Hybridization is continually documented in primates, but effects of natural and anthropogenic hybridization on biodiversity are still unclear and differentiating between these contexts remains challenging in regards to primate evolution and conservation. Here, we examine hybridization effects on the mitochondrial DNA (mtDNA) control region of Callithrix marmosets, which provide a unique glimpse into interspecific mating under distinct anthropogenic and natural conditions. DNA was sampled from 40 marmosets along a 50-km transect from a previously uncharacterized hybrid zone in NE Brazil between the ranges of Callithrix jacchus and Callithrix penicillata. DNA was also collected from 46 marmosets along a 30-km transect in a hybrid zone in Rio de Janeiro state, Brazil, where exotic marmosets appeared in the 1980s. Combining Callithrix DNA sampled inside and outside of these hybrid zones, phylogenetic and network analyses show C. jacchus and C. penicillata being parental species to sampled hybrids. We expand limited Callithrix population genetics work by describing mtDNA diversity and demographic history of these parental species. We show ancient population expansion in C. jacchus and historically constant population size in C. penicillata, with the latter being more genetically diverse than the former. The natural hybrid zone contained higher genetic diversity relative to the anthropogenic zone. While our data suggest hybrid swarm formation within the anthropogenic zone due to removed physical reproductive barriers, this pattern is not seen in the natural hybrid zone. These results suggest different genetic dynamics within natural and anthropogenic hybridization contexts that carry important implications for primate evolution and conservation.

Ecological networks describe the interactions between species, the underlying structure of communities, the function and stability of ecosystems. To date, network analyses have been extensively applied to understand mutualistic and antagonistic interactions, but few have examined commensal interactions, particularly in neotropical regions. The inselbergs of southeastern Brazil are considered one of the three most important regions in the world in terms of terrestrial species diversity and endemism but are poorly studied. In this study, we constructed the first epiphyte-phorophyte commensalistic network in a Brazilian inselberg and examined its structure and robustness to simulated species loss. A total of 138 phorophyte individuals belonging to eight species were observed in 20 2 m × 50 m transects, interacting with 5,039 individuals of vascular epiphytes belonging to 85 species. The epiphyte-phorophyte network structure exhibited a low degree of specilization (H2'), low connectance and robustness; when the most connected phorophyte species were sequentially removed the number of secondary extinctions was high, based on robustness metrics. One generalist phorophyte, Pseudobombax sp. nov., was particularly important, hosting a high number of epiphyte species. A single phorophyte individual of Pseudobombax supported 46% of the total richness of the epiphyte community studied. Our results demonstrate that the richness and abundance of epiphytes were correlated with phorophyte size (as mensured by the DBH, diameter at breast height), probably due to increased habitat area and the time available for colonization. We conclude that phorophyte size and species identuty are important factors for predicting the structure of epiphyte-phorophyte interaction networks. 2We discuss the conservation implications of phorophyte loss and secondary extinctions of epiphytes in Atlantic Forest inselbergs.

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