Drifting or walking? colonisation routes used by different instars and species of lotic, macroinvertebrate filter feeders

Downes, Barbara J., Bellgrove, Alecia and Street, Jodie L. 2005, Drifting or walking? colonisation routes used by different instars and species of lotic, macroinvertebrate filter feeders, Marine and freshwater research, vol. 56, no. 6, pp. 815-824.

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Title Drifting or walking? colonisation routes used by different instars and species of lotic, macroinvertebrate filter feeders
Author(s) Downes, Barbara J.
Bellgrove, Alecia
Street, Jodie L.
Journal name Marine and freshwater research
Volume number 56
Issue number 6
Start page 815
End page 824
Publisher CSIRO Publishing
Place of publication Collingwood, Vic.
Publication date 2005-09-27
ISSN 1323-1650
1448-6059
Keyword(s) dispersal
habitat selection
hydropsychids
recruitment
Summary Many views of stream invertebrate populations centre on drift as the major route of larval dispersal, but few studies have presented unambiguous information about the role of drift. We present the results from an experiment designed to determine whether the major route of colonisation of substrata by hydropsychid larvae (commonly found in the drift) is by drifting directly onto substrata or by walking along the stream bottom. The experimental design contained four treatments: substrata open to drifters and walkers; fenced substrata open to drifters only; and two treatments open to drifters and walkers that provided forms of fence controls. Fifteen replicates of each treatment were set out at random locations within a riffle at each of three sites, with each site on a different river (the Little River, the Steavenson River and the Acheron River) in the Acheron River catchment. The experiment was run twice, once during autumn (April 1999) and once during early summer (January 2000). Both experiments were colonised by three species of hydropsychids, Asmicridea sp. AV1, and Smicrophylax sp. AV1 and AV2. We found that 2nd/3rd instars of Asmicridea sp. AV1 walked as well as drifted, whereas all others primarily drifted. No relation between numbers of recruits and water speed was found when substrata were open only to drifters, whereas substrata open also to walkers gained more recruits in faster flows. Additionally, larvae more frequently abandoned nets in slow than fast flows, indicating that drifting into unfavourable flow environments may result in mortality or redispersal of larvae. These findings demonstrate that, although drift is important, it is not necessarily the only method used by hydropsychids to colonise substrata. Larvae may have more capacity to choose substrata in fast flows when they colonise substrata by walking. Spot measures of hydropsychid distribution cannot distinguish between these explanations. The finding that walkers can sometimes comprise significant numbers of recruits raises the prospect that hydropsychids can be sourced locally and have not inevitably drifted in from upstream locations.
Language eng
Field of Research 060204 Freshwater Ecology
HERDC Research category C1 Refereed article in a scholarly journal
Copyright notice ©2005, CSIRO
Persistent URL http://hdl.handle.net/10536/DRO/DU:30006504

Document type: Journal Article
Collection: School of Life and Environmental Sciences
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