MEPS 284:147-161 (2004)  -  doi:10.3354/meps284147

Closely related Symbiodinium spp. differ in relative dominance in coral reef host communities across environmental, latitudinal and biogeographic gradients

T. C. LaJeunesse1,2,6,*, R. Bhagooli3, M. Hidaka3, L. deVantier4, T. Done4, G. W. Schmidt1, W. K. Fitt2, O. Hoegh-Guldberg5

1Department of Plant Biology, Plant Sciences Building, 2Institute of Ecology, University of Georgia, Athens, Georgia 30602, USA 3Department of Chemistry, Biology and Marine Sciences, University of the Ryukyus, Nishihara, Okinawa 903-0213, Japan 4Australian Institute of Marine Science, Private Mail Box 3, Townsville, Queensland 4810, Australia
5Centre for Marine Studies, University of Queensland, St. Lucia, Queensland 4072, Australia
6Present address: Department of Biology, Florida International University, University Park Campus, OE 245 11200SW 8th Street, Miami, Florida, 33199, USA

ABSTRACT: The diversity and community structures of symbiotic dinoflagellates are described from reef invertebrates in southern and central provinces of the Great Barrier Reef (GBR), Australia, and Zamami Island, Okinawa, Japan. The symbiont assemblages from region to region were dominated by Clade C Symbiodinium spp. and consisted of numerous host-specific and/or rare types (specialists), and several types common to many hosts (generalists). Prevalence in the host community among certain host-generalist symbionts differed between inshore and offshore environments, across latitudinal (central versus southern GBR) gradients, and over wide geographic ranges (GBR versus Okinawa). One particular symbiont (C3h) from the GBR had a dramatic shift in dominance. Its prevalence ranged from being extremely rare, or absent on high-latitude reefs to dominating the scleractinian diversity on a mid-latitude inshore reef. These changes occurred among coral fauna whose larvae must acquire symbionts from environmental sources (horizontal symbiont acquisition). Such differences did not occur among ‘vertical transmitters’ such as Porites spp., Montipora spp. and pocilloporids (corals that directly transmit symbionts to their offspring) or among those hosts displaying ‘horizontal acquisition’, but that associate with specific symbionts. Most host-specialized types were found to be characteristic of a particular geographic region (i.e. Okinawa versus Central GBR versus Southern GBR). The mode of symbiont acquisition may play an important role in how symbiont composition may shift in west Pacific host communities in response to climate change. There is no indication that recent episodes of mass bleaching have provoked changes in host-symbiont combinations from the central GBR.

KEY WORDS: Symbiodinium · Zooxanthellae biodiversity · Coral symbiosis · Phylogeography · Community structure

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