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Range expansion of a habitat-modifying species leads to loss of taxonomic diversity: a new and impoverished reef state


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Ling, SD 2008 , 'Range expansion of a habitat-modifying species leads to loss of taxonomic diversity: a new and impoverished reef state' , Oecologia, vol. 156, no. 4 , pp. 883-894 , doi: 10.1007/s00442-008-1043-9.

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Global climate change is predicted to have
major negative impacts on biodiversity, particularly if
important habitat-modifying species undergo range shifts.
The sea urchin Centrostephanus rodgersii (Diadematidae)
has recently undergone poleward range expansion to relatively
cool, macroalgal dominated rocky reefs of eastern
Tasmania (southeast Australia). As in its historic environment,
C. rodgersii in the extended range is now found in
association with a simplified ‘barrens’ habitat grazed free
of macroalgae. The new and important role of this habitatmodifier
on reef structure and associated biodiversity was
clearly demonstrated by completely removing C. rodgersii
from incipient barrens patches at an eastern Tasmanian site
and monitoring the macroalgal response relative to unmanipulated
barrens patches. In barrens patches from which
C. rodgersii was removed, there was a rapid proliferation
of canopy-forming macroalgae (Ecklonia radiata and
Phyllospora comosa), and within 24 months the algal
community structure had converged with that of adjacent
macroalgal beds where C. rodgersii grazing was absent. A
notable scarcity of limpets on C. rodgersii barrens in
eastern Tasmania (relative to the historic range) likely
promotes rapid macroalgal recovery upon removal of the
sea urchin. In the recovered macroalgal habitat, faunal
composition redeveloped similar to that from adjacent
intact macroalgal beds in terms of total numbers of taxa,
total individuals and Shannon diversity. In contrast, the
faunal community of the barrens habitat is overwhelmingly
impoverished. Of 296 individual floral/faunal taxa recorded,
only 72 were present within incipient barrens, 253
were present in the recovered patches, and 221 were
present within intact macroalgal beds. Grazing activity of
C. rodgersii results in an estimated minimum net loss of
approximately 150 taxa typically associated with Tasmanian
macroalgal beds in this region. Such a
disproportionate effect by a single range-expanding species
demonstrates that climate change may lead to unexpectedly
large impacts on marine biodiversity as key habitat-modifying
species undergo range modification.

Item Type: Article
Authors/Creators:Ling, SD
Keywords: Biodiversity - Centrostephanus rodgersii - Climate change - Kelp beds - Sea urchin barrens
Journal or Publication Title: Oecologia
ISSN: 0029-8549
DOI / ID Number: 10.1007/s00442-008-1043-9
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