Study: Manatee's future in danger due to lack of genetic diversity

William DeShazer/Staff 
 A manatee floats in the water at Manatee Park in Fort Myers on Friday Jan. 4, 2013.

Photo by WILLIAM DESHAZER, Naples Daily News // Buy this photo

William DeShazer/Staff A manatee floats in the water at Manatee Park in Fort Myers on Friday Jan. 4, 2013.

William DeShazer/Staff 
 A manatee spins in the water at Manatee Park in Fort Myers on Friday Jan. 4, 2013.

Photo by WILLIAM DESHAZER, Naples Daily News // Buy this photo

William DeShazer/Staff A manatee spins in the water at Manatee Park in Fort Myers on Friday Jan. 4, 2013.

Manatees can be such carbon copies of one another that often the easiest way to tell them apart is by the pattern of boat propeller scars across their backs.

Turns out, though, their alikeness is more than just skin deep.

In a recently published study, led by a research team from the University of Florida and the U.S. Geological Survey found a lack of genetic diversity in the manatee population that suggests the endangered marine mammal remains at risk despite growing numbers of them.

"It's not good news at all, but it's not the worst news either," said Maryland-based Stevenson University biologist Kim Pause Tucker, co-lead author of the study.

The finding comes as the U.S. Fish and Wildlife Service considers moving the manatee from endangered status to threatened, one step closer to being taken off the list altogether.

Less genetic diversity makes manatees, or any species, less able to overcome environmental threats — from disease or toxic algae blooms — and makes them more prone to inbreeding, which can cause problems all its own.

Health problems associated with inbreeding pushed the Florida panther to the brink of extinction. Fewer than 30 panthers were left until eight female Texas cougars were relocated to South Florida to broaden the gene pool. Now as many as 160 roam the wild, scientists say.

William DeShazer/Staff 
 A manatee comes up for air at Manatee Park in Fort Myers on Friday Jan. 4, 2013.

Photo by WILLIAM DESHAZER, Naples Daily News // Buy this photo

William DeShazer/Staff A manatee comes up for air at Manatee Park in Fort Myers on Friday Jan. 4, 2013.

The manatee study found that concerns about low genetic diversity "are not severe at this time," but warned the situation could change drastically if the population were to start getting smaller or breeding patterns changed.

The news would be worse for the manatee had the study found that smaller genetically isolated subpopulations of manatee existed, Tucker said. Instead, the study found that Florida's manatee population is sharing the same single gene pool.

Researchers used skin samples collected from the tails of 362 manatees, some of them dead and some of them clipped alive using a cattle ear-notcher.

Molecular-level comparisons found "moderate inbreeding" and evidence of a population bottleneck in the Gulf Coast population of manatees, according to the study.

An annual aerial count in 2010 found a record-high 5,076 manatees gathered at warm water refuges that winter compared to fewer than 2,000 manatees during the 2000 count. The numbers are considered a minimum population.

An annual aerial count in 2010 found a record-high 5,076 manatees gathered at warm water refuges that winter compared to fewer than 2,000 manatees during the 2000 count. The numbers are considered a minimum population.

Manatee advocate Patrick Rose said manatees will have to adapt to a host of threats to survive and a lack of genetic diversity could hamper that ability.

"It's the kind of thing that if things go wrong, they could really go wrong," Rose said.

Limited-government advocates at the Pacific Legal Foundation have petitioned the federal government to drop the manatee's listing as endangered, citing past federal and state reviews that recommended the downlisting.

Florida pulled back from changing the manatee's status, deciding instead to rewrite the rules for listing a species in the first place. The state is now waiting to see what federal list-makers will do, spokeswoman Carol Knox said.

U.S. Fish and Wildlife Service spokesman Chuck Underwood said the federal government hasn't followed through on the downlisting recommendation because of a lack of funding and other higher priorities.

He said the agency will consider the study, along with other data like population trends and adult survival rates, when making its delisting decision. There is no timetable for making the decision, he said.

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