Abstract
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.
Highlights
In 2005, Donlan et al [1] suggested that the restoration of North American ecosystems might be fostered through the reintroduction of the Pleistocene megafauna
None of our loci exhibits a high level of variation and this constrains the power of our analyses
The low level of genetic diversity in G. flavomarginatus likely results from the evolutionary history of the species
Summary
In 2005, Donlan et al [1] suggested that the restoration of North American ecosystems might be fostered through the reintroduction of the Pleistocene megafauna. Most of those species are extinct and, would require taxonreplacement [2], the Bolson tortoise (Gopherus flavomarginatus) provided the opportunity to ‘‘rewild’’ the Chihuahuan Desert of the United States with an extant, but locally extirpated species. Its current range is limited to a relatively small region of Mexico, the Bolson de Mapimı, at the intersection of the states of Chihuahua, Durango and Coahuila.
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