Data from: Genetic pedigree analysis of the pilot breeding program for the rediscovered Galapagos giant tortoise from Floreana island

An aim of many captive breeding programs is to increase population sizes for reintroduction and establishment of self-sustaining wild populations. Genetic analyses play a critical role in these programs: monitoring genetic variation, identifying the origin of individuals, and assigning parentage to track family sizes. Here we use genetic pedigree analyses to examine three seasons of a pilot breeding program for the Floreana island Galapagos giant tortoise, C. niger, that had been declared extinct for ~150 years until individuals with mixed ancestry were recently discovered. We determined that eight of nine founding individuals were assigned parentage to at least one of 130 offspring produced, though there was considerable reproductive skew. In addition, we observed that genetic diversity of the progeny was lower than that of the founders. Despite the observed reproductive skew, we did not see evidence for assortative mating based on relatedness, but there was a trend towards reduced fitness when more related individuals bred. Finally, we found that the majority of progeny had ancestry assigned to the Floreana species (mean±SE = 0.51±0.02), though individual estimates varied. The success of these pilot seasons bodes well for a larger breeding program to help restore the previously extinct tortoise from Floreana island. Future efforts should continue to monitor for reproductive skew and assortative mating in order to maintain allelic diversity. We would also recommend forming smaller breeding groups and rotating individuals among them to prevent long-term reproductive skew among pairs.诸多圈养繁育计划的核心目标之一，便是扩大种群规模，以实现物种的再引入并建立可自我维持的野生种群。遗传分析在这类计划中发挥着关键作用：可用于监测遗传变异、鉴定个体起源，以及通过亲子鉴定追踪种群家系规模。本研究借助遗传谱系分析，对一项针对弗洛雷亚纳岛加拉帕戈斯巨龟（C. niger）的试点繁育项目的三个繁育季展开研究——该物种曾被认定灭绝约150年，直至近期才发现带有混合血统的个体。研究确定，在本次繁育产生的130只后代中，9只奠基个体中有8只被指派了至少1只后代的亲子关系，不过种群存在显著的繁殖偏倚。此外，研究观察到后代群体的遗传多样性低于奠基个体。尽管存在繁殖偏倚，但未发现基于亲缘关系的选型交配证据；不过当亲缘关系较近的个体进行繁育时，存在繁殖适合度下降的趋势。最后，研究发现绝大多数后代被指派的血统归属为弗洛雷亚纳物种（平均±标准误=0.51±0.02），但个体间的血统估计值存在差异。本次试点繁育季的成果，为后续更大规模的繁育计划奠定了良好基础，有望助力恢复这一此前已从弗洛雷亚纳岛灭绝的巨龟物种。未来的研究应持续监测繁殖偏倚与选型交配情况，以维持种群的等位基因多样性。同时，建议组建规模更小的繁育群体，并在群体间轮换个体，以避免配对间出现长期的繁殖偏倚。