Density-dependent facilitation cascades determine epifaunal community structure in temperate Australian mangroves

Melanie J. Bishop, James E. Byers, Benjamin J. Marcek, Paul E. Gribben

Research output: Contribution to journalArticleResearchpeer-review

Abstract

Co-occurring foundation species can determine biological community structure via facilitation cascades. We examined the density dependencies of facilitation cascades, including how the density of a basal foundation species influences the density of secondary foundation species, and how the density of secondary foundation species influences community structure. The system in which we assessed density dependencies was a temperate mangrove forest in which pneumatophores trap the fucoid alga Hormosira banksii and provide substrate for the oyster, Saccostrea glomerata. The alga and oyster in turn determine benthic community structure. In the field, algal biomass was positively correlated with pneumatophore density. Oysters, by contrast, were highly over-dispersed and correlated with the presence/ absence of pneumatophores. Epifaunal abundance and species richness were positively correlated with algal and oyster abundance, but their effects were independent. The positive effect of pneumatophore density on epifauna was primarily an indirect effect of trapping more algae. Pneumatophores did not directly influence invertebrate communities. Experiments revealed that, at very low pneumatophore densities, algal retention was insufficient to facilitate epifauna above that found on pneumatophores alone. At higher densities, however, increasing the density of pneumatophores increased algal retention, and the density and diversity of associated invertebrates. Shading by the mangrove canopy reduced algal biomass but did not modify the density-dependent nature of the cascade. Our results extend facilitation theory by showing that the density of both basal and secondary foundation species can be critical in triggering facilitation cascades. Our study also reveals that, where foundation species cooccur, multiple, independent cascades may arise from a single basal facilitator. These findings enhance our understanding of the role of density-dependent facilitation cascades in community assembly.

LanguageEnglish
Pages1388-1401
Number of pages14
JournalEcology
Volume93
Issue number6
DOIs
Publication statusPublished - Jun 2012

Fingerprint

facilitation
mangrove
community structure
algae
oysters
epifauna
alga
Saccostrea glomerata
invertebrate
invertebrates
pneumatophores
mangrove forests
biomass
shading
temperate forests
benthos
trapping
shade
traps
species richness

Bibliographical note

Copyright 2012 by the Ecological Society of America. Article published in Ecology Vol. 93, Issue 6, pp. 1388–1401 by Bishop, Melanie J., James E. Byers, Benjamin J. Marcek, and Paul E. Gribben.

Cite this

Bishop, Melanie J. ; Byers, James E. ; Marcek, Benjamin J. ; Gribben, Paul E. / Density-dependent facilitation cascades determine epifaunal community structure in temperate Australian mangroves. In: Ecology. 2012 ; Vol. 93, No. 6. pp. 1388-1401.
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Density-dependent facilitation cascades determine epifaunal community structure in temperate Australian mangroves. / Bishop, Melanie J.; Byers, James E.; Marcek, Benjamin J.; Gribben, Paul E.

In: Ecology, Vol. 93, No. 6, 06.2012, p. 1388-1401.

Research output: Contribution to journalArticleResearchpeer-review

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