The genetic crisis of the Mexican Bolson Tortoise (Gopherus flavomarginatus: Testudinidae)

Abstract

Gopherus flavomarginatus (Testudinidae) is endemic to a series of discontinuous, isolated basins collectively known as the Bolson de Mapimí in the Chihuahuan Desert. Its numbers declined after catastrophic levels of exploitation during the mid-20th century. However currently, the Bolson Tortoise appears to be on a path to recovery owing to intensive, sustained conservation efforts. We sequenced an 842-bp-long fragment of the D-loop from 76 individuals distributed throughout the species' range. The results revealed only two haplotypes. An AMOVA showed that 95% of the variance occurred among populations, whereas the remaining 5% was explained by genetic differences within populations. Tectonic processes together with ecological transformation during the Pleistocene and Holocene may be responsible for the reduction in this species' genetic variation. A bottleneck during which a significant percentage of the haplotype diversity was lost would result in genetic homogeneity. Although there is demographic growth, the lack of genetic diversity is indicative of the potential crisis that the Bolson Tortoise is facing, and awareness must be brought to this situation.

Genetic Assessments and Parentage Analysis of Captive Bolson Tortoises (Gopherus flavomarginatus) Inform Their “Rewilding” in New Mexico

“…The dearth of genetic diversity in our mtDNA results suggests that wild Bolson tortoises have experienced tremendous reductions in population size since at least the last glacial maximum. This is consistent with a recent study by Urena-Aranda and de los Monteros [44] who found 74 of 76 wild G. flavomarginatus sampled from throughout the Bolsón de Mapimí had the same mtDNA haplotype among only two identified in their study. The low level of STR allelic richness ( Table 3B ) and the limited genetic differentiation observed between the Appleton and Durango populations (F ST = 0.025) also support that the species has reduced genetic diversity.…”

Using Range-Wide Abundance Modeling to Identify Key Conservation Areas for the Micro-Endemic Bolson Tortoise (Gopherus flavomarginatus)

“…Gopherus flavomarginatus (the Bolson tortoise) is endemic to a portion of the Mapimí Basin, in the Chihuahuan Desert, Mexico ( Fig 1 ). Widespread until the Pleistocene when it ranged from southern USA to central Mexico [ 22 ], several factors have brought the Bolson tortoise to the verge of extinction: climate changes in the Pleistocene-Holocene transition, recent anthropogenic activities, including habitat destruction due to overgrazing and agriculture, overexploitation for wildlife trade [ 23 – 26 ], and low genetic variation [ 27 ].…”