Tropical birds waited for land crossing between North and South America: UBC study

December 09, 2009

Despite their ability to fly, tropical birds waited until the formation of the land bridge between North and South America to move northward, according to a University of British Columbia study published this week in the Proceedings of the National Academy of Sciences Early Edition.

"While many North American birds simply flew across the marine barriers that once separated the continents, tropical birds, especially those in Amazon forest regions, began colonization of North America almost entirely after the completion of the land bridge," says lead author Jason Weir, who conducted the study as part of his PhD at UBC.

"This study is the most extensive evidence to date that shows the land bridge playing a key role in the interchange of bird species between North and South America and the abundant biodiversity in the tropical regions," says Weir, now a post-doctoral fellow at the University of Chicago.

The Isthmus of Panama land bridge was completed between three and four million years ago, and today consists of the country of Panama. It is believed to have initiated the Great American Biotic Interchange, bringing mammals that evolved uniquely in South America during its "island isolation" - the armadillo, opossum and porcupine - to North America.

Fossil records have shown that mammalian species also travelled across the land bridge from North to South America, increasing biodiversity in the tropical regions. "But a lack of bird fossils has made it difficult to determine if the land bridge was equally instrumental in the interchange of avian species," says Weir.

By analyzing the DNA of 457 bird species on either side of the land bridge, Weir and colleagues at UBC and the Smithsonian Tropical Research Institute in Panama were able to reconstruct a "family tree" of species closely related to one another and revealed a "hidden chapter" in the impact of the land bridge to biodiversity. They found a dramatic increase in the rates of interchange after the land bridge completion.

"This is a bit surprising," says co-author Dolph Schluter, UBC zoology professor and Canada Research Chair in Evolutionary Biology. "Couldn't the birds have flown across the gap? Some did, but most tropical birds waited for the land crossing."

The researchers believe the inability of many tropical birds to fly long distances across open water - some are reluctant even to cross rivers as narrow as 200 metres - may have contributed to the few north-bound movements prior to the land bridge completion.
-end-
A photo of the red-legged honeycreeper, one of the species examined in this study, is available by request. The paper is available online at http://www.pnas.org/content/early/2009/12/07/0903811106.full.pdf+html

University of British Columbia

Related Biodiversity Articles from Brightsurf:

Biodiversity hypothesis called into question
How can we explain the fact that no single species predominates?

Using the past to maintain future biodiversity
New research shows that safeguarding species and ecosystems and the benefits they provide for society against future climatic change requires effective solutions which can only be formulated from reliable forecasts.

Changes in farming urgent to rescue biodiversity
Humans depend on farming for their survival but this activity takes up more than one-third of the world's landmass and endangers 62% of all threatened species.

Predicting the biodiversity of rivers
Biodiversity and thus the state of river ecosystems can now be predicted by combining environmental DNA with hydrological methods, researchers from the University of Zurich and Eawag have found.

About the distribution of biodiversity on our planet
Large open-water fish predators such as tunas or sharks hunt for prey more intensively in the temperate zone than near the equator.

Bargain-hunting for biodiversity
The best bargains for conserving some of the world's most vulnerable salamanders and other vertebrate species can be found in Central Texas and the Appalachians, according to new conservation tools developed at the National Institute for Mathematical and Biological Synthesis (NIMBioS) at the University of Tennessee, Knoxville.

Researchers solve old biodiversity mystery
The underlying cause for why some regions are home to an extremely large number of animal species may be found in the evolutionary adaptations of species, and how they limit their dispersion to specific natural habitats.

Biodiversity offsetting is contentious -- here's an alternative
A new approach to compensate for the impact of development may be an effective alternative to biodiversity offsetting -- and help nations achieve international biodiversity targets.

Biodiversity yields financial returns
Farmers could increase their revenues by increasing biodiversity on their land.

Biodiversity and wind energy
The location and operation of wind energy plants are often in direct conflict with the legal protection of endangered species.

Read More: Biodiversity News and Biodiversity 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.