Browsing by Author "Caccone, Adalgisa"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
Item A new lineage of Galapagos giant tortoises identified from museum samples(2022) Jensen, Evelyn L.; Quinzin, Maud C.; Miller, Joshua M.; Russello, Michael A.; Garrick, Ryan C.; Edwards, Danielle L.; Glaberman, Scott; Chiari, Ylenia; Poulakakis, Nikos; Tapia, Washington; Gibbs, James P.; Caccone, AdalgisaThe Galapagos Archipelago is recognized as a natural laboratory for studying evolutionary processes. San Cristóbal was one of the first islands colonized by tortoises, which radiated from there across the archipelago to inhabit 10 islands. Here, we sequenced the mitochondrial control region from six historical giant tortoises from San Cristóbal (five long deceased individuals found in a cave and one found alive during an expedition in 1906) and discovered that the five from the cave are from a clade that is distinct among known Galapagos giant tortoises but closely related to the species from Española and Pinta Islands. The haplotype of the individual collected alive in 1906 is in the same clade as the haplotype in the contemporary population. To search for traces of a second lineage in the contemporary population on San Cristóbal, we closely examined the population by sequencing the mitochondrial control region for 129 individuals and genotyping 70 of these for both 21 microsatellite loci and >12,000 genome-wide single nucleotide polymorphisms [SNPs]. Only a single mitochondrial haplotype was found, with no evidence to suggest substructure based on the nuclear markers. Given the geographic and temporal proximity of the two deeply divergent mitochondrial lineages in the historical samples, they were likely sympatric, raising the possibility that the lineages coexisted. Without the museum samples, this important discovery of an additional lineage of Galapagos giant tortoise would not have been possible, underscoring the value of such collections and providing insights into the early evolution of this iconic radiation.Item Temporal monitoring of the Floreana Island Galapagos giant tortoise captive breeding program(2022) Gray, Rachel; Fusco, Nicole; Miller, Joshua M.; Tapia, Washington; Mariani, Carol; Caccone, Adalgisa; Jensen, Evelyn L.Captive breeding programs benefit from genetic analyses that identify relatedness between individuals, assign parentage to offspring, and track levels of genetic diversity. Monitoring these parameters across breeding cycles is critical to the success of a captive breeding program as it allows conservation managers to iteratively evaluate and adjust program structure. However, in practice, genetic tracking of breeding outcomes is rarely conducted. Here, we examined the first three offspring cohorts (2017–2020) of the genetically informed captive breeding program for the Floreana Island Galapagos giant tortoise, Chelonoidis niger. This captive breeding program is unique as the Floreana tortoise has been extinct since the 1800s, but its genome persists, in part, in the form of living hybrids with the extant Volcano Wolf tortoise, C. becki. Breeding over the study period took place at the Galapagos National Park Directorate breeding facility in four corrals, each containing three females and two males. Using 17 microsatellite markers, we were able to assign parentage to 94 of the 98 offspring produced over the study period. We observe that despite the addition of more founders since the pilot breeding program, the effective population size remains low, and changes to the arrangements of breeding corrals may be necessary to encourage more equal reproductive output from the males. This study demonstrates the value of hybrids for species restoration and the importance of continually reassessing the outcomes of captive breeding.