Genomic signatures in Maned Three-Toed Sloths from historical to
contemporary shifts in Brazil's threatened Atlantic Forest
Abstract
Maned Three-Toed Sloths (Xenarthra: Bradypodidae) are endemic to the
highly fragmented Atlantic Forest of Brazil. Both species, known as
Northern Maned Sloths (Bradypus torquatus Illiger, 1811) and Southern
Maned Sloths (Bradypus crinitus Gray, 1850), exhibit disconnected
populations across the distributions. Our study investigates the
evolutionary and demographic trajectories of these two sloth lineages,
utilizing whole-genome resequencing data compared against a high-quality
genome assembly. Our analysis reveals that the Southern Maned Sloth
exhibits lower genetic diversity and a smaller historical population
size compared to the Northern Maned Sloth. These disparities likely stem
from differing environmental and climatic historical changes along the
Atlantic Forest distribution during the Pleistocene, which was
characterized by greater climate stability and larger refugia areas in
the north. Nonetheless, the northern population has experienced a fast
increase in inbreeding levels in the last 20 years, in a region of Bahia
State with extensive recent deforestation associated with livestock
farming, agriculture, and urban development. In addition, the northern
lineage presented a higher genetic load, which could imply higher
fitness costs for this population if inbreeding patterns persist. Taken
together, these results confirm the independent evolutionary paths of
these two lineages and underscore the conservation challenges faced due
to historical evolutionary events and current deforestation of the
Atlantic Forest.