SFB-TRR 212

Niche conformance in a holometabolous invertebrate: adjustments of behavioural, physiological and chemical phenotypes and fitness consequences

The life conditions and physiology of holometabolous insects can drastically change after metamorphosis. In these insects, both the ecological and the social environment differ between larvae and adults, making phenotypic adjustments and adaptations to the environment necessary that eventually result in conformance to the individual niche. In previous work on leaf beetles, we demonstrated that the environment experienced as larva as well as the adult environment can influence behavioural dimensions to different extents, even though both life stages share the same feeding style. However, research is lacking how larval experience and differences in niches influence the adult behaviour, physiology and metabolic phenotype (metabotype) in insect species, in which larvae and adults have distinct feeding modes. Moreover, the environment experienced in one generation may influence life-history, fitness and behaviour of the subsequent generation, but still little is known on such transgenerational effects. Insects may show various physiological and molecular adaptations in the short-term (within one generation), which may be modified or become more pronounced over long-term (across two generations).

This project aims to determine in which way individuals of a herbivorous invertebrate conform to distinct ecological and social niches and in how far these adjustments are adaptive. Using the sawfly Athalia rosae, an important pest of Brassica crops, as model system, this project will elucidate in which way individual sawflies conform to distinct ecological and social niches and in how far these processes are adaptive.

Larval niches will be manipulated by different food availability offered to individuals. Adults of A. rosae only feed nectar but also pharmacophagously take up clerodendrins, which play an important role in sexual behaviour and may significantly influence the adult's social niche. As these compounds act antimicrobial, they may also affect the immunocompetence of adults. Clerodendrins are acquired by the adults from leaves and stems of Lamiales but potentially also from other A. rosae adults that had access to clerodendrin-containing plants. Therefore, I hypothesise that niche conformance is influenced by the individual's experience, i.e., individuals adjust their life-history, metabotype and behavioural phenotype based on physiological adaptations to distinct environmental conditions. Thereby, under mismatching conditions the individual's niche conformance may result in reduced fitness. In detail, this project addresses the following main research topics:

1. Effects of matching and mismatching conditions on life-history traits, fitness and behaviour in relation to niche conformance.
2. Effects of matching and mismatching conditions on physiology and immunity in relation to niche conformance.
3. Relationships between metabotype and behavioural phenotype and mechanisms of clerodendrin transfer.
4. Social niche choice in dependence of the individual ecological niche.