The Evolution of Genetics and the California Condor
Since the inception of the California Condor Recovery Program, many dedicated people from multiple organizations have provided expertise in the conservation management efforts for this critically endangered bird. The staff of the genetics division at the San Diego Zoo Institute for Conservation Research is proud of the contributions we have made to this collaborative program.
We first became involved in the early 1980s when our group developed a method for sexing condors by visually identifying chromosomes, allowing us to determine the sex of wild condors and Topa-Topa, the only captive condor at the time. As genetic techniques advanced, we began providing DNA-based sex identification in 1994; since 1997, polymerase chain reaction (PCR) amplification methods have been used to sex all captive and wild California condors.
When the question of relatedness among individuals in the decreasing condor population arose, we used DNA fingerprinting methodology to analyze the level of genetic diversity remaining in the population. The results of our study, showing three surviving clans, proved invaluable when decisions were made on pairing birds after all remaining individuals were brought into captivity.
The breeding success of the captive condors allowed the Recovery Team to take the step of condor reintroduction. Beginning with the first egg laid by birds back in the wild, field biologists wanted a means to confirm their behavioral observations, and asked us to help by verifying the parents of chicks hatched from wild-laid eggs.
We employed a genotyping method similar to that used by human labs for determining “who’s your daddy.” The screening of a California condor-specific microsatellite library provided us with a DNA toolkit for determining parentage of the chicks in question.
Recently, at the request of Recovery Team members, we began to confirm parentage for all the condors hatched from eggs laid in the wild. Questions had arisen due to unexpected mating and nesting observations including a trio of two males and a female observed taking care of a chick in Arizona, extra-pair matings seen in central California, and in a couple instances, behavior not correlating with the assigned sex.
We have currently genotyped over 285 wild and captive birds from DNA samples obtained through the sexing work. To date, 35 of the birds hatched from wild-laid eggs have been examined, and for 29 we confirmed that the parents assigned in the studbook, based on behavioral observations, are correct.
However, in the other cases we found that one of the assigned parents did not have the genetic make-up to have produced the offspring in question. Three of these cases have been resolved through testing of other potential parents. Although parentage of chicks by males and females that did not attend the young at the nest has been confirmed in other bird species, we recently documented the first instance of “extra-pair parentage” in the wild California condor population! Our evaluations will continue as samples are collected opportunistically from additional wild birds.
Other genetic studies that will enhance condor management include expanding our toolkit of DNA markers and genome sequencing of founders or their offspring. A comprehensive California condor genome project could, for the first time, encompass all DNA variation of a species. This information can lead to a deeper understanding of the loss of genetic diversity due to population bottlenecks, and more information regarding relatedness of the founder population.
For over 30 years our Genetics group has assisted the Recovery Team in its management of wild and captive California condors, and we are excited about how genetics might help in the future!
By Leona Chemnick, Researcher, Genetics Division