Comparing two methods for estimating floral resource availability for insect pollinators in semi-natural habitats

Pollinator and flowering plant interactions play a critical role in maintaining most terrestrial ecosystems, including agroecosystems. Although estimates of floral resource availability are essential to understand plant–pollinator relationships, no generally accepted methodology exists to date. We compared two methods for sampling floral resources in a single meadow. About every three days, we recorded species lists of insect-pollinated plants with abundance categories assigned to each species (hereafter referred to as scanning) and we counted the flowering shoots in 36 2 × 2 m quadrats (hereafter quadrat sampling). These methods were compared with respect to (i) the number of species detected, (ii) estimated floral resource abundance, and (iii) temporal changes in flowering. With scanning, we found more potential nectar-plant species and species were found earlier than with quadrat sampling. With the latter, abundant species were found with higher probability than the scarce. Flower abundances were correlated between the two methods. We predicted that a cover of 6.3 ± 3.6% should be used for an appropriate estimate of flower abundance in our study site, although the optimal cover probably varies across different habitats. Furthermore, flower abundance changed 6% per day compared to the flowering peak. Overall, scanning seems to be more appropriate for detecting presence and the timing of species, while quadrats may provide higher resolution for abundance estimates. Increased sampling coverage and frequency may enhance research accuracy and using scanning and quadrat sampling simultaneously may help to optimize research effort. We encourage further development of sampling protocols.     

Powdery mildew suppresses herbivore‐induced plant volatiles and interferes with parasitoid attraction in Brassica rapa

The co‐occurrence of different antagonists on a plant can greatly affect infochemicals with ecological consequences for higher trophic levels. Here we investigated how the presence of a plant pathogen, the powdery mildew Erysiphe cruciferarum, on Brassica rapa affects (1) plant volatiles emitted in response to damage by a specialist herbivore, Pieris brassicae; (2) the attraction of the parasitic wasp Cotesia glomerata and (3) the performance of P. brassicae and C. glomerata. Plant volatiles were significantly induced by herbivory in both healthy and mildew‐infected plants, but were quantitatively 41% lower for mildew‐infected plants compared to healthy plants. Parasitoids strongly preferred Pieris‐infested plants to dually‐infested (Pieris + mildew) plants, and preferred dually infested plants over only mildew‐infected plants. The performance of P. brassicae was unaffected by powdery mildew, but C. glomerata cocoon mass was reduced when parasitized caterpillars developed on mildew‐infected plants. Thus, avoidance of mildew‐infested plants may be adaptive for C. glomerata parasitoids, whereas P. brassicae caterpillars may suffer less parasitism on mildew‐infected plants in nature. From a pest management standpoint, the concurrent presence of multiple plant antagonists can affect the efficiency of specific natural enemies, which may in turn have a negative impact on the regulation of pest populations.     

Organic farming affects the potential of a granivorous carabid beetle to control arable weeds at local and landscape scales

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Vriesea friburgensis: A natural trap or a nurse plant in coastal sand dunes?

Positive interactions between plants play a fundamental role in environments with extreme conditions, such as coastal sand dunes, where the establishment of many species is limited by high temperature, and low availability of water and nutrients in the soil. The ability to store water and enrich the soil with nutrients characterizes bromeliads as potential nurse plants for other species. This study aimed to analyze the potential of the bromeliad Vriesea friburgensis to act as a nurse plant, and to compare this interaction in coastal dunes in herbaceous versus scrub vegetation. The study was performed on Santa Catarina Island in Brazil. Juveniles of other species associated with V. friburgensis were collected within and under bromeliad tanks and on adjacent plots beside each bromeliad. The abundance, species richness and height of juveniles were recorded. We found that abundance and richness of Vf‐associated juveniles were lower than those Vf‐not associated, in herbaceous vegetation (negative interaction). However, the height of some shrubs species, like Eupatorium casarettoi and Tibouchina urvilleana, was greater when Vf‐associated (positive interaction). In scrub vegetation, the abundance and richness of juveniles were not significantly affected by V. friburgensis presence (neutral interaction). However, the height of some shrubs and trees species, like Clusia criuva, Eugenia catharinae, Myrsine parvifolia and Ocotea pulchella, was greater when Vf‐associated. Species composition associated with V. friburgensis differed from the assemblage in adjacent plots, indicating that some species interact more with nurse plants, whereas others fail to develop when associated with this bromeliad; the difference between groups in species composition was less evident in scrub vegetation areas. Clusia criuva was considered an indicator species for Vf‐associated juveniles in both vegetation types. Despite the fact that these tank bromeliads do not function as nurse plants for some species, there are others that seem to be favoured by this interaction.     

Emergence and accumulation of novel pathogens suppress an invasive species

Emerging pathogens are a growing threat to human health, agriculture and the diversity of ecological communities but may also help control problematic species. Here we investigated the diversity, distribution and consequences of emerging fungal pathogens infecting an aggressive invasive grass that is rapidly colonising habitats throughout the eastern USA. We document the recent emergence and accumulation over time of diverse pathogens that are members of a single fungal genus and represent multiple, recently described or undescribed species. We also show that experimental suppression of these pathogens increased host performance in the field, demonstrating the negative effects of emerging pathogens on invasive plants. Our results suggest that invasive species can facilitate pathogen emergence and amplification, raising concerns about movement of pathogens among agricultural, horticultural, and wild grasses. However, one possible benefit of pathogen accumulation is suppression of aggressive invaders over the long term, potentially abating their negative impacts on native communities.     

Metabolic engineering for the production of plant isoquinoline alkaloids

Several plant isoquinoline alkaloids (PIAs) possess powerful pharmaceutical and biotechnological properties. Thus, PIA metabolism and its fascinating molecules, including morphine, colchicine and galanthamine, have attracted the attention of both the industry and researchers involved in plant science, biochemistry, chemical bioengineering and medicine. Currently, access and availability of high‐value PIAs [commercialized (e.g. galanthamine) or not (e.g. narciclasine)] is limited by low concentration in nature, lack of cultivation or geographic access, seasonal production and risk of overharvesting wild plant species. Nevertheless, most commercial PIAs are still extracted from plant sources. Efforts to improve the production of PIA have largely been impaired by the lack of knowledge on PIA metabolism. With the development and integration of next‐generation sequencing technologies, high‐throughput proteomics and metabolomics analyses and bioinformatics, systems biology was used to unravel metabolic pathways allowing the use of metabolic engineering and synthetic biology approaches to increase production of valuable PIAs. Metabolic engineering provides opportunity to overcome issues related to restricted availability, diversification and productivity of plant alkaloids. Engineered plant, plant cells and microbial cell cultures can act as biofactories by offering their metabolic machinery for the purpose of optimizing the conditions and increasing the productivity of a specific alkaloid. In this article, is presented an update on the production of PIA in engineered plant, plant cell cultures and heterologous micro‐organisms.     

Precocious flowering of juvenile citrus induced by a viral vector based on Citrus leaf blotch virus: a new tool for genetics and breeding

The long juvenile period of citrus trees (often more than 6 years) has hindered genetic improvement by traditional breeding methods and genetic studies. In this work, we have developed a biotechnology tool to promote transition from the vegetative to the reproductive phase in juvenile citrus plants by expression of the Arabidopsis thaliana or citrus FLOWERING LOCUS T (FT) genes using a Citrus leaf blotch virus‐based vector (clbvINpr‐AtFT and clbvINpr‐CiFT, respectively). Citrus plants of different genotypes graft inoculated with either of these vectors started flowering within 4–6 months, with no alteration of the plant architecture, leaf, flower or fruit morphology in comparison with noninoculated adult plants. The vector did not integrate in or recombine with the plant genome nor was it pollen or vector transmissible, albeit seed transmission at low rate was detected. The clbvINpr‐AtFT is very stable, and flowering was observed over a period of at least 5 years. Precocious flowering of juvenile citrus plants after vector infection provides a helpful and safe tool to dramatically speed up genetic studies and breeding programmes.     

Wetland ecosystem comparison using a suite of plant assessment measures

In light of extensive human impact on wetlands it is necessary that we develop an effective way to monitor the effects of impact in order to prevent further destruction. One method is plant community assessment, specifically Floristic Quality Assessment (FQA), which is common, but can be subjective. In this case study, we implement FQA, as well as specific morphological and chemical assessment measures over a two-year period in order to compare two wetlands in the Lake George watershed in the Adirondack mountains and their response to human impact. While the wetlands studied demonstrated very different water chemistry profiles makeups, FQA did not reveal substantial differences between plant communities. However, more specific analyses of plant morphology and tissue chemistry did reveal significant differences that reflected the level of impact at these two sites. Namely, the simple plant Lemna minor had consistently shorter roots and Nuphar lutea contained higher amounts of nitrogen in above ground tissues when growing in an anthropogenically impacted wetland. We suggest that FQA and specific plant morphology and tissue chemistry measurements be performed concurrently to provide indication of both long- and short-term effects of human impact in wetland ecosystems.