Final answer:
Exotic species pose a particular threat to island ecosystems, where they can rapidly become dominant and disrupt native ecological balances. Freshwater and estuarine ecosystems are also highly susceptible to alterations and invasions by exotic species.
Step-by-step explanation:
Exotic species are especially threatening to certain types of ecosystems, with the potential for significantly altering native biodiversity and ecological balance. While exotic species can be damaging to many environments, certain ecosystems are particularly vulnerable. One of the most threatened by these introductions is the island ecosystem, where native species often have no natural defenses against the invaders, leading to drastic changes or even extinction of endemic species.
Islands typically have less biodiversity when compared to larger land masses, so the introduction of an exotic species can quickly become dominant. This disrupts the pre-existing ecological equilibrium and can lead to serious conservation challenges. Similarly, freshwater and estuarine ecosystems are also among the most altered and invaded systems, where exotic species combined with human alteration and climate change put significant pressure on native species and biodiversity.