Biological Invasions

, Volume 11, Issue 7, pp 1569–1585 | Cite as

The impacts of rats on the endangered native flora of French Polynesia (Pacific Islands): drivers of plant extinction or coup de grâce species?

Invasive Rodents on Islands

Abstract

Although rats have clearly contributed to bird extinctions on islands, their role in plant extinctions is not as clear. Paleoenvironmental studies suggest rats were responsible for the demise of several island palm species. French Polynesia’s islands provide an opportunity to evaluate “modern” impacts of rats on native flora. Our study shows that 15 threatened taxa (nine families) are damaged by rats. All 12 subjected to seed predation are woody plants with large-seeded drupes. Three experience severe predation and recruitment depression (Santalum insulare, Ochrosia tahitensis, Nesoluma nadeaudii). Three-year monitoring of Polynesian sandalwood (Santalum insulare) populations in Tahiti during rat control suggested that over 99% of fruits were eaten before ripening. Seed predation on sandalwood appeared to be lower on islands without black rats Rattus rattus. Studies from Indo-Pacific islands document rat impact on at least 56 taxa (28 families). Certain families (Arecaceae, Elaeocarpaceae, Rubiaceae, Santalaceae, and Sapotaceae) are particularly vulnerable to seed predation. Other soft-barked trees (Araliaceae, Euphorbiaceae, and Malvaceae) suffer from stem or bark damages, especially during dry seasons. Although rats depress seedling recruitment and alter vegetation dynamics, no evidence demonstrates that they are solely responsible for current plant extinctions. Most of French Polynesia’s endangered species impacted by rats occur in severely degraded habitats. We therefore suggest that rats can be viewed more as coup de grâce species (i.e., that give the final stroke of death), rather than as main drivers of plant extinctions. More research is needed to clarify the impacts of rat species and their importance in plant population decline or demise.

Keywords

Island flora Plant extinctions Rats Sandalwood Seed predation 

Notes

Acknowledgements

The authors deeply thank Donald Drake (University of Hawai’i at Manoa, Honolulu, Hawai’i, USA) for the opportunity to attend the Conference on “Rats, Humans, and their Impacts on Islands” in Honolulu in 2007 and address oral presentations; Jean-Claude Thibault (Parc Naturel Régional de Corse, France) for his invaluable comments on a first draft of the manuscript on bird species decline and extinction and rat distribution in French Polynesia; Jacques Florence (IRD, Muséum national d’Histoire naturelle de Paris, France) for sharing his precious knowledge on the flora of French Polynesia; Chuck Chimera (Halekala National Park, Maui, Hawai’i, USA), Christophe Lavergne (Conservatoire Botanique National de Mascarin, Saint-Leu, La Réunion, France), Christoph Kueffer (University of Hawaii, Honolulu, Hawai’i, USA), and Heinke Jäger (Technische Universität Berlin, Institute für Ökologie, Berlin, Germany) for providing useful references and for their personal communications on rat impacts in Hawai’i, La Réunion, Seychelles, and Galápagos, respectively; Ravahere Taputuarai (Délégation à la Recherche, Tahiti) for his precious help in the field; and Walter Teamotuaitau for his efforts to track and find remnant populations of endangered plant species in Tahiti. We thank the two anonymous reviewers for their constructive comments to improve this paper.

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Copyright information

© Springer Science+Business Media B.V. 2008

Authors and Affiliations

  1. 1.Délégation à la Recherche, Government of French PolynesiaPapeeteFrench Polynesia
  2. 2.Laboratoire de Chimie des Substances NaturellesUniversity of French PolynesiaFaaaFrench Polynesia

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