To be or Not to be Hybrids? A Case‐Study in an Allochthonous Population Involving Illegal Introductions of the Endangered Golden‐Headed and Golden Lion Tamarins

Allochthonous species can negatively impact biodiversity by introducing new pathogens, intensifying competition for resources, promoting habitat changes, and causing ecosystem disruption. Introduced species can also spread into areas designated for the conservation of native species. This colonization and, eventually, contact between historically isolated lineages can cause hybridization, resulting in decreased offspring fitness or, conversely, promoting hybrid vigor, threatening the integrity of native populations and increasing their risk of extinction. Here, we analyzed an allochthonous population from a fragment of Brazilian Atlantic Forest, where both endangered Golden-headed lion tamarins and Golden lion tamarins were illegally introduced into the natural range of the Golden lion tamarin in the 1990s. We performed Genotyping by Sequencing and complementary mitochondrial analysis to investigate hybridization and to assess the genetic diversity and structure of the invasive population. Our results were able to rule out the existence of hybrids among the samples analyzed, providing relevant information about the genetic diversity of the alien population and effectively contributing to conservation programs and management actions for both species. Conservation actions and effective surveillance policies to prevent new illegal introductions should be mandatory to ensure the protection of these threatened charismatic species which are targets of illegal trade and trafficking.