Indicator species

An indicator species is any biological species that defines a trait or characteristic of the environment. For example, a species may delineate an ecoregion or indicate an environmental condition such as a disease outbreak, pollution, species competition or climate change. Indicator species can be among the most sensitive species in a region, acting as an early warning to monitoring biologists.

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Indicators of range

As an indicator species of a range, an environmental ecoregion is typically defined. The Chitymomma is an Agave that regionally helps define the Chihuahuan Desert of Northern Mexico and the SW United States. In Central America, the Guatemalan magnolia elevationally defines the limits of the cloud forests of mountains.

For paleoclimates, an extant species may be an indicator of a former climate condition. The Discus macclintocki snail defines a former Ice sheet region of the northern Midwestern United States.

In some cases entire groups of fauna and flora may be an indicator of range. Invasive species that enter an ecoregion advance at rates dependent on environmental conditions such as temperature, food supply and physical barriers. An example is the spread of the Africanized bee as it enters southern North America.

Specialized uses

Prospecting has been a minor use of indicator species. Folklore may lead to recent attempts to use some species as an indicator to search for specific natural resources, such as water. For finding uranium, botanical prospecting uses various plants, including Astragalus, Oenothera, and Desert trumpet.

Indicators of environmental condition

Recent examples of North American species affected by environmental changes are the American Dipper and the Gray Jay. The American Dipper is a bird that requires a habitat of clear, mountainous streams, and can be displaced by siltation from land development, land-wasting runoff and forest fire runoff. The Gray Jay has become less common in southerly (warmer) parts of its range, apparently because its food supply has been affected by rising temperatures due to global warming.

Many indicator species of the ocean systems are fish, invertebrates, periphyton, macrophytes and specific species of ocean birds (like the Atlantic Puffin). Amphibians are also common indicator species, as they may have become repositories of bioindicator chemicals, or of ecological conditions relating to global warming, air pollution chemicals, newly extant diseases (fungus), or environmental pressure on the ecosystem, which affect the population numbers, and the quality of the individuals.

Lichens are indicators of air quality. They are particularly sensitive to sulphur dioxide, a gas emitted from exhaust and industrial fumes, and so are rarely found in large cities and towns or by roads. Filamentose, fruticose and foliose varieties are particularly sensitive. Their presence indicates air very low in sulphur dioxide. Crustose, leprose and squamulose varieties are more tolerant of poor air.

See also

• Indicator plant
• Bioindicator
• Botanical prospecting for uranium

References

• Farr, Daniel (2002), , in Encyclopedia of Environmetrics (eds. A H El-Sharaawi and W W Piegorsch), John Wiley & Sons, Ltd., ISBN 978-0-471-89997-6
• Noss, Reed (1990), , Conservation Biology 4: 355-364
• Shrivastava, Rahul (2007), , in Encyclopedia of Environment and Society (ed. Paul Robins), Thousand Oaks : Sage Publications, ISBN 1412927617