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Abstract

Range expanding species can have major
impacts on marine ecosystems but experimental field
based studies are often lacking. The urchin Centrostephanus
rodgersii has recently undergone a southerly
range expansion to the east coast of Tasmania,
Australia. We manipulated densities of C. rodgersii
and algal regrowth in urchin barrens habitat to test
effects of the urchin on biotic interactions between two
native herbivores, black-lip abalone (Haliotis rubra)
and another urchin (Heliocidaris erythrogramma), and
their benthic habitat. After 13 months, removals of
only C. rodgersii resulted in overgrowth of barrens
habitat by algae and sessile invertebrates. Densities of
abalone increased (?92 %) only in patches from
which C. rodgersii was removed and algal regrowth
allowed. In contrast, densities of H. erythrogramma
increased in all treatments (?45, ?28, ?25 %) in
which C. rodgersii was removed, irrespective of the
algal regrowth manipulations. These results suggest
that C. rodgersii has a negative influence on the
densities of abalone through competition for food and
on densities of H. erythrogramma through competition
for preferred habitat. Densities of abalone (?65 %)
but not H. erythrogramma (?25 %), were lower in the
patches from which C. rodgersii and canopy algae
regrowth were removed relative to patches from which
only C. rodgersii was removed (?92 and ?28 %,
respectively). These results suggest that C. rodgersii
overgrazing of canopy-algae results in loss of structural
complexity which could increase abalone susceptibility
to predation, cause abalone to seek shelter
in cryptic microhabitats and/or prevent their return to
patches where canopy algae are absent. The ongoing
spread of C. rodgersii and expansion of barrens habitat
in eastern Tasmania will continue to negatively affect
populations of these two native herbivores and their
associated fisheries at a range of spatial scales. This
example shows that habitat modifying species which
become highly invasive can have disproportionate
negative impacts on the structure and dynamics of the
recipient community.

Item Type:	Article
Authors/Creators:	Strain, EMA and Johnson, CR
Journal or Publication Title:	Biological Invasions
ISSN:	1387-3547
DOI / ID Number:	https://doi.org/10.1007/s10530-012-0378-7
Additional Information:	Copyright 2013 Springer
Item Statistics:	View statistics for this item

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