Species-area relationships of primates in tropical forest fragments: a global analysis.
Abstract
While in general the tropics and large-bodied tropical forest mammals are poorly understood, the effects of fragmentation on tropical forest and the tropical mammalian order of primates are relatively well studied. Nevertheless, no quantitative synthesis exists of the response of primates to habitat fragmentation. We therefore conducted a meta-analysis of the literature on the species-area relationships of primates in forest fragments in order to investigate regularities and differences among continents and sites. The sample comprised 136 forest fragments (≤100 km2) at 33 sites in four continents (Africa, Asia, Madagascar and South America). We conducted our analysis at three spatial scales: global, continent and site. As richness (number of species) per site varied, we analysed both richness and proportional richness by area. Study sites and size of fragments were unequally distributed across the globe. South America had three times as many sites as any other continent, for which we found less than 10 sites each. Fragment size was small in all continents (global median 1.0 km2). Despite considerable noise in the data, primate richness and proportional richness generally declined significantly and linearly with fragment area at all spatial scales except in Africa. Neither isolation (distance of fragment from main forest block) nor age of fragment was an obvious influence on proportional richness. However, the global median isolation was only 2 km. Synthesis and applications. Fragmentation of habitat clearly threatens the survival of primates. However, study of the effects of fragmentation on primates might be directed in the wrong place. Estimates of minimum area requirements for primate species exceed tens of km2, yet most forest fragments studied measure less than 1 km2. Both to elucidate the biology of contrasts between species in susceptibility to fragmentation and to use research sites for associated conservation efforts, it might be better to direct more attention to fragments of a size in which long-term persistence of some species is possible.