Chemotypic variation in terpenes emitted from storage pools influences early aphid colonisation on tansy

Abstract

Tansy plants (Tanacetum vulgare L.) exhibit high chemical variation, particularly in mono- and sesquiterpenes that are stored in specialised glands on the plant surface. In the present work we investigated the effects of terpene chemotypes on Metopeurum fuscoviride, an aphid species specialised on tansy, and their tending ants, at the field scale. Previous studies have chemotyped tansy by assessing dominant compounds; here we propose a method of chemotyping using all volatile compounds that are likely emitted from the storage glands. The analysis is based on two extraction methods: GC-MS analysis of leaf hexane extracts and SBSE analysis of headspace emissions. In an initial screening we identified the subset of compounds present in both chemical patterns, labelled as ‘compounds likely emitted from storage’. In a large field survey we could show that the putative chemotypic emission pattern from storage pools significantly affected the early aphid colonisation of tansy. Moreover, the statistical analyses revealed that minor compounds exerted a stronger influence on aphid and tending-ant presence than dominant compounds. Overall we demonstrated that within the enormous chemotypic variation of terpenes in tansy plants, chemical signatures of volatile terpenes can be related to the occurrence of insects on individual plants in the field.

Habitat variation, mutualism and predation shape the spatio‐temporal dynamics of tansy aphids

“…The presence of ants on tansy plants, before aphid colonisation, was recently shown to vary across different plant chemotypes, suggesting they are attracted or repelled by certain chemical compounds emitted by the plant (Clancy et al, 2016). floral nectaries) were not present in the early and mid-season, ants were present on currently unoccupied tansy plants.…”

Effect of plant chemical variation and mutualistic ants on the local population genetic structure of an aphid herbivore

“…In addition to variation in the VOCs, we showed-through untargeted metabolomic profiling of the leaves-that all plants of certain metabotypes (clusters of plants with similar metabolomic profiles) were colonised by aphids at the peak of the season (even on "less preferred" volatile chemotypes) (Clancy et al, 2018). The two common mutualistic ant species in this system also responded to plant chemical variation (Clancy et al, 2016), and the presence of ants increased colonisation success and benefited the population growth of M. fuscoviride aphids (Flatt & Weisser, 2000;Senft, Weisser, & Zytynska, 2017). Interestingly, there was no association between plant volatile chemotype and metabotype, leading to a unique system where we can disentangle effects of these two aspects of chemical diversity (Clancy et al, 2018).…”

“…We used the plant volatile chemical information on 22 compounds, emitted from specialised storage structures on the plant (identified using GC-MS), from Clancy et al (2016), and secondary metabolite information of 1,020 mass features as identified using LC-MS by Clancy et al (2018) (for more details, see Appendix S1). Our focus was only on those plants that were colonised by aphids, so we performed new cluster analyses on these 87 plants to obtain chemotype and metabotype plant groupings, using the package "pvclust" (Suzuki & Shimodaira, 2015) in R v3.3.0 in RStudio v0.99.896.…”

“…Tansy plants (T. vulgare L.) are characterised by high chemical variability in terpenoids, which has a genetic basis (Keskitalo, Linden, & Valkonen, 1998). Recently, we have shown that plant-to-plant variation in the profile of VOCs (terpenes), identified as being putatively emitted from specialised storage structures on the leaves, affected the field colonisation of tansy plants by specialised aphids (Metopeurum fuscoviride Stroyan (Aphididae)) in the early part of the season (Clancy et al, 2016). Recently, we have shown that plant-to-plant variation in the profile of VOCs (terpenes), identified as being putatively emitted from specialised storage structures on the leaves, affected the field colonisation of tansy plants by specialised aphids (Metopeurum fuscoviride Stroyan (Aphididae)) in the early part of the season (Clancy et al, 2016).…”

“…Based on the strong effects of both volatile and non-volatile chemical compounds in the plants on aphid-ant interactions in this system (Clancy et al, 2018(Clancy et al, , 2016Senft et al, 2019), we asked whether plant chemical variation could also lead to fine-scale structuring of the aphid population at the genetic level. Based on the strong effects of both volatile and non-volatile chemical compounds in the plants on aphid-ant interactions in this system (Clancy et al, 2018(Clancy et al, , 2016Senft et al, 2019), we asked whether plant chemical variation could also lead to fine-scale structuring of the aphid population at the genetic level.…”