High mushroom coral biodiversity (Scleractinia: Fungiidae) in the region of Pulisan (north-eastern coast of Sulawesi, Indonesia)

Abstract

Species richness and assemblages of corals belonging to the family Fungiidae (mushroom corals) were studied in various reef habitats in the region of Pulisan, located on the northeast coast of the island of Sulawesi in Indonesia. This area lies near the centre for global marine biodiversity, known as the «Coral Triangle». Observations were carried out in the field by SCUBA-diving to a maximum depth of 36 meters during the summer of 2004 (8-17 August). Twenty-one sites, covering a total surface of 74 km2, were surveyed for presence of mushroom corals. Fungiid species represent 11% of the zooxanthellate sclaractinian coral species observed in this region. A total of 41 fungiid species was recorded, which is more than that from any other area studied so far. The number of fungiid species at visually sampled sites ranged from 2 to 26, with an average of 11.23 ± 5.41 per site. A cluster analysis of Bray-Curtis similarity indices showed that the different sites cluster together, except for a site characterized by extreme environmental conditions (exposed steep slope) which made it unsuitable for mushroom corals. Some species were common and occured at almost all sites (Ctenactis echinata, Fungia fungites, F. granulosa, F. paumotensis, Halomitra pileus, Herpolitha limax and Polyphyllia talpina), whereas others were rare and only observed at one site (Cantharellus jebbi, Cycloseris curvata, C. erosa, C. patelliformis, C. tenuis, Diaseris distorta. Fungia scabra, F. spinifer, Herpolitha weberi, Lithophyllon undulatum, Podabacia crustacea, Sandalolitha robusta and Zoopilus echinatus). When occurence at individual site is considered, 29% of the species were observed at single sites (represented by one or more specimens) and only 30% were present at more than 6 sites. A comparison of the mushroom coral fauna of Pulisan region with those of other areas in or near the «Coral Triangle» indicates that species classified as «rare» at one place can be common elsewhere and vice versa. The exceptional mushroom coral biodiversity found in the region of Pulisan could be explained by the great variety of reef habitats that exists in that region (shallow reef environments, reef slopes more or less exposed to wave action, soft inter-reef substrates...). In terms of conservation biology, the area of Pulisan is a particularly important area because it assembles, on a very restricted surface (74 km 2), a great number of mushroom coral species, including several rare species. Its protection would make it possible to constitute a species reservoir likely to provide species in other areas subjected to more or less important natural or anthropic disturbances.