Abstract

CRUZ MARQUEZ et al. ¿Por qué tan pocas Opuntia en la Isla Española-Galápagos?. Ecol. apl. [online]. 2003, vol.2, n.1, pp.21-29. ISSN 1726-2216.

This article attempts to explain why Opuntia megasperma var. orientalis is now rare in Española Island, Galapagos. We give a detailed description of the principal components of the island ecosystem that could have interacted, from the past to the present, and could have molded the stages of ecological succession, resulting in the present rarity of Opuntia cactus. Since we do not know whether this species of cactus was abundant or rare in the past, our investigation begins with the study of the current situation of those elements in the ecosystem that interact, whether as dispersal agents, consumers, or competitors of Opuntia, and could have had an influence as such in the past. We provide current data on the densities of cactus and Española giant tortoises. We analyze the impact that goats could have had on Opuntia and on the ecosystem in general and how other elements, such as tortoises, birds, and plant species, currently limit the natural recuperation of the cactus. We conclude that the effect of goats, by itself, does not completely explain the present rarity of O. megasperma var. orientalis on Española, but that there are additional factors involved.

Keywords : Española; Opuntia few; Galapagos Island.

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