Three types of rescue can avert extinction in a changing environment

Setting aside high-quality large areas of habitat to protect threatened populations is becoming increasingly difficult as humans fragment and degrade the environment. Biologists and managers therefore must determine the best way to shepherd small populations through the dual challenges of reductions in both the number of individuals and genetic variability. By bringing in additional individuals, threatened populations can be increased in size (demographic rescue) or provided with variation to facilitate adaptation and reduce inbreeding (genetic rescue). The relative strengths of demographic and genetic rescue for reducing extinction and increasing growth of threatened populations are untested, and which type of rescue is effective may vary with population size. Using the flour beetle (Tribolium castaneum) in a microcosm experiment, we disentangled the genetic and demographic components of rescue, and compared them with adaptation from standing genetic variation (evolutionary rescue in t...

随着人类活动导致环境破碎化与退化，通过划定优质大面积栖息地以保护受威胁种群的难度与日俱增。因此，生物学家与保育管理者亟需确定最优策略，助力小型种群应对个体数量与遗传变异水平双双下降的双重挑战。通过引入外来个体，受威胁种群既可扩大种群规模（demographic rescue，种群救助），也可获得遗传变异以助力适应性演化并降低近交风险（genetic rescue，遗传救助）。目前尚未有研究验证种群救助与遗传救助在降低受威胁种群灭绝风险、提升种群增长速率方面的相对效力，且有效救助类型可能随种群规模而异。本研究以赤拟谷盗（Tribolium castaneum）为实验对象开展微宇宙实验（microcosm experiment），解析了救助效应的遗传与种群动态组分，并将其与源自现存遗传变异的适应性演化（evolutionary rescue，演化救助）……