Factors determining mammal species richness on habitat islands and isolates: habitat diversity, disturbance, species interactions and guild assembly rules

1 For over three decades the equilibrium theory of island biogeography has galvanized studies in ecological biogeography. Studies of oceanic islands a nd of natural habitat islands share some similarities to continental studie s, particularly in developed regions where habitat fragmentation results fr om many land uses. Increasingly, remnant habitat is in the form of isolates created by the clearing and destruction of natural areas. Future evolution of a theory to predict patterns of species abundance may well come from th e application of island biogeography to habitat fragments or isolates. 2 In this paper we consider four factors other than area and isolation that influence the number and type of mammal species coexisting in one place: h abitat diversity, habitat disturbance, species interactions and guild assem bly rules. In all examples our data derive from mainland habitat, fragmente d to differing degrees, with different levels of isolation. 3 Habitat diversity is seen to be a good predictor of species richness. Inc reased levels of disturbance produce a relatively greater decrease in speci es richness on smaller than on larger isolates. Species interactions in the recolonization of highly disturbed sites, such as regenerating mined sites , is analogous to island colonization. Species replacement sequences in sec ondary successions indicate not just how many, but which species are includ ed. Lastly, the complement of species established on islands, or in insular habitats, may be governed by guild assembly rules. These contributions may assist in taking a renewed theory into the new millennium.