Community responses to experimental food depletion: resource tracking by stream invertebrates

Citation
L. Rowe et Js. Richardson, Community responses to experimental food depletion: resource tracking by stream invertebrates, OECOLOGIA, 129(3), 2001, pp. 473-480
Citations number
46
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Environment/Ecology
Journal title
OECOLOGIA
ISSN journal
0029-8549 → ACNP
Volume
129
Issue
3
Year of publication
2001
Pages
473 - 480
Database
ISI
SICI code
0029-8549(200111)129:3<473:CRTEFD>2.0.ZU;2-I
Abstract
The regulation of population processes for most organisms depends upon the strength and rate of feedback between resources and consumers. We conducted an experimental manipulation of leaf packs in stream channels, a patchy an d ephemeral resource, which is consumed by a number of detritivorous invert ebrates. We reduced the number of available food patches (red alder leaf pa cks) by half and then measured a variety of community responses, including emigration rate, aggregation on remaining food patches, decomposition rate of food patches, and species-specific differences in these responses. Repla cement of removed leaf packs with polyester mimics resulted in no statistic al difference in emigration rates or aggregation on remaining resources whe n compared to those removal channels without replacement. These results ind icate that leaf packs are not used primarily for refuge. In the removal cha nnels (including those with leaf pack mimics) emigration rate nearly double d relative to control channels. Those invertebrates that did not emigrate f rom removal channels aggregated on remaining leaf packs, which led to more rapid decomposition of leaf packs relative to control channels. The increas e in emigration rate only became apparent 2-3 days after the manipulation, presumably because animals colonized the remaining leaf packs and did not e migrate until food patch value per individual had been reduced by higher de nsities or due to increased discharge. Discharge through the channels incre ased slightly starting 3 days after the manipulation, resulting in increase d emigration rates in all channels. Despite the increase in discharge, the effect of the manipulation remained strong. These results show that stream invertebrates colonizing leaf packs responded in predictable ways to a shor t-term reduction in food resources which would be adaptive in a system whic h is heterogeneous in space and time.