CSIRO PUBLISHING Marine and Freshwater Research http://dx.doi.org/10.1071/MF14150 Community structure of reef fishes on a remote oceanic island (St Peter and St Paul’s Archipelago, equatorial Atlantic): the relative influence of abiotic and biotic variables Osmar J. LuizA,G, Thiago C. MendesB, Diego R. BarnecheA, Carlos G. W. FerreiraC, Ramon NoguchiD, Roberto C. Villac¸aB, Carlos A. RangelE, Joa˜o L. GaspariniF and Carlos E. L. FerreiraB ADepartment of Biological Sciences, Macquarie University, Sydney, NSW 2109, Australia. BDepartamento de Biologia Marinha, Universidade Federal Fluminense, Nitero´i, RJ, 24001-970, Brazil. CDepartamento de Oceanografia, Instituto de Estudos do Mar Almirante Paulo Moreira, Arraial do Cabo, RJ, 28930-000, Brazil. DPrograma de Po´s Graduac¸a˜o em Ecologia, Universidade Federal de Rio de Janeiro, Rio de Janeiro, RJ, 68020, Brazil. EProjeto Ilhas do Rio, Instituto Mar Adentro, Rio de Janeiro, RJ, 22031-071, Brazil. FDepartamento de Oceanografia e Ecologia, Universidade Federal do Espı´rito Santo, Vito´ria, ES, Brazil. GCorresponding author. Email:
[email protected] Abstract. This study investigates the reef fish community structure of the world’s smallest remote tropical island, the St Peter and St Paul’s Archipelago, in the equatorial Atlantic. The interplay between isolation, high endemism and low species richness makes the St Peter and St Paul’s Archipelago ecologically simpler than larger and highly connected shelf reef systems, making it an important natural laboratory for ecology and biogeography, particularly with respect to the effects of abiotic and biotic factors, and the functional organisation of such a depauperate community. Boosted regression trees were used to associate density, biomass and diversity of reef fishes with six abiotic and biotic variables, considering the community both as a whole and segregated into seven trophic groups.