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Invertebrate grazing during the regenerative phase affects the ultimate structure of macrophyte communities

Elger, A.F. and Willby, N. and Cabello-Martinez, M. (2009) Invertebrate grazing during the regenerative phase affects the ultimate structure of macrophyte communities. Freshwater Biology, 54, 1246-1255. ISSN 0046-5070.

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Official URL: http://dx.doi.org/10.1111/j.1365-2427.2009.02171.x

Abstract

1. Although the biomass of freshwater macrophytes consumed by invertebrate herbivores (excluding crayfish) is usually low, there is growing evidence that invertebrates do exert a structuring effect on macrophyte communities. To explain this, we postulated that the effect of invertebrates may be concentrated on macrophytes during their regenerative phase. 2. We tested this hypothesis by means of a mesocosm-based experiment, in which we investigated the effects of different densities of pond snails [Lymnaea stagnalis (L.)] on macrophytes regenerating from the natural sediment propagule bank. 3. After 2 months, a diverse macrophyte community had established in the absence of snails, mainly from sexual propagules. Under moderate snail grazing (4 individuals m−2), the ultimate biomass of macrophytes was similar, but its species composition differed dramatically. Only a few unpalatable taxa, such as Ceratophyllum demersum and Nymphaeaceae, persisted. Moreover, the relative success of macrophytes regenerating from vegetative rather than sexual propagules improved. Under higher snail graz 4. These results confirm that snails at natural densities can have a strong effect on the ultimate structure of macrophyte communities by selectively consuming some species at a juvenile stage. Therefore, the regenerative phase can be seen as a window of opportunity for invertebrate grazers, which can have a qualitative effect on communities that is disproportionate to the biomass consumed.

Item Type:Article
Institutes:Nederlands Instituut voor Ecologie (NIOO)
ID Code:6250
Deposited On:23 Mar 2010 01:00
Last Modified:04 Sep 2014 09:49

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