Local distribution patterns of Opuntia echios echios, Bursera graveolens and Scalesia crockeri on Santa Cruz Island, Galapagos

Runkle, James R. and Runkle, William A. (2005) Local distribution patterns of Opuntia echios echios, Bursera graveolens and Scalesia crockeri on Santa Cruz Island, Galapagos. Galapagos Research, 63, pp. 26-31.

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Abstract

We mapped stems of three plant species in a 2.36 ha plot in the arid zone near the coast of eastern Santa Cruz Island, Galapagos, Ecuador, to determine factors influencing their local distribution. The three species were Opuntia echios var. echios (Cactaceae), a large cactus, Bursera graveolens (Burseraceae), a small tree that dominates dry woodland near the coast, and the shrub Scalesia crockeri (Asteraceae). In our plot, Opuntia was most abundant near the coast, while Bursera and Scalesia increased in density inland and with increased relief. Scalesia also increased in density with increases in Bursera and decreases in other woody plants and was most abundant 200–250 m from the coast. Both Opuntia and Bursera were clumped in the plot as a whole but selected stem size classes were randomly dispersed within homogeneous portions of the sample area. CDF Contribution Number 1012.

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