Morphology of<Emphasis Type="Italic"> Ecklonia radiata</Emphasis> (Phaeophyta: Laminarales) along its geographic distribution in south-western Australia and Australasia |
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| Authors: | Email author" target="_blank">T?WernbergEmail author M?Coleman A?Fairhead S?Miller M?Thomsen |
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| Institution: | (1) School of Plant Biology, University of Western Australia, Botany Building MO90, 6009 Crawley, WA, Australia;(2) Centre for Research on Ecological Impacts of Coastal Cities, University of Sydney, Marine Ecology Labs (A11), 2006 Sydney, NSW, Australia;(3) Department of Environmental Biology, University of Adelaide, North Tce, 5005 Adelaide, SA, Australia;(4) Department of Botany, University of Otago, PO Box 56, Dunedin, New Zealand;(5) Department of Environmental Science, University of Virginia, Clark Hall, Charlottesville, VA 22903, USA |
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| Abstract: | Ecklonia radiata (C. Ag.) J. Agardh is a common macroalga on reefs in the warm-temperate parts of the southern hemisphere. It is a dominant habitat-former and as such has a strong structuring effect on associated algal assemblages. Morphological variation in E. radiata potentially affects its interactions with the surroundings and contributes to confusion about its taxonomy. We quantified the magnitude of morphological variation in fully developed E. radiata sporophytes across Australasia and tested the hypotheses that E. radiata has different morphology at different locations and that the degree of morphological difference depends on spatial distances among locations. A total of 11 morphological characters were sampled from 11 locations along the Australian coastline from Kalbarri in Western Australia to Sydney in New South Wales as well as from Doubtful Sound, New Zealand. Most morphological characters varied considerably from one location to another. For example, the average (±SE) thallus length was 135.2±12.5 cm in Kalbarri and only 69.7±5.5 cm in Sydney. There were no consistent spatial patterns of variation among individual morphological characters, and, generally, variations among individual characters were poorly correlated (-0.5< R<0.5). This suggests that individual morphological characters develop independently of each other in response to processes operating at different spatial scales. Multivariate measures of morphology were found to be different among some locations and similar among others (-0.37=Clarke's R=1), but there was no correlation (Spearman's R=0.08) between morphological similarity and distance between locations. Consequently, our results do not support clinal variation in E. radiata morphology. Rather, they suggest the presence of discrete morphologically different populations, in which the morphology at any one location reflects multiple forcing factors operating on different morphological characters at different spatial scales. |
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