Alienígenas existem! E estão substituindo uma das espécies de primatas mais ameaçadas da Mata Atlântica | Aliens exist! And they are replacing one of the most threatened primate species in the Atlantic Forest | An endangered native species is being replaced by hybrids: the new normal for primate conservation in the Brazilian Atlantic Forest | Surrounded by invaders: the situation of a protected area and the conservation of primates in the Atlantic Forest

Intense human activity modifies the native landscape, leading to fragmentation and habitat loss, that enhance biological invasions and approximation between allochthonous and native species. Among primates, the genus Callithrix, endemic to Brazil, has the highest records of invasive species in the Neotropics and is one of the greatest threats to native species, as they will compete for resources and hybridize with local species that are often already endangered. These marmoset invasions and the hybridization process occur in many areas of the Atlantic Forest and are even observed in protected areas, such as the Rio Doce State Park (RDSP), in the state of Minas Gerais. The park is one of the few protected areas of natural occurrence of one of the most endangered primates in the world, C. aurita. However, the population there is threatened by the invasion of other allochthonous marmosets, C. geoffroyi and C. penicillata. We seek to understand how C. aurita is affected by marmoset invasions in the RDSP and in forest fragments around it. Initially, we combined the playback method with N-mixture occupancy models to estimate the abundance and probability of detection for Callithrix spp. in areas inside the RDSP. Subsequently, we combined single-season occupancy models with playbacks to assess whether forest fragments that surround the park, in addition to the types of land use and cover, would influence the distribution of Callithrix spp. We also evaluated which regions around the RDSP would be more vulnerable to new introductions of allochthonous marmosets into the park. Our results showed the high level of threat to C. aurita, since we identified groups of marmosets, predominantly, formed by hybrid individuals between the invasive species (C. geoffroyi and C. penicillata) and these with C. aurita, both inside the RDSP, and in remnants to the west and south. The number of individuals of C. aurita was extremely low in the RDSP, and no individuals of the species were recorded in the surrounding remnants. The abundance of Callithrix spp., especially for hybrid individuals, was higher in locations close to the forest edge of the park, probably due to the high availability of food and shelter resources in these areas. The probability of occupancy of Callithrix spp. was also higher in forest fragments closer to the RDSP, showing that the fragments present in the western and southern regions of the park are more vulnerable to the new introduction of allochthonous marmosets, possibly because they have high connectivity between them and the RDSP and greater permeability for the movement of these primates. These findings indicate a great threat from invasive marmosets and their hybrids to C. aurita. Given the current scenario, our work indicates the necessity to implement urgent measures for the conservation of C. aurita, such as a management plan for the few individuals native inside the RDSP and the manage allochthonous marmoset populations and their hybrids in the forest fragments around the park, in order to guarantee the genetic integrity of C. aurita and their populations viability.

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