Predation sharpens the adaptive peaks: survival trade-offs in sympatric sticklebacks

This study tests whether living in different lake habitats in benthic and limnetic sticklebacks (Gasterosteus aculeatus complex) has resulted in divergence of antipredator traits and habitat-associated survival trade-offs. Adult benthics were larger than limnetics, had poorly developed defensive armour and showed no tendency to school with conspeciÞ cs. Limnetics, in contrast, were smaller, had well developed defensive armour and demonstrated strong schooling behaviour. In littoral arenas, juvenile limnetics were signiÞ cantly more vulnerable than juvenile benthics to predation by adult benthics and backswimmers (Notonecta sp.) but not dragonß y larvae (Aeshna sp.). This pattern was reversed in open water arenas when adult benthics and limnetics were exposed to diving avian predators, double-crested cormorants (Phalacrocorax auritus). These Þ ndings show that divergence in antipredator traits between benthic and limnetic sticklebacks has accompanied divergence in foraging traits, resulting in survival trade-offs in addition to those previously observed for foraging success and growth rates across habitats.