Today, it is accepted that the ecological and evolutionary consequences of invasions are greater than previously
thought. Relatively recent studies of highly invaded
coastal systems are changing our understanding of the
degree to which invaders have altered natural habitats,
and what is now known about the ecological and evolutionary changes brought about by non-native coastal
species may be just a small part of a very large environmental problem (Grosholz, 2002).
The most common sources of introductions in
estuaries are ballast water, aquarium trade, and aquaculture (Ruiz et al., 1997; Ruiz et al., 2000; Naylor et al.,
2001).
After an introduction of an exotic species, the next step
may be an invasion. In 1958, Charles Elton published the
book “The Ecology of Invasions by Animals and Plants”
which launched the systematic study of biological invasions. Invasion ecology has grown to become an important multidisciplinary subfield of ecology with growing
links to many other disciplines (Richardson and
Py, 2008).
Conclusions
Biotic changes in estuarine ecosystems via species
invasions and extinctions caused by human activities have
altered ecosystem goods and services in many welldocumented cases, and several of these changes are
difficult, expensive, or impossible to reverse or fix with
technological solutions (Hooper et al., 2005). Invasion
research has shown that the scope and complexity of consequences greatly exceed earlier perceptions (Simberloff
et al., 2013). Half a century after its publication, Charles
Elton’s book on invasions remains influential, but massive
changes in the status of invasions and other environmental
issues worldwide, together with advances in technology,
are reshaping the rules and priorities of invasion ecology
(Richardson and Py, 2008).
Bibliography
Grosholz, E., 2002. Ecological and evolutionary consequences.
Trends in Ecology and Evolution, 17, 22–27.
Hooper, D. U., Chapin, F. S., Ewel, J. J., Hector, A., Inchausti, P.,
Lavorel, S., Lawton, J. H., Lodge, D. M., Loreau, M., Naeem,
S., Schmid, B., Setala, H., Symstad, A. J., Vandermeer, J., and
Wardle, D. A., 2005. Effects of biodiversity on ecosystem
functioning: a consensus of current knowledge. Ecological
Modelling, 75, 3–35.
Naylor, R. L., Williams, S. L., and Strong, D. R., 2001. Aquaculture: a gateway for exotic species. Science, 294, 1655–1656.
Richardson, D. M., and Py, P., 2008. Fifty years of invasion
ecology – the legacy of Charles Elton. Diversity and Distributions, 14, 161–168.
Ruiz, G. M., Carlton, J. T., Grosholz, E. D., and Hines, A. H., 1997.
Global invasions of marine and estuarine habitats by
non-indigenous species: mechanisms, extent, and consequences.
Integrative and Comparative Biology, 37, 621–632.
Ruiz, G. M., Rawlings, T. K., Dobbs, F. C., Drake, L. A., Mullady,
T., Huq, A., and Colwell, R. R., 2000. Global spread of microorganisms by ships. Nature, 408, 49–50.
Sakai, A. K., Allendorf, F. W., Holt, J. S., Lodge, M., Molofsky, J.,
With, K. A., Cabin, R. J., Cohen, J. E., Norman, C., McCauley,
D. E., Neil, P. O., Parker, M., Thompson, J. N., and Weller,
S. G., 2001. The population biology of invasive species. Annual
Review of Ecology and Systematics, 32, 305–332.
Simberloff, D., Martin, J.-L., Genovesi, P., Maris, V., Wardle, D. A.,
Aronson, J., Courchamp, F., Galil, B., García-Berthou, E.,
Pascal, M., Pyšek, P., Sousa, R., Tabacchi, E., and Vilà, M.,
2013. Impacts of biological invasions: what’s what and the
way forward. Trends in Ecology and Evolution, 28, 58–66.
Cross-references
Exotic Species
Invasive Species
INVASIVE SPECIES
Judith S. Weis
Department of Biological Sciences, Rutgers University,
Newark, NJ, USA
Synonyms
Alien species; Exotics; Nonindigenous species;
Nonnatives
Definition
An invasive species is an introduced species (also called
“nonindigenous” or “nonnative”) that adversely affects
the new habitat ecologically or economically. Invasive
species may be microbes, plants, or animals and may disrupt the new area by dominating particular habitats
because of loss of natural biological controls present in
its native range, such as predators or diseases.
Introduction
When nonnative species arrive in a new location, most of
them either are harmless or do not survive. However, some
do flourish, and the small percentage that thrive and reproduce may eventually become invasive by outcompeting,
eating, or parasitizing native species. If a nonindigenous
species displaces or competes with a native species, it
reduces diversity. If a plant that functions as habitat or
food for certain animals is replaced by a different plant,
the animals that depended on it may be unable to survive.
Vectors: how they are transported
Early oceangoing ships were built of wood, and their hulls
became covered with attached organisms such as barnacles and algae, which were transported to other ports
around the world. Ships took on ballast in their home port
in the form of rocks or sand in order to provide stability at
sea, and terrestrial organisms in the ballast were dumped
along with the rocks to lighten the ship when it arrived at
its destination so it could enter a shallow harbor in
a foreign port. Water is now used as ballast, and millions
of gallons of water, along with resident organisms, are
362
INVASIVE SPECIES
thought. Relatively recent studies of highly invaded
coastal systems are changing our understanding of the
degree to which invaders have altered natural habitats,
and what is now known about the ecological and evolutionary changes brought about by non-native coastal
species may be just a small part of a very large environmental problem (Grosholz, 2002).
The most common sources of introductions in
estuaries are ballast water, aquarium trade, and aquaculture (Ruiz et al., 1997; Ruiz et al., 2000; Naylor et al.,
2001).
After an introduction of an exotic species, the next step
may be an invasion. In 1958, Charles Elton published the
book “The Ecology of Invasions by Animals and Plants”
which launched the systematic study of biological invasions. Invasion ecology has grown to become an important multidisciplinary subfield of ecology with growing
links to many other disciplines (Richardson and
Py, 2008).
Conclusions
Biotic changes in estuarine ecosystems via species
invasions and extinctions caused by human activities have
altered ecosystem goods and services in many welldocumented cases, and several of these changes are
difficult, expensive, or impossible to reverse or fix with
technological solutions (Hooper et al., 2005). Invasion
research has shown that the scope and complexity of consequences greatly exceed earlier perceptions (Simberloff
et al., 2013). Half a century after its publication, Charles
Elton’s book on invasions remains influential, but massive
changes in the status of invasions and other environmental
issues worldwide, together with advances in technology,
are reshaping the rules and priorities of invasion ecology
(Richardson and Py, 2008).
Bibliography
Grosholz, E., 2002. Ecological and evolutionary consequences.
Trends in Ecology and Evolution, 17, 22–27.
Hooper, D. U., Chapin, F. S., Ewel, J. J., Hector, A., Inchausti, P.,
Lavorel, S., Lawton, J. H., Lodge, D. M., Loreau, M., Naeem,
S., Schmid, B., Setala, H., Symstad, A. J., Vandermeer, J., and
Wardle, D. A., 2005. Effects of biodiversity on ecosystem
functioning: a consensus of current knowledge. Ecological
Modelling, 75, 3–35.
Naylor, R. L., Williams, S. L., and Strong, D. R., 2001. Aquaculture: a gateway for exotic species. Science, 294, 1655–1656.
Richardson, D. M., and Py, P., 2008. Fifty years of invasion
ecology – the legacy of Charles Elton. Diversity and Distributions, 14, 161–168.
Ruiz, G. M., Carlton, J. T., Grosholz, E. D., and Hines, A. H., 1997.
Global invasions of marine and estuarine habitats by
non-indigenous species: mechanisms, extent, and consequences.
Integrative and Comparative Biology, 37, 621–632.
Ruiz, G. M., Rawlings, T. K., Dobbs, F. C., Drake, L. A., Mullady,
T., Huq, A., and Colwell, R. R., 2000. Global spread of microorganisms by ships. Nature, 408, 49–50.
Sakai, A. K., Allendorf, F. W., Holt, J. S., Lodge, M., Molofsky, J.,
With, K. A., Cabin, R. J., Cohen, J. E., Norman, C., McCauley,
D. E., Neil, P. O., Parker, M., Thompson, J. N., and Weller,
S. G., 2001. The population biology of invasive species. Annual
Review of Ecology and Systematics, 32, 305–332.
Simberloff, D., Martin, J.-L., Genovesi, P., Maris, V., Wardle, D. A.,
Aronson, J., Courchamp, F., Galil, B., García-Berthou, E.,
Pascal, M., Pyšek, P., Sousa, R., Tabacchi, E., and Vilà, M.,
2013. Impacts of biological invasions: what’s what and the
way forward. Trends in Ecology and Evolution, 28, 58–66.
Cross-references
Exotic Species
Invasive Species
INVASIVE SPECIES
Judith S. Weis
Department of Biological Sciences, Rutgers University,
Newark, NJ, USA
Synonyms
Alien species; Exotics; Nonindigenous species;
Nonnatives
Definition
An invasive species is an introduced species (also called
“nonindigenous” or “nonnative”) that adversely affects
the new habitat ecologically or economically. Invasive
species may be microbes, plants, or animals and may disrupt the new area by dominating particular habitats
because of loss of natural biological controls present in
its native range, such as predators or diseases.
Introduction
When nonnative species arrive in a new location, most of
them either are harmless or do not survive. However, some
do flourish, and the small percentage that thrive and reproduce may eventually become invasive by outcompeting,
eating, or parasitizing native species. If a nonindigenous
species displaces or competes with a native species, it
reduces diversity. If a plant that functions as habitat or
food for certain animals is replaced by a different plant,
the animals that depended on it may be unable to survive.
Vectors: how they are transported
Early oceangoing ships were built of wood, and their hulls
became covered with attached organisms such as barnacles and algae, which were transported to other ports
around the world. Ships took on ballast in their home port
in the form of rocks or sand in order to provide stability at
sea, and terrestrial organisms in the ballast were dumped
along with the rocks to lighten the ship when it arrived at
its destination so it could enter a shallow harbor in
a foreign port. Water is now used as ballast, and millions
of gallons of water, along with resident organisms, are
362
INVASIVE SPECIES