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.