Morphological and Genetic Variation Among Callithrix Hybrids in Rio de Janeiro, Brazil

Callithrix jacchus and C. penicillata have successfully established anthropogenic introduced populations throughout Rio de Janeiro state, where the endangered buffy-tufted-ear marmoset, Callithrix aurita, naturally occurs. These three species can produce fertile hybrids, which represent a challenge to C. aurita conservation. Callithrix anthropogenic hybrids show an overall increase in phenotypic variation and in genetic diversity in relation to parental populations and can also form hybrid swarms. Here, we examined ear tuft variation, cranial morphometrics and mitochondrial DNA sequences in three marmoset species (C. jacchus, C. penicillata and C. aurita) and their hybrids from anthropogenic environments in several localities of Rio de Janeiro state. Our data suggest that the sample evaluated is mostly composed of hybrids of C. jacchus and C. penicillata, excepted by one individual which has C. aurita ancestry. The phenotypes of hybrids were highly variable, with six external morphotypes varying from intermediate to parental-like. Cranial morphometric analyses revealed a mosaic of parental traits in hybrids, although there were some transgressive traits, while molecular analyses indicate higher genetic diversity among hybrids relative to parental species. No clear geographical association was found in relation to hybrid distribution, with the hybrid haplotypes occurring randomly throughout Rio de Janeiro state.