Biological Journal of the Linnean Society, 2005, 85, 235–246. With 6 figures © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 85, 235–246 235 Blackwell Science, LtdOxford, UKBIJBiological Journal of the Linnean Society0024-4066The Linnean Society of London, 2005? 2005 852 235246 Original Article EVOLUTION OF DIVERSITY GRADIENTS M. BÖHM and P. J. MAYHEW *Corresponding author. E-mail: pjm19@york.ac.uk Historical biogeography and the evolution of the latitudinal gradient of species richness in the Papionini (Primata: Cercopithecidae) MONIKA BÖHM and PETER J. MAYHEW* Department of Biology, University of York, PO Box 373, York, YO10 5YW, UK Received 22 April 2004; accepted for publication 16 August 2004 We apply historical biogeography techniques to the macaques, baboons and their relatives (Primata: Papionini) and relate the inferred history of range shifts, and associated evolutionary events, to the latitudinal distribution of extant species, which is strongly tropical. The results of reversible parsimony, weighted ancestral area and dispersal-vicar- iance analyses all agree that Central Africa was part of the range of the ancestor of the tribe. Tropical regions with high current species richness (Central Africa, South-east Asia, Indonesia) have: (1) had a relatively long history of occupation, (2) experienced both a greater number and a greater average rate of speciation events and (3) given rise to more dispersal events to other regions. However, nested sister-taxon comparisons across the tribe show no overall association between differences in latitude and differences in rates of cladogenesis. Our historical reconstructions are largely consistent with previous hypotheses and fossil data, and suggest that both the passage of time since col- onization and rates of cladogenesis have enhanced tropical species richness. Historical biogeography may thus con- siderably aid understanding of this and other spatial problems in macroecology. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 85, 235–246. ADDITIONAL KEYWORDS: adaptive radiation – macroevolution – origination – primates – speciation – tropical diversity. INTRODUCTION In recent years, the revolutionary advances in cladis- tic and molecular analyses have made phylogenetic information on living species available as never before. This information provides a potential window on the past that is, to an extent, independent of that provided by the fossil record, and has made it possible to infer the history of evolutionary changes in taxa where it was previously impossible to do so (see Har- vey et al., 1996; Pagel, 1999). One type of data that may be combined with phylo- genetic information is the spatial location of extant species. Given appropriate techniques, known collec- tively by the term ‘historical biogeography’ (Morrone & Crisci, 1995), past geographical distributions can be inferred, together with the processes that have created them, such as the different forms of specia- tion, extinction and dispersal events (see Croizat, 1958; Nelson & Platnick, 1981; Humphries & Parenti, 1986; Myers & Giller, 1988; Wiley, 1988; Morrone & Crisci, 1995; Avise, 2000). Information on such processes is also useful for macroecologists attempting to understand large-scale spatial patterns such as latitudinal gradients in species richness, body size and geographical range (see Brown, 1995; Gaston & Blackburn, 2000). In this paper we attempt to use such information to uncover the origins of a macroecological pattern; the latitudinal gradient in species richness in the tribe Papionini (Primata: Cercopithecidae). Although historical biogeography has been estab- lished as a discipline for more than 180 years (Mor- rone & Crisci, 1995), few studies have attempted to relate the results of such analyses to major macroeco- logical patterns (see Gaston & Blackburn, 2000). A recent study by Bleiweiss (1998) investigated the his-