Behaviour and body size: plasticity and genotypic diversity in larval Ischnura elegans as a response to predators (Odonata: Coenagrionidae)

Abstract

Phenotypic plasticity represents an adaptive tool in organisms including odonates to cope with heterogeneous environmental conditions. However, while some odonate species can occupy various changing habitats, other species are adapted to a narrow range of environmental conditions. Commonly, behavioural modifications are applied to avoid detection and encounters with predators. But reduced behavioural activity results in decelerated growth and reduced body size, a key fitness attribute in odonates. Using larval Ischnura elegans we quantified predator induced plastic behavioural reaction norms in order to manifest variance, and by this evolvability of larval behavioural plasticity. In addition we test for potentially underlying genetic correlations of behavioural traits with body size. Our results show that there is large genotypic variance in plastic reaction norms. Furthermore, no present genetic constraints between behaviour and body size were detected, suggesting potential for independent optimisation of behaviour and body size across environments. Our data indicate that independent phenotypic plasticity in behaviour and body size might enable species to occupy a wide range of environmental conditions.