Morphological defences and defence–cost trade?offs in <i>Daphnia</i> in response to two co?occurring invertebrate predators

Inducible morphological defences are crucial for understanding predator–prey interactions. Such have been mostly studied in a single-predator context, ignoring the fact that prey organisms often exposed to multiple predators. In deep peri-Alpine European lakes, keystone grazer Daphnia coexists with two cladoceran predators, Bythotrephes longimanus and Leptodora kindtii. Up now, life history responses of these predators not analysed systematically. We (age at first reproduction, offspring production) five traits (body size, body width, head spina eye diameter) eight galeata clones presence common garden experiment. compared each response trait between treatments using linear mixed models, investigated covariation defence demographic costs (neonate Our results show predator- trait-specific. developed typical helmet larger only Bythotrephes, Leptodora. contrast, both induced sizes longer spines. Age reproduction was latest were highest treatment, suggesting development exceeds elongation. The revealed defence-cost trade-off formation elongation treatment. Hence, despite being closely related co-occurring responds unique combination changes trade-offs predator-specific clonal suggests invertebrate can drive different evolutionary processes natural zooplankton communities. Disentangling ecology phenotypic species will require multi-trait, multi-clone studies antipredator defences.