Navigation Links
Caribbean frogs started with a single, ancient voyage on a raft from South America


Red frog from mountains of Haiti. Eleutherodactylus audanti, from
Massif de la Selle.
Nearly all of the 162 land-breeding frog species on Caribbean islands, including the coqui frogs of Puerto Rico, originated from a single frog species that rafted on a sea voyage from South America about 30-to-50-million years ago, according to DNA-sequence analyses led by a research group at Penn State, which will be published in the 12 June 2007 issue of the Proceedings of the National Academy of Sciences and posted in the journal's online early edition this week. Similarly, the scientists found that the Central American relatives of these Caribbean amphibians also arose from a single species that arrived by raft from South America.

"This discovery is surprising because no previous theories of how the frogs arrived had predicted a single origin for Caribbean terrestrial frogs and because groups of close relatives rarely dominate the fauna of an entire continent or major geographic region," explained Penn State's Blair Hedges, the evolutionary biologist and professor of biology who directed the research. "Because land connections among continents have allowed land-dwelling animals to disperse freely over millions of years, the fauna of any one continent is usually a composite of many types of animals."
Yellow and black spotted frog from caves in Haiti. Eleutherodactylus
counouspeus
.

The field work for the study required nearly three decades to complete because many of the species are restricted to remote and isolated mountain tops or other inaccessible areas. Some species included in the study now are believed to be extinct because of habitat degradation and possibly other causes such as climate change. A recent global assessment of amphibians found that the Caribbean Islands have the highest proportion of amph ibian species threatened with extinction. Hedges and coauthor William Duellman, a professor emeritus of the University of Kansas, were involved in much of the field work. A third co-author of the study is Penn State graduate student Matthew Heinicke, who performed DNA sequencing and analysis.

One prominent theory had proposed that frog species on the large islands of Cuba, Jamaican, Hispaniola, and Puerto Rico had walked there across land bridges that existed when those islands were connected in a geologic arc about 70-to-80-million years ago. A second major theory proposed that they arrived, instead, by rafting across the Caribbean Sea after the giant asteroid impact near Cuba 65-million years ago, which is widely believed to have exterminated the dinosaurs. "Both theories acknowledged that the frog faunas must have arrived by rafting over water to the smaller and younger islands, the Lesser Antilles, because they never were connected by land to South America, but neither theory proposed that all of the Caribbean-island frog species had a single common ancestor," Hedges said. __IMAGE_3

The anatomy of Caribbean frogs previously had led the advocates of both theories to conclude that species in Cuba and other western-Caribbean islands were related to different mainland species than were the species on Puerto Rico and other eastern-Caribbean islands, regardless of how they got there. "Discovering a single origin for all of these species from throughout the Caribbean islands was completely unexpected," Hedges said.

To make their discovery, the researchers sequenced the DNA of nearly 300 species of Caribbean, Central American, and South American frogs and used three mitochondrial genes and two nuclear genes in their study, building trees of relationships among the species and timing the divergences of the species with molecular-clock methods. "Molecular clocks work by counting the number of DNA-sequence mutations separating two spec ies and then dividing that number by the rate of change, which is established with the help of fossils and geologic information," explained Hedges.

The study's DNA research revealed that, while many ocean dispersals may have occurred over time, only two led to the current faunas: one for the Caribbean islands and another for Central America. The scientists speculate that it may not be coincidental that these ancient and successful dispersals happened after the asteroid collision rather than earlier. "The asteroid impact generated giant waves that devastated the islands, probably eliminating any existing fauna at that time," Hedges said.

The original frogs that successfully colonized the Caribbean islands likely hitched a ride on floating mats of vegetation called flotsam, which is the method typically used by land animals to travel across salt water. "Some rafts of flotsam, if they are washed out of rivers during storms and caught in ocean currents, can be more than a mile across and could include plants that trap fresh water and insect food for frogs," Hedges said. It is not likely that the frog species dispersed simply by swimming because frogs dry easily and are not very tolerant of salt water.

In addition to the study's discoveries about Caribbean and Central American frogs, the research also revealed and defined an unusually large and unpredicted group of species in South America. "The South American group may have more than 400 species and is mostly associated with the large Andes mountains of South America," Hedges said.

"Until now, the entire group of these terrestrial, tropical frog species -- the eleutherodactylines -- have been considered a "black hole" in amphibian biology because of the poor understanding of their evolutionary history," explained Hedges. Scientists consider the knowledge of evolutionary relationships, also called "phylogeny," to be fundamental to many fields of biology, including medicine, a natomy, physiology, ecology, and conservation.


'"/>

Source:Penn State


Related biology news :

1. Parts of the Caribbean and Central America are likely to have less summer rain
2. A whole lot of shaking goin on triggers early hatching in red-eyed tree frogs
3. Picky female frogs drive evolution of new species in less than 8,000 years
4. Laos ?a lost world for frogs
5. Rare Chinese frogs communicate by means of ultrasonic sound
6. Crucial site for endangered frogs and birds saved
7. Study shows frogs can play key role in stem cell research
8. Leptin found to control appetite and limb development in frogs
9. Race to halt global amphibian crisis boosted by rediscovery of endangered Colombian frogs
10. Researchers find missing genes of ancient organism
11. Family trees of ancient bacteria reveal evolutionary moves

Post Your Comments:
*Name:
*Comment:
*Email:


(Date:4/19/2017)... 19, 2017 The global military ... is marked by the presence of several large global ... by five major players - 3M Cogent, NEC Corporation, ... for nearly 61% of the global military biometric market ... the global military biometrics market boast global presence, which ...
(Date:4/17/2017)... 2017 NXT-ID, Inc. (NASDAQ: NXTD ) ... of its 2016 Annual Report on Form 10-K on Thursday April ... ... in the Investor Relations section of the Company,s website at ... at http://www.sec.gov . 2016 Year Highlights: ...
(Date:4/13/2017)... 13, 2017 According to a new market research ... Analytics, Identity Administration, and Authorization), Service, Authentication Type, Deployment Mode, Vertical, and ... is expected to grow from USD 14.30 Billion in 2017 to USD ... 17.3%. ... MarketsandMarkets Logo ...
Breaking Biology News(10 mins):
(Date:5/24/2017)... 2017 As Ebola resurfaces in the ... 20 suspected cases now reported, a new analysis of the ... a correlation between the 2014 and 2017 outbreaks of the ... in 2012-13, which preceded the 2014 outbreak. An analysis of ... Replikin counts in 2014-15, which again precedes the current outbreak ...
(Date:5/23/2017)... ... May 23, 2017 , ... A recent survey conducted by the Weed Science ... control weed in 12 categories of broadleaf crops, fruits and vegetables, while common lambsquarters ... U.S. and Canada participated in the 2016 survey, the second conducted by WSSA. ...
(Date:5/23/2017)... , ... May 23, 2017 , ... ... this month its 20th anniversary, marking the occasion with a strong presence at ... meeting’s Welcome Reception and further extends an invitation to all attendees to view ...
(Date:5/23/2017)... ... May 22, 2017 , ... A new Technology Hot Topics ... this August will feature high-level speakers on quantum devices, graphene electronic tattoo sensors, ... Photonics, the largest multidisciplinary optical sciences meeting in North America, will run 6-10 ...
Breaking Biology Technology: