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Revista Chilena de Historia Natural 84 (4): 553-570, 2011
Spatio-temporal variability in ontogenetic guild structure of an intertidal fish assemblage in central Chile
Species resource use can vary throughout ontogeny, potentially affecting community dynamics. This can be particularly important for species facing high variability in environmental conditions and going through several orders of magnitude in size, as intertidal fishes. However, the influence of the resulting ontogenetic changes in guild membership on the spatio-temporal structure of fish assemblages remains virtually unknown. Here we assessed the spatial and temporal variability in the ontogenetic feeding guild (OFG) structure of the fish assemblage inhabiting the temperate rocky intertidal zone along central Chilean coast. This was done applying principal component analysis (PCA) and randomization tests (R-test) on the relative OFG composition of fish assemblages, obtained from seasonal samples from ten pools located at two heights in the intertidal zone in three localities between 33º and 34º S. Overall, the PCA and R-tests suggest that spatial variability dominated over temporal variability in OFG structure, mainly due to a higher representation of omnivore species at high intertidal pools in two of the three sampled localities. However, phenology-related changes in the representation of fish size-classes (i.e. carnivore recruitment in spring-summer) along with ontogenetic differences in habitat selection (e.g., selection for low intertidal pools by bigger-sized carnivore OFG) contributed to both spatial and temporal differentiation in OFG structure. Finally, the relative representation of each OFG correlated with that of their dominant species, without evidence for density compensation. This suggests low levels of functional redundancy among species in each OFG, highlighting the vulnerability of assemblage functioning to size-biased disturbances as fishing.
Key words:
intertidal fishes, ontogenetic feeding guilds, spatio-temporal variability

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