DOI: 10.5061/dryad.vhhmgqp1k
title: Data from: Chemodiversity affects preference for Tanacetum vulgare chemotypes in two aphid species

description: Plants of the same species can strongly differ in their specialized
 metabolite profiles, which can affect insect presence and abundance in the
 field. However, how specialized chemistry shapes plant attractiveness to
 herbivorous insects is not fully understood. Here, we used common tansy
 (Tanacetum vulgare L., Asteraceae) – a perennial plant that is highly
 diverse in terpenoid composition and is known to have variable chemotypes
 – to test whether 1) plants with different chemotype profiles differ in
 attractiveness to two specialist aphid species, Macrosiphoniella
 tanacetaria and Uroleucon tanaceti, in pairwise choice assays; 2) the
 diversity of the terpenoid blend affects plant attractiveness to aphids;
 3) how plant chemical traits relate to plant morphological traits and
 which traits best explain aphid preference. We found that M. tanacetaria
 preferred two out of five chemotypes, dominated by α-thujone/β-thujone and
 β-trans-chrysanthenyl acetate, while avoiding a chemotype dominated by
 α-pinene/sabinene. Uroleucon tanaceti showed no clear preference towards
 chemotypes, but when given a choice between chemotypes dominated by
 α-thujone/β-thujone and by α-pinene/sabinene, they preferred the former.
 Importantly, plant attractiveness to aphids was marginally negatively
 correlated with chemodiversity, i.e., the number of terpenoid compounds,
 in M. tanacetaria, but not in U. tanaceti. Interestingly, the relative
 concentration and number of terpenoids were generally higher in larger and
 bushier plants. Hence, we did not observe a tradeoff between plant growth
 and defence. We conclude that plant chemical composition affects plant
 attractiveness to aphids and hence may contribute to variation in natural
 aphid colonization patterns on plants of the same species.
description: Leaf samples of <em>tanacetum vulgare</em> were
 collected and plants were chemotyped based on their terpenoid profiles,
 using hexane extractions and comparing retention indices and mass spectra
 to available synthetic reference compounds from the library entries of the
 National Institute of Standards and Technology (NIST) 2014, Pherobase and
 mass spectra reported in Adams (2007; Adams, R. P. (2007). Identification
 of Essential Oil Composition by Gas Chromatography/Mass Spectrometry, 4th
 Edn. Carol Stream, IL: Allured Publishing Corporation). Plant terpenoid
 profiles were then clustered using unsupervised hierarchical k-means
 clustering. Plants from five chemotypes were
 propagated. In choice assays one aphid was placed into a petri dish
 containing a leaf from two different chemtoypes each. After two and five
 hours the observed aphid preference was recorded. All
 statistical analyzes were performed in R, using the "survival",
 "vegan" and "RcmdrMisc" package.
description: # Data from: Chemodiversity affects preference for Tanacetum vulgare
 chemotypes in two aphid species
 ## Description of the data
 and file structure We collected data on aphid choice via observations. We
 tested two aphid species (**Aphid_Species**). One aphid individual was
 given a choice between leaves from two chemotypes, placed on the left side
 of the petri dish (**Chemotype1_SideA**) or the right
 (**Chemotype2_SideB**). Every chemotype comprised three daughters
 (**Daughter1_SideA**; **Daughter2_SideB**). As we used 5 chemotypes, ten
 combinations (**Combination_of_Chemotypes**) were possible. For
 *Macrosiphoniella tanacetaria*, we tested each combination 23 times
 (**Replication_of Combinations_tested**), while for *Uroleucon tanaceti*
 combinations were replicated 13 times. After two and five hours the side
 of the leave with the aphid on, was noted (**Choice_after_2h**;
 **Choice_after_5h**) and translated into the chemotype
 (**Selected_Chemotype_2h**; **Selected_Chemotype_5h**) and the respective
 daughter (**Selected_Daugher_2h**; **Selected_Daughter_2h**). The observer
 was also noted (**Observer**). The choice assays were done over the course
 of three different days (**Round_of_Observation**). When no data within
 the specific variable was available, this was coded as "NA",
 e.g. if an aphid died before the observationpoint after two hours, and
 hence did not make a choice, the Choice_after_2h was filled with
 "NA". ## Code/Software We used R to analyze our data, including
 the "survival", "vegan" and "RcmdrMisc"
 packages.