Introduced species
The process of human-caused introduction is distinguished from biological colonization, in which species spread to new areas through "natural" (non-human) means such as storms and rafting.
The Latin expression neobiota captures the characteristic that these species are new biota to their environment in terms of established biological network (e.g. food web) relationships.
[4][5] In the broadest and most widely used sense, an introduced species is synonymous with "non-native" and therefore applies as well to most garden and farm organisms; these adequately fit the basic definition given above.
However, some sources add to that basic definition "and are now reproducing in the wild",[6] which means that species growing in a garden, farm, or house may not meet the criteria unless they escape and persist.
[12] The biological definition of invasive species, on the other hand, makes no reference to the harm they may cause, only to the fact that they spread beyond the area of original introduction.
[6] From a regulatory perspective, it is neither desirable nor practical to list as undesirable or outright ban all non-native species (although the State of Hawaii has adopted an approach that comes close to this).
Early detection and rapid response is the most effective strategy for regulating a pest species and reducing economic and environmental impacts of an introduction.
Several introduced exotic trees served as nest sites for resident waterbird species in Udaipur city, India.
For example, soybeans, kiwi fruit, wheat, honey bees, and all livestock except the American bison and the turkey are non-native species to North America.
The apple snail was released in Southeast Asia with the intent that it be used as a protein source, and subsequently to places like Hawaii to establish a food industry.
Companies such as Monsanto that earn much of their profit through the selling of genetically modified seeds has added to the controversy surrounding introduced species.
[20] Pet animals have also been frequently transported into new areas by humans, and their escapes have resulted in several introductions, such as feral cats,[21] parrots,[22] and pond slider.
In other cases, species have been translocated for reasons of "cultural nostalgia", which refers to instances in which humans who have migrated to new regions have intentionally brought with them familiar organisms.
A more recent example is the introduction of the common wall lizard (Podarcis muralis) to North America by a Cincinnati boy, George Rau, around 1950 after a family vacation to Italy.
This involves the purposeful introduction of a natural enemy of the target species with the intention of reducing its numbers or controlling its spread.
[26] Examples of successful reintroductions include wolves to Yellowstone National Park in the U.S., and the red kite to parts of England and Scotland.
Increasing rates of human travel are providing accelerating opportunities for species to be accidentally transported into areas in which they are not considered native.
For example, three species of rat (the black, Norway and Polynesian) have spread to most of the world as hitchhikers on ships, and arachnids such as scorpions and exotic spiders are sometimes transported to areas far beyond their native range by riding in shipments of tropical fruit.
[28] Further there are numerous examples of marine organisms being transported in ballast water, among them the invasive comb jelly Mnemiopsis leidyi, the dangerous bacterium Vibrio cholerae, or the fouling zebra mussel.
[29] Busy harbors are all potential hotspots as well: over 200 species have been introduced to the San Francisco Bay in this manner making it the most heavily invaded estuary in the world.
[37] This species has become invasive in Australia, where it threatens native rare plants and causes erosion and soil slumping around river banks.
Examples of introduced animals that have become invasive include the gypsy moth in eastern North America, the zebra mussel and alewife in the Great Lakes, the Canada goose and gray squirrel in Europe, the beaver in Tierra del Fuego, the muskrat in Europe and Asia, the cane toad and red fox in Australia, nutria in North America, Eurasia, and Africa, and the common brushtail possum in New Zealand.
Originating in a region encompassing Iran and India, it was introduced to the West Indies and Hawaii in the late 1800s for pest control.
[42] For example, escaped horses and donkeys that have gone feral in the Americas may play ecological roles similar to those of the equids that became extinct there at the end of the Pleistocene.
Some species, such as the Western honey bee, brown rat, house sparrow, ring-necked pheasant, and European starling, have been introduced very widely.
In addition there are some agricultural and pet species that frequently become feral; these include rabbits, dogs, ducks, snakes, goats, fish, pigs, and cats.
Many water fleas such as Daphnia, Bosmina and Bythotrephes have introduced around the world, causing dramatic changes in native freshwater ecosystems.
In plants, introduced species have been observed to undergo rapid evolutionary change to adapt to their new environments, with changes in plant height, size, leaf shape, dispersal ability, reproductive output, vegetative reproduction ability, level of dependence on the mycorrhizal network, and level of phenotype plasticity appearing on timescales of decades to centuries.
[50] It has been hypothesized that invasive species of microbial life could contaminate a planetary body after the former is introduced by a space probe or spacecraft, either deliberately or unintentionally.
[52] "This protocol was defined in concert with Viking, the first mission to face the most stringent planetary protection requirements; its implementation remains the gold standard today."
