>>>>>>Somethings are never abbreviated and botanical names, I believe (could be wrong)
>>>>>>are among them. So chat. referring to Chateaubriand would not be correct
>>>>>>botanical Latin. It would be Chateaubriandiensis, meaning he was the one that
>>>>>>discovered the Quercus ruslanicus. 

No, no. "Quercus ruslanicus Chat." is of course correct.

"Chat." here is an abbreviation of author's surname (=person who described the species), as "L." for Linnaeus and "Nab." for Nabokov.

 "chateaubriandiensis" (or more correctly "chateaubriandi") would be the species name (epithet), teh second word in Linnaean binomen.

Say, in "Quercus chateaubriandi S. K.-B."

Victor Fet