ORIGINAL ARTICLE Ecogeographical variation in skull shape of capuchin monkeys Nilton C aceres 1 , Carlo Meloro 2 , Francesco Carotenuto 2 , Federico Passaro 2 , Jonas Sponchiado 3 , Geruza Leal Melo 4 and Pasquale Raia 2 * 1 Department of Biology, CCNE, Federal University of Santa Maria, Santa Maria, RS, 97110-970, Brazil, 2 Dipartimento di Scienze della Terra, dell’Ambiente e delle Risorse, Universit a degli Studi di Napoli ‘Federico II’, 80138, Napoli, Italy, 3 Programa de P os- Graduac ßao em Biodiversidade Animal, Department of Biology, CCNE, Federal University of Santa Maria, Santa Maria, RS, 97110-970, Brazil, 4 Programa de P os- Graduac ß~ ao em Ecologia e Conservac ß~ ao, CCBS, Universidade Federal do Mato Grosso do Sul, Campo Grande, MS, 79.070-900, Brazil *Correspondence: Pasquale Raia, Dipartimento di Scienze della Terra, Universit a degli Studi di Napoli ‘Federico II’, L.go San Marcellino 10, 80138, Napoli, Italy. E-mail: pasquale.raia@unina.it ABSTRACT Aim Because of their recent evolutionary radiation, capuchin monkeys repre- sent an ideal group with which to investigate ecomorphological adaptations in relation to geography and climate. Our aim was to identify patterns of both skull size and shape variation in capuchins in relation to environmental vari- ables and latitude. Location Tropical and subtropical South America. Methods We performed geometric morphometric analyses of skull shape in 228 capuchin monkey individuals belonging to either the genera Sapajus (seven species) or Cebus (two species), representing 94 localities in South America. Twenty-three homologous landmarks were digitized to describe skull shape. We regressed skull shape against latitude, longitude, skull size and environmen- tal variables, using ordinary and partial least squares regressions. Variation par- titioning was used to test for the relative contribution to shape variance by taxonomy, allometry and environment, and their interaction terms. Results We found a significant impact of latitude, climate and size on skull shape. The allometric component of shape variation, although large, is not congruent with shape differences between species, and probably reflects ontoge- netic effects. Partial least squares between bioclimatic variables and skull shape explain some 98% of the covariation between environment and shape. Species distributed in drier, more seasonal southern localities exhibit a narrow skull with elongated muzzle and relatively larger teeth. Variation partitioning sug- gests that the difference in skull shape between species is highly correlated with climatic variation but not with skull size. Main conclusions Skull shape in capuchins is significantly related to both environment and skull size. The former, but not the latter, is significantly asso- ciated with shape differences between species. The Sapajus clade originated in the south, and experienced an evolutionary radiation during the Pleistocene. As new Sapajus species moved to the north, they adapted to the local environ- mental conditions, eventually resembling Cebus in skull shape as they reached the Amazon rain forest, in response to their shared environmental conditions. Keywords Amazon rain forest, Cebidae, climate, geometric morphometrics, partial least squares, primates, South America, variation partitioning. INTRODUCTION Tropical South America exhibits a complex vegetation struc- ture, including forests, savannas and semi-arid scrublands. The main ecoregions are the Amazon, Cerrado, Caatinga and Atlantic biomes. The forest patches in the Amazon and Atlantic biomes are separated from each other by savanna- like formations in the Cerrado, and by thorny scrubland veg- etation in the semi-arid Caatinga (Ab’Saber, 1977). During the Pleistocene, forested areas were connected to each other ª 2013 John Wiley & Sons Ltd http://wileyonlinelibrary.com/journal/jbi 1 doi:10.1111/jbi.12203 Journal of Biogeography (J. Biogeogr.) (2013)