But the word is also suggested for something very different: an invasive species that disrupts an ecosystem and drives native species to extinction without necessarily thriving itself.  These 'ghosts', notes Olivia Judson:
have been detected in mathematical models more often than they’ve been sighted in nature. In fact, it’s not clear that they exist.
 See, for example, this from Scott Wiedensaul, 2002. I first used the term this way in a talk in June 2007. It appears in the title of a piece by Robert Macfarlane discussed here.
 The ghost of competition present. Miller, T. E., Horst, C. P. and Burns, J. H. American Naturalist 173: 347-353. (pdf )