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Facilitation and competition between invasive and indigenous mussels over a gradient of physical stress

Facilitation and competition between invasive and indigenous mussels over a gradient of physical stress
Facilitation and competition between invasive and indigenous mussels over a gradient of physical stress
The interactions between invasive exotic and indigenous species can have profound harmful effects on the recipient community; however, not all such interactions are negative. Facilitation is increasingly recognised as important in shaping natural communities and is believed to vary under different conditions. Earlier studies have shown that the indigenous intertidal mussel Perna perna initially facilitates survival of the invasive Mytilus galloprovincialis in the low mussel zone by providing protection against waves, but later excludes M. galloprovincialis through interference competition for space. Here, we examined interactions between these species in the mid and upper mussel zones, moving mussels to experimental plots in different combinations of densities and species. Mussels were left on the shore for more than a year and treatment effects on mortality, shell length and condition were compared. In the high zone, treatment had no effects and P. perna showed greater mortality than M. galloprovincialis, indicating that its exclusion from the high shore is due to emersion stress. In the mid zone, treatment had no significant effects on M. galloprovincialis, but multiple comparisons among treatments involving P. perna showed that facilitation occurred. P. perna survived better at higher densities, but survived even better when mixed with the physiologically more tolerant M. galloprovincialis. Length data indicated both inter- and intraspecific competition for P. perna in the mid zone. Whereas facilitation occurs strongly in the low zone (P. perna facilitates M. galloprovincialis) and weakly in the mid zone (M. galloprovincialis facilitates P. perna), the lack of facilitation in the high zone suggests that the probability of facilitation is not linearly linked to increasing physical stress. Instead it is likely to be hump shaped: relatively unimportant under conditions that are benign for a particular species, significant under more severe conditions, and overridden by physical stress under very harsh conditions.
facilitation, competition, mytilus galloprovincialis, perna perna, mussels, intertidal
1439-1791
607-613
Rius, Marc
c4e88345-4b4e-4428-b4b2-37229155f68d
McQuaid, Christopher D.
97f8c217-f30c-405c-8cf3-f616208b5008
Rius, Marc
c4e88345-4b4e-4428-b4b2-37229155f68d
McQuaid, Christopher D.
97f8c217-f30c-405c-8cf3-f616208b5008

Rius, Marc and McQuaid, Christopher D. (2009) Facilitation and competition between invasive and indigenous mussels over a gradient of physical stress. Basic and Applied Ecology, 10 (7), 607-613. (doi:10.1016/j.baae.2009.03.008).

Record type: Article

Abstract

The interactions between invasive exotic and indigenous species can have profound harmful effects on the recipient community; however, not all such interactions are negative. Facilitation is increasingly recognised as important in shaping natural communities and is believed to vary under different conditions. Earlier studies have shown that the indigenous intertidal mussel Perna perna initially facilitates survival of the invasive Mytilus galloprovincialis in the low mussel zone by providing protection against waves, but later excludes M. galloprovincialis through interference competition for space. Here, we examined interactions between these species in the mid and upper mussel zones, moving mussels to experimental plots in different combinations of densities and species. Mussels were left on the shore for more than a year and treatment effects on mortality, shell length and condition were compared. In the high zone, treatment had no effects and P. perna showed greater mortality than M. galloprovincialis, indicating that its exclusion from the high shore is due to emersion stress. In the mid zone, treatment had no significant effects on M. galloprovincialis, but multiple comparisons among treatments involving P. perna showed that facilitation occurred. P. perna survived better at higher densities, but survived even better when mixed with the physiologically more tolerant M. galloprovincialis. Length data indicated both inter- and intraspecific competition for P. perna in the mid zone. Whereas facilitation occurs strongly in the low zone (P. perna facilitates M. galloprovincialis) and weakly in the mid zone (M. galloprovincialis facilitates P. perna), the lack of facilitation in the high zone suggests that the probability of facilitation is not linearly linked to increasing physical stress. Instead it is likely to be hump shaped: relatively unimportant under conditions that are benign for a particular species, significant under more severe conditions, and overridden by physical stress under very harsh conditions.

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More information

Published date: October 2009
Keywords: facilitation, competition, mytilus galloprovincialis, perna perna, mussels, intertidal
Organisations: Ocean Biochemistry & Ecosystems

Identifiers

Local EPrints ID: 354684
URI: http://eprints.soton.ac.uk/id/eprint/354684
ISSN: 1439-1791
PURE UUID: 44905d72-571a-4726-80b5-537f7daa6f67

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Date deposited: 17 Jul 2013 11:33
Last modified: 14 Mar 2024 14:22

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Author: Marc Rius
Author: Christopher D. McQuaid

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