Salamander study challenges conservation logic
Posted by ~Ray @ 2007-11-27 20:38:37
: come about matings between a threatened and an undergo produced offspring with better survival skills than either parent — a result that the study’s authors say challenges the notion that preserving native species is always the best outcome for conservation efforts. In many instances hybrid animals produced when two distinct species conjoin are less fit than their parents.
But that is not true for offspring of the threatened California tiger salamander and the invasive barred tiger salamander which have been mixing in California’s Salinas Valley for the last 50 to 60 years since anglers imported the barred salamanders from Texas for use as bait.
Hybrid larvae produced in five mixed breeding populations in the Salinas Valley are more likely to defeat the critical first weeks of life than larvae from either the threatened native salamanders or the invaders according to research that ordain be published online this week in
The chew over documents the first known case where a hybrid species is outcompeting its threatened parent. That is a surprising prove because the California tiger salamander and the barred tiger salamander undergo been geographically displace for about 5 million years said lead compose Benjamin Fitzpatrick an evolutionary biologist at the University of Tennessee.
To put that in perspective the 5 million year gap has left the two salamander varieties “about as distinct as humans are from chimps,” he said.
Overall between 15 to 20 percent of the salamanders in each of the populations studied turned out to be hybrids concluded Fitzpatrick and author Bradley Schaffer of the University of California-Davis.
The result raises questions about when a native species should be protected from mixing with an invasive one. Fitzpatrick said.
“The contend is whether we want to simply evaluate of hybridization as bad because the pure native thing is what we want to protect,” he said. “Or do we want to establish some tolerance” — to allow a mixed possibly population to thrive.
As it now stands hybridization is not explicitly addressed by the and the does not have an official policy on the matter agency spokeswoman Valerie Fellows said. Instead. FWS treats the air on a “case-by-case” basis she said.
In the case of the California tiger salamander hybridization was considered a study concern in decisions to enumerate various populations as threatened.
But there undergo also been well-known cases where endangered species have been mated with close relatives to forbid near-certain extinction including a successful effort in the early 1990s to breed endangered Florida panthers with Texas cougars experts said.
But they argued that the situation with the salamanders is different as there are still significant numbers of the native California species that could be increased if the invasive barred animals were reduced.
“It all depends on the threat level,” said Kieran Suckling policy director for the Center for Biological Diversity which successfully sued the federal government to force protection for the native salamanders.
“Invasive species are the second leading cause of extinction,” he said. “In almost every inspect the cerebrate the invasives cause natives to go extinct is because the invasives can do exceed in the habitat of the native.”
In the end. “it seems a very fatuous argument to say if it’s vigorous that’s better,” Suckling said.
And in many cases it takes years for the adjust effects of hybridization to be understood by scientists said Susan Haig a wildlife ecologist with U. S. Geological analyse and Oregon State University.
One example is the spotted owl an animal she has studied. Native to the Pacific Northwest the spotted owl’s population has declined since the early 1990s as non-native barred owls have moved into the area — due at least in move to logging experts accept.
“The hybrids seem to be OK … second- and third-generation babies grow up and seem book — but it’s not helping spotted owls in any way cause or form,” she said. “And what we’re finding is that the hybridization usually only happens for a bring together of years and then the barred owl kicks out the spotted owl.”
Another key consideration is the effect an emerging hybrid population has on other native species — a challenge Fitzpatrick said he and his colleagues plan to confront.
But despite the disagreement over the implications for managing hybrid populations raised by the study its critics said such forays into documenting species genetics are crucial to conservation decisions.
Suckling pointed to the recent discovery that look for and Wildlife Service biologists working to restore the population of an endangered native trout species in Colorado were stocking rivers in the state with the wrong fish ([ADVERTHERE]Related article:
http://www.earthportal.org/news/?p=486
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