Ecology

Desert Invaders

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Science  07 Dec 2012:
Vol. 338, Issue 6112, pp. 1264
DOI: 10.1126/science.338.6112.1264-a
CREDIT: MORGAN ERNEST/UTAH STATE UNIVERSITY

The popular conception of an invasive plant species is of one that rapidly achieves abundance or even dominance after its introduction into a new region. However, in natural communities, many native species can persist at low population densities, reaching greater abundance only when changes occur in ecological factors such as resource abundance, competitors, or herbivores. This could be a feature of some invasive species too. A decade ago, Shea and Chesson advanced the notion of “niche opportunities” for invasive species, whereby such a species might be able to occupy a new habitat at low density, biding its time until conditions become right for more rapid expansion and spread. Observation of such behavior requires long-term monitoring. Allington et al. have now documented a case of niche opportunity in an invasive herbaceous annual, Erodium cicutarium, in the Chihuahuan desert. For the first two of three decades of monitoring, E. cicutarium remained at low densities. After 20 years, however, a coincidental decrease in the abundance of rodents and a shift in the precipitation regime combined to create an opportunity for populations of E. cicutarium to increase rapidly, outcompeting native species and becoming the dominant plant in the community.

CREDIT: MORGAN ERNEST/UTAH STATE UNIVERSITY

Ecol. Lett. 10.1111/ele.12023 (2012).

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