Characteristics species diversity, in isolated geographic regions, is maintained by barriers like large rivers, seas, oceans, mountains, and deserts. Ships and airplanes now import or export species, from one continent to other on a time scale of days.
Alien species affect native species’ composition and distribution.
Invasive species are generally hardy, long-lived, and voracious with high rapid reproduction rate, high dispersal ability, and phenotypic plasticity. In absence of natural enemies, they control the ecosystem, and compete with native species for survival.
The scourge of Invasive Alien Species (IAS) is probably the second important threat to biodiversity, after habitat destruction. Introduction of Nile perch resulted in the extinction of more than 200 other fish species. The continuous release of the mosquito fish is a remarkable example of biological invasion.
IAS presently are a focus of international conservation concern. The Invasive Species Specialist Group (ISSG)
, a specialist group of the Species Survival Commission (SSC) of the World Conservation Union (IUCN) listed “100 of the World’s Worst Invasive Alien Species” into 12 groups like microorganism, macro fungi, aquatic plant, land plant, aquatic invertebrate, land invertebrate, amphibian, fish, bird, reptile ,and mammal. Brief description of IAS like Crazy Ant (Anoplolepis gracilipes
), Brown Tree Snake( Boiga irregularis),
Caulerpa Seaweed( Caulerpa taxifolia),
Avian Malaria ( Plasmodium relictum
),Feral pig( Sus scrofa),
Strawberry Guava( Psidium cattleianum
), Miconia( Miconia calvescens
), Western Mosquito fish( Gambusia affinis),
Small Indian Mongoose( Herpestes javanicus auropunctatus
), Rosy Wolfsnail( Euglandina rosea),
Water Hyacinth( Eichhornia crassipes
), Nile Perch ( Lates niloticus
) and a complete list 100 IAS are available in "100 of the World's Worst Invasive Alien Species