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The effects of an invasive habitat modifier on the biotic interactions between two native herbivorous species and benthic habitat in a subtidal rocky reef ecosystem

journal contribution
posted on 2023-05-17, 19:14 authored by Elisabeth StrainElisabeth Strain, Craig JohnsonCraig Johnson
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.

History

Publication title

Biological Invasions

Volume

15

Issue

6

Pagination

1391-1405

ISSN

1387-3547

Department/School

School of Natural Sciences

Publisher

Springer

Place of publication

Netherlands

Rights statement

Copyright 2012 Springer Science+Business Media

Repository Status

  • Restricted

Socio-economic Objectives

Assessment and management of terrestrial ecosystems

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