Survival and malformations, swimming performance and tadpole traits

Targeted gene flow (TGF) could bolster the adaptive potential of isolated populations threatened by climate change, but could also lead to outbreeding depression. Here, we explore these possibilities by creating mixed- and within-population crosses in a terrestrial-breeding frog species threatened by a drying climate. We reared embryos on wet and dry soils and quantified fitness-related traits upon hatching. TGF produced mixed outcomes in hybrids which depended on crossing direction (origin of gametes from each sex). North-south crosses led to low embryonic survival if eggs were of a southern origin, and high malformation rates when eggs were from a northern population. Conversely, east-west crosses led to one instance of hybrid vigour, evident by increased fitness and desiccation tolerance of hybrid offspring relative to offspring produced from within-population crosses. These contrasting results highlight the need to experimentally evaluate the outcomes of TGF for focal species across generations prior to implementing management actions.

定向基因流（Targeted gene flow）可增强受气候变化威胁的隔离种群的适应潜力，但亦可能引发远交衰退（outbreeding depression）。本研究以一种受气候干旱化威胁的陆育蛙类为对象，通过构建种群内杂交与混合杂交组合，对上述两种可能性展开探究。我们将胚胎分别置于湿润与干燥土壤环境中培育，并在孵化后量化适合度相关性状。定向基因流对杂交后代的影响存在混合结果，且取决于杂交方向（即两性配子的来源）。南北方向的杂交，若卵来自南方种群则胚胎存活率偏低，若卵来自北方种群则后代畸形率升高。与之相反，东西方向的杂交则出现一例杂种优势（hybrid vigour）现象：相较于种群内杂交产生的后代，杂交后代的适合度与耐旱性均显著提升。上述迥异的研究结果提示，在针对目标物种实施相关管理措施前，需通过实验多世代评估定向基因流的应用效果。