorded but updated by/when is still null though the last update on 2011-06-11 was definetly with a user logged in (admin).