Intraspecific and intra-individual chemodiversity and phenotypic integration of terpenes across plant parts and development stages in an aromatic plant

Some plant species produce an extraordinary diversity of specialized metabolites. The diverse class of terpenes is characteristic for many aromatic plants, and terpenes can occur as both emitted volatiles and stored compounds. Little is known about how intraspecific chemodiversity and phenotypic integration of both emitted volatile and stored terpenes differ intra-individually across plant development and between different plant parts, and studies considering both spatial and temporal scales are scarce. To comprehensively investigate this diversity, we used the aromatic plant Tanacetum vulgare that differs in foliar terpene composition, forming chemotypes. We collected emitted volatile terpenes of both young and old leaves during the rosette, elongated stem, and flowering stage as well as emitted volatiles of flower heads at the flowering stage. Moreover, at the flowering stage, stored terpenes were extracted from different plant parts, including roots. Terpene profiles were measured with (TD)-GC-MS. The composition of emitted volatile terpenes depended on the specific combination of chemotype, plant part, and time point; the chemodiversity of emitted volatiles was mainly affected by the development stage, indicating that at specific development stages individuals require a higher chemodiversity, potentially to mediate different interactions. For stored terpenes, intra-individual differences, mostly between aboveground and belowground plant parts, were found only for specific components of chemodiversity, such as richness and evenness, but not for functional Hill diversity. Phenotypic integration differed mainly across development stage and plant part for emitted volatile terpenes, and across chemotype and plant part for stored terpenes. Our results suggest that intraspecific chemodiversity of terpenes and their integration is a highly plastic trait that may be shaped in dependence of interactions with the environment, and the value that each plant part contributes to the fitness of an individual. Such variation on different scales, both spatially and temporally, should be considered in chemical ecological studies.