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Published: February 23, 2011

Scientists discover striking new species of cloud-forest rodent in Peru

Bruce Patterson, MacArthur Curator of Mammals, Integrative Research Center

A strikingly unusual animal was recently described from the cloud-forests of Peru. The large rodent is about the size of a squirrel and looks a bit like one, except its closest relatives are spiny rats.  The nocturnal, climbing rodent is beautiful yet strange looking, with long dense fur, a broad blocky head, and thickly furred tail. A blackish crest of fur on the crown, nape and shoulders add to its distinctive appearance.

Isothrix barbarabrownae, as the new species has been named, is described in a recent issue of Mastozoología Neotropical , the principal mammalogy journal of South America.

The journal cover, with a beautiful drawing by Velizar Simeonovski

The authors of the study found the rodent in 1999 while conducting field research in Peru's Manu National Park and Biosphere Reserve in Southern Peru along the eastern slope of the Andes. Extending from lowland tropical forests in the Amazon Basin to open grasslands above the Andean tree line, Manu is home to more species of mammals and birds than any equivalently sized area in the world.  "Like other tropical mountain ranges, such as the Himalayas, Ruwenzoris, Virungas and Kinabalu, the Andes support a fantastic variety of habitats," said Bruce Patterson, MacArthur Curator of Mammals at The Field Museum and lead author on the study. "These in turn support some of the richest faunas on the planet."

Although the Field Museum is famous for rapid inventory techniques that answer many biodiversity questions, surveys like this one are thorough, careful and time-consuming. This discovery was part of a three-year sampling scheme that involved as many as 14 people for 10 weeks of fieldwork annually.  More about that effort can be found on the Manu Project pages.  Eleven other mammal species new to science were discovered during the same work, including other rodents, bats and a marsupial. Amazingly, nearly 1 in 10 species that the team encountered was an undescribed species!

The new rodent was discovered at an elevation of 6,200 feet (1920 m), shown by the red star in the map below. Little is known about its lifestyle because subsequent efforts to locate and observe the animal were fruitless.  I. barbarabrownae belongs to a family of rodents known as "spiny rats" because most of the species in that family bristle with spines. Its discovery has necessitated a re-examination of this tropical American family, especially its closest relatives, the bush-tailed tree rats found in South America's lowlands. As a result of the recent discovery, the authors have used The Field Museum's Pritzker Lab for Molecular Systematics and Evolution to resolve the evolutionary relationships among all of these rodents.  "The new species is not only a handsome novelty," Patterson said. "Preliminary DNA analyses suggest that its nearest relatives, all restricted to the lowlands, may have arisen from Andean ancestors. The newly discovered species casts a striking new light on the evolution of an entire group of arboreal rodents."

Locations of other members of the brush-tailed tree rat genus Isothrix

Paul Velazco, the junior author of this paper, was a PhD student at the University of Illinois at Chicago and student-in-residence at The Field Museum at the time this study was conducted. He is now a post-doctoral fellow at the American Museum of Natural History in New York.  The new species is named after Scientific Associate Barbara E. Brown, who has worked at The Field Museum since 1970.

Broader work published in Fieldiana

The work of the international field research team that discovered I. barbarabrownae stretched over three seasons (1999-2001) and 3000 meters (10,000 feet) of elevation.  The work resulted in the discovery of 11 additional species new to science in a single river valley: 1 opossum, 7 bats, and 3 rodents. In November 2006, a synopsis of the entire project was published in Fieldiana: Zoology, a scientific publication of The Field Museum. The article is called "Mammals and Birds of the Manu Biosphere Reserve, Peru." It lists 222 species of mammals, 94 of which are bats, and 1,005 species of birds, twice the number of bird species breeding in the United States and Canada combined.  "Students from San Marcos University in Lima made up two-thirds of the team collecting mammals, birds, and their parasites," Patterson said. "Peruvian students have described most of the new species while pursuing graduate studies overseas. Manu trainees are now enrolled in universities in Illinois, Texas, Michigan, Mexico and the United Kingdom." The research was sponsored by the National Science Foundation, the Museo de Historia Natural at the Universidad Nacional Mayor de San Marcos in Lima, and The Field Museum.

The new rodent is described in this 2006 paper from the journal Mastozoología Neotropical

The new rodent's evolutionary affinities are detailed in the 2008 article in the journal Molecular Phylgenetics and Evolution.

Listen to Bruce's interview with the Canadian Broadcasting Company's Quirks & Quarks on 27 Jan 2007.


Bruce Patterson

I study several topics in evolutionary biology, focusing on the diversification, distribution and conservation of mammals. The breadth of my research is testimony to the facts that no interesting biological questions are ever fully answered and progress towards answering them invariably opens up a variety of others.  Curiosity, opportunity, and a bit of wanderlust have diversified my program and caused it to span two continents.

 

Density of terrestrial vertebrate species (savingspecies.org). Wonder why I study tropical animals?!

For most of my career, I have used museum specimens to study the systematics and biogeography of Neotropical mammals.  Collaborating with scientists and students in Ecuador, Peru, Bolivia, Brazil, and Chile, I have worked throughout the Andes, Amazonia, as well as Atlantic, Valdivian, and Magellanic Forests. While documenting some of the world's richest and most highly endemic faunas, we regularly discover and describe new taxa of marsupials, rodents, and bats and use them in regional and continental reconstructions of phylogeny and biogeography. The program offers abundant training opportunities for American and Latin American students, both in the lab and in the field.  Beginning in 2011, I started a parallel project on the The Bats of Kenya with colleagues Paul Webala and Carl Dick.  This project is designed to document the distribution and status of more than 100 species of bats that occur in Kenya and to shed light on their ecological roles and current status.

Collecting parasites in the course of these systematic studies led to my interest in host-parasite coevolution.  Ectoparasites recovered from mammals and birds are used to reconstruct the radiation of parasite groups and to assess their distributions across hosts and geography.  These studies identify factors that govern the distribution, abundance, and host specificity of parasites.  Together with Carl Dick (until 2009 a post-doc here at the Museum, now at Western Kentucky University) and Katharina Dittmar (SUNY Buffalo), we have developed a broad range of studies on the ecology, coevolution, and phylogeny of these interesting flies.  Interest in the unstudied ectoparasite communities of African bats helped fuel our collaborations with Kenyan Paul Webala to survey the diverse bat communities of Kenya.        

 

A Hipposideros bat with an ectoparasitic Penicillidia bat fly

A second, derivative program focuses on host-parasite coevolution.  Ectoparasites recovered from mammal and bird specimens are used to reconstruct the evolutionary radiations of parasite groups and assess their current distributions across hosts and geography, factors governing their distribution, abundance, and host specificity.  Work on bat flies has been developed with Carl Dick (until 2009 a post-doc here at the Museum, but now at Western Kentucky University) and Katharina Dittmar (SUNY Buffalo) on their ecology and phylogeny. With NSF funding, we recently curated the world's largest collection of flies, which now guides our understanding of host associations and fuels the taxon-sampling in our phylogenetic work (also supported by NSF). Undergrad and grad students are involved in this work in Chicago, Buffalo, and Bowling Green. Interest in the mostly unexplored ectoparasite communities of African bats helped fuel my collaboration with Kenya Wildlife Service ecologist Paul Webala on surveying the diverse bat communities of Kenya (see above). 

Photo by B. A. Harney in Tsavo, Kenya (July 2007)
 

A research program that I am now concluding focused on the Tsavo lions, infamous as man-eaters a century ago but more remarkable because many of them lack manes. In a series of papers, I have explored the morphology, genetics, behavior, and ecology of lions in SE Kenya with Samuel Kasiki (Kenya Wildlife Service) and Alex Mwazo (Kenyatta University), Roland Kays (NY State Museum), Jean Dubach (Loyola University), Justin Yeakel (UC Santa Cruz), and others.  Our aim has been to understand this distinctive and environmentally-plastic trait (manelessness) at genetic, hormonal, histological, anatomical, and behavioral levels. Concurrently, we gathered information to mitigate the impacts of lion depredations on livestock to ensure their continued survival and the preservation of their habitats. Until 2009, this project had the help of volunteers from the Earthwatch Institute.

As detailed in Students, interactions with undergraduate and graduate students enrich, extend, and complement these studies. All four research arenas offer opportunities for student research projects and post-graduate collaborations alike.