Does the River Continuum Concept apply on a tropical island? Longitudinal variation in a Puerto Rican stream.
Abstract: We examined whether a tropical stream in Puerto Rico matched
predictions of the river continuum concept (RCC) for macroinvertebrate
functional feeding groups (FFGs). Sampling sites for
macroinvertebrates, basal resources, and fishes ranged from headwaters
to within 2.5 km of the fourth-order estuary. In a comparison with a
model temperate system in which RCC predictions generally held, we used
catchment area as a measure of stream size to examine truncated RCC
predictions (i.e., cut off to correspond to the largest stream size
sampled in Puerto Rico). Despite dominance of generalist freshwater
shrimps, which use more than one feeding mode, RCC predictions held for
scrapers, shredders, and predators. Collector-filterers showed a trend
opposite to that predicted by the RCC, but patterns in basal resources
suggest that this is consistent with the central RCC theme:
longitudinal distributions of FFGs follow longitudinal patterns in
basal resources. Alternatively, the filterer pattern may be explained
by fish predation affecting distributions of filter-feeding shrimp. Our
results indicate that the RCC generally applies to running waters on
tropical islands. However, additional theoretical and field studies
across a broad array of stream types should examine whether the RCC
needs to be refined to reflect the potential influence of top-down
trophic controls on FFG distributions.
Greathouse, E. A., and C. M. Pringle. 2006. Does the River Continuum Concept apply on a tropical island? Longitudinal variation in a Puerto Rican stream. Canadian Journal of Fisheries and Aquatic Sciences. 63: 134-152.
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