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Population dynamics of an ecologically important range-extender: kelp beds versus sea urchin barrens

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Ling, SD and Johnson, CR (2009) Population dynamics of an ecologically important range-extender: kelp beds versus sea urchin barrens. Marine Ecology Progress Series, 374. pp. 113-125. ISSN Print 0171-8630 Online 1616-1599

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Abstract

The barrens-forming sea urchin Centrostephanus rodgersii (Diadematidae) has recently
undergone poleward range-extension to Tasmania where grazing of diverse and economically
important macroalgal beds has occurred. We compared growth, biometric, dietary and morphometric
characteristics of C. rodgersii between macroalgal habitat and adjacent barrens to inform population
dynamics of the sea urchin within the newly extended range. The age structure of C. rodgersii in
macroalgal habitat and adjacent barrens is similar, suggesting that both habitats have been influenced
by similar recruitment events. However, there are clear differences in body size, body mass,
spine length and diet of sea urchins in the 2 habitat types. We identified 2 broad morphologies of
C. rodgersii. The first is of relatively large size with thick test, rapid growth and short spines, that
grazes macroalgal beds (macroalgal eco-morph). The second ecomorph persists on the barrens habitat
and demonstrates smaller body size, slower growth and thinner test, with gut contents dominated
by closely cropped filamentous and/or coralline algae; but occurs at higher density, possesses longer
spines and appears to enhance the persistence stability of barrens habitat once it is formed (barrens
ecomorph). Invading dense, swell-prone macroalgal habitat of eastern Tasmania, the phenotypic
plasticity displayed by this sea urchin appears to be an important mechanism facilitating colonisation
of reef habitats within the extension region. Importantly, habitat-specific patterns in population
dynamics are broadly consistent with those observed from within the historical range, suggesting
that patterns in macroalgal–sea urchin dynamics and the ecological importance of this species will be
similar across the newly extended range.

Item Type: Article
Keywords: Centrostephanus rodgersii · Climate change · Invasion · Morphology · Growth · Reproduction · Seaweed beds · Sea urchin barrens
Journal or Publication Title: Marine Ecology Progress Series
Page Range: pp. 113-125
ISSN: Print 0171-8630 Online 1616-1599
Identification Number - DOI: 10.3354/meps07729
Additional Information:

© Inter-Research 2009

Date Deposited: 30 Jan 2009 02:14
Last Modified: 18 Nov 2014 03:55
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