Alien species are highly invasive and threat to indigenous species.Substantiate this statement with any two examples.

Explanation

Exotic species or Alien species are plant oranimal species that are introduced deliberatel or accidentally into a new habitat, to which they are not native. Exotic species may be introduced deliberately by man and sometimes inadvertently. Most of the species fail to survive outside their home range but some of these species may be predators, and have features make them very competitive (invasive).
They may even eliminate the endemic species, some examples of such species are,-
(a) Eicchornia ( water hyacinth) which is a very fast growing weed in many eutrophic (nutrier rich ) lakes and rivers in tropical countries including India. It binders the growth and multiplication of other plants and even causes problems in navigation.
(b) Parthenium (carrot grass ) is another exotic weed which grows very rapidly. it has invade a large number o forestrs and adversely affected the growth and multiplication of other species.
(i) Habitat destruction
(ii) Fragmentation
(iii) Introduction of Exotic species till multiplication of other species