Featured Research

from universities, journals, and other organizations

Rafting Rodents From Africa May Have Been Ancestors Of South American Species

Date:
October 17, 2001
Source:
Texas A&M University
Summary:
Forty million years ago, rodents from Africa may have colonized South America by rafting or swimming across the Atlantic, Texas A&M University biologists theorize by studying the evolution of rodents, looking at their genes instead of their fossils - an approach that promises to revolutionize the field of evolutionary biology.

COLLEGE STATION, - Forty million years ago, rodents from Africa may have colonized South America by rafting or swimming across the Atlantic, Texas A&M University biologists theorize by studying the evolution of rodents, looking at their genes instead of their fossils - an approach that promises to revolutionize the field of evolutionary biology.

"We have good evidence that suggests that South America was founded by a single ancestral stock of caviomorph relatives from Africa," says Rodney Honeycutt, a Texas A&M professor of biology who has been studying the evolution of rodents for the last eight years.

"The radiations of these rodents to South America are too young for continental drift to have played a role in their colonization by African ancestors. This presents a dilemma, because either caviomorph ancestors dispersed to South America from Africa over water (e.g., by rafting) or the caviomorph radiations are considerably older than suggested by the paleontological evidence. We're seeking answers by using molecular data to address these questions."

Honeycutt, his Ph.D. student, Diane Rowe, and a former student, Ron Adkins from the University of Massachusetts, are using genetics to study the evolution of South American and African rodents. The approach has been to sequence specific genes from several diverse rodent species and then use changes in these genes to reconstruct the evolutionary history of these rodents.

Scientists sequenced genes of several rodents and looked at the changes - or mutations - among the genes. Then they compared the number of changes between the genetic sequences of the rodents and constructed the rodents' evolutionary tree.

"We found that the South American and African radiations were unique but they do share a common ancestry," Honeycutt says, adding that the time when the two groups diverged may be considerably older (45 million years) than what the fossils are suggesting (36 million years).

"This radiation was unusual because these rodents became the grazers of South America," he continued. "Many caviomorphs were extremely large; indeed, today some species are the largest rodents in the world. In fact, unlike most rodents, many species of caviomorphs are highly social and have a metabolism and reproductive strategy more like large mammals."

The idea that the South American group shares a common ancestry with the African group has been controversial for years. Scientists have indeed suggested that caviomorph rodents in South America had multiple origins.

This new research by Honeycutt and his colleagues suggests that the ancestors of all South America caviomorph rodents colonized South America from Africa by rafting along oceanic currents connecting the two continents, Honeycutt says.

The novelty of this research pertains to the use of molecular techniques to address evolutionary questions posed decades ago primarily by paleontologists.

"Recent discoveries in molecular evolutionary biology are changing significantly the traditional ideas about mammalian evolution," Honeycutt says.

"For example, in the late 1960s and early 1970s Wilson and Saich, two scientists from the University of California at Berkeley, proposed that the human and chimpanzee shared a common ancestry to the exclusion of the gorilla, and the separation between humans and chimpanzees was no greater than six million years. That finding sent the entire palentological community in a tailspin because it was so counter to what they had been proposing.

Though molecular evolutionary biology is providing unprecedented insight into animal evolution, it cannot provide information on extinct animals.

"The problem is that we cannot sequence genes on some of the fossils, because they are too old," Honeycutt says. "The big questions are: 'How many fossils have anything to do with a direct ancestry of the lineages we see living today? And how do we fit those fossils to the genetic evolutionary tree?'"

So scientists are trying to combine data from fossils and living forms, genetic data and morphological characteristics.

"For a long time, the study of microevolutionary processes and macroevolutionary processes were two separate things," Honeycutt says, "but what we are finding with genetics and molecular evolutionary biology will allow us to merge those two fields."

Talking about the recent results of his group about the evolution of rodents, Honeycutt says they will help answer more general questions about the origin of mammals and how they relate to each other.

"This work will help reconstruct more accurately the tree of life, which is a really important goal for the future," he says.


Story Source:

The above story is based on materials provided by Texas A&M University. Note: Materials may be edited for content and length.


Cite This Page:

Texas A&M University. "Rafting Rodents From Africa May Have Been Ancestors Of South American Species." ScienceDaily. ScienceDaily, 17 October 2001. <www.sciencedaily.com/releases/2001/10/011012073342.htm>.
Texas A&M University. (2001, October 17). Rafting Rodents From Africa May Have Been Ancestors Of South American Species. ScienceDaily. Retrieved October 21, 2014 from www.sciencedaily.com/releases/2001/10/011012073342.htm
Texas A&M University. "Rafting Rodents From Africa May Have Been Ancestors Of South American Species." ScienceDaily. www.sciencedaily.com/releases/2001/10/011012073342.htm (accessed October 21, 2014).

Share This



More Fossils & Ruins News

Tuesday, October 21, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Fish Fossil Shows First-Ever Sex Was Done Side By Side

Fish Fossil Shows First-Ever Sex Was Done Side By Side

Newsy (Oct. 19, 2014) A 380-million-year-old fish may be the first creature to have copulative sex - and it was side by side with arms linked, like square dancers. Video provided by Newsy
Powered by NewsLook.com
As Sweden Hunts For Sub, "Cold War" Comparisons Flourish

As Sweden Hunts For Sub, "Cold War" Comparisons Flourish

Newsy (Oct. 19, 2014) With Sweden on the look-out for a suspected Russian sub, a lot of people are talking about the Cold War, but is it an apt comparison? Video provided by Newsy
Powered by NewsLook.com
So, Kangaroos Didn't Always Hop

So, Kangaroos Didn't Always Hop

Newsy (Oct. 16, 2014) Researchers believe an extinct kangaroo species weighed 500 pounds or more and couldn't hop. Video provided by Newsy
Powered by NewsLook.com
1000-Year-Old Viking Treasure Hoard Found in Scotland

1000-Year-Old Viking Treasure Hoard Found in Scotland

Reuters - Light News Video Online (Oct. 14, 2014) A hoard of Viking artifacts dating back over 1,000 years is discovered by a treasure hunter with a metal detector in Scotland. Elly Park reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins