Is a citation typically considered plural or singular in academia? My question parallels that of https://english.stackexchange.com/q/99886/117318, which asks whether "Gamma et al." should be considered singular or plural for verb conjugation. The top and accepted answer says that it depends whether the verb refers to the researchers (since the translation of the Latin is "Gamma and others", which is plural), or if it refers to the publication/work. 

Which usage is conventional in academia? 
Is there significant variation across fields that anyone is aware of? Are there best practices to avoid confusion?
If you say "Gemma et al." to mean the paper, then it is singular.  This is the usual case.  If you say "Gemma et al." to mean all the authors of the paper, then it is plural.  


  Gemma et al. describes the ants of Southeast Asia.  
  
  But note: Gemma et al. have never actually been to Southeast Asia.


added
Comments show this varies by field.  So look at some of the best recent papers in your own area, and see how they do it.  In fact, some areas do not write "Gemma et al." but something like "[7]" or "[Gem 1995]" or whatever code is in the bibliography.  Then of course we may write 


  [Gem 1995] describes the exceptional Lie algebras   


even if there are three authors.  Or, if you claim papers cannot take any actions,  


  [Gem 1995] contains a description of the exceptional Lie algebras