Effects of rearing conditions on behavioural phenotypes in specialist versus generalist leaf beetles
Final Report Abstract
The behavioural phenotype and the life history of animals are influenced by various factors. Whereas this relation has been well studied for certain life stages, little is known how these traits may change over an animal's lifetime, even though organisms likely have to face various environments throughout life. Such niche shifts can particularly occur in organisms that pass through a metamorphosis. However, empirical studies about the specific role of larval versus adult experiences with their environment for shaping of the behavioural phenotype are rare, especially in (holometabolous) insects. We demonstrated that the behaviour of two leaf beetle species, the specialist (Phaedon cochleariae) and the generalist (Galeruca tanaceti), is consistent across contexts and over time during adulthood. Remarkably, in P. cochleariae the behavioural dimensions activity and boldness were also present throughout all tested larval stages and the adult life (population level). At the individual level, we found age- and sex-specific differences in certain behavioural traits. Both leaf beetles are obviously also well able to compensate for poor food conditions. Moreover, P. cochleariae were able to compensate during adulthood for feeding at a lower quality host (watercress) as larvae. Consequently, adults reared on the high nutritional crop cabbage had a higher reproductive output compared to individuals reared on watercress, regardless of the larval host. Furthermore, feeding preferences (for cabbage) were only expressed when insects were feeding on the high quality host, potentially due to a positive feedback. Thus, positive feedbacks may induce a preference for highly nutritious crops, potentially turning herbivores into pests of crops. When manipulation a social factor (population density), we could detect a silver spoon effect. Larvae which were raised under less competitive conditions (low population density) were able to gain a fitness advantage in the adult stage (higher reproductive output, as fitness related trait), regardless of the adult population density. Thus, the adult behavioural phenotype depends on the specific conditions experienced during the larval or the adult stage. Finally, we could show that, at least under no-choice situations, no precopulatory inbreeding avoidance mechanisms exist in P. cochleariae, although sibling mates could potentially be distinguished by family-specific cuticular hydrocarbon (CHC) profiles and although inbreeding depression occurred (reduced hatching rate of sibling pairs). The family-specific CHC profiles might still function for post-copulatory mechanisms to avoid the costs of inbreeding, either driven by females or males. The long-term observations of various life history traits revealed an increase of body mass and a decrease of egg number over the adult life span of eight weeks. Overall, our experiments reveal novel empirical insights in the recently intensely discussed research questions of how the behavioural phenotype and the life history are affected by different environmental factors and which developmental stages are most sensitive towards these factors.
Publications
- (2013) Insect personality depends on environmental conditions. Behav Ecol 24: 386-392
Tremmel M, Müller C
(See online at https://doi.org/10.1093/beheco/ars175) - (2013) The consequences of alternating diet on performance and food preferences of a specialist leaf beetle. J Insect Physiol 59: 840-847
Tremmel M, Müller C
(See online at https://doi.org/10.1016/j.jinsphys.2013.05.009) - (2014) Diet dependent experience and physiological state shape behavior of a generalist herbivore. Physiol Behav 129: 95-103
Tremmel M, Müller C
(See online at https://doi.org/10.1016/j.physbeh.2014.02.030) - (2015) Behavioural phenotypes over the lifetime of a holometabolous insect. Front Zool 12 (Suppl. 1): S8
Müller T, Müller C
(See online at https://doi.org/10.1186/1742-9994-12-S1-S8) - (2015) New perspectives in behavioural development: adaptive shaping of behaviour over a lifetime? Front in Zool12 (Suppl 1): S1
Trillmich F, Günther A, Müller C, Reinhold K, Sachser N
(See online at https://doi.org/10.1186/1742-9994-12-S1-S1) - Effects of larval versus adult density conditions on reproduction and behavior of a leaf beetle. Behav Ecol Sociobiol
Müller T, Küll CL, Müller C
(See online at https://doi.org/10.1007/s00265-016-2212-1) - (2016) Adult beetles compensate for poor larval conditions. J Insect Physiol 88: 24-32
Müller T, Müller C
(See online at https://doi.org/10.1016/j.jinsphys.2016.02.009) - (2016) Consequences of mating with siblings and non-siblings on the reproductive success in a leaf beetle. Ecol Evol 6: 3185-3197
Müller T, Müller C
(See online at https://doi.org/10.1002/ece3.2103)
