Movement of species

Alien or exotic species my become established at any trophic level in the ecosystem. These follow several shared features:
·They have enhanced survival rates
·they lack any natiuve predator
·susceptible to indigenous diseases

The UK has some notable examples of deliberate introductions:
·Game species
·Plant species for scenic purposes
·species brought in on purpose (eg hedgehogs)

There are also accidental introductions:
·species brought in ships
·species brought by air transport
·Well intentioned introductions can go wrong