RESEARCH ARTICLE Morphological Variation in Wild Marmosets (Callithrix penicillata and C. geoffroyi) and Their Hybrids Lisieux Franco Fuzessy • Ita de Oliveira Silva • Joanna Malukiewicz • Fernanda F. Rodrigues Silva • Marcella do Carmo Po ˆnzio • Vanner Boere • Rebecca Rogers Ackermann Received: 19 March 2014 / Accepted: 22 May 2014 Ó Springer Science+Business Media New York 2014 Abstract Evolutionary theory and observation predict wider phenotypic variation in hybrids than parental species. Emergent phenotypic novelty in hybrids may in turn drive new adaptations or speciation by breaking parental phe- notypic constraints. Primate hybridization is often docu- mented through genetic evidence, but knowledge about the primate hybrid phenotype remains limited due to a small number of available studies on hybrid primate morphology. Here, we examine pelage and morphometric variation in two Brazilian marmoset species (Callithrix penicillata and C. geoffroyi) and their hybrids. Hybrids were sampled in an anthropogenic hybrid zone in the municipality of Vic ¸osa, Minas Gerais state, Brazil. We analyzed hybrid facial and body pelage color variation, and compared 13 morphometric measures between hybrids and parental species. Five different hybrid facial morphotypes were observed, varying from intermediate to parental-like. Hybrid facial morphotypes were biased towards C. peni- cillata, suggesting that the pelage of this species may be dominant to that of C. geoffroyi in this context, and indi- cating that mate preference, and therefore gene flow/ introgression, may be biased towards C. penicillata within the hybrid zone. Hybrid morphometric features were on average intermediate to parental species traits, but trans- gressive hybrids were also observed, suggesting that mor- phometric variation for the studied traits is consistent with Rieseberg’s complementary allele model. Finally, we observed a decoupling of facial patterning and size/shape in hybrids, relative to parent phenotypes, suggesting that an important factor driving phenotypic novelty within the Vic ¸osa marmoset hybrid zone might be the loosening of evolutionary constraints on phenotypic trait integration. Keywords Hybridization Á Pelage color Á Transgressive segregation Á Heterosis Á Phenotypic integration Introduction The importance of hybridization, i.e. interbreeding between individuals from genetically differentiated lineages (typi- cally at or above the rank of subspecies) that produces viable offspring (Baack and Rieseberg 2007), is increas- ingly being recognized in animal evolution. Theoretical expectations regarding phenotypic diversity within hybrid populations predict a complex range of phenotypes that can include individuals that resemble either parental population (cryptic hybrids), those that are morphologically interme- diate to parental populations, as well as individuals that Electronic supplementary material The online version of this article (doi:10.1007/s11692-014-9284-5) contains supplementary material, which is available to authorized users. L. F. Fuzessy Department of Plant Biology, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil I. O. Silva Á F. F. R. Silva Á M. C. Po ˆnzio Department of Animal Biology, Universidade Federal de Vic ¸osa, Vic ¸osa, MG, Brazil J. Malukiewicz School of Life Sciences, Arizona State University, Tempe, AZ, USA V. Boere Department of Biochemistry and Molecular Biology, Universidade Federal de Vic ¸osa, Vic ¸osa, MG, Brazil R. R. Ackermann (&) Department of Archaeology, University of Cape Town, Rondebosch 7701, South Africa e-mail: dr_becky@email.com 123 Evol Biol DOI 10.1007/s11692-014-9284-5