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Swan foraging shapes spatial distribution of two submerged plants, favouring the preferred prey species.

Sandsten, Håkan LU and Klaassen, Marcel (2008) In Oecologia 156. p.569-576
Abstract
Compared to terrestrial environments, grazing intensity on belowground plant parts may be particularly strong in aquatic environments, which may have great effects on plant-community structure. We observed that the submerged macrophyte, Potamogeton pectinatus, which mainly reproduces with tubers, often grows at intermediate water depth and that P. perfoliatus, which mainly reproduces with rhizomes and turions, grows in either shallow or deep water. One mechanism behind this distributional pattern may be that swans prefer to feed on P. pectinatus tubers at intermediate water depths. We hypothesised that when swans feed on tubers in the sediment, P. perfoliatus rhizomes and turions may be damaged by the uprooting, whereas the small round... (More)
Compared to terrestrial environments, grazing intensity on belowground plant parts may be particularly strong in aquatic environments, which may have great effects on plant-community structure. We observed that the submerged macrophyte, Potamogeton pectinatus, which mainly reproduces with tubers, often grows at intermediate water depth and that P. perfoliatus, which mainly reproduces with rhizomes and turions, grows in either shallow or deep water. One mechanism behind this distributional pattern may be that swans prefer to feed on P. pectinatus tubers at intermediate water depths. We hypothesised that when swans feed on tubers in the sediment, P. perfoliatus rhizomes and turions may be damaged by the uprooting, whereas the small round tubers of P. pectinatus that escaped herbivory may be more tolerant to this bioturbation. In spring 2000, we transplanted P. perfoliatus rhizomes into a P. pectinatus stand and followed growth in plots protected and unprotected, respectively, from bird foraging. Although swan foraging reduced tuber biomass in unprotected plots, leading to lower P. pectinatus density in spring 2001, this species grew well both in protected and unprotected plots later that summer. In contrast, swan grazing had a dramatic negative effect on P. perfoliatus that persisted throughout the summer of 2001, with close to no plants in the unprotected plots and high densities in the protected plots. Our results demonstrate that herbivorous waterbirds may play a crucial role in the distribution and prevalence of specific plant species. Furthermore, since their grazing benefitted their preferred food source, the interaction between swans and P. pectinatus may be classified as ecologically mutualistic. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Cygnus, Mutualism, Potamogeton, Predator–prey interactions, Subterranean herbivory
in
Oecologia
volume
156
pages
569 - 576
publisher
Springer
external identifiers
  • pmid:18335250
  • wos:000255680000009
  • scopus:43349092921
ISSN
1432-1939
DOI
10.1007/s00442-008-1010-5
language
English
LU publication?
yes
id
8ee4556c-811f-44af-b1ae-bb904a24c9d3 (old id 1052564)
date added to LUP
2008-04-28 12:32:25
date last changed
2017-01-01 06:10:16
@article{8ee4556c-811f-44af-b1ae-bb904a24c9d3,
  abstract     = {Compared to terrestrial environments, grazing intensity on belowground plant parts may be particularly strong in aquatic environments, which may have great effects on plant-community structure. We observed that the submerged macrophyte, Potamogeton pectinatus, which mainly reproduces with tubers, often grows at intermediate water depth and that P. perfoliatus, which mainly reproduces with rhizomes and turions, grows in either shallow or deep water. One mechanism behind this distributional pattern may be that swans prefer to feed on P. pectinatus tubers at intermediate water depths. We hypothesised that when swans feed on tubers in the sediment, P. perfoliatus rhizomes and turions may be damaged by the uprooting, whereas the small round tubers of P. pectinatus that escaped herbivory may be more tolerant to this bioturbation. In spring 2000, we transplanted P. perfoliatus rhizomes into a P. pectinatus stand and followed growth in plots protected and unprotected, respectively, from bird foraging. Although swan foraging reduced tuber biomass in unprotected plots, leading to lower P. pectinatus density in spring 2001, this species grew well both in protected and unprotected plots later that summer. In contrast, swan grazing had a dramatic negative effect on P. perfoliatus that persisted throughout the summer of 2001, with close to no plants in the unprotected plots and high densities in the protected plots. Our results demonstrate that herbivorous waterbirds may play a crucial role in the distribution and prevalence of specific plant species. Furthermore, since their grazing benefitted their preferred food source, the interaction between swans and P. pectinatus may be classified as ecologically mutualistic.},
  author       = {Sandsten, Håkan and Klaassen, Marcel},
  issn         = {1432-1939},
  keyword      = {Cygnus,Mutualism,Potamogeton,Predator–prey interactions,Subterranean herbivory},
  language     = {eng},
  pages        = {569--576},
  publisher    = {Springer},
  series       = {Oecologia},
  title        = {Swan foraging shapes spatial distribution of two submerged plants, favouring the preferred prey species.},
  url          = {http://dx.doi.org/10.1007/s00442-008-1010-5},
  volume       = {156},
  year         = {2008},
}