Untangling the branches in the mammal tree of life

December 04, 2019

New Haven, Conn. -- The mammal tree of life is a real leaner. Some branches are weighed down with thousands of species -- we're looking at you, rodents and bats -- while others hold just a few species.

Now we may have a better idea why.

In a new study published in the journal PLOS Biology, researchers at Yale University unveil a complete overhaul of the way species data is brought together and analyzed to construct an evolutionary tree of life for mammals. It's aimed at giving scientists, conservation managers, policymakers, and environmentalists more accurate, comprehensive information about species diversity and relationships, past and present.

"The fossil and genomic data we use are often fragmentary and messy, but the reality is we are reconstructing events that occurred millions of years ago in long-extinct mammals," said Nathan Upham, a Yale postdoctoral associate in ecology and evolutionary biology and first author of the study.

Of the roughly 6,000 species of living mammals, most of them are rodents (42%) or bats (24%), while common mammals such as cows, pigs, sheep, cats, raccoons, and monkeys consist of relatively few species. Yet up to this point, attempts to formulate a tree of life for mammals have been unable to explain this unevenness of species diversity.

Upham and senior author Walter Jetz, professor of ecology and evolutionary biology at Yale, took a new approach. They reconstructed the evolutionary relationships of species by creating "patches" of smaller, more accurate evolutionary trees that were then linked to a carefully developed "backbone" representing the deep divergences in the tree. This resulted in 10,000 big trees -- designed so they can be studied individually or together -- that also point out the remaining gaps in data for the overall mammal tree of life.

"We're calling it a 'backbone-and-patch' approach," Jetz said. "For the first time, we're able to characterize the genetic relationships of essentially all living mammals while transparently relaying the parts that remain uncertain. It should enable advances in a variety of fields, including comparative biology, ecology, and conservation."

The completeness and accuracy of this information is important, Jetz added, as evolutionary distinctiveness is increasingly used to determine conservation priorities. Therefore, it can be useful for researchers and policymakers in the U.S. to know that the closest genetic relatives of the pronghorn antelope in the U.S. are not nearby mammal species, but giraffes and okapi in Africa.

The researchers also developed an interactive tool for exploring the mammal tree of life. The interface, which is downloadable, lets users examine information both at the species level and also more broadly.

Upham said further research will use the new information to look at how the uneven distribution of species in the mammal tree of life is related to geographic isolation among mammal populations, which can lead to higher rates of speciation -- the evolutionary process of forming new species -- and extinction.
-end-
Jacob Esselstyn of Louisiana State University is co-author of the study.

Yale University

Related Conservation Articles from Brightsurf:

New guide on using drones for conservation
Drones are a powerful tool for conservation - but they should only be used after careful consideration and planning, according to a new report.

Elephant genetics guide conservation
A large-scale study of African elephant genetics in Tanzania reveals the history of elephant populations, how they interact, and what areas may be critical to conserve in order to preserve genetic diversity of the species.

Measuring the true cost of conservation
BU Professor created the first high-resolution map of land value in the United states.

Environmental groups moving beyond conservation
Although non-governmental organizations (NGOs) have become powerful voices in world environmental politics, little is known of the global picture of this sector.

Hunting for the next generation of conservation stewards
Wildlife ecology students become the professionals responsible for managing the biodiversity of natural systems for species conservation.

Conservation research on lynx
Scientists at the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) and the Leibniz Institute for Molecular Pharmacology (Leibniz-FMP) discovered that selected anti-oxidative enzymes, especially the enzyme superoxide dismutase (SOD2), may play an important role to maintain the unusual longevity of the corpus luteum in lynxes.

New 'umbrella' species would massively improve conservation
The protection of Australia's threatened species could be improved by a factor of seven, if more efficient 'umbrella' species were prioritised for protection, according to University of Queensland research.

Trashed farmland could be a conservation treasure
Low-productivity agricultural land could be transformed into millions of hectares of conservation reserve across the world, according to University of Queensland-led research.

Bats in attics might be necessary for conservation
Researchers investigate and describe the conservation importance of buildings relative to natural, alternative roosts for little brown bats in Yellowstone National Park.

Applying biodiversity conservation research in practice
One million species are threatened with extinction, many of them already in the coming decades.

Read More: Conservation News and Conservation Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.