Species Research

To: Birding Aus <>
Subject: Species Research
From: Laurie&Leanne Knight <>
Date: Mon, 15 Jul 2002 22:20:20 +1000
Following on from the recent thread on different perspectives on speciation, the
following item from the New York Times may be of interest to some - I have
appended a key excerpt ...
Crossbreeding to Save Species and Create New Ones


The new research on hybridization is casting new light on evolutionary processes
and raising questions about biodiversity and the preservation of endangered
species. In the mid-1990's, wildlife biologists saved the endangered Florida
panther from extinction by crossbreeding it with the closely related Texas
cougar. That program opened the way for the use of hybridization in saving
endangered species. 
Most species cannot crossbreed because the genetic, behavioral and ecological
barriers are too great to overcome. An elephant will not interbreed with a lion
or wildebeest, nor will a wolf mate with a bear or a prairie dog with a
squirrel. Still, the new findings indicate that hybridization between species
does occur and can sometimes produce new species ? calling into question the
longstanding view that a species is a population of interbreeding organisms that
is reproductively isolated from other species. 
Many hybrids are little more than evolutionary failures that fade away, said Dr.
Michael Arnold, a professor of biology at the University of Georgia and the
author of "Natural Hybridization and Evolution" (1997). But hybrid lineages can
also become new species given the right circumstances, he added. 
Some captive wild animals are hybrids. Wolf-dog hybrids are popular, if
dangerous, pets, as are hybrids of wild cats and several subspecies of tiger
kept by private collectors. But biologists say such hybrids are human constructs
? subject to artificial, not natural, selection ? and thus reveal little about
evolutionary processes. 
Scientists have long recognized that the mixing of different lineages usually
occurs in areas called hybrid zones. Ranging in size from a few feet to many
miles, these zones are often border areas, Dr. Rieseberg said: between a wetland
and dry
upland, for example. Or they may be disturbed habitats, often resulting from
human activities. 
Hybrids created in those zones may ultimately vanish if not constantly
recreated, Dr. Rieseberg said, but unless they are sterile, they can serve to
transfer thousands of genes between the parent populations. Those genes may play
no evolutionary role, he added, but they can provide organisms with the genetic
flexibility to colonize new habitats. 
Finding whether transferred genes do affect an organism's evolution requires
detailed genetic and ecological analyses that can stretch the limits of current
technology and knowledge, researchers say. But Dr. Rieseberg has already
documented the formation of new species of sunflowers through hybridization.
He is preparing to publish studies demonstrating that specific groups of genes
passed from one species into another are producing different physical
characteristics, or phenotypes, in sunflowers that allow them to colonize new
Already, hybridization has become an important issue in conservation biology,
and its significance is expected to grow as habitats shrink and ecosystems
change, bringing some formerly separate populations into contact and isolating
Citing the rescue of the Florida panther in the mid-1990's, many experts say the
injection of new genes through hybridization may be the only way to save
distinct lineages from extinction. But they urge using that strategy
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