Although tropical mammals account for most discoveries, studies in temperate regions are more robust

A survey of 1,116 new species descriptions published between 1990 and 2025 reveals improved quality, though authors from the Global North use more lines of evidence in their studies.

By André Julião  |  Agência FAPESP – Between 1990 and 2025, 1,116 new mammal species were described. Of those, 999 (89.51%) were from tropical countries, which have the world’s greatest biodiversity. Despite increased access to advanced tools and technical capabilities among its scientists over the past 35 years, descriptions of mammals from this region remain less robust than those from wealthy countries, which contributed only 117 new species during the same period.

These findings are from a study published in the Journal of Systematics and Evolution by researchers supported by FAPESP.

“We’ve observed that mammal taxonomy is becoming more robust over time, using more techniques, analyzing more specimens, and consequently, the descriptions are less likely to be contested later on. That’s a good sign for conservation studies and policies, which require reliable data to be more accurate,” says Matheus Moroti, one of the lead authors of the study. He conducted the study during his postdoctoral research at the Institute of Biology of the State University of Campinas (IB-UNICAMP) in São Paulo, Brazil, with a fellowship from FAPESP. 

Although they have described far fewer native species (117), studies in European countries and the United States make greater use of descriptive techniques, such as genetic tools and analysis of internal anatomy via computed tomography. 

“In addition to many of these tools having been developed in those countries – naturally reaching researchers there first – in lower-income countries, they’re very expensive, and their use is sometimes unfeasible,” adds Jhonny Guedes, also a postdoctoral researcher at IB-UNICAMP and a co-author of the study with Moroti.

The study is part of the project “Big Data & Biodiversity Conservation: Assessing the Impact of Biodiversity Knowledge Accumulation on Conservation Planning”, coordinated by Mário Moura at IB-UNICAMP.

“We assess how the robustness of diagnoses – that is, the amount of information used to distinguish a new species from others – can be affected by biological factors, such as body size, taxonomic richness, geographical factors, such as characteristics associated with the specimen collection site, and historical or socioeconomic factors, such as the number of authors, year of description, internationalization metrics, type of study,” explains Moura, who is currently a professor at the Federal University of Paraíba (UFPB).

Biological factors may partly explain why 41% of the mammals described during the period were rodents and 26% were bats. One explanation is that these groups are extremely diverse. Not surprisingly, their descriptions tend to involve comparing a larger number of specimens using various tools. However, biases in capture and collection also affect the documentation of new species. In bats, for instance, species with smaller body sizes had fewer specimens analyzed.

Internationalization

The researchers noted a decrease in the average number of countries per author, which is a sign that countries are conducting the entire description process independently within their own territories. One possible explanation is the falling cost of molecular tools, which makes them more accessible. 

International collaborations are more common in descriptions based solely on molecular characters. However, when it comes to rodents and bats, these studies involved fewer countries than those based on other lines of evidence. Taxonomic revisions, which reevaluate species in light of new data or interpretations, also involved fewer countries.

“South America is becoming self-sufficient in descriptions, relying less on collaboration with countries in the Global North,” says Guedes.

Another characteristic of these descriptions is the increased involvement of the collector of the specimen of a new species. In a study on mollusk descriptions coordinated by Moura, the authors noted the absence of the professionals who collected the specimens used to describe the species in the papers (read more at agencia.fapesp.br/56702). 

In 2021, Guedes and other authors conducted a study on reptile descriptions and found that when the collector does not participate in the species description, it can take decades – or even more than 100 years – to be published.

“Knowing that taxonomy has become more robust leads to more stable classifications and consistent conservation policies over time. Furthermore, it leads to the recognition of more species. Without that, one could be conserving one species when, in reality, there are two or more, and some of them may be threatened with extinction, for example. With the evolution toward what we call integrative taxonomy, we’re seeing greater stability that contributes to species conservation,” Moroti concludes. 

The study also received support from FAPESP in the form of scientific initiation scholarships for co-authors Giovana Lopes Diegues (22/14674-2) and Guilherme Morasco Missio (23/16169-6). 

The article “Historical shifts, geographic biases, and biological constraints shape mammal species discovery” can be read at onlinelibrary.wiley.com/doi/10.1111/jse.70040.