Spatial scale and the aggregation of stream macroinvertebrates associated with leaf packs

1. An experimental field study examined the aggregation of stream macroinvertebrates associated with leaf packs over different spatial scales (several metres–km) (extent), at different patch sizes (grain) and temporal scales (2 and 4 weeks). 2. Standardized leaf packs were constructed and set in eig...

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Bibliographic Details
Published in:	Freshwater biology Vol. 39; no. 2; pp. 325 - 337
Main Authors:	Murphy, John F., Giller, Paul S., Horan, Margaret A.
Format:	Journal Article
Language:	English
Published:	Oxford, UK Blackwell Science Ltd, UK 01-03-1998 Blackwell Science
Subjects:	Animal and plant ecology Animal, plant and microbial ecology Biological and medical sciences Fresh water ecosystems Freshwater Fundamental and applied biological sciences. Psychology Synecology Europe Ireland Eire, Cork, Douglas R Intraspecific relation Periphyton Environmental factor Plant leaf Coexistence Spatial scale Freshwater environment Aggregation Animal community Stream Models Invertebrata Interspecific relation
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Summary:	1. An experimental field study examined the aggregation of stream macroinvertebrates associated with leaf packs over different spatial scales (several metres–km) (extent), at different patch sizes (grain) and temporal scales (2 and 4 weeks). 2. Standardized leaf packs were constructed and set in eighteen blocks of nine equally spaced packs in glide areas over a 2 km stretch of a wooded stream. The distribution of macroinvertebrates colonizing the artificial leaf packs was investigated to examine the extent of both intraspecific and interspecific aggregation across leaf packs. 3. All major colonizing taxa were intraspecifically aggregated across the leaf packs. Aggregation decreased with increasing patch size (grain) (from pack to block), and also decreased with decreasing spatial extent (from 2 km stretch to within‐block scale) with patch size held constant. Interspecific associations among all major taxa were not common on most occasions at the short temporal scale, although the proportion of significant associations tended to increase somewhat over time and with spatial scale, but did not exceed 42% of all possible associations. The vast majority of significant associations were positive rather than negative. 4. The influence of heterogeneity in a number of environmental variables measured for each leaf pack (accumulated detritus and sediment, leaf mass, flow and depth) on the distribution of invertebrates was considered, but this could only partially explain the variation in macroinvertebrate abundance across leaf packs. 5. The roles of intrinsic aggregation and stochastic processes were examined as alternative explanations for the distribution patterns observed. It is apparent from this study that intrinsic aggregation, in concert with resource partitioning, influences the community structure of stream macroinvertebrates associated with leaf packs. These findings may also have implications for the distribution of taxa in the benthos as a whole.
Bibliography:	istex:54647E80D236A9F6C041EE2EF52ECF8EAB0E34F8 ArticleID:FWB284 ark:/67375/WNG-75DSVL5X-D ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 ObjectType-Article-1 ObjectType-Feature-2
ISSN:	0046-5070 1365-2427
DOI:	10.1046/j.1365-2427.1998.00284.x