Although it came close to extinction, the California condor possesses a high degree of genetic diversity that bodes well for its long-term survival, according to a new analysis by researchers at the University of California.
Almost 40 years ago, the state’s wild condor population was reduced to a perilous 22. This led to inbreeding which could have jeopardized the health of the population and reduced the bird’s genetic diversity. , which may reduce its ability to adapt to changing environmental conditions.
By comparing the complete genomes of two California condors with those of an Andean condor and a turkey vulture, scientists at UC San Francisco and UC Berkeley found genetic evidence for inbreeding over the years. centuries, but overall a wealth of diversity in most countries. the genome.
“You need genetic diversity to adapt, and the more genetic diversity they (California condors) have, hopefully the more likely they are to adapt and persist,” said Jacqueline Robinson, postdoctoral fellow at UCSF and first author of an article on the analysis published today in the journal Current biology. “Our study is the first to begin quantifying diversity across the entire genome of California condors, which provides us with a lot of background information and will inform future research and conservation.
The health of the bird’s genome is probably due to the great abundance of the species in the past. Robinson and his colleagues, including Rauri Bowie, professor of integrative biology at UC Berkeley, used statistical techniques to estimate the bird’s historical population and found it to be much more abundant in the United States there is a million years old than even the turkey vulture, the most common in America. vulture today. The bird numbered probably in the tens of thousands, soaring and foraging from New York and Florida to California and Mexico.
“They have this inheritance of high genetic diversity from their former abundance, so I think there’s a chance that with the genetic information we could manage the population in the future to really maintain the genetic diversity that they are. have it now and they don’t have any further loss, “said Robinson.” You can even choose individual mates to, in a sense, reverse inbreeding. “
Co-author Cynthia Steiner, associate director of conservation genetics for the San Diego Zoo Wildlife Alliance, a non-profit conservation organization affiliated with the San Diego Zoo, agreed that genomic information will help refine conservation strategies. to maintain genetic diversity and reduce inbreeding. Inbreeding can already cause an increase in wild condors in a lethal form of dwarfism, chondrodystrophy, and leading to an increase in some birds in the number of tail feathers, from 12 to 14.
“We finally have a genomic resource or tool in hand for species that will help understand the genetic basis of the disease and phenotypic traits, such as chondrodystrophy and 14-tailed feather syndrome, and potentially manage these deleterious traits in the breeding program, ”Steiner says.
Bowie, curator of ornithology at UC Berkeley’s Museum of Vertebrate Zoology (MVZ), hopes to continue working with the San Diego Zoo to analyze the genomes of the original 22 individual condors from the founding population – the ancestors of all condors. living in California – assess the overall genetic diversity of the species. With captive breeding, the goal has always been to mate unrelated condors in order to avoid inbreeding. By generating genomic profiles of all individuals of an endangered species, conservationists could fine-tune the selection to eliminate any negative health consequences known as inbreeding depression.
“With most endangered species, when you look at their genomes, they have very little genetic diversity left. In other words, they have very little capacity to adapt to change,” he said. “This is certainly not the case with the California condor. With this genomic data in hand, there may be a way to alleviate chondrodystrophy by crossing certain individuals or finding other ways to help them do so. confronted with this.”
The constant decline of Condor
The California condor, Gymnogyps californianus, is considered critically endangered, despite Herculean efforts to save the species that began in 1987. This involved capturing all wild condors – 27 at that time – and removing them. breed in zoos. The success of the program was celebrated in 1991 with the reintroduction of captive-bred condors to the wild. Today, more than 300 individuals roam California, Mexico, Arizona and Utah, while 200 others remain in captivity. With a wingspan larger than any other bird in the United States – up to 3 meters, or nearly 10 feet, slightly less than that of the Andean condor (Vultur gryphus), its closest relative – it is also one of the longest living birds, often surviving to the age of 60 years.
Based on the team’s genetic analysis of two California condor genomes over the past million years, condor populations gradually fluctuated downward until a precipitous decline began to emerge. when humans first settled in the Americas 15,000 years ago. This coincides with the disappearance of large land animals – megafauna – which were likely wiped out by America’s first inhabitants 10,000 to 12,000 years ago. North American megafauna carcasses were undoubtedly a major food source for these carrion-eating scavengers, and condors might be restricted to the Pacific coast because they could take advantage of marine mammal carcasses after the animals. terrestrials have become less abundant.
The decline has accelerated over the past hundred years with increasing destruction of condor habitat, increased human poaching, and persistent lead poisoning from the ingestion of shotgun pellets.
Small inbreeding population
Robinson, who works in the lab of co-author Jeffrey Wall, professor at the Institute of Human Genetics at UCSF, focused on genetic studies of small populations where inbreeding increases the incidence of normally rare recessive traits. , many of which are deleterious. She is currently involved in genetic studies on the Mexican vaquita, the world’s smallest porpoise, which is critically endangered in its range in the Gulf of California. She co-authored a report last year that found very low diversity in the vaquita genome, which is a result of its natural scarcity and historically low abundance before its recent human-induced population collapse. , she said.
She embarked on the ongoing study after Bowie collaborated with the San Diego Zoo and Baylor College of Medicine to produce what he called a “Rolls Royce” version of the condor genome – a genome of high quality which is rare for any wild animal. and which rivals the quality of known genomes of commercial chickens and laboratory mice.
“What I mean by Rolls Royce genome is that it contains very few fragments – basically all the chromosomes are intact,” she said. “With that, you can get a very good assessment not only of genetic diversity, but also of how it is distributed throughout the genome. And this is really useful if you are trying to find genes related to the disease or if you are interested in things that are important in allowing condors to do what they do – adaptive genes. “
Robinson compared the genome of the Bowie condor, obtained from the blood of an Arizona condor, and the condor genome from the San Diego Zoo with the genomes of the Andean condor and the turkey vulture (Cathartes aura), that had already been sequenced.
Surprisingly, given the history of the California condor, both genomes contained the highest levels of diversity among the three species.
“Andean condors are somewhat rare, but Turkish vultures are extremely abundant, so this result was a bit unexpected, as it does not match the current population size,” said Robinson. “Genetic diversity is linked to the abundance of species, so the high genetic diversity of California condor genomes stands in stark contrast to the extremely small number living today.”
Bowie attributes the condor’s success in getting through its near-extinction bottleneck while retaining much of its original genetic diversity to the bird’s long lifespan and slow reproduction, which determine its generation time.
“Even though their numbers dropped dramatically, due to their generation time they had not passed through many generations, much of that genetic diversity was retained,” he said.
The California Condor Project is part of Bowie’s current focus on genetic diversity among all living and extinct vultures. Graduate student Mackenzie Kirchner-Smith is currently analyzing vulture skulls in the collections of the MVZ and the UC Paleontology Museum to understand past vulture populations, while Bowie has just launched an effort to sequence the genomes of the living vulture species around the world, in part to understand how the scavenger lifestyle developed independently among three very distinct groups of birds.
Robinson also hopes to continue the condor’s work. Although she has visited condor habitat in the past, she saw her first condor just a few weeks ago during a visit to Pinnacles National Park, a popular hangout for condors along the central coast of California.
“Looking at them, I literally thought, these are almost gone in my lifetime. It would have been such a tragedy, ”she said. “I would say we shouldn’t write off any species just because there are only a few left. The California condor has returned from a population of only 22 individuals.”
Robinson’s co-authors, in addition to Bowie, Steiner, and Wall, include David Mindell of the Museum of Vertebrate Zoology at UC Berkeley. The work was funded in part by the National Science Foundation (DEB-1441652).