Lonesome George and the 'near' extinction of Chelonoidis abingdoni
Lonesome George was the last living tortoise of C. abingdoni from Pinta Island, he passed away in June 2012 and left no offspring.
To the right there is a picture of Lonesome George on Pinta in 1972 (photo taken by Ole Hamann). The last, member of his species.
Thanks to M. Russello's previous work on Galapagos tortoises we know that in Isabela's northernmost volcano some individuals showed a signature of shared ancestry with Lonesome George's C. abingdoni lineage from Pinta Island. Mike Russello's study was insightful but we needed more evidence in order to substantiate a 'genetic rescue' of any C. abingdoni genetic ancestry left among extant tortoises from Volcano Wolf.
In particular, we needed a larger reference data set including more Pinta individuals from which a single individual was left (Lonesome George). I embarked in the task of extracting historical DNA from Pinta specimens kept in a few museums to provide with an adequate reference panel of genetic information. I helped increasing the number of complete genotypes from one (Lonesome George) and ended up adding genotypes for 21 individuals in total. With this new data set we applied the same approach successfully used by Michael Russello et al. to detect Floreana-ancestry individuals among Wolf tortoises.
Our results showed that at least 17 Wolf tortoises had some degree of shared ancestry with C. abingdoni. Remarkably, some may even be first generation hybrids and equally interesting, these tortoises did not seem related to each other.
How this Pinta tortoises ended up in Volcano Wolf?. The answer is rather historical and likely caused by human disturbances. Before modern times, most vessels leaving the Archipelago would use a northern route and before completely leaving the archipelago some threw away alive tortoises that they did not need. It is possible that some of these tortoises were originally captured in Pinta found the way to Northern Isabela by using favorable ocean currents.
This hypothesis is somehow validated by the levels of hybrid co-ancestry that we have recovered. Can this individuals be used to repopulate Pinta with Galapagos tortoises?. Well, while these 'founder' population would not represent all the genetic variability of the original species they would probably harbor some of the additive genetic variation that made C. abingdoni survive and adapt to Pinta Island unique environments.
So the answer is yes. Cautious optimism?.
To the right there is a picture of Lonesome George on Pinta in 1972 (photo taken by Ole Hamann). The last, member of his species.
Thanks to M. Russello's previous work on Galapagos tortoises we know that in Isabela's northernmost volcano some individuals showed a signature of shared ancestry with Lonesome George's C. abingdoni lineage from Pinta Island. Mike Russello's study was insightful but we needed more evidence in order to substantiate a 'genetic rescue' of any C. abingdoni genetic ancestry left among extant tortoises from Volcano Wolf.
In particular, we needed a larger reference data set including more Pinta individuals from which a single individual was left (Lonesome George). I embarked in the task of extracting historical DNA from Pinta specimens kept in a few museums to provide with an adequate reference panel of genetic information. I helped increasing the number of complete genotypes from one (Lonesome George) and ended up adding genotypes for 21 individuals in total. With this new data set we applied the same approach successfully used by Michael Russello et al. to detect Floreana-ancestry individuals among Wolf tortoises.
Our results showed that at least 17 Wolf tortoises had some degree of shared ancestry with C. abingdoni. Remarkably, some may even be first generation hybrids and equally interesting, these tortoises did not seem related to each other.
How this Pinta tortoises ended up in Volcano Wolf?. The answer is rather historical and likely caused by human disturbances. Before modern times, most vessels leaving the Archipelago would use a northern route and before completely leaving the archipelago some threw away alive tortoises that they did not need. It is possible that some of these tortoises were originally captured in Pinta found the way to Northern Isabela by using favorable ocean currents.
This hypothesis is somehow validated by the levels of hybrid co-ancestry that we have recovered. Can this individuals be used to repopulate Pinta with Galapagos tortoises?. Well, while these 'founder' population would not represent all the genetic variability of the original species they would probably harbor some of the additive genetic variation that made C. abingdoni survive and adapt to Pinta Island unique environments.
So the answer is yes. Cautious optimism?.
