Data from: Genetic rescue, the greater prairie chicken and the problem of conservation reliance in the Anthropocene

A central question in conservation is how best to manage biodiversity, despite human domination of global processes (= Anthropocene). Common responses (i.e. translocations, genetic rescue) forestall potential extirpations, yet have an uncertain duration. A textbook example is the greater prairie chicken (GRPC: Tympanuchus cupido pinnatus), where translocations (1992–1998) seemingly rescued genetically depauperate Illinois populations. We re-evaluated this situation after two decades by genotyping 21 microsatellite loci from 1831 shed feathers across six leks in two counties over 4 years (2010–2013). Low migration rates (less than 1%) established each county as demographically independent, but with declining-population estimates (4 year average N = 79). Leks were genetically similar and significantly bottlenecked, with low effective population sizes (average Ne = 13.1; 4 year Ne/N = 0.166). Genetic structure was defined by 12 significantly different family groups, with relatedness r = 0.31 > half-sib r = 0.25. Average heterozygosity, indicating short-term survival, did not differ among contemporary, pre- and post-translocated populations, whereas allelic diversity did. Our results, the natural history of GRPC (i.e. few leks, male dominance hierarchies) and its controlled immigration suggest demographic expansion rather than genetic rescue. Legal protection under the endangered species act (ESA) may enhance recovery, but could exacerbate political–economic concerns on how best to manage ‘conservation-reliant’ species, for which GRPC is now an exemplar.

生物多样性保育领域的核心议题之一，是在人类主导全球生态进程（即人类世（Anthropocene））的背景下，如何以最优方式管理生物多样性。常见的保育干预手段（即种群易地移植（translocation）、遗传拯救（genetic rescue））能够延缓潜在的局部灭绝事件，但其干预效果的持续时长尚不明确。一个经典的教科书案例便是大草原松鸡（greater prairie chicken，缩写GRPC：*Tympanuchus cupido pinnatus*）：1992至1998年间开展的种群易地移植操作，似乎拯救了遗传多样性匮乏的伊利诺伊州种群。时隔二十年后，我们重新评估了这一案例：在2010至2013年的四年间，我们对两个县的6个求偶场（lek）上收集的1831根脱落羽毛进行基因分型，共检测了21个微卫星位点。种群迁移率不足1%，证实两个县的种群在种群统计学上彼此独立，且种群数量持续下滑：四年间平均种群绝对数量（N）为79。各求偶场的遗传结构相似，但均经历了显著的种群瓶颈效应，且有效种群规模（effective population size，Ne）极低：四年平均Ne为13.1，Ne与N的四年平均比值为0.166。种群遗传结构由12个存在显著遗传分化的家族类群构成，个体间的平均亲缘系数（relatedness, r）为0.31，高于半同胞（half-sib）的典型亲缘系数0.25。平均杂合度（average heterozygosity）可反映种群短期存活能力，当代种群、移植前种群与移植后种群的平均杂合度并无显著差异，但等位基因多样性（allelic diversity）则存在显著分化。结合本研究结果、大草原松鸡的自然生活史特征（即求偶场数量稀少、雄性存在等级支配关系）以及其受控的迁入模式，我们认为该种群的变化更倾向于种群统计学上的扩张，而非遗传拯救效应。根据《濒危物种法案》（Endangered Species Act，ESA）提供的法律保护或可助力种群恢复，但可能会加剧关于如何最优管理“依赖保育物种（conservation-reliant species）”的政治与经济争议，而大草原松鸡现已成为这类物种的典型代表。