ABSTRACT
The high diversity of fishes found on coral reefs is traditionally attributed to the high complexity and large number of distinct microhabitats available within reef habitats (e.g., Ross 1986). Habitat complexity is important in facilitating the co-existence of species across a broad range of size classes (Beukers and Jones 1998), largely by moderating predation. The diversity of microhabitats meanwhile, may lead to increased diversity of reef associated fishes (Messmer et al. 2011), especially in case of sympatric fishes that exhibit highly specialised and complementary patterns of habitat use. One striking example of this is the very high levels of habitat specialisation and clear partitioning of anemone species by anemonefishes (e.g., Allen 1972, Fautin and Allen 1997, Elliot and Mariscal 2001). It is apparent, however, that sympatric fishes often do not exhibit clear resource partitioning (Sale 1977). Most coral reef fishes use a very wide and often broadly overlapping range of different resources (Roughgarden 1974, Pratchett 2005). Highly specialised reef fishes may also exhibit highly convergent habitat preferences and high resource overlap (e.g., Munday 2004, Pratchett et al. 2012). On the northern Great Barrier Reef, highly specialised coral-dwelling damselfishes (Dascyllus aruanus, D. reticulatus, and Pomacentrus moluccensis) all prefer the same coral host, Pocillopora damicornis (Pratchett et al. 2012).
