Ocean channel in Bahamas marks genetic divide in Brazilian free-tailed bats

August 18, 2017

GAINESVILLE, Fla. --- Brazilian free-tailed bats are expert flyers, capable of migrating hundreds of miles and regularly traveling more than 30 miles a night. But they pull up short at a narrow ocean channel that cuts across the Bahamas, dividing bat populations that last shared an ancestor hundreds of thousands of years ago.

A new study published in Ecology and Evolution uncovers a dramatic and unexpected genetic rift between populations of Tadarida brasiliensis on either side of the Northwest and Northeast Providence Channels, about 35 miles across at their most narrow point.

Genetic analysis of the populations suggests that bats from Florida colonized the northern Bahamian islands while bats from other parts of the Caribbean likely colonized the southern Bahamas. Why the bats balk at crossing a channel so narrow they can likely see land on the other side while in flight remains a mystery, said Kelly Speer, the study's lead author who completed the research while a master's student at the Florida Museum of Natural History.

"Based on their mainland population behavior, we know they're able to disperse much farther than the distances between islands in the Caribbean," said Speer, now a doctoral student at the American Museum of Natural History. "It doesn't seem like distance is the factor, and there's no association with wind direction. We don't have any idea why they don't cross this channel."

Because they can fly, bats are good models for studying mammal movement in fragmented habitats, Speer said. The ability to disperse, or spread genes by moving to other areas, plays a key role in the evolution of animal populations, and a barrier to bats' dispersal is likely a barrier to less mobile animals.

"Many mammals undertake long migrations, but bats are unique in their ability to cross ocean channels," she said. "You'd expect there to be no barriers to the dispersal, but that's not the case. There are lots of barriers, many of which we wouldn't expect."

One of the most abundant mammals in North America, Brazilian free-tailed bats -- also known as Mexican free-tailed bats -- inhabit a range that stretches from Argentina to Oregon. But despite being so common, the species has been understudied, said study co-author David Reed, Florida Museum curator of mammals and associate director of research and collections.

When the University of Florida Bat House's internal structure collapsed in 2009 Reed and Speer suddenly had dozens of free-tailed bat specimens at hand and saw an opportunity to take a closer look at how the species disperses. They sampled and compared the genetics of free-tailed bats from Florida and the Bahamas, thinking the DNA would bear out their hypothesis: With long, narrow-tipped wings, well suited for swift flight in open spaces and at high altitudes, the bats would have had no trouble spreading throughout the Bahamas.

Wing shape and flight patterns had proven reliable predictors of bat dispersal in the Caribbean before. Most previous studies focused on a different family of bats, Phyllostomidae, or leaf-nosed bats. If Brazilian free-tailed bats are like jets, built for distance and speed, leaf-nosed bats are like helicopters. They have shorter, wider wings, better adapted for slow flight and easy maneuvering in cluttered environments. Studies showed that leaf-nosed bats are homebodies, sticking to their respective islands, presumably a result of the bats' wing shape.

Reed and Speer expected Brazilian free-tailed bats would instead freewheel between the islands. When they sequenced a bat from one of the southern islands, however, its genetics were so different from bats on the northern islands that they thought they had tested the wrong bat. But further sampling gradually revealed a clear divide between populations on either side of the channel.

The bats are so genetically distinct from one another that the populations on the southern islands may be a different species, Speer said. "We need to do more work to confirm that, but we think the population on the southern islands might belong to a broader Caribbean species of free-tailed bat that has never been described," she said. "The nice thing about science is that when you make a hypothesis and your data tell you it's wrong, you still find something we didn't know before."

Florida Museum of Natural History

Related Bats Articles from Brightsurf:

These masked singers are bats
Bats wear face masks, too. Bat researchers got lucky, observing wrinkle-faced bats in a lek, and copulating, for the first time.

Why do bats fly into walls?
Bats sometimes collide with large walls even though they detect these walls with their sonar system.

Vampire bats social distance when they get sick
A new paper in Behavioral Ecology finds that wild vampire bats that are sick spend less time near others from their community, which slows how quickly a disease will spread.

Why doesn't Ebola cause disease in bats, as it does in people?
A new study by researchers from The University of Texas Medical Branch at Galveston uncovered new information on why the Ebola virus can live within bats without causing them harm, while the same virus wreaks deadly havoc to people.

The genetic basis of bats' superpowers revealed
First six reference-quality bat genomes released and analysed

Bats offer clues to treating COVID-19
Bats carry many viruses, including COVID-19, without becoming ill. Biologists at the University of Rochester are studying the immune system of bats to find potential ways to ''mimic'' that system in humans.

A new social role for echolocation in bats that hunt together
To find prey in the dark, bats use echolocation. Some species, like Molossus molossus, may also search within hearing distance of their echolocating group members, sharing information about where food patches are located.

Coronaviruses and bats have been evolving together for millions of years
Scientists compared the different kinds of coronaviruses living in 36 bat species from the western Indian Ocean and nearby areas of Africa.

Bats depend on conspecifics when hunting above farmland
Common noctules -- one of the largest bat species native to Germany -- are searching for their fellows during their hunt for insects above farmland.

Tiny insects become 'visible' to bats when they swarm
Small insects that would normally be undetectable to bats using echolocation suddenly become detectable when they occur in large swarms.

Read More: Bats News and Bats 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.