On Climatic Conditions, Vegetation Types, and Leaf Size in the Galapagos Islands

Abstract

Studies of vegetation on 10 islands in the Galipagos demonstrate that the pattern of distribution of various vegetation types, ranging from desert scrub to evergreen forest, is closely associated with the pattern of variation in the local climatic conditions. The variation in average leaf size of the plant communities and of different layers in the communities is on the one hand associated with variations in altitude and exposure, and on the other hand with variations in the structure of the communities. The average leaf size of a plant community is considered to be a useful diagnostic feature for classifying the vegetation types. Structural features of the plant communities, for example, stratification and coverage, influence the leaf size of lower layers within the same community: the variation in leaf size of the shrub and of the herb layer is associated with the variation in coverage of the layer above. Variation in leaf size in the Acalypha complex and in Croton scouleri is suggested to be related to the structural variations in the communities: the structure of the plant communities may impose a selection pressure on the species of Acalypha and Croton, whereby they tend to develop the leaf size optimally fitted for the requirements of their particular environment.