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The northern and southern maned sloths may look very similar from the outside, but their genomes reveal different stories: The two species have faced very distinct conditions in Brazil's Atlantic Forest in the past and confront different conservation threats today.

In an article recently in the journal Molecular Ecology, scientists from the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) in partnership with the Brazilian NGO Instituto Tamandu谩 show that the southern, and currently more endangered, lineage displays lower genetic diversity than the northern lineage, which shows a rapid rise in inbreeding in recent decades. The findings demonstrate that genomic studies can offer critical insights for conservation of endangered species.

From November 10 to 21, conservation leaders from across the globe meet in Brazil at the 30th Conference of the Parties (COP30) of the United Nations Framework Convention on Climate Change (UNFCCC). The country is home to several biodiversity hotspots of global importance, regions that not only boast species diversity but also contribute to a stable global climate鈥攊f sufficiently protected. The new study by the Leibniz-IZW and the Instituto Tamandu谩 offers important insights for biodiversity conservation in tropical forests in Brazil.

The Atlantic Forest, South America's highly diverse coastal tropical forest, used to cover a significant portion of Brazil's territory. Due to human activities such as clearing for agriculture and urbanization, today only about 8% of its original extent remains. Even though severely reduced and fragmented, the Atlantic Forest still serves as habitat for a multitude of fascinating鈥攁nd resilient鈥攕pecies. Among these species are the maned sloths, which can be found nowhere else on the planet.

Collaborating closely with the Brazilian conservation NGO Instituto Tamandu谩, scientists from Leibniz-IZW were able to sequence whole genomes of two closely related sloth species from Brazil's Atlantic Forest: the northern maned sloth (Bradypus torquatus) and the southern maned sloth (Bradypus crinitus).

A species genome is equivalent to its genetic "blueprint" and the process of genome sequencing consists of converting the information contained in the DNA to data scientists can analyze.

By studying the sloth's genomes, the goal was to investigate how ancient climatic shifts and recent human-driven habitat changes have shaped the species' genetic diversity, population history and current conservation status.

Genomic insights for conservation

Some of the studies' key results show that the southern maned sloth, which currently is more endangered, displays lower genetic diversity and also lower historical population sizes compared to the northern relatives. This finding likely reflects the distinct environmental and climatic conditions the two areas have experienced in the past.

But the situation is also worrisome for the northern maned sloth: despite its higher genetic diversity and larger current population sizes, there has been a rapid rise in inbreeding鈥攃haracterized by the mating of related individuals鈥攊n recent decades. This is likely owing to recent deforestation and habitat fragmentation in the northern region.

The study also shows that the northern lineage carries a higher genetic load (i.e., more disadvantageous gene variants), which could be dangerous if the trend of population decline is not reversed. "By revealing key aspects of the species' genetic health, these findings allow us to design conservation actions that are truly focused on what the species needs most," said Larissa Arantes, scientist at Leibniz-IZW who led the work.

These key finds buried deep in the sloth's genomes show that each lineage has unique conservation needs, shaped by both deep-time environmental change and modern threats to their tropical habitat.

Why it matters

This study provides genomic insight into a species living in one of the world's most threatened biodiversity hotspots. Despite the importance of these mega diverse regions, this kind of data is only available for a very limited number of species found there. The work offers actionable genetic information for managing vulnerable populations. In particular, the findings highlight the urgency of preserving genetic diversity, mitigating inbreeding, and maintaining habitat connectivity for the long-term survival of these sloths.

"Genomic erosion poses a serious threat to populations under pressure, especially with rising inbreeding. This should serve as a warning that fragmentation is reducing the maned sloth's chances of survival, particularly in the northern region of Bahia. We will continue our close partnership with Instituto Tamandu谩 to assess the extent of the impact on the maned sloth's genomic health," says Camila Mazzoni, Research Group Leader in Evolutionary and Conservation Genomics at Leibniz-IZW and senior author of the study.

Far beyond collecting the samples that made this genomic study possible, the NGO Instituto Tamandu谩 has years of experience leading a wide range of hands-on actions to protect these and other species of sloths and anteaters. From describing a new species of maned sloth to restoring its native habitat through reforestation, all of the organization's actions are guided by science and generate new scientific knowledge, including studies like this one.