Tag Archives: species range limits

A role for biotic interactions in limiting species’ range limits

Biotic interactions are more often important at species’ warm versus cool range edges (2021) Paquette & Hargreaves, Ecology Letters, https://doi.org/10.1111/ele.13864

Image credit: Malonecr7, CC BY-SA 3.0, via Wikimedia Commons, image cropped

The Crux

In the natural world, most organisms are limited by the environment as to where they can live. While this can be as drastic as a whale being limited to the ocean and humans being limited to the land, there are also more subtle limitations. That is, black and grizzly bears live in temperate environments, but polar bears are inhabit the arctic where it is MUCH colder. Due to the limitations imposed by the environment, black and grizzly bears cannot live further north.

Historically, most studies have focused on abiotic variables (i.e., non-living), like temperature and precipitation, as there is a clear role for the climate in determining where and when a species can live. However, biotic variables (i.e., living) like predation or competition can also play a role in defining the limits of a species range, though this has proven more difficult to test than abiotic factors, as many tests of biotic variables produce species-specific results. Charles Darwin proposed a framework in 1859 that the importance of biotic interactions would vary predictably with latitude and elevation. That is, at cooler, high-altitude locations abiotic interactions would be more important, while biotic interactions would be more important at warmer, low-altitude locations. Although a number of studies have attempted to test the three predictions (see Did You Know? ) derived from this framework, the results are contradictory and come from data testing different predictions using different data. Today’s authors sought to test all three predictions at once in order to resolve these contradictory results.

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