Ecology and Evolution of Intraspecific Chemodiversity of Plants

Intraspecific chemical variation of Tanacetum vulgare affects plant growth and reproductive traits in field plant communities

The study investigated the impact of intraspecific plant chemodiversity on plant growth and reproductive traits at both the plant and plot levels. It also aimed to understand how chemodiversity at stand level affects ecosystem functioning and plant-plant interactions. We describe a biodiversity experiment in which we manipulated intraspecific plant chemodiversity at the plot level using six different chemotypes of common tansy (Tanacetum vulgare L., Asteraceae). We tested the effects of chemotype identity and plot-level chemotype richness on plant growth and reproductive traits and plot-level headspace emissions. The study found that plant chemotypes differed in growth and reproductive traits and that traits were affected by the chemotype richness of the plots. Although morphological differences among chemotypes became less pronounced over time, reproductive phenology patterns persisted. Plot-level trait means were also affected by the presence or absence of certain chemotypes in a plot, and the direction of the effect depended on the specific chemotype. However, chemotype richness did not lead to overyielding effects. Lastly, chemotype blends released from plant communities were neither richer nor more diverse with increasing plot-level chemotype richness, but became more dissimilar as they became more dissimilar in their leaf terpenoid profiles. We found that intraspecific plant chemodiversity is crucial in plant-plant interactions. We also found that the effects of chemodiversity on plant growth and reproductive traits were complex and varied depending on the chemotype richness of the plots. This long-term field experiment will allow further investigation into plant-insect interactions and insect community assembly in response to intraspecific chemodiversity.

Population-Related Variability in Qualitative and Quantitative Secondary Metabolite Profile of Gentianella austriaca (A. & J. Kern.) Holub

Phytochemical profiling of six natural populations of Gentianella austriaca was performed by HPLC identification and quantification of a number of secondary metabolites, and evaluation of time series of peak areas by chemometric analysis. Phytochemical analysis of G. austriaca revealed the presence of iridoids, flavone-C-glucosides and xanthones. Twelve secondary metabolites were identified in the aerial parts, roots and seeds, including swertiamarin (SWM), gentiopicrin (GP), sweroside (SWZ), isoorientin (ISOOR), swertisin (SWE), demethylbellidifolin-8-O-glucoside (DMB-8-O-glc), bellidifolin-8-O-glucoside (BDF-8-O-glc), mangiferin (MGF), corymbiferin (CBF), corymbiferin-1-O-glucoside (CBF-1-O-glc), bellidifolin (BDF) and campestroside. Multivariate statistical analyses showed relatively low variability among populations according to secondary metabolite content. However, some pharmacologically important compounds were found in higher amounts in a few populations, which could be useful for conservation and future biotechnological procedures.

Plant–herbivore interactions: Experimental demonstration of genetic variability in plant–plant signalling

Plant-herbivore interactions mediated by plant-plant signalling have been documented in different species but its within-species variability has hardly been quantified. Here, we tested if herbivore foraging activity on plants was influenced by a prior contact with a damaged plant and if the effect of such plant-plant signalling was variable across 113 natural genotypes of Arabidopsis thaliana. We filmed the activity of the generalist herbivore Cornu aspersum during 1 h on two plants differing only in a prior contact with a damaged plant or not. We recorded each snails' first choice, and measured its first duration on a plant, the proportion of time spent on both plants and leaf consumption. Overall, plant-plant signalling modified the foraging activity of herbivores in A. thaliana. On average, snails spent more time and consumed more of plants that experienced a prior contact with a damaged plant. However, the effects of plant-plant signalling on snail behaviour was variable: depending on genotype identity, plant-plant signalling made undamaged plants more repellant or attractive to snails. Genome-wide associations revealed that genes related to stress coping ability and jasmonate pathway were associated to this variation. Together, our findings highlight the adaptive significance of plant-plant signalling for plant-herbivore interactions.

Quantifying chemodiversity considering biochemical and structural properties of compounds with the R package chemodiv

Plants produce large numbers of phytochemical compounds affecting plant physiology and interactions with their biotic and abiotic environment. Recently, chemodiversity has attracted considerable attention as an ecologically and evolutionary meaningful way to characterize the phenotype of a mixture of phytochemical compounds. Currently used measures of phytochemical diversity, and related measures of phytochemical dissimilarity, generally do not take structural or biosynthetic properties of compounds into account. Such properties can be indicative of the compounds' function and inform about their biosynthetic (in)dependence, and should therefore be included in calculations of these measures. We introduce the R package chemodiv, which retrieves biochemical and structural properties of compounds from databases and provides functions for calculating and visualizing chemical diversity and dissimilarity for phytochemicals and other types of compounds. Our package enables calculations of diversity that takes the richness, relative abundance and - most importantly - structural and/or biosynthetic dissimilarity of compounds into account. We illustrate the use of the package with examples on simulated and real datasets. By providing the R package chemodiv for quantifying multiple aspects of chemodiversity, we hope to facilitate investigations of how chemodiversity varies across levels of biological organization, and its importance for the ecology and evolution of plants and other organisms.

Revisiting plant defense-fitness trade-off hypotheses using Solanum as a model genus

Plants possess physical and chemical defenses which have been found to deter herbivores that feed and oviposit on them. Despite having wide variety of defenses which can be constitutive or induced, plants are attacked and damaged by insects associated with different mouthparts and feeding habits. Since these defenses are costly, trade-offs for growth and defense traits play an important role in warding off the herbivores, with consequences for plant and herbivore growth, development and fitness. Solanum is a diverse and rich genus comprising of over 1,500 species with economic and ecological importance. Although a large number of studies on Solanum species with different herbivores have been carried out to understand plant defenses and herbivore counter defenses, they have primarily focused on pairwise interactions, and a few species of economic and ecological importance. Therefore, a detailed and updated understanding of the integrated defense system (sum of total defenses and trade-offs) is still lacking. Through this review, we take a closer look at the most common plant defense hypotheses, their assumptions and trade-offs and also a comprehensive evaluation of studies that use the genus Solanum as their host plant, and their generalist and specialist herbivores from different feeding guilds. Overall, review emphasizes on using ubiquitous Solanum genus and working toward building an integrated model which can predict defense-fitness-trade-offs in various systems with maximum accuracy and minimum deviations from realistic results.

European oak chemical diversity - from ecotypes to herbivore resistance

Climate change is increasing insect pressure and forcing plants to adapt. Although chemotypic differentiation and phenotypic plasticity in spatially separated tree populations are known for decades, understanding their importance in herbivory resistance across forests remains challenging. We studied four oak forest stands in Germany using nontarget metabolomics, elemental analysis, and chemometrics and mapped the leaf metabolome of herbivore-resistant (T-) and herbivore-susceptible (S-) European oaks (Quercus robur) to Tortrix viridana, an oak pest that causes severe forest defoliation. Among the detected metabolites, we identified reliable metabolic biomarkers to distinguish S- and T-oak trees. Chemotypic differentiation resulted in metabolic shifts of primary and secondary leaf metabolism. Across forests, T-oaks allocate resources towards constitutive chemical defense enriched of polyphenolic compounds, e.g. the flavonoids kaempferol, kaempferol and quercetin glucosides, while S-oaks towards growth-promoting substances such as carbohydrates and amino-acid derivatives. This extensive work across natural forests shows that oaks' resistance and susceptibility to herbivory are linked to growth-defense trade-offs of leaf metabolism. The discovery of biomarkers and the developed predictive model pave the way to understand Quercus robur's susceptibility to herbivore attack and to support forest management, contributing to the preservation of oak forests in Europe.

Epigenetics and the success of invasive plants

Biological invasions impose ecological and economic problems on a global scale, but also provide extraordinary opportunities for studying contemporary evolution. It is critical to understand the evolutionary processes that underly invasion success in order to successfully manage existing invaders, and to prevent future invasions. As successful invasive species sometimes are suspected to rapidly adjust to their new environments in spite of very low genetic diversity, we are obliged to re-evaluate genomic-level processes that translate into phenotypic diversity. In this paper, we review work that supports the idea that trait variation, within and among invasive populations, can be created through epigenetic or other non-genetic processes, particularly in clonal invaders where somatic changes can persist indefinitely. We consider several processes that have been implicated as adaptive in invasion success, focusing on various forms of 'genomic shock' resulting from exposure to environmental stress, hybridization and whole-genome duplication (polyploidy), and leading to various patterns of gene expression re-programming and epigenetic changes that contribute to phenotypic variation or even novelty. These mechanisms can contribute to transgressive phenotypes, including hybrid vigour and novel traits, and may thus help to understand the huge successes of some plant invaders, especially those that are genetically impoverished. This article is part of the theme issue 'How does epigenetics influence the course of evolution?'

Inter-Individual versus Inter-Population Variability of Calendula suffruticosa subsp. algarbiensis Hexane Extracts

Calendula suffruticosa subsp. algarbiensis (Boiss.) Nyman is very common on the Portuguese coast, but it has only recently begun to be studied chemically and belongs to a genus of difficult taxonomic classification. To improve the knowledge on the chemical variability of this taxon and evaluate the possible use of this tool for taxonomical purposes, the aim of this work was to determine the extent of chemical variation between individuals collected in the same geographic region, and to compare with samples mixing fragments of several individuals each (populations) from different local environments. Overall, hexane extract analysis by GC/MS allowed to identify 42 compounds, eight fatty acids, 24 terpenoids, three alcohols, five alkanes, and two pollutants. Greater chemical differences were found between individuals, grown in the same region, than were found between population samples from different regions. Additionally, 25 phytochemicals were identified for this taxon for the first time and may be used for taxonomic classification, even to distinguish between subspecies of C. suffruticosa. Furthermore, plants collected near urban areas accumulated pollutants, indicating the importance of controlling local environmental conditions when C. suffruticosa cultivation is for human consumption.

Open science in practice: 300 published research ideas and outcomes illustrate how RIO Journal facilitates engagement with the research process

Since Research Ideas and Outcomes was launched in late 2015, it has stimulated experimentation around the publication of and engagement with research processes, especially those with a strong open science component. Here, we zoom in on the first 300 RIO articles that have been published and elucidate how they relate to the different stages and variants of the research cycle, how they help address societal challenges and what forms of engagement have evolved around these resources, most of which have a nature and scope that would prevent them from entering the scholarly record via more traditional journals. Building on these observations, we describe some changes we recently introduced in the policies and peer review process at RIO to further facilitate engagement with the research process, including the establishment of an article collections feature that allows us to bring together research ideas and outcomes from within one research cycle or across multiple ones, irrespective of where they have been published.

Flower Production, Headspace Volatiles, Pollen Nutrients, and Florivory in Tanacetum vulgare Chemotypes

Floral volatiles and reward traits are major drivers for the behavior of mutualistic as well as antagonistic flower visitors, i.e., pollinators and florivores. These floral traits differ tremendously between species, but intraspecific differences and their consequences on organism interactions remain largely unknown. Floral volatile compounds, such as terpenoids, function as cues to advertise rewards to pollinators, but should at the same time also repel florivores. The reward composition, e.g., protein and lipid contents in pollen, differs between individuals of distinct plant families. Whether the nutritional value of rewards within the same plant species is linked to their chemotypes, which differ in their pattern of specialized metabolites, has yet not been investigated. In the present study, we compared Tanacetum vulgare plants of five terpenoid chemotypes with regard to flower production, floral headspace volatiles, pollen macronutrient and terpenoid content, and floral attractiveness to florivorous beetles. Our analyses revealed remarkable differences between the chemotypes in the amount and diameter of flower heads, duration of bloom period, and pollen nutritional quality. The floral headspace composition of pollen-producing mature flowers, but not of premature flowers, was correlated to that of pollen and leaves in the same plant individual. For two chemotypes, florivorous beetles discriminated between the scent of mature and premature flower heads and preferred the latter. In semi-field experiments, the abundance of florivorous beetles and flower tissue miners differed between T. vulgare chemotypes. Moreover, the scent environment affected the choice and beetles were more abundant in homogenous plots composed of one single chemotype than in plots with different neighboring chemotypes. In conclusion, flower production, floral metabolic composition and pollen quality varied to a remarkable extend within the species T. vulgare, and the attractiveness of floral scent differed also intra-individually with floral ontogeny. We found evidence for a trade-off between pollen lipid content and pollen amount on a per-plant-level. Our study highlights that chemotypes which are more susceptible to florivory are less attacked when they grow in the neighborhood of other chemotypes and thus gain a benefit from high overall chemodiversity.