Poor Replacements

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Science  19 Apr 2013:
Vol. 340, Issue 6130, pp. 250
DOI: 10.1126/science.340.6130.250-a

The loss of large herbivore species can have very noticeable ecological impacts. Replacement of lost species with similar species expected to perform the ecological roles of those lost may temper some of these changes. Caution is needed, however: History is full of biological introductions that have not turned out as planned. Hunter et al. tested the effectiveness of ecological equivalency in the Galapagos, where extinctions of giant tortoises have had significant ecological impacts. Sterilized tortoises with two distinct shell morphologies, domed and saddleback, were introduced to Pinta Island. The now-extinct native species had saddleback-shaped shells and were dispersers of prickly pear cactus. Introduced saddleback tortoises also selected prickly pear–rich habitats and thus have the potential to fill the same ecological role. Tortoises with dome-shaped shells, on the other hand, migrated to high elevations and showed no inclination toward prickly pear habitat. This was somewhat surprising, because despite differences in shell shape, domed-shell tortoises are more closely related to the extinct saddleback tortoises. Controlled experimentation, therefore, may be essential when considering ecological replacement strategies.

Conserv. Biol. 10.1111/cobi.12038 (2013).

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