When the environment changes suddenly, it upsets the species balance. A newcomer species can then take over in a population explosion because it has elsewhere previously adapted to the new local conditions giving it a competitive advantage over the native species. For example, global warming has allowed a virulent tropical fungus Cryptospordium Gattii to overwhelm the native fungi species on eastern Vancouver Island. One microbiologist said she was as astounded to see it so far north as she would at Godzilla making an appearance.
~ Roedy (born: 1948-02-04 age: 61)