ORIGINAL ARTICLE The Serra da Mantiqueira, south-eastern Brazil, as a biogeographical barrier for fishes Leonardo F. S. Ingenito* and Paulo A. Buckup INTRODUCTION Because primary (sensu Myers, 1938) freshwater fishes have limited ability to disperse overland and have a low tolerance to salt water, they constitute an excellent subject for studies in historical biogeography (Weitzman & Weitzman, 1982; Vari, 1988; Unmack, 2001; Montoya-Burgos, 2003). Water- shed divides such as high mountains are often regarded as effective dispersal barriers for fish, and fish distributions are often described in terms of hydrographic basin limits. It is conceivable, however, that main river lowlands might act equally well as barriers for fish dispersal. Buckup & Melo (2005), for example, demonstrated that phylogenetic relation- ships among populations of the Characidium lauroi species group span river basin limits, but that species boundaries are restricted to hill-side streams associated with particular mountain ranges. Here we explore the role of the Serra da Mantiqueira as a biogeographical dispersal barrier for Setor de Ictiologia, Departamento de Vertebrados, Museu Nacional, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil *Correspondence: Leonardo F. S. Ingenito, Setor de Ictiologia, Departamento de Vertebrados, Museu Nacional, Universidade Federal do Rio de Janeiro, Quinta da Boa Vista, 20940-040 Rio de Janeiro, RJ, Brazil. E-mail: lfsi@uol.com.br ABSTRACT Aim To present a fish fauna survey from rivers draining the south-western region of the Serra da Mantiqueira, and to investigate the effectiveness of that mountain range as a biogeographical barrier isolating the fish faunas of the Paraı´ba do Sul basin and the upper Parana ´ river. Location Six drainages from the south-western portion of the Serra da Mantiqueira in the region of Campos do Jorda ˜o, Brazil, were studied. They included three drainages belonging to the Paraı´ba do Sul basin (Piracuama, Grande and Buenos), and three belonging to the Sapucaı´ basin, Rio Parana ´ system (Sapucaı´-Mirim, upper Sapucaı´ and Santo Anto ˆ nio). Methods The survey was conducted in two sampling trips supplemented by examination of specimens preserved in museum collections. Parsimony analysis of endemicity (PAE) was used to detect the hierarchy of relationships among the six drainages. Results A total of 47 species of fishes was recorded in the six drainages. The main watershed divide is an effective barrier between the two basins, with 28 species occurring exclusively in the Paraı´ba do Sul versant, and 15 occurring exclusively on the slope of the Sapucaı ´ basin. The PAE of 18 species with cladistically informative distributions and unproblematic taxonomic diagnoses produced a single area cladogram, with complete congruence among 14 species. Main conclusions The main Mantiqueira watershed divide is an effective biogeographical barrier isolating the fish faunas of the Paraı´ba do Sul and the Sapucaı´ basin (upper Parana ´ system). Previous hypotheses of a past connection between the upper Parana ´ and the Paraı´ba do Sul are not supported by extant species distributions in the Serra da Mantiqueira region. Within-basin drainage differentiation, however, is relatively low. Keywords Brazil, freshwater fishes, historical biogeography, PAE, Serra da Mantiqueira, upper Parana ´ system, Paraı ´ba do Sul basin. Journal of Biogeography (J. Biogeogr.) (2007) 34, 1173–1182 ª 2007 The Authors www.blackwellpublishing.com/jbi 1173 Journal compilation ª 2007 Blackwell Publishing Ltd doi:10.1111/j.1365-2699.2007.01686.x