Genetic assessments and parentage analysis of captive Bolson tortoises (Gopherus flavomarginatus) inform their "rewilding" in New Mexico.
Taylor Edwards, Elizabeth Canty Cox, Vanessa Buzzard, Christiane Wiese, L Scott Hillard, Robert W Murphy
Author Information
Taylor Edwards: University of Arizona Genetics Core, University of Arizona, Tucson, Arizona, United States of America.
Elizabeth Canty Cox: University of Arizona Genetics Core, University of Arizona, Tucson, Arizona, United States of America.
Vanessa Buzzard: Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona, United States of America.
Christiane Wiese: Turner Endangered Species Fund, Ladder Ranch, Caballo, New Mexico, United States of America.
L Scott Hillard: Turner Endangered Species Fund, Ladder Ranch, Caballo, New Mexico, United States of America; Department of Ecology and Evolutionary Biology, University of California Los Angeles, Los Angeles, California, United States of America.
Robert W Murphy: Centre for Biodiversity and Conservation Biology, Royal Ontario Museum, Toronto, Canada.
The Bolson tortoise (Gopherus flavomarginatus) is the first species of extirpated megafauna to be repatriated into the United States. In September 2006, 30 individuals were translocated from Arizona to New Mexico with the long-term objective of restoring wild populations via captive propagation. We evaluated mtDNA sequences and allelic diversity among 11 microsatellite loci from the captive population and archived samples collected from wild individuals in Durango, Mexico (n = 28). Both populations exhibited very low genetic diversity and the captive population captured roughly 97.5% of the total wild diversity, making it a promising founder population. Genetic screening of other captive animals (n = 26) potentially suitable for reintroduction uncovered multiple hybrid G. flavomarginatus×G. polyphemus, which were ineligible for repatriation; only three of these individuals were verified as purebred G. flavomarginatus. We used these genetic data to inform mate pairing, reduce the potential for inbreeding and to monitor the maintenance of genetic diversity in the captive population. After six years of successful propagation, we analyzed the parentage of 241 hatchlings to assess the maintenance of genetic diversity. Not all adults contributed equally to successive generations. Most yearly cohorts of hatchlings failed to capture the diversity of the parental population. However, overlapping generations of tortoises helped to alleviate genetic loss because the entire six-year cohort of hatchlings contained the allelic diversity of the parental population. Polyandry and sperm storage occurred in the captives and future management strategies must consider such events.
