Origin, autecology, and spread of some of the world’s most troublesome aquatic weeds

Abstract

Abstract Aquatic plants are only troublesome when they grow where they are not wanted. There is no aquatic plant that is ipso facto harmful and can be considered a weed throughout its geographical range. There are even cases of plants that are protected in one region and ‘hunted’ in another, for example, Heteranthera reniformis (mud plantain) is on the list of endangered plants in Connecticut, USA, and is perhaps the worst weed today in the northern Italian rice fields. Trapa natans (water chestnut) is extinct or endangered in many parts of Europe, an important crop plant in India, a noxious weed in eastern North America and a very serious threat to the sturgeon fisheries (caviar industry) in the southern part of the Caspian Sea.