Temporal patterns of reproduction and outcrossing in weedy populations of Echium plantagineum

Single and multilocus estimates of outcrossing rates were made in three populations of Echium plantagineum. Despite spatial separation, variations in population size (though not density) and reproductive output, no statistically significant difference was detected in outcrossing rates between the populations. Similarly, only slight differences in outcrossing rates were detected within populations when estimates were based on seed collected from flowers open at different times in the flowering season. The earliest flowers tended to have a lower estimated rate of outcrossing. In all cases, multilocus outcrossing rates were high, ranging from 0.81 to 1.05.
In all three populations flower production extended over a period of more than 2 months but the majority of seed was produced by flowers that opened during the first third of the (lowering season. This was largely caused by a high rate of flower production during the early part of the season and not changes in the number of seeds set per flower. The average number of seeds produced per flower varied both between individuals within populations, and between the different populations, but neither of these differences were significant.
Controlled pollination of flowers with self or outcross pollen, applied either singly or together, failed to detect any differences in the likelihood that either type of pollen would give rise to fertile seeds.     

Honeybees and the nectar of Echium plantagineum L. in southeastern Australia

An account is given of the flower of Echium plantagineum in south-eastern Australia, including stages and timing of flowering, behaviour of raindrops in the flower and aspects of floral microclimate. The concentration of nectar solutes varied with time and site, with means varying from 2 to 62% (as g sucrose/100 g solution). There was a significant negative correlation between nectar solute concentration and ambient relative humidity: the drier the air, the more concentrated the nectar. Rates of nectar secretion per flower varied with the bagging method, with long-term bagging reducing net secretion rates, possibly because of re-absorption. Rates varied with time, day and site, with a temporal pattern of change suggesting a link between rates of photosynthesis and secretion. Maximum nectar secretion rates in short-term bagging experiments were ca. 300 μg sugar/flower/hr (equivalent to > 2 mglflower/24 hr). Secretion rate was correlated with flower density. As flower density increased, secretion rate per flower decreased; rate of sugar production per unit area increased relatively more slowly than flower density. E. plantagineum could produce > 500 mg sugar/m²/day. Honeybees foraged on E. plantagineum only at ambient air temperatures above ca. 17°C unless irradiance exceeded ca. 750 W m^-2. Foragers collected nectar or pollen alone, or both, with the type of visit significantly correlated with nectar solute concentration. Below 35% (as g sucrose/100 g solution) most bees took pollen only; above 40%, most took nectar. Mean standing crop of nectar was generally < 100 μg/flower when most bees were taking nectar, but could exceed 1000 μg/flower when bees were absent or foraging mainly for pollen. Honeybees did not always remove all nectar from flowers they probed. Reabsorption of residual nectar may augment the following day's secretion.     

Ecological studies on Thrips imaginis Bagnall (Thysanoptera) in flowers of Echium plantagineum L. in Australia

Aspects of the ecology of Thrips imaginis Bagnall in flowers of Echium plantagineum L. are described and subjected to experimental analysis. Thrips eggs were mostly laid in plant parts that were not lost when the short-lived flowers abscissed. The abundance of adults and larvae in flowers from the bud stage through to abscission was determined. Larvae usually required more than one flower to complete development and so had to migrate between flowers to survive. Larvae generally remained between the bases of the stamen filaments when in direct sunlight, but moved along the filaments to the anthers for rapid pollen feeding during low light intensity, especially at night. There was little spatial and temporal overlap between thrips larvae and honeybees in the flowers. Ants can cause much damage to the flowers and can feed on thrips. Pollen feeding of T. imaginis is described. The species of pollen grain affects feeding, and this may influence breeding success. Low u.v.-reflecting white, blue and yellow water traps caught more T. imaginis that green, red, black and high u.v.-reflecting white. These results agree well with the numbers of adults in several native and non-native flowers of various colours. Adult female thrips colour variation is correlated with for ewing length, and hence reflects factors acting on a pre-adult stage.     

Fire Promotes Pollinator Visitation: Implications for Ameliorating Declines of Pollination Services

Pollinators serve critical roles for the functioning of terrestrial ecosystems, and have an estimated annual value of over $150 billion for global agriculture. Mounting evidence from agricultural systems reveals that pollinators are declining in many regions of the world, and with a lack of information on whether pollinator communities in natural systems are following similar trends, identifying factors which support pollinator visitation and services are important for ameliorating the effects of the current global pollinator crisis. We investigated how fire affects resource structure and how that variation influences floral pollinator communities by comparing burn versus control treatments in a southeastern USA old-field system. We hypothesized and found a positive relationship between fire and plant density of a native forb, Verbesina alternifolia, as well as a significant difference in floral visitation of V. alternifolia between burn and control treatments. V. alternifolia density was 44% greater and floral visitation was 54% greater in burned treatments relative to control sites. When the density of V. alternifolia was experimentally reduced in the burn sites to equivalent densities observed in control sites, floral visitation in burned sites declined to rates found in control sites. Our results indicate that plant density is a proximal mechanism by which an imposed fire regime can indirectly impact floral visitation, suggesting its usefulness as a tool for management of pollination services. Although concerns surround the negative impacts of management, indirect positive effects may provide an important direction to explore for managing future ecological and conservation issues. Studies examining the interaction among resource concentration, plant apparency, and how fire affects the evolutionary consequences of altered patterns of floral visitation are overdue.     

Effect of patch size and plant density of Paterson"s curse (Echium plantagineum) on the oviposition of a specialist weevil, Mogulones larvatus

This study examines the oviposition response of a specialist weevil (Mogulones larvatus) to patches of its host, the noxious weed Paterson"s curse/salvation Jane (Echium plantagineum). We simultaneously examined the effect of patch size and plant density (and their interaction), on the recorded oviposition patterns. Our results show that oviposition first occurred on the largest patches with the highest number of plants. However, there was no significant effect of patch size or number of plants per patch at the end of the experiment. At this time the level of attack per plant was negatively correlated with plant density. This negative effect of density on the level of oviposition was not mediated by a reduction in plant size at higher densities. The pattern observed may indicate a risk-spreading strategy by females. Received: 15 July 1999 / Accepted: 14 April 2000     

Solid-phase extraction and HPLC-MS profiling of pyrrolizidine alkaloids and their N-oxides: a case study of Echium plantagineum

Pyrrolizidine alkaloids and their N-oxides can be extracted from the dried methanolic extracts of plant material using dilute aqueous acid. The subsequent integration of solid-phase extraction (with a strong cation exchanger) of the alkaloids and N-oxides from the aqueous acid solution, together with analysis using HPLC-ESI/MS, provides a method for the simultaneous profiling of the pyrrolizidine alkaloids and their N-oxides in plant samples and the collection of useful structural data as an aid in their identification. The N-oxide character of the analytes may be confirmed by treating analytical samples with a redox resin and observing the formation of the corresponding parent pyrrolizidine alkaloids. The present case study of Echium plantagineum highlighted a higher ratio of N-oxides to the parent tertiary bases than has been previously reported. Furthermore, a higher proportion of acetylated pyrrolizidine-N-oxides was observed in the flower heads relative to the leaves. Six pyrrolizidine alkaloids or pyrrolizidine-N-oxides, not previously reported from E. plantagineum, were tentatively identified on the basis of MS and biogenetic considerations. Three of these, 3'-O-acetylintermedine/lycopsamine, leptanthine-N-oxide and 9-O-angelylretronecine-N-oxide, have been reported elsewhere, whilst three others, 3'-O-acetylechiumine-N-oxide, echimiplatine-N-oxide and echiuplatine-N-oxide, appear unreported from any other source.     

Metabolic profiling in Echium plantagineum: presence of bioactive pyrrolizidine alkaloids and napthoquinones from accessions across southeastern Australia

Geographically distinct populations of Paterson’s curse (Echium plantagineum L., Boragineacea), found near roadsides across New South Wales and Victoria, Australia were surveyed along 3 distinct longitudinal transects in spring of 2011 for presence of pyrrolizidine alkaloids and naphthoquinones in sampled plants. Composite samples of shoots and roots were collected from each of 45 sites; shoot extracts were subjected to solid phase extraction and LC-ESI/MS for determination of pyrrolizidine alkaloids (PAs) and related N-oxides (PANOs), while root periderm extracts were analysed for naphthoquinone content spectrophotometrically and by LC-ESI/MS. Metabolic profiling of 12 possible PAs and PANOs showed their consistent appearance in all shoot extracts, with lepthamine N-oxide, echimidine-N oxide and echumine N-oxide predominant. The three major PANOs were significantly higher in northern sampling locations than those further south. Root extracts contained shikonin and several related naphthoquinones, as well as two of the major PANOs found in the leaves. Naphthoquinones were highest in the northwest corner of the sampled region. The patterns of abundance of secondary metabolites in E. plantagienum suggest that climate change might result in greater production of defensive compounds by E. plantagineum, making this weed increasingly toxic to livestock.     

Interactive effects of elevated CO2 and temperature on the leaf-miner Dialectica scalariella Zeller (Lepidoptera: Gracillariidae) in Paterson's Curse, Echium plantagineum (Boraginaceae)

Doubling of the current atmospheric CO₂ concentration, and an increase in global mean annual temperatures of 1.5–6 °C, have been predicted to occur by the end of this century. Whilst the separate effects of CO₂ and temperature on plant–insect interactions have been examined in a number of studies, few have investigated their combined impact. We carried out a factorial experiment to explore the effect of a doubling of CO₂ concentration and a 3 °C temperature increase on the development of a complete generation of the leaf‐miner, Dialectica scalariella, in the host plant Paterson's Curse, Echium plantagineum. Elevated CO₂ increased biomass, reduced leaf N and increased C:N ratios in the host plants. Leaf thickness also increased under elevated CO₂, but only in the high‐temperature treatment. Female D. scalariella did not discriminate between plants grown at the different CO₂ levels when ovipositing, despite the reduction in foliage quality under elevated CO₂. Overall, the negative response of D. scalariella to elevated CO₂ was greater than for many species of free‐living insects, presumably because of the limited mobility imposed by the leaf‐mining habit. Development was accelerated at the high temperature and slowed under elevated CO₂. The net result was a reduction in development time of ～14 days in the elevated CO₂/high temperature treatment, compared to the ambient CO₂/low temperature treatment. Larval survivorship and adult moth weight were both affected by a significant interaction between CO₂ and temperature. At the low temperature, CO₂ had little effect on survivorship, but at the high temperature, survivorship was significantly reduced under elevated CO₂. Similarly, elevated CO₂ had a stronger negative effect on adult moth weight when combined with the high‐temperature treatment. A possible explanation for these results is that the high temperature accelerated insect development to such an extent that the larvae did not have sufficient feeding time to compensate for the poorer quality of the foliage. The frequency with which interactions between CO₂ and temperature affected both plant and insect performance in this study highlights the need for caution when predicting the effects of future climate change on plant–insect interactions from single‐factor experiments.     

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Pyrrolizidine alkaloids from Echium glomeratum (Boraginaceae)

The methanolic extract of the whole plant of Echium glomeratum Poir. (Boraginaceae) has afforded five pyrrolizidine alkaloids, three that were (7S, 8R)-petranine (1), (7S, 8S)-petranine (2), and (7R, 8R)-petranine (3a) or (7R, 8S)-petranine (3b), comprising a tricyclic pyrrolizidine alkaloids subclass; and two that were known but to the species: 7-angeloylretronecine (4) and 9-angeloylretronecine (5). All compounds were tested against a human tumor panel for cytotoxicity; no activity was observed (EC(50) values>20mug/ml).     

Rapid Development of Adaptive,Climate-Driven Clinal Variation in Seed Mass in the Invasive Annual Forb Echium plantagineum L.

We examined adaptive clinal variation in seed mass among populations of an invasive annual species, Echium plantagineum, in response to climatic selection. We collected seeds from 34 field populations from a 1,000 km long temperature and rainfall gradient across the species'' introduced range in south-eastern Australia. Seeds were germinated, grown to reproductive age under common glasshouse conditions, and progeny seeds were harvested and weighed. Analyses showed that seed mass was significantly related to climatic factors, with populations sourced from hotter, more arid sites producing heavier seeds than populations from cooler and wetter sites. Seed mass was not related to edaphic factors. We also found that seed mass was significantly related to both longitude and latitude with each degree of longitude west and latitude north increasing seed mass by around 2.5% and 4% on average. There was little evidence that within-population or between-population variation in seed mass varied in a systematic manner across the study region. Our findings provide compelling evidence for development of a strong cline in seed mass across the geographic range of a widespread and highly successful invasive annual forb. Since large seed mass is known to provide reproductive assurance for plants in arid environments, our results support the hypothesis that the fitness and range potential of invasive species can increase as a result of genetic divergence of populations along broad climatic gradients. In E. plantagineum population-level differentiation has occurred in 150 years or less, indicating that the adaptation process can be rapid.     

特早花甘蓝型油菜的开花特征及特早花候选基因鉴定

开花是植物从营养生长进入生殖生长的重要阶段.油菜早花早熟,可有效解决油菜与其他夏季作物的茬口矛盾.挖掘不同的早花油菜资源,研究油菜早花性状形成的分子机理,可促进利用分子技术快速选育早熟油菜的育种进程.本研究以1个新发现的稳定遗传的特早花油菜迎春一号为研究对象,在覆盖全年9个月的时间中设计了15个不同的播种期,调查其开花...     

Minimal Effects of an Invasive Flowering Shrub on the Pollinator Community of Native Forbs

Biological invasions can strongly influence species interactions such as pollination. Most of the documented effects of exotic plant species on plant-pollinator interactions have been observational studies using single pairs of native and exotic plants, and have focused on dominant exotic plant species. We know little about how exotic plants alter interactions in entire communities of plants and pollinators, especially at low to medium invader densities. In this study, we began to address these gaps by experimentally removing the flowers of a showy invasive shrub, Rosa multiflora, and evaluating its effects on the frequency, richness, and composition of bee visitors to co-flowering native plants. We found that while R. multiflora increased plot-level richness of bee visitors to co-flowering native plant species at some sites, its presence had no significant effects on bee visitation rate, visitor richness, bee community composition, or abundance overall. In addition, we found that compared to co-flowering natives, R. multiflora was a generalist plant that primarily received visits from generalist bee species shared with native plant species. Our results suggest that exotic plants such as R. multiflora may facilitate native plant pollination in a community context by attracting a more diverse assemblage of pollinators, but have limited and idiosyncratic effects on the resident plant-pollinator network in general.     

Selection on pollen donors by Echium vulgare (Boraginaceae)

Fewer than 25% of the ovules of Echium vulgare in the field develop into viable seeds, even with no pollen limitation. The loss of ovules could enhance the fitness of the maternal parent, if less fit embryos are selectively aborted. Two pollination experiments were performed to examine the selectivity of maternal parents on self-pollen and different cross-pollen sources. Pollinated with one pollen genotype per flower, self-pollen was, on average, as successful in siring seeds as cross-pollen. However, the relative success of self-pollen compared to outcross-pollen differed significantly among the maternal parents. These results suggest that, under certain conditions, selfing can produce a greater number of seeds than cross-pollination. Pollen donors differed significantly in outcrossing success. The plants that were more successful in selfing were also more successful pollen donors in outcross-pollinations. No significant interaction between maternal parent and paternal genotype was found. Pollinations with a pollen mixture produced selfed and outcrossed seeds in the same ratios as the single-donor experiment. Overall, only slight differences were found between the single- and mixed-donor experiments. Pollen tube growth did not show a significant correlation with the success of the parental genotypes in the mixed-donor experiment, indicating that pollen tube growth is not the determining factor controlling the paternity of the seeds. These results are discussed with reference to possible mediating mechanisms.     

Host specificity of the two lace bugs,Dictyla echii andDictyla nassata [Hem.: Tingidae] potential biological control agents for paterson's curse (Echium plantagineum)

Two species of lace bugs,Dictyla echii (Schrank) andDictyla nassata (Puton), were tested for host specificity as potential biological control agents for Paterson's curse,Echium plantagineum L. A range of test plants from the family Boraginacea, from related families in the order Laminales and from species of economic importance in Australia which have had inadequate exposure in their countries of origin, were tested under both choice and non-choice conditions. These bugs proved to be oligophagous within the Boraginaceae and attacked a number of Australian native species. Because of this,D. echii andD. nassata are not considered sufficiently specific to release from quarantine and tests were abandoned before completion of the test plant list.

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Résumé La spécificité parasitaire deDictyla echii (Schrank) etD. nassata (Puton) a été étudiée en tant qu'agents de lutte biologique potentiels contreEchium plantagineum L. Dans les conditions de choix et d'absence de choix, une série de plantes ont été testées provenant de la famille des Boraginacées, des familles voisines de l'ordre des Laminales et d'espèces d'importance économique en Australie qui n'avaient pas fait l'objet de tests suffisants dans leur pays d'origine. Ces punaises se révèlent oligophages en ce qui concerne les Boraginacées et s'attaquent à de nombreuses espèces indigènes d'Australie. Pour cette raison,D. echii etD. nassata ne sont pas considérées comme suffisamment spécifiques pour les relacher à partir de la quarantaine et les tests ont été abandonnés avant d'épuiser la totalité des plantes prévues sur la liste.

     

Pollinator attraction of the wasp-flower Scrophularia umbrosa (Scrophulariaceae)

Certain species of Scrophularia (Scrophulariaceae), such as S. nodosa and S. umbrosa, are mainly pollinated by social wasps and are consequently described as wasp-flowers. Because plants attract their pollinators with the help of various floral cues, such as floral odour and/or optical cues, we have investigated the role of olfactory and visual floral signals responsible for wasp attraction in S. umbrosa. Using a combination of chemical (GC, GC-MS) and electrophysiological analyses (GC-EAD), we identified ten compounds in the complex floral odour bouquet that are detectable by the wasps' antennae. As in the wasp-flower Epipactis helleborine, we found so-called 'green leaf volatiles' (GLVs) in the floral odour; these GLVs are highly attractive to the wasps. GLVs, mostly six-carbon aldehydes, alcohols and acetates, and other volatile organic compounds (VOCs), are emitted by many plants infested with herbivores, e.g. caterpillars. In contrast to other investigated wasp-flowers, behavioural experiments have demonstrated that, in addition to the floral odour of S. umbrosa, visual cues are involved in pollinator attraction.     

Integrated Analysis of COX-2 and iNOS Derived Inflammatory Mediators in LPS-Stimulated RAW Macrophages Pre-Exposed to Echium plantagineum L. Bee Pollen Extract

Oxidative stress and inflammation play important roles in disease development. This study intended to evaluate the anti-inflammatory and antioxidant potential of Echium plantagineum L. bee pollen to support its claimed health beneficial effects. The hydromethanol extract efficiently scavenged nitric oxide (^•NO) although against superoxide (O₂ ^•−) it behaved as antioxidant at lower concentrations and as pro-oxidant at higher concentrations. The anti-inflammatory potential was evaluated in LPS-stimulated macrophages. The levels of ^•NO and L-citrulline decreased for all extract concentrations tested, while the levels of prostaglandins, their metabolites and isoprostanes, evaluated by UPLC-MS, decreased with low extract concentrations. So, E. plantagineum bee pollen extract can exert anti-inflammatory activity by reducing ^•NO and prostaglandins. The extract is able to scavenge the reactive species ^•NO and O₂ ^•− and reduce markers of oxidative stress in cells at low concentrations.