Depends on what you mean by “invasive species”, and whether you're willing to look at both, the negative and positive connotations to them, rather than just the negative. read more
Using the convenient definition that an “invasive species” is any species that is introduced by humans, wittingly or unwittingly, into an environment which it has never habitated before, I think I do know the most widespread “invasive genus” in India, which I first came across in the Nilgiris, Tamil Nadu; my parents’ favourite holiday destination. read more
This is a list of 100 of the "worst" invasive species in the Global Invasive Species Database, as of 2014. The IUCN Invasive Species Specialist Group (ISSG), which maintains the list, acknowledges that it is "very difficult to identify 100 invasive species from around the world that really are 'worse' than any others." read more
The black rat is most likely one of the first invasive species to ever be inadvertently distributed by humans. The species originated in tropical Asia, but is believed to have reached Europe by the first century A.D. before spreading across the world, hitching rides en masse on European ships. read more