ABSTRACT
Habitat Associations Gobies inhabit most microhabitats associated with coral reefs (Fig. 4.2.1), and at the same time are among the most habitat-specialized reef fish groups. This apparent contradiction occurs because at the family level, gobies occupy nearly every habitat type present on coral reefs, yet many species are habitat-specialist with precise microhabitat requirements (Munday et al., 1997; Greenfield and Johnson, 1999; Depczynski and Bellwood, 2004; Herler, 2007). Most coral reef gobies are epibenthic or cryptobenthic (Miller, 1996); there are very few nektonic species. Coral reefs are physically complex structures that off er many options for cryptobenthic life-styles (Fig. 4.2.2). Th e small body size of gobies enables them to exploit habitats and food resources that are not available to larger species. Th e opportunity to utilize a wide range of microhabitats at small spatial scales appears to have contributed to the extraordinary diversity of species within some genera, such as Trimma, Eviota and Gobiodon (Munday and Jones, 1998; Munday et al., 2004). Th e most habitat-specialized gobies are found in obligate association with living hosts, including sponges (Larson, 1990; Rocha et al., 2000; Colin, 2002; Taylor and Hellberg, 2005), hydrozoans (Larson, 1985; Herler and Hilgers, 2005), octocorals (Larson, 1985, 1990), scleractinian corals (Larson, 1985; Munday et al., 1997; Herler, 2007), antipatharians (Munday et al., 2002; Herler, 2007), ascidians (Larson, 1990) and even plants, such as seagrasses (Larson, 1990). Th e best studied of these habitat specialists are the coral-dwelling gobies from the genus Gobiodon, which live among the branches of scleractinian corals from the family Acroporidae. Th ese coraldwelling gobies have been used as a model group for understanding the evolution and ecology of habitat specialization (e.g. Munday et al., 1997, 2001; Munday et al., 2004), and the consequences of habitat specialization in the face of increasing anthropogenic stresses to coral reefs (Munday, 2004b; Feary, 2007; Schiemer et al., 2009). Although all species of coraldwelling gobies can be considered habitat-specialists in the broad sense, there is a vast diff erence in the degree of specialization among species. Some species of Gobiodon are associated with just a single coral species throughout their entire geographic range (Munday, 2002; Munday et al., 2004), whereas other species inhabit up to 10 - 20 diff erent species of coral and change preferences among locations depending on the availability of diff erent coral species (Munday et al., 1997; Munday, 2002; Dirnwöber and Herler, 2007).
