Historical DNA of Cotton-top tamarins

During the last century, the critically endangered cotton-top tamarin (Saguinus oedipus) has been threatened by multiple anthropogenic factors that drastically affected their habitat and population size. As the genetic impact of these pressures is largely unknown, this study aimed to establish a genetic baseline with the use of temporal sampling to determine the genetic makeup before detrimental anthropogenic impact. Genomes were resequenced from a combination of historical museum samples and modern wild samples at low-medium coverage to unravel how the cotton-top tamarin population structure and genomic diversity may have changed during this period. Our data suggest two populations, probably historically separated by the mountain ranges by Paramillo Massif. Although this population structure persists in the current populations, modern samples exhibit genomic signals consistent with recent inbreeding, such as long runs of homozygosity and a reduction in genome-wide heterozygosity, likely as the consequence of a population reduction since 1960 ´s. However, genetic load analysis insinuates a decrease in deleterious mutations in modern populations. We anticipate that the historical genetic baseline created in this study can be used to provide insight to alteration in the modern population influenced by a drastic reduction in population size as well as providing background information that can be used for future decision-making for the species conservation efforts.