Neobiota (Greek: néos “new”, bíos “life”) are organisms that occur in an area that is not their native distribution region. While this definition technically includes all kinds of organisms (fungi, bacteria, lichens, etc.), the ones receiving arguably the most attention in science and literature are higher plants and higher animals. In English, many terms for these organisms exist, such as non-native, non-indigenous, exotic, introduced or alien organisms.
In the literature of several European countries, the date that is used for defining what is native or non-native is usually the year of Columbus’ arrival to what would later become America, 1492 (see for example Kowarik 2003). According to this definition, organisms that did not occur in a certain region prior to 1492 but existed there afterwards are called non-native to that region. If a plant was introduced to a region before 1492, it is usually referred to as archeophyte. However, studies from other countries, including the USA, often do not use these stringent, time-based definitions. In such a case non-native species are simply defined as “species living outside their native distributional range”. For additional information about nomenclature, see Sukopp (2000). Non-native organisms are dispersed with the aid of humans, either accidentally or intentionally. Depending on the kind of organism, intentional introductions happen for example in the form of agricultural, silvicultural or horticultural cultivation. Unintentional introductions often occur by means of organisms escaping human cultivation, dispersal by livestock feces or hair, or in the form of “stow-aways” in ships’ ballast water or in train or wagon cargo, etc. Additionally, plant propagules can be spread by humans by sticking to their bodies, clothes or shoes. If a non-native organism that is cultivated escapes cultivation and reproduces without human help in the wild, this organism is then called “naturalized” (this process is referred to as “naturalization”). The strong interdependency between non-native organisms and humans constitutes a special kind of entanglement: by influencing virtually all ecosystems of the planet, man constantly creates new corridors for the dispersal of exotic organisms. This characteristic becomes visible in the high invasion rates of anthropogenic ruderal (disturbed) sites. Non-native plants are commonly found along man-made roads, railway tracks and canals.
Obviously, unlike plants that cannot actively fly, walk or swim, animals can move by themselves and are thus capable of reaching new habitats quicker and easier than plants. For covering long (trans-continental) distances however, they require human activity nevertheless. Examples of non-native animals in North America include Sus scrofa (common wild boar, native to Europe and Central Asia) and Mus musculus (house mouse, native to Europe and Asia) while in South America the following examples are considered non-native: Lepus europaeus (brown hare, native to Europe) and Castor canadensis (North American beaver, native to the USA and Canada).
If seeds or propagules of non-indigenous plants are able to survive initial long-distance transport to a new continent, e.g. South America, they might then manage to colonize new habitats. From these colonies, isolated populations can establish afterwards under certain conditions (e.g. fast growth, efficient resource use, fitting climate and soil) and finally, if requirements such as high fecundity, phenotypic plasticity, fast generation time, heterogeneity of landscape and suitable dispersal corridors are met, they may spread on a landscape scale (Theoharides & Dukes 2007). Examples of non-native plants in North America are Centaurea solstitialis (yellow star thistle, native to Eurasia), Agrostis stolonifera (creeping bentgrass, native to Eurasia and North Africa) and Melilotus spec. (sweet clover, native to Eurasia). Non-indigenous plants in South America include for example Glycine max (soy bean, native to East Asia) and Eucalyptus spec. (Eucalyptus tree, native to Australia).
Animals and plants reaching the potential of spreading on a landscape scale can cause the competitive balance of whole ecosystems to be highly altered (Di Tomaso 1998). Often, these alterations can be the source of tremendous ecological, economic as well as animal and human health threats (Federal Interagency Committee for MNEW & Westbrooks 1998). In such a case, the species is termed “invasive”: “Invasive species are those that are not native to the ecosystem under consideration and that cause or are likely to cause economic or environmental harm or harm to human, animal, or plant health.” (Beck et al. 2008).
In this context, ecological harm usually refers to a loss of biodiversity, a direct result of invasive organisms out-competing their native counterparts. Economic harm is a result of sometimes very costly measures employed to control, contain or even eradicate invasive species. Additionally, several invasive species can pose a health threat if they are digested or touched by other plants or animals. Bacterial and viral pathogens, despite their obvious capability to cause health hazards, are usually not included with invasive species. This is due to the fact that they are mainly discussed in medical research rather than in population ecology. GMOs (genetically modified organisms) are not included with invasive species either, unless the non-modified variant of the organism is already considered invasive.
For plants, often the terms “weedy plants”, “weeds” or “NIPS” (short for non-native invasive plant species) refer to this kind of species. For both plants and animals, the terms “pest species” or “IAS” (short for invasive alien species) are sometimes used. While it is common to refer to the process of non-native plants becoming invasive as “plant invasion”, the term “animal invasion” is seldomly used. The capability for a certain species to become invasive is called “invasiveness” and is not only influenced by plant or animal traits (for example their biological fitness, ability to adapt, rate of reproduction, etc.) but also by environmental factors (for example, temperature, intensity of sun radiation, water availability, available dispersal corridors) of the new habitat.
Due to questions about which factors to consider, it is difficult to calculate economic damage caused by invasive species. Depending on how it is calculated, Pimentel et al. (2005) estimated the annual cost caused by invasive species to be more than $ 120 billion in the USA alone. However, other assessments question this number and position the expenses in much lower ranges (Wolff & Köck 2004). Interestingly, the intercontinental direction of non-native plant introductions is asymmetrical and parallels historical patterns in colonization (Theoharides & Dukes 2007): Eurasia, possessing about 4% of the world’s plant species diversity, contributes almost 60% of non-indigenous species to other continents (Pyšek 1998), with highest numbers in the Americas and Africa (Vermeij 2005).
Clara Gläve and Alexander Mosena
Please cite as:
Gläve, Clara and Alexander Mosena. 2015. “Neobiota.” InterAmerican Wiki: Terms - Concepts - Critical Perspectives. www.uni-bielefeld.de/cias/wiki/n_Neobiota.html.
Beck, K. George; Zimmerman, Kenneth; Schardt, Jeffrey D.; Stone, Jeffrey; Lukens, Ronald R.; Reichard, Sarah et al. 2008. "Invasive Species Defined in a Policy Context: Recommendations from the Federal Invasive Species Advisory Committee." In: Invasive Plant Science and Management 1 (4), p. 414–421.
Di Tomaso, Joseph M. 1998. "Impact, Biology, and Ecology of Saltcedar (Tamarix spp.) in the Southwestern United States." In: Weed Technology 12 (2), p. 326–336.
"Federal Interagency Committee for the Management of Noxious and Exotic Weeds; Westbrooks, Randy G. 1998. Invasive Plants: Changing the Landscape of America." In: All U.S. Government Documents (Utah Regional Depository) 490.
Kowarik, Ingo. 2003. Biologische Invasionen. Neophyten und Neozoen in Mitteleuropa. Ulmer.
Pimentel, David; Zuniga, Rodolfo; Morrison, Doug. 2005. Update on the environmental and economic costs associated with alien-invasive species in the United States (3).
Pysek, Petr. 1998. "Alien and native species in Central European urban floras: a quantitative comparison." In: J Biogeography 25 (1), p. 155–163.
Sukopp, Herbert. 2000. Neophyten. Available online at http://pages.unibas.ch/botges/pdf/bauhinia15%282001%2919-37.pdf, last checked 19.06.2013.
Theoharides, Kathleen A.; Dukes, Jeffrey S. 2007. "Plant invasion across space and time: factors affecting nonindigenous species success during four stages of invasion." In: New Phytologist 176 (2), p. 256–273.
Vermeij, G. J. 2005. "Invasion as expectation: a historical fact of life." In: Dov F. Sax, John J. Stachowicz und Steven D. Gaines (Ed.): Species invasions. Insights into ecology, evolution, and biogeography. Sunderland, Mass: Sinauer Associates, p. 315–339.