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Biodiversity and Conservation

, Volume 17, Issue 7, pp 1613–1625 | Cite as

Guadalupe Island: Lost paradise recovered? Overgrazing impact on extinction in a remote oceanic island as estimated through accumulation functions

  • Pedro P. GarcillánEmail author
  • Exequiel Ezcurra
  • Ernesto Vega
Original Paper

Abstract

Guadalupe Island, an oceanic island in the northwest of Mexico, is an outlier of the California Floristic Province that has been disturbed by introduced goats for more than a century, with dramatic effects of goats on plant communities and local species extinctions. In 2004 the island went through a successful eradication program. Since then, six previously unrecorded species have been discovered and four supposed extinct species have been found again. Quantifying the true species richness of the island at the time of eradication, to set a benchmark for the future monitoring of this large-scale natural experiment, is both a challenge and a necessity. For this purpose, we estimated (a) current and (b) accumulated historical plant species richness of the island through accumulation functions. Estimation of current species richness was based on the geographical accumulation process of species richness (80 species) obtained from sampling 110 (50 m × 2 m) transects distributed along the island in year 2004. Historical species richness was estimated through the temporal accumulation of species richness (119 species) from botanical records (1,960 specimens reviewed) between 1875 and 2000. The predicted value of historical richness (213 species) is similar to known historical records (218 species), but estimation of current richness (203 species) is significantly higher than accepted extant plant richness (187 species). Our results suggest that currently there may be more plant species living in the island than estimated through recent botanical exploration. Future monitoring of the island as it recovers will clarify this hypothesis.

Keywords

Guadalupe Island Accumulation functions Richness estimation Plant extinction Plant diversity Overgrazing 

Notes

Acknowledgements

We are grateful to Luciana Luna and Francisco Casillas for their help in the field work, to Eulogio López for his assistance in checking the herbaria, to Charlotte E. González-Abraham for her work with figures, and to an anonymous reviewer for excellent criticism and advice. We also thank Secretaría de Marina de México and GECI for the facilities during field work. We are especially indebted to the CAS, DS, SD, and UC Herbaria staff for their invaluable help. The financial support that made possible this work was provided by Instituto Nacional de Ecología, México (INE). The second author (EE) thanks the financial support of the Packard Foundation and the Pew Fellowship Program on Marine Conservation.

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Copyright information

© Springer Science+Business Media B.V. 2008

Authors and Affiliations

  • Pedro P. Garcillán
    • 1
    Email author
  • Exequiel Ezcurra
    • 2
  • Ernesto Vega
    • 3
    • 4
  1. 1.Dpto. Biología de la ConservaciónCICESEEnsenadaMexico
  2. 2.Biodiversity Research Center of the CaliforniasSan Diego Natural History MuseumSan DiegoUSA
  3. 3.Instituto Nacional de EcologíaMexicoMexico
  4. 4.IFEVA-Facultad de Agronomía (UBA)/CONICETBuenos AiresArgentina

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