Scientists Uncover First Known Cases of California Condors Born Through Asexual Reproduction
Two California are currently the superstars of the science world.
According to a release from the San Diego Zoo Wildlife Alliance (SDZWA), a group of their conservation scientists recently reported an 'extraordinary discovery" — shared in the Journal of Heredity, the official journal of the American Genetic Association — that "could have rippling effects for wildlife genetics and conservation science."
The conservation scientists stumbled upon this discovery during a routine analysis of biological samples from two deceased California condors that were part of the SDZWA's managed breeding program to determine each bird's parentage. The tests on the samples confirmed that both of the condors were genetically related to the female condors (known as dams) that laid and hatched their eggs.
But the test also uncovered "that neither bird was genetically related to a male — meaning both chicks were biologically fatherless; and accounted for the first two instances of asexual reproduction, or parthenogenesis, to be confirmed in the California condor species," per SDZWA. This is not the only surprising first that the scientists' routine analysis unearthed.
According to SDZWA, the female birds that laid the unfertilized eggs that hatched were "continuously housed with fertile male partners. So, this parthenogenesis discovery is not only the first to be documented in condors but is also the first discovered through the use of molecular genetic testing and the first in any avian species where the female bird had access to a mate."
"This is truly an amazing discovery," Oliver Ryder, Ph.D., the director of conservation genetics at SDZWA, who is co-author of the Journal of Heredity study, said in a statement. "We were not exactly looking for evidence of parthenogenesis, it just hit us in the face. We only confirmed it because of the normal genetic studies we do to prove parentage. Our results showed that both eggs possessed the expected male ZZ sex chromosomes, but all markers were only inherited from their dams, verifying our findings."
Parthenogenesis is a form of asexual reproduction in which an embryo that is not fertilized by sperm continues to develop, containing only the mother's genetic materials, SDZWA shared. The resulting offspring are called parthenotes.
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Parthenogenesis has been observed in other animals, including those living in captivity, but is relatively rare in birds. When it does occur, it usually happens when females have no access to males. For the California condor parthenotes, each of their dams had access to fertile males and had a history of producing offspring with mates, including after the newly-discovered parthenotes hatched.
Scientists confirmed this astounding discovery thanks to the extensive historical genetic records available to the SZDWA as part of their collaboration with the California Condor Recovery Program. Unfortunately, both of the condor parthenotes died before the SDZWA's realization that the birds were the result of asexual reproduction.
SDZWA plans to continue its genotyping efforts in hopes of uncovering more missed parthenogenetic cases in California condors and perhaps other species as well.
"These findings now raise questions about whether this might occur undetected in other species," Ryder added.