Spatial variation in the fatty acid composition of elaiosomes in an ant-dispersed plant: Differences within and between individuals and populations

Euphorbia characias is a common myrmecochorous plant of the western Mediterranean Basin whose seeds are dispersed by ants following fruit explosion. The variation in elaiosomes’ fatty acid composition of this species was studied at three hierarchical levels (sub-individual, individual and population) in four populations from the Iberian Peninsula. We found that differences in fruit location on the inflorescence do not seem to influence the fatty acid composition of elaiosomes, providing to each propagule an equal chance of being dispersed. However, significant differences in elaiosome fatty acid composition between individuals and populations were found for most of the compounds identified. The content of oleic acid, a key mediator in the ant–seed interaction, differed widely between populations, probably reflecting geographic variations in co-adaptation between plants and their dispersers. The finding that the fatty acid composition of E. characias elaiosomes is distinct from that of the seed itself, but very similar to that of elaiosomes from unrelated species, reinforces the idea of convergent evolution in the chemical composition of these structures.     

Resin acids of Pinus resinosa needles

The principal resin acids in the needles of Pinus resinosa are the labdane diterpenes, the new 8,13-epoxy-14-labden-19-oic acid (epimanoyl oxide acid), 8,13β-epoxy-14-labden-19-oic acid (manoyl oxide acid), 8(17),E-12,14-labdatrien-19-oic acid (communic acid) and 15-oxo-8(17)-labden-19-oic acid (imbricataloic acid). A survey of needles from representative populations of P. resinosa showed a limited variability in resin acid composition consistent with the uniformity of other traits. The composition of needle resin acids for putative P. nigra x resinosa hybrids strongly suggests the improbability of P. resinosa as the pollen parent.     

Geographic and genetic variation in the leaf surface resin components of Mimulus aurantiacus from southern California

Nearly 30% of the dry weight of leaves of the chaparral subshrub Mimulus aurantiacus comprise leaf surface resins. This resin provides some defense against the insect herbivore, Euphydryas chalcedona and may also protect plants from desiccation and UV light injury. The resin is composed of several components and the different components may contribute differentially to the resin's multiple protective roles. The quantities of each of seven resin components from field-grown plants, from six southern California populations of M. aurantiacus spanning a range of water availability and differing in attack by E. chalcedona, and clones from these plants grown in a common garden, were determined. Two predictions were tested: (1) E. chalcedona will attack plant populations with relatively low quantities of total resins and/or concentrations of the ortho dihydroxy resins, and (2) plant populations in drier environments will produce resin that is relatively richer in the methoxylated components than plant populations in more mesic environments. Although resin composition differed genetically among plant populations, the pattern of variation was not as predicted. Insect attack was not associated with lower levels of ortho dihydroxy compounds, and populations with higher proportions of methoxylated flavonoids were not found in the drier sites. The pattern of genetic variation among populations in resin composition therefore was not explained by the differences in chemical structure that were predicted to influence the role of the components as herbivore protectants or antidesiccants.     

Quantitative variation in leaf pocket resin composition in Hymenaea courbaril

Leaf pocket resin sesquiterpenes have been quantitatively analyzed in 22 geographic populations of the widespread Hymenaea courbaril. Highly stable quantitative resin composition in Meso-American populations of H. courbaril contrasts with greater variability in several South American populations. In some of the latter, bimodality in quantitative content of several correlated sesquiterpenes results in overall resin compositional relationships of two or three distinct types. Variance-weighted similarity coefficients between all populational pairs are single-linkage clustered to visualize chemical relationships.     

Metabolomics Reveals the Origins of Antimicrobial Plant Resins Collected by Honey Bees

The deposition of antimicrobial plant resins in honey bee, Apis mellifera, nests has important physiological benefits. Resin foraging is difficult to approach experimentally because resin composition is highly variable among and between plant families, the environmental and plant-genotypic effects on resins are unknown, and resin foragers are relatively rare and often forage in unobservable tree canopies. Subsequently, little is known about the botanical origins of resins in many regions or the benefits of specific resins to bees. We used metabolomic methods as a type of environmental forensics to track individual resin forager behavior through comparisons of global resin metabolite patterns. The resin from the corbiculae of a single bee was sufficient to identify that resin''s botanical source without prior knowledge of resin composition. Bees from our apiary discriminately foraged for resin from eastern cottonwood (Populus deltoides), and balsam poplar (P. balsamifera) among many available, even closely related, resinous plants. Cottonwood and balsam poplar resin composition did not show significant seasonal or regional changes in composition. Metabolomic analysis of resin from 6 North American Populus spp. and 5 hybrids revealed peaks characteristic to taxonomic nodes within Populus, while antimicrobial analysis revealed that resin from different species varied in inhibition of the bee bacterial pathogen, Paenibacillus larvae. We conclude that honey bees make discrete choices among many resinous plant species, even among closely related species. Bees also maintained fidelity to a single source during a foraging trip. Furthermore, the differential inhibition of P. larvae by Populus spp., thought to be preferential for resin collection in temperate regions, suggests that resins from closely related plant species many have different benefits to bees.     

Effectiveness of the fatty acid and sterol composition of seeds for the chemotaxonomy of Coffea subgenus Coffea

The chemotaxonomic relationships between Coffea (subgenus Coffea) species have been poorly studied to date and the compounds tested so far - chlorogenic acids, diterpenoids and purine alkaloids - did not enable the establishment of phylogenetic relationships analogous to those revealed by chloroplast and nuclear DNA studies. In the present study, the relationships between African Coffea species were assessed on the basis of their seed lipid composition. Fatty acids and sterols were determined in 59 genotypes belonging to 17 distinct Coffea species/origins. Principal Component Analysis of fatty acid and sterol data enabled easy identification of the few species for which one or several compounds could serve as a quantitative signature. Hierarchical Clustering classified the Coffea species in seven groups with both fatty acids and sterols. However, while groupings based on seed fatty acid composition showed remarkable ecological and geographical coherence, no phylogeographic explanation was found for the clusters retrieved from sterol data. When compared with previous phylogenetic studies, the groups deduced from seed fatty acid composition were remarkably congruent with the clades inferred from nuclear and plastid DNA sequences.     

EVOLUTIONARY IMPLICATIONS OF LEAF RESIN POCKET PATTERNS IN THE TROPICAL TREE HYMENAEA (CAESALPINIOIDEAE: LEGUMINOSAE)

ABSTRACT: Measurement of the size (volume), distribution, and density of resin pockets are compared in margin and center areas of leaves in 11 species (including six varieties of two widespread species) of Hymenaea. Resin composition and yield (mg/g leaf tissue) were analyzed by gas-liquid chromatography. Resin pocket patterns in certain species are highly distinctive; also a relationship seems to exist between patterns of closely related species, with variation having occurred in species or populations of widespread species which have radiated into different kinds of habitats. Thus these patterns may provide useful taxonomic characters, but we suggest that some of the patterns (and thus composition and yield of resin of different portions of the leaf) have evolved under selective pressures of herbivorous insects.     

Bacterial Inhibitors in Lake Water

The populations of six bacterial genera fell rapidly after their addition to sterile lake water but not after their addition to buffer. The decline in numbers of two species that were studied further, Klebsiella pneumoniae and Micrococcus flavus, occurred even when the buffer was added to sterile lake water. The inhibition of K. pneumoniae by substances in lake water varied with the season of the year, and the rate and extent of decline of both species were different in sterile samples of different lakes. The extent of reduction in the density of K. pneumoniae was independent of initial population size and was diminished by the addition of 10 μg of glucose per ml of lake water. The toxin was removed from lake water by dialysis and by a cation-exchange resin but not by an anion-exchange resin, and it was destroyed by heating. The inhibition of K. pneumoniae was not evident in lake water buffered at a pH value above 8.0. We suggest that toxins may be important in determining the composition of the bacterial community of lakes.     

Compositional variation of leaf pocket sesquiterpenes in Trachylobium verrucosum

Greenhouse-grown plants originating from Kenyan and Madagascan populations of Trachylobium verrucosum are qualitatively identical in leaf pocket resin sesquiterpene composition, but differ quantitatively.     

Diterpene resin acids from the needle oleoresin of pinus strobus

The resin acid components of P. strobus needles were isolated, and the major constituents identified as labdenoic diterpenes. In addition to anticopalic and strobic acids previously reported in the needles, 3-oxoanticopalic, 3β-acetoxyanticopalic, 3β-hydroxyanticopalic acids and the 8α-hydroxy derivative of anticopalic acid were found along with two new compounds. The structures of the two new compounds, a cycloanticopalic acid and an abcoanticopalic acid, were determined by NMR. The composition of the diterpene resin acids was obtained for several samples of P. strobus needles from provenance tests.     

Seasonal variation in the leaf resin components of Mimulus aurantiacus

The chaparral subshrub, Mimulus aurantiacus, produces leaf surface resins in excess of 30% of leaf dry weight. The resin provides some defense against the insect herbivore, Euphydryas chalcedona, and perhaps from desiccation and injury from UV light. The resin comprises six flavanones and an α-pyrone. The different components may differ in their ecological roles. Methoxylated components may be most effective as antidesiccants. Because plants face different risks at different times of the year, they may vary seasonally in resin composition. The quantities of each component from plants from five different populations but reared in a common garden were determined at 12 monthly intervals. Three hypotheses were tested: (1) plants would produce greater proportions of methoxylated components as drought stress increased during the season, (2) such increases would be greater for plants from the more xeric sites, and (3) the production of methoxylated components would occur at the expense of analogous unmethoxylated components. Resin quantity and composition differed significantly and consistently among populations, however, the seasonal increase in the proportional production of methoxylated components was slight relative to the consistent differences among populations. The production of all but one component was highly, positively correlated. The strong positive correlations among the concentrations of the five geranylflavanones suggests that their synthesis is limited by the synthesis of the geranylflavanone nucleus, and not by the attachment of different functional groups with presumably differing ecological roles.     

Restoration of species‐rich grasslands by transfer of local plant material and its impact on species diversity and genetic variation—Findings of a practical restoration project in southeastern Germany

Restoration of species‐rich grasslands is a key issue of conservation. The transfer of seed‐containing local plant material is a proven technique to restore species‐rich grassland, since it potentially allows to establish genetically variable and locally adapted populations. In our study, we tested how the transfer of local plant material affected the species diversity and composition of restored grasslands and the genetic variation of the typical grassland plant species Knautia arvensis and Plantago lanceolata.For our study, we selected fifteen study sites in southeastern Germany. We analyzed species diversity and composition and used molecular markers to investigate genetic variation within and among populations of the study species from grasslands that served as source sites for restoration and grasslands, which were restored by transfer of green hay and threshed local plant material.The results revealed no significant differences in species diversity and composition between grasslands at source and restoration sites. Levels of genetic variation within populations of the study species Knautia arvensis and Plantago lanceolata were comparable at source and restoration sites and genetic variation among populations at source and their corresponding restoration sites were only marginal different.Our study suggests that the transfer of local plant material is a restoration approach highly suited to preserve the composition of species‐rich grasslands and the natural genetic pattern of typical grassland plant species.     

Seed protein and amino acid composition of WildVigna radiata var.sublobata (Fabaceae) and Two Cultigens,V. mungo andV. radiata

WildVigna radiata var.sublobata populations, inhabiting the mountains of India, and two cultigens,V. mungo andV. radiata, were examined for seed-protein content and amino acid composition. The protein content in the populations varied from 15.2 to 21%. Lysine, valine, isoleucine, leucine, phenylalanine, and tyrosine contents were invariably higher in wild populations as compared with the FAO reference pattern. The variation encountered in wild populations is largely genetic in origin. Total essential amino acids in the wild populations varied from 38.3 to 42.2; in the cultigens, from 29.2 to 37.5 (g/100 g protein). There was marked variation in the amino acid composition of the populations for the two different ecozones studied, suggesting a broad genetic base.     

Diversity in the composition of monoterpenoids of Origanum microphyllum (Labiatae)

The variability in the composition of the volatile compounds of Origanum microphyllum, a species endemic to Crete, was examined. Headspace analysis was carried out on leaves from five natural populations and subsequently from the same plants from uniform cultivation. Plants were rich in cis-sabinene-hydrate (3–68%), sabinene (3–45%) and trans-sabinene-hydrate (0.5–34%). Four chemical profiles were distinguished, the extremes being either rich in sabinene and trans-sabinene-hydrate, or rich in cis-sabinene-hydrate. Furthermore, different chemical profiles were present in all populations to varying proportions, which explains the high variation observed within each population and the apparent small variation between them. The pattern of distribution of the different profiles among populations suggested a possible closer relation between neighbouring populations. There is a strong evidence of genetic control in the composition of the volatiles of O. microphyllum since it remained nearly unchanged in cultivation when the same plants were examined a year later.     

Population study of Astarte sulcata, da Costa, 1778, (Mollusca,Bivalvia) from two Norwegian fjords based on the fatty acid composition of the adductor muscle

Multivariate analyses of fatty acid composition of Astarte sulcata, collected in Northwest Norway in October 2005, showed significant differences between geographically close populations. This biochemical heterogeneity may have been caused by high genetic drift due to the direct development of the species. The results indicate that deep basins may provide an alternative bathymetric guide for spreading of offspring rather than being carried on currents crossing such basins. Thus, the combination of biology and topography might have led to the observed pattern that populations from opposite sides of a fjord are biochemically more distant than populations along the same side of a fjord/basin.     

Bioactive constituents in Prunus africana: Geographical variation throughout Africa and associations with environmental and genetic parameters

Prunus africana – an evergreen tree found in Afromontane forests – is used in traditional medicine to cure benign prostate hyperplasia. Different bioactive constituents derived from bark extracts from 20 tree populations sampled throughout the species’ natural range in Africa were studied by means of GC–MSD. The average concentration [mg/kg w/w] in increasing order was: lauric acid (18), myristic acid (22), n-docosanol (25), ferulic acid (49), β-sitostenone (198), β-sitosterol (490), and ursolic acid (743). The concentrations of many bark constituents were significantly correlated and concentration of n-docosanol was highly significantly correlated with all other analytes. Estimates of variance components revealed the highest variation among populations for ursolic acid (66%) and the lowest for β-sitosterol (20%). In general, environmental parameters recorded (temperature, precipitation, altitude) for the samples sites were not correlated with the concentration of most constituents; however, concentration of ferulic acid was significantly correlated with annual precipitation. Because the concentration of compounds in bark extracts may be affected by tree size, the diameter of sampled plants at 1.3 m tree height (as proxy of age) was recorded. The only relationship with tree diameter was a negative correlation with ursolic acid. Under the assumption that genetically less variable populations have less variable concentrations of bark compounds, correlations between variation parameters of the concentration and the respective genetic composition based on chloroplast and nuclear DNA markers were assessed. Only variation of β-sitosterol concentration was significantly correlated with haplotypic diversity. The fixation index (F_IS) was positively correlated with the variation in concentration of ferulic acid. Principal Components Analysis (PCA) indicated a weak geographic pattern. Mantel tests, however, revealed associations between the geographic patterns of bioactive constituents and the phylogenetic relationship among the populations sampled. This suggests an independent evolution of bark metabolism within different phylogeographical lineages, and the molecular phylogeographic pattern is partly reflected in the variation in concentration of bark constituents. The results have important implications for the design of strategies for the sustainable use and conservation of this important African tree species.     

Multilocus Sequence Analysis of Xanthomonads Causing Bacterial Spot of Tomato and Pepper Plants Reveals Strains Generated by Recombination among Species and Recent Global Spread of Xanthomonas gardneri

Four Xanthomonas species are known to cause bacterial spot of tomato and pepper, but the global distribution and genetic diversity of these species are not well understood. A collection of bacterial spot-causing strains from the Americas, Africa, Southeast Asia, and New Zealand were characterized for genetic diversity and phylogenetic relationships using multilocus sequence analysis of six housekeeping genes. By examining strains from different continents, we found unexpected phylogeographic patterns, including the global distribution of a single multilocus haplotype of X. gardneri, possible regional differentiation in X. vesicatoria, and high species diversity on tomato in Africa. In addition, we found evidence of multiple recombination events between X. euvesicatoria and X. perforans. Our results indicate that there have been shifts in the species composition of bacterial spot pathogen populations due to the global spread of dominant genotypes and that recombination between species has generated genetic diversity in these populations.     

Geographic variation in the essential oils and morphology of natural populations of Melaleuca alternifolia (Myrtaceae)

In recent decades, Melaleuca alternifolia has been grown in plantations for the commercial production of tea tree oil extracted from harvested leaf and stem material by steam distillation. Plantations are grown from seedlings raised from seeds collected from wild populations of this endemic Australian species. Considerable variation in morphology and leaf oil composition and yield has been observed and studies have demonstrated genetic and phenotypic heterozygosity between populations.Here we examine the variation in leaf oil chemical composition (chemotypes) between geographically defined locations of wild populations of M. alternifolia and investigate the relationships between tree size, chemotype and geographic location.Forty separate populations of M. alternifolia distributed amongst three river catchments (two in a warm moist coastal region and one in cool drier highlands) were studied. Total variation in tree size was significantly greater within individual sites than between them. However, the highland catchment populations exhibited significantly smaller mean tree size and a significantly different chemotype profile than the lowland populations. Contrary to the observation of lower genetic diversity, the highland catchment populations had greater chemotypic diversity. Furthermore, highly significant differences in population chemotypes were demonstrated between catchments.The possibilities that these differences could be ascribed to either genetic divergence or to environmental differences are discussed.     

The response of leaf resin to artificial herbivory in Eriodictyon californicum

Herbivore damage induces the production of defensive chemicals in many plant species. However, defensive chemicals sometimes have functions other than protection from herbivores, and these chemicals may respond to hervibory differentialy than those which are primarily defensive. A well-studied group of leaf constituents with multiple functions is the phenolic leaf resins, which protect leaves from herbivores, UV radiation, and possibly excess water loss. The effects of herbivory on phenolic leaf resins were investigated in the chapparral shrub Eriodictyon californicum by artificially damaging leaves during the growing season and subsequently measuring resin content and composition. We found that (i) resin content declined in leaves damaged by artificial herbivory; (ii) resin declined (at the P < 0.1 level) in undamaged leaves present on the same plant as those heavily damaged; and (iii) resin composition, as measured by the ratio of the major components, was unaffected by artificial herbivory.     

Plant Species Composition Alters the Sign and Strength of an Emergent Multi-Predator Effect by Modifying Predator Foraging Behaviour

The prediction of pest-control functioning by multi-predator communities is hindered by the non-additive nature of species functioning. Such non-additivity, commonly termed an emergent multi-predator effect, is known to be affected by elements of the ecological context, such as the structure and composition of vegetation, in addition to the traits of the predators themselves. Here we report mesocosm experiments designed to test the influence of plant density and species composition (wheat monoculture or wheat and faba bean polyculture) on the emergence of multi-predator effects between Adalia bipunctata and Chrysoperla carnea, in their suppression of populations of the aphid Metopolophium dirhodum. The mesocosm experiments were followed by a series of behavioural observations designed to identify how interactions among predators are modified by plant species composition and whether these effects are consistent with the observed influence of plant species composition on aphid population suppression. Although plant density was shown to have no influence on the multi-predator effect on aphid population growth, plant composition had a marked effect. In wheat monoculture, Adalia and Chrysoperla mixed treatments caused greater suppression of M. dirhodum populations than expected. However this positive emergent effect was reversed to a negative multi-predator effect in wheat and faba bean polyculture. The behavioural observations revealed that although dominant individuals did not respond to the presence of faba bean plants, the behaviour of sub-dominants was affected markedly, consistent with their foraging for extra-floral nectar produced by the faba bean. This interaction between plant composition and predator community composition on the foraging behaviour of sub-dominants is thought to underlie the observed effect of plant composition on the multi-predator effect. Thus, the emergence of multi-predator effects is shown to be strongly influenced by plant species composition, mediated, in this case, by the provision of extra-floral nectar by one of the plant species.