Data from: Genetic rediscovery of an ‘extinct’ Galápagos giant tortoise species

Genes from recently extinct species can live on in the genomes of extant individuals of mixed ancestry. Recently, Poulakakis et al. detected genetic signatures of the giant Galápagos tortoise once endemic to Floreana Island (Chelonoidis elephantopus) within eleven hybrid individuals of otherwise pure C. becki on Volcano Wolf, Isabela Island. Movement of tortoises among islands by pirate and whaling ships was not uncommon during the 1800’s, representing a likely mechanism by which individuals from Floreana were translocated to northern Isabela, despite being presumed extinct soon after Charles Darwin’s historic voyage to the Galápagos Islands in 1835. These eleven hybrid individuals with C. elephantopus ancestry were thought to be the last genetic vestiges of a unique evolutionary lineage in the wild. Here we report that reproductively mature purebred tortoises of the recently ‘extinct’ C. elephantopus from Floreana Island are very likely still alive today, as identified and tracked through the genetic footprints’ left in the genomes of very recent hybrid offspring on Volcano Wolf, Isabela Island. If found, these purebred C. elephantopus individuals could constitute core founders of a captive breeding program directed towards resurrecting this species.

近期灭绝物种的基因，可留存于携带混合血统的现存个体的基因组内。近期，Poulakakis等学者在伊莎贝拉岛沃尔夫火山的11只本应为纯血统贝克陆龟（C. becki）的杂交个体中，检测到了曾仅分布于弗洛雷阿纳岛的加拉帕戈斯巨龟（Chelonoidis elephantopus）的遗传标记。19世纪，海盗与捕鲸船跨岛转运陆龟的情况并不罕见，这一途径极有可能将弗洛雷阿纳岛的陆龟转移至伊莎贝拉岛北部——尽管该物种在1835年查尔斯·达尔文标志性的加拉帕戈斯群岛科考之旅后不久，就被认定已野外灭绝。这11只携带有C. elephantopus血统的杂交个体，曾被认为是该独特演化支系在野外留存的最后遗传遗迹。本研究通过对伊莎贝拉岛沃尔夫火山近期诞生的杂交后代基因组中留存的遗传印迹进行鉴定与追踪，证实来自弗洛雷阿纳岛、曾被认定为‘灭绝’的C. elephantopus纯血统陆龟，如今极大概率仍存活且已达到性成熟。若能找到这些纯血统C. elephantopus个体，它们将可作为圈养繁殖计划的核心奠基种群，助力该物种的复活保育项目。