Greater occupancy of invasive hybrid marmosets compared to a threatened native species in the fragmented Atlantic Forest: implications for conservation.

Endemic to the Atlantic Forest, Callithrix aurita faces endangerment due to habitat loss, fragmentation, and yellow fever epidemics, exacerbated by the introduction of non-native marmoset species, which heightens the risk of competition, hybridization, and genetic erosion. In this study, we employed playback methods and occupancy models to investigate habitat use by C. aurita and hybrid marmoset groups (Callithrix spp.) across 15 forest fragments in Guidoval, state of Minas Gerais, Brazil. We examined the influence of forest connectivity and distance from Guidoval's urban center on the occupancy of both C. aurita and Callithrix spp. We also assessed the influence of fragment size on their detection probability. Our findings revealed a mean occupancy probability of 0.65 for C. aurita and 0.83 for Callithrix spp. Interestingly, C. aurita occupancy correlated negatively with distance from Guidoval's urban center, possibly due to historical fragmentation processes that provided protection to certain groups in closer, less invaded fragments. Conversely, Callithrix spp. occupancy showed no correlation with any variable, highlighting their adaptability and raising concerns about their potential to threaten native species through hybridization and substitution. Additionally, fragment size did not influence detection probability of both taxa, this implies that the sampled areas may not be large enough for this variable to have an effect. Overall, our results underscore the urgent need for conservation efforts to mitigate the impacts of habitat fragmentation and invasive species on endangered marmoset populations in the Atlantic Forest.