Here are some common traits belonging to invasive species . A tourist fulfills most of the criteria on the checklist.

• The ability to reproduce both asexually as well as sexually (garbage and cultural leavings as a byproduct)
  
• Fast growth
• Rapid reproduction (not restricted to babies)
  
• High dispersal ability (planes trains tour-buses cruise ships)
• Phenotypic plasticity (the ability to alter one’s growth form to suit current conditions) (dress native, get all the right travel gear, dip in and out of cultures)

• Tolerance of a wide range of environmental conditions (generalist) (again, specialized gear)
• Ability to live off of a wide range of food types (generalist) (when in Rome…)
• Association with humans (anthro-fetishism and the McDonald’s phenomenon)
• Other successful invasions (war and peace)

(from wikipedia)