Browsing by Author "DURAN, LR"

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    HUMAN EXCLUSION FROM THE ROCKY INTERTIDAL ZONE OF CENTRAL CHILE - THE EFFECTS ON CONCHOLEPAS CONCHOLEPAS (GASTROPODA)
    (1985) CASTILLA, JC; DURAN, LR
    The ecological role played by man as a top predator in a rocky intertidal environment of central Chile was studied. Human exclusion from a rocky intertidal stretch of coast (non-harvested area) at punta El Lacho, for nearly two years, resulted in a substantial density increase of the economically important high trophic level predator muricid Concholepas concholepas. This was followed by a dramatic decline in the cover of the competitive dominant intertidal mussel Perumytilus purpuratus. According to current ecological theory the removal of the competitively superior primary space dominant species led to a pattern of increasing species diversity. We conclude that in the absence of human interference C. concholepas plays the role of a key species in central Chile rocky intertidal environments. We suggest that the interpretation of the structure and dynamics of intertidal landscapes should include the key role played by man. Comparison of monitoring programs between intertidal areas with and without human interference will prove critical to our understanding of such environments.
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    VARIATION AND PERSISTENCE OF THE MIDDLE ROCKY INTERTIDAL COMMUNITY OF CENTRAL CHILE, WITH AND WITHOUT HUMAN HARVESTING
    (1989) DURAN, LR; CASTILLA, JC
    Humans are an important intertidal predator in central Chile. Following a five-year study we report on the effects of the exclusion of humans from the rocky intertidal at Las Cruces, central Chile. The middle intertidal of harvested and non-harvested areas diverged in species diversity and composition during the experiment. In harvested areas the middle intertidal rocky shore was dominated throughout the study by a monoculture of mussels, Perumytilus purpuratus. When humans were excluded, the middle intertidal community switched to one dominated by barnacles (predominantly Jehlius cirratus and Chthamalus scabrosus); this community has persisted for at least three years, despite the presence of forces e.g. mussel larvae, that have the potential to alter the community structure. Such changes were mediated by the muricid gastropod Concholepas concholepas, a key-stone predator. As a consequence of the above changes, the species diversity, H'', (primary space occupiers) in the non-harvested area increased from H'' = 0 at the beginning of the study in 1983 (when the middle intertidal community was dominated by mussels), to values ca H'' = 2 toward the middle of the study in 1984 (which coincided with the maximum predatory impact of C. concholepas), and subsequently decreasing to ca H'' = 0.5 at the end of the study in 1987 (when the middle intertidal community was dominated by barnacles).