Effects of Endolithic Parasitism on Invasive and Indigenous Mussels in a Variable Physical Environment

Gerardo Ivan Zardi,Christopher David Mcquaid,Katy Rebecca Nicastro,Marcos Gektidis

doi:10.1371/journal.pone.0006560

Gerardo Ivan Zardi, Christopher David Mcquaid + Show 2 more

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https://doi.org/10.1371/journal.pone.0006560

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Journal: PloS one	Publication Date: Aug 10, 2009
Citations: 85	License type: CC BY 4.0

Affiliation: Rhodes University, University of Erlangen-Nuremberg

Abstract

Biotic stress may operate in concert with physical environmental conditions to limit or facilitate invasion processes while altering competitive interactions between invaders and native species. Here, we examine how endolithic parasitism of an invasive and an indigenous mussel species acts in synergy with abiotic conditions of the habitat. Our results show that the invasive Mytilus galloprovincialis is more infested than the native Perna perna and this difference is probably due to the greater thickness of the protective outer-layer of the shell of the indigenous species. Higher abrasion due to waves on the open coast could account for dissimilarities in degree of infestation between bays and the more wave-exposed open coast. Also micro-scale variations of light affected the level of endolithic parasitism, which was more intense at non-shaded sites. The higher levels of endolithic parasitism in Mytilus mirrored greater mortality rates attributed to parasitism in this species. Condition index, attachment strength and shell strength of both species were negatively affected by the parasites suggesting an energy trade-off between the need to repair the damaged shell and the other physiological parameters. We suggest that, because it has a lower attachment strength and a thinner shell, the invasiveness of M. galloprovincialis will be limited at sun and wave exposed locations where endolithic activity, shell scouring and risk of dislodgement are high. These results underline the crucial role of physical environment in regulating biotic stress, and how these physical-biological interactions may explain site-to-site variability of competitive balances between invasive and indigenous species.

Highlights

Biological invasions are affecting the earth’s ecosystems profoundly [1], and a major challenge in invasion biology lies in identifying the processes regulating invasion success [2,3,4,5]
M. galloprovincialis mussels were 48.5% and 38.2% more infested than P. perna, on the open coast and in bay habitats respectively, while infestation increased with shell length (Fig. 3)
Our results demonstrate a synergistic effect of biotic stress and physical environment on the coexistence between an invasive and a native species

Summary

Introduction

Biological invasions are affecting the earth’s ecosystems profoundly [1], and a major challenge in invasion biology lies in identifying the processes regulating invasion success [2,3,4,5]. Parasites play a crucial role in the hosts’ ecology in plant and animal communities [13,14]. They can have a direct, negative impact on host population density and growth rate [15,16] or can indirectly interact with competition and predation [e. The role of parasites can be critical in biological invasions because they can affect the proliferation of an invader and its interaction with native competitors, shifting competitive dominance from one species to another [19,20]. Parasites in the recipient range can affect the establishment and spread of an introduced species either directly, or operating in concert with environmental conditions to determine the local success of an invader [21,22]

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Conclusion