Ken Keefover-Ring

A chemical polymorphism in a multitrophic setting: thyme monoterpene composition and food web structure.

We investigated the effects of chemical variation in thyme (Thymus vulgaris L.) on its interactions with competitors, herbivores, and herbivore predators. Four different thyme monoterpene phenotypes (chemotypes) were grown in a \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape

Rapid modulation of ultraviolet shielding in plants is influenced by solar ultraviolet radiation and linked to alterations in flavonoids

4\times 2\times 2

Patterns of Phytochemical Variation in Mimulus guttatus (Yellow Monkeyflower)

\end{document} factorial of chemotype, caging (sham half‐cages vs. full cages), and competition (control vs. the grass Bromus madritensis L.). Cages reduced numbers of arthropod predators. Thyme‐feeding aphids Aphis serpylli Koch passed through full cage walls to increase more than fourfold. As a result, freed from their predators, aphids had a large negative effect on thyme size and flowering. Similarly, competition from Bromus had a negative effect on thyme size and flowering. Individual effects of aphids and competition were nonadditive, however, and their combined effect was significantly less than that predicted by a multiplicative null model. Differential thyme sizes among chemotypes were not mediated by herbivores or competitors, but differential flowering was due to the effects of chemotype on aphids. We thus document differential selection by aphids among thyme chemotypes and the influence of Bromus on the strength of these negative effects of aphids.

No Evidence of Geographical Structure of Salicinoid Chemotypes within Populus Tremula

Although extreme climatic events may have profound effects on ecological systems, there is a marked lack of information on adaptation to such events. In this study, we employed reciprocal transplantation on both a geographic scale (experimental sites 200 km apart in different parts of the range of the study species) and a local landscape scale (reciprocal populations separated by 2-8 km) to study the performance of different chemical forms of Thymus vulgaris which naturally occur in different climatic environments. Survival and growth were analyzed in relation to long-term and contemporary climate data in natural populations and our experimental sites. The reciprocal transplants involved a period of six years for clones transplanted in experimental field sites on a geographic scale and three years for seedlings transplanted among natural populations at the local landscape level. Cloned transplants on a geographic scale produced evidence for local adaptation to either summer drought, primarily following the extreme summer drought of 2003, or severe early-winter freezing. Chemotypes that show high survival after intense summer drought showed poor survival after intense early- winter freezing and vice versa, results which directly accord with climate data for their original sites. On the local landscape scale, we found further evidence for local adaptation to summer drought but not to winter freezing (probably due to the absence of extreme freezing during the three years of this study). Future modifications to the occurrence and frequency of extreme climate events may have a profound influence on the spatial distribution of thyme chemotypes.

Making scents of defense: do fecal shields and herbivore-caused volatiles match host plant chemical profiles?

The accumulation of ultraviolet (UV)-absorbing compounds (flavonoids and related phenylpropanoids) and the resultant decrease in epidermal UV transmittance (TUV ) are primary protective mechanisms employed by plants against potentially damaging solar UV radiation and are critical components of the overall acclimation response of plants to changing solar UV environments. Whether plants can adjust this UV sunscreen protection in response to rapid changes in UV, as occurs on a diurnal basis, is largely unexplored. Here, we use a combination of approaches to demonstrate that plants can modulate their UV-screening properties within minutes to hours, and these changes are driven, in part, by UV radiation. For the cultivated species Abelmoschus esculentus, large (30-50%) and reversible changes in TUV occurred on a diurnal basis, and these adjustments were associated with changes in the concentrations of whole-leaf UV-absorbing compounds and several quercetin glycosides. Similar results were found for two other species (Vicia faba and Solanum lycopersicum), but no such changes were detected in Zea mays. These findings reveal a much more dynamic UV-protection mechanism than previously recognized, raise important questions concerning the costs and benefits of UV-protection strategies in plants and have practical implications for employing UV to enhance crop vigor and quality in controlled environments.

Variable Phytotoxic Effects of Thymus vulgaris (Lamiaceae) Terpenes on Associated Species

Abstract Foliage was collected from flowering individuals of large thyme (Thymus pulegioides L.) at seven localities in southern Denmark. The leaf material was soaked in 96% ethanol and subsequently analyzed for terpenes using GC and GC/MS. Five chemotypes were detected: carvacrol, linalool, geraniol and thymol, all of which are known to appear in large thyme. In addition, individuals containing the monoterpene cis-sabinene hydrate as the dominant component of their essential oil were found. A sabinene hydrate chemotype has not previously been detected in large thyme, although it does occur in other thyme species.

Variable Chemistry and Herbivory of Ponderosa Pine Cones

The search for general patterns in the production and allocation of plant defense traits will be facilitated by characterizing multivariate suites of defense, as well as by studying additional plant taxa, particularly those with available genomic resources. Here, we investigated patterns of genetic variation in phytochemical defenses (phenylpropanoid glycosides, PPGs) in Mimulus guttatus (yellow monkeyflower). We grew plants derived from several natural populations, consisting of multiple full-sibling families within each population, in a common greenhouse environment. We found substantial variation in the constitutive multivariate PPG phenotype and in constitutive levels of individual phytochemicals within plants (among leaves of different ages), within populations (among full-sibling families), and among populations. Populations consisting of annual plants generally, but not always, had lower concentrations of phytochemicals than did populations of perennial plants. Populations differed in their plastic response to artificial herbivory, both in the overall multivariate PPG phenotype and in the individual phytochemicals. The relationship between phytochemistry and another defense trait, trichomes, differed among populations. Finally, we demonstrated that one of the PPGs, verbascoside, acts as a feeding stimulant rather than a feeding deterrent for a specialist herbivore of M. guttatus, the buckeye caterpillar (Junonia coenia Nymphalidae). Given its available genetic resources, numerous, easily accessible natural populations, and patterns of genetic variation highlighted in this research, M. guttatus provides an ideal model system in which to test ecological and evolutionary theories of plant-herbivore interactions.

Defence syndromes in lodgepole – whitebark pine ecosystems relate to degree of historical exposure to mountain pine beetles

Salicinoids are well-known defense compounds in salicaceous trees and careful screening at the population level is warranted to fully understand their diversity and function. European aspen, Populus tremula, is a foundation species in Eurasia and highly polymorphic in Sweden. We exhaustively surveyed 102 replicated genotypes from the Swedish Aspen collection (SwAsp) for foliar salicinoids using UHPLC-ESI-TOF/MS and identified nine novel compounds, bringing the total to 19 for this species. Salicinoid structure followed a modular architecture of a salicin skeleton with added side groups, alone or in combination. Two main moieties, 2′-cinnamoyl and 2′-acetyl, grouped the SwAsp population into four distinct chemotypes, and the relative allocation of salicinoids was remarkably constant between different environments, implying a highly channeled biosynthesis of these compounds. Slightly more than half of the SwAsp genotypes belonged to the cinnamoyl chemotype. A fraction synthesized the acetyl moiety alone (∼7%) or in combination with cinnamoyl (∼2%), and close to forty percent lacked either of the two characteristic moieties, and thus resemble P. tremuloides in their salicinoid profile. The two most abundant chemotypes were evenly distributed throughout Sweden, unlike geographical patterns reported for SwAsp phenology traits, plant defense genes, and herbivore community associations. Here we present the salicinoid characterization of the SwAsp collection as a resource for future studies of aspen chemical ecology, salicinoid biosynthesis, and genetics.