Revista Chilena de Historia Natural 81 (4): 533-546, 2008
RESEARCH ARTICLE
Trophic characterization of the intertidal placophoran Enoplochiton niger in
northern Chile: environmental variation and dietary patterns at local and regional levels
The role and impact of herbivores on rocky intertidal food webs could be more complex
and diverse than previously considered, particularly in the case of larger and more abundant consumers such as the placophoran
mollusc Enoplochiton niger. This species is one of the largest (up to 20 cm) and ecologically most important grazers on
rocky shores of northern Chile, but also one of the lesser known species in trophic terms. This work presents an assessment of the
dietary patterns of E. niger in four communities of northern Chile, distributed along 1,000 km of coastline and sampled
seasonally from winter 2004 to autumn 2006. The analysis included the relationship of its diet with physical and biological factors, and
particularly the potential effect of the 2004-2005 El Niño event that occurred during the study period. At a regional level, the dietary
spectrum of E. niger comprised a total of 98 food resources (60 algal items and 38 invertebrate items), and the most
important items were sessile organisms of encrusting and layer-forming growth habits. E. niger exhibited a very high niche
breadth at both local and regional levels (ranging from 20.7 to 28.0; Levins’ index), and its dietary richness at the individual level was
independent from its body size. Both the number of dietary items consumed per individual and the taxonomic composition of the diet
did not show statistical differences among communities, but they were significantly different between the El Niño and non-El Niño
periods. There was no clear relationship between the dietary patterns of E. niger and the contrasting levels of upwelling
intensity among the communities studied. The results show that E. niger is a generalist polyphagous consumer, and a
potential omnivore, which could have a high level of impact on space occupancy patterns in the intertidal community.
Key words:
chiton, body size,
omnivory, upwelling, El Niño
