Effects of aggregation and species identity on the growth and behavior of mushroom corals
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EVects of aggregation and species identity on the growth and behavior of mushroom corals R. Elahi
Received: 25 January 2008 / Accepted: 7 July 2008 / Published online: 6 August 2008 © Springer-Verlag 2008
Abstract Aggregations of fungiid corals are common on Indo-PaciWc reefs, but visible signs of direct competition are uncommon. Although negative interactions between fungiids are generally thought to be negligible, the results of an experiment manipulating aggregation and species identity indicated that per capita calciWcation rates of Fungia concinna were depressed when surrounded by Wve other Fungia. The reduction in growth did not vary if neighbors were Fungia concinna or Fungia paumotensis, suggesting that these two related species overlap substantially in their competitive impacts. However, mucus production and movement occurred more frequently in heterospeciWc than conspeciWc groups. These results suggest that there is a cost to group living, but depressed growth must be weighed against the potential beneWts of successful spawning in conspeciWc aggregations. Keywords Fungiidae
Competition · Neighbor eVect · Scleractinia ·
Introduction On tropical reefs, scleractinian corals often compete for space by using mesenterial Wlaments (Lang 1973) and sweeper tentacles (Richardson et al. 1979), and such direct competition is manifested as tissue mortality along colony Electronic supplementary material The online version of this article (doi:10.1007/s00338-008-0403-6) contains supplementary material, which is available to authorized users. Communicated by Ecology Editor Professor Peter Mumby R. Elahi (&) Department of Biology, University of Washington, 24 Kincaid Hall, Box 351812, Seattle, WA 98195-1800, USA e-mail: [email protected]
margins. Aggression has been documented extensively between species of corals (e.g., Wellington 1980; Van Veghel et al. 1996; Lapid et al. 2004) but less frequently within species (Rinkevich and Loya 1983; Hidaka 1985), suggesting that interspeciWc aggression may be more common (Logan 1984). However, the relative eVects of intra- versus inter-speciWc competition on growth have been quantiWed only rarely in corals, with contrasting results (Dizon and Yap 2005; Idjadi and Karlson 2007). Aggregations of mushroom corals (Fungiidae) provide a striking contrast to the aggression between sessile coral colonies. Unlike other scleractinians, most fungiids are solitary, free-living polyps capable of limited mobility (Hoeksema 1989). They can be found in large (10–100 individuals) conspeciWc and heterospeciWc groups, in contact with their surrounding neighbors, but usually without any obvious signs of competition (Sheppard 1979). However, experimental manipulations have demonstrated fungiids to be aggressive and competitively superior to other scleractinians (Chadwick 1988). These observations spurred the main question behind this study: do individual fungiids incur a physiological cost when living in aggregations? By manipulating groups of corals in the Weld, this study tested the hyp
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