Does Caulerpa prolifera with Its Bacterial Coating Represent a Promising Association for Seawater Phytoremediation of Diesel Hydrocarbons?

Anthropic diesel-derived contamination of Mediterranean coastal waters is of great concern. Nature-based solutions such as phytoremediation are considered promising technologies to remove contaminants from marine environments. The aim of this work was to investigate the tolerance of the Mediterranean autochthonous seaweed Caulerpa prolifera (Forsskal) Lamouroux to diesel fuel and its hydrocarbon degradation potential. Changes in C. prolifera traits, including its associated bacterial community abundance and structure, were determined by fluorescence microscopy and next-generation sequencing techniques. Thalli of C. prolifera artificially exposed to increasing concentration of diesel fuel for 30 days and thalli collected from three natural sites with different levels of seawater diesel-derived hydrocarbons were analysed. Gas chromatography was applied to determine the seaweed hydrocarbon degradation potential. Overall, in controlled conditions the lower concentration of diesel (0.01%) did not affect C. prolifera survival and growth, whereas the higher concentration (1%) resulted in high mortality and blade damages. Similarly, only natural thalli, collected at the most polluted marine site (750 mg L-1), were damaged. A higher abundance of epiphytic bacteria, with a higher relative abundance of Vibrio bacteria, was positively correlated to the health status of the seaweed as well as to its diesel-degradation ability. In conclusion, C. prolifera tolerated and degraded moderate concentrations of seawater diesel-derived compounds, especially changing the abundance and community structure of its bacterial coating. The protection and exploitation of this autochthonous natural seaweed-bacteria symbiosis represents a useful strategy to mitigate the hydrocarbon contamination in moderate polluted Mediterranean costal environments.

Plant invasion risk inside and outside protected areas: Propagule pressure, abiotic and biotic factors definitively matter.

Invasive alien species are among the main global drivers of biodiversity loss posing major challenges to nature conservation and to managers of protected areas. The present study applied a methodological framework that combined invasive Species Distribution Models, based on propagule pressure, abiotic and biotic factors for 14 invasive alien plants of Union concern in Italy, with the local interpretable model-agnostic explanation analysis aiming to map, evaluate and analyse the risk of plant invasions across the country, inside and outside the network of protected areas. Using a hierarchical invasive Species Distribution Model, we explored the combined effect of propagule pressure, abiotic and biotic factors on shaping invasive alien plant occurrence across three biogeographic regions (Alpine, Continental, and Mediterranean) and realms (terrestrial and aquatic) in Italy. We disentangled the role of propagule pressure, abiotic and biotic factors on invasive alien plant distribution and projected invasion risk maps. We compared the risk posed by invasive alien plants inside and outside protected areas. Invasive alien plant distribution varied across biogeographic regions and realms and unevenly threatens protected areas. As an alien's occurrence and risk on a national scale are linked with abiotic factors followed by propagule pressure, their local distribution in protected areas is shaped by propagule pressure and biotic filters. The proposed modelling framework for the assessment of the risk posed by invasive alien plants across spatial scales and under different protection regimes represents an attempt to fill the gap between theory and practice in conservation planning helping to identify scale, site, and species-specific priorities of management, monitoring and control actions. Based on solid theory and on free geographic information, it has great potential for application to wider networks of protected areas in the world and to any invasive alien plant, aiding improved management strategies claimed by the environmental legislation and national and global strategies.

Ragweed is in the Air: Ambrosia L. (Asteraceae) and Pollen Allergens in a Changing World.

Globally Ambrosia species (Asteraceae), commonly called ragweed, are recognized to be one of the most problematic groups of invasive weeds and one of the main allergenic genus. Climate and land-use change and air pollution are expected to promote ragweed spread, increase airborne ragweed pollen concentrations (the source of allergens), extend the pollen season, and promote longdistance transport of pollen or sub-pollen particles containing allergens. The allergenicity of pollen itself is going to increase. Likely, all these factors will have meaningful effects in the exacerbation of the sensitization to ragweed pollen and the severity of allergy symptoms. Globally the major health concern regards A. artemisiifolia, because of its very wide global distribution and highly invasive behavior. Together with A. artemisiifolia, also A. trifida and A. psilostachya are species of health concern distributed across different continents, widespread and invasive in several regions. The present review summarizes the characteristics of these species and gives an overview of factors contributing to their allergenicity.

High Phenotypic Plasticity in a Prominent Plant Invader along Altitudinal and Temperature Gradients.

Studies on plant growth and trait variation along environmental gradients can provide important information for identifying drivers of plant invasions and for deriving management strategies. We used seeds of the annual plant invader Ambrosia artemisiifolia L. (common ragweed) collected from an agricultural site in Northern Italy (226 m. a.s.l; Mean Annual Air Temperature: 12.9 °C; precipitations: 930 mm) to determine variation in growth trajectories and plant traits when grown along a 1000-m altitudinal gradient in Northern Italy, and under different temperature conditions in the growth chamber (from 14/18 °C to 26/30 °C, night/day), using a non-liner modeling approach. Under field conditions, traits related to plant height (maximum height, stem height, number of internodes) followed a three-parameter logistic curve. In contrast, leaf traits (lateral spread, number of leaves, leaf length and width) followed non-monotonic double-Richards curves that captured the decline patterns evident in the data. Plants grew faster, reaching a higher maximum plant height, and produced more biomass when grown at intermediate elevations. Under laboratory conditions, plants exhibited the same general growth trajectory of field conditions. However, leaf width did not show the recession after the maximum value shown by plants grown in the field, although the growth trajectories of some individuals, particularly those grown at 18 °C, showed a decline at late times. In addition, the plants grown at lower temperatures exhibited the highest value of biomass and preserved reproductive performances (e.g., amount of male inflorescence, pollen weight). From our findings, common ragweed exhibits a high phenotypic plasticity of vegetative and reproductive traits in response to different altitudes and temperature conditions. Under climate warming, this plasticity may facilitate the shift of the species towards higher elevation, but also the in situ resistance and (pre)adaptation of populations currently abundant at low elevations in the invasive European range. Such results may be also relevant for projecting the species management such as the impact by possible biocontrol agents.

The interactive effect of herbivory, nutrient enrichment and mucilage on shallow rocky macroalgal communities.

This paper focuses on the interactive short and long-term effect of three different stressors on a macroalgal assemblage. Three stressors are considered: herbivory, nutrients and mucilage. The experiment was conducted in Tavolara Punta Coda Cavallo Marine Protected Area (Mediterranean Sea) during a bloom of the benthic mucilage-producing microalga Chrysophaeum taylorii (Pelagophyceae); this microalga is recently spreading in the Mediterranean Sea. On a rocky substratum, 36 plots 20 × 20 cm in size were prepared. Factorial combinations of three experimental treatments were applied in triplicate, including three grazing levels crossed with two nutrient enrichment and two mucilage removal treatments. Significant differences were observed among treatments 8 weeks later, at the end of summer. In particular, dark filamentous algae were more abundant in all enriched plots, especially where mucilage and macroalgae had been removed; a higher percent cover of crustose coralline algae was instead observed where nutrients had been increased and no grazing pressure acted. Furthermore, the abundance of Dictyota spp. and Laurencia spp. was significantly higher in enriched mucilage-free plots where the grazing pressure was null or low. However, the effects of the treatments on the overall assemblage of the macroalgal community were not long persistent (36 weeks later). These results illustrate the capacity of a shallow-water macroalgal community to quickly recover from the simultaneous impacts of herbivory, nutrient enrichment, and mucilage.

Ambrosia artemisiifolia L. temperature-responsive traits influencing the prevalence and severity of pollinosis: a study in controlled conditions.

BACKGROUND: Ambrosia artemisiifolia L. is one of the most important sources of allergenic pollen in many regions of the world. Its health impact increased over the last decades and is expected to further increase in consequence of climate change. However little information is available on the specific role played by temperature on allergy rising. The aim of this work was to evaluate the effect of temperature on A. artemisiifolia growth, flowering and pollen allergenicity, the major plant functional traits influencing the prevalence and severity of pollinosis. RESULTS: Plants were grown in controlled conditions at three thermal regimes: "Low" (LT: 18-14 °C light-dark), "Intermediate" (IT: 24-20 °C light-dark) and "High" (HT: 30-26 °C light-dark). During plant development, plant vegetative and reproductive morpho-functional traits were measured and, at the end of plant life-cycle, mature pollen was collected and analyzed for its allergenic properties by slot blot, 1D- and 2D-western blot (by using a pool of sera from ragweed-allergic patients) and liquid chromatography-tandem mass spectrometry. A. artemisiifolia showed a great development plasticity leading to a broad temperature tolerance. Shoot architecture, growth rate, number of male inflorescence and pollen allergenicity were temperature-responsive traits. Pollen allergenicity increased in parallel with temperature and differences were related to allergen synthesis and Amb a 1-IgE-binding. Flavonoids whose concentration in pollen decreased with the increase of temperature, were recognized as the cause of the negligible Amb a 1-IgE binding in LT pollen. CONCLUSIONS: Results show that temperature governs plant development and pollen allergenicity influencing the temporal and spatial magnitude of subject exposure to allergens.

Phylogenetically informed spatial planning as a tool to prioritise areas for threatened plant conservation within a Mediterranean biodiversity hotspot.

Global plant diversity is at risk due to anthropogenic changes to ecosystems, but given severely limited conservation resources, a reliable prioritisation strategy for species and sites is needed. Our objective was to identify key areas for conserving the phylogenetic diversity (PD) of threatened vascular plants in Italy, one of the most species-rich regions in the Mediterranean Basin. We used spatial data and the conservation status of 995 threatened vascular plants and applied a phylogenetically informed spatial planning to minimize conservation costs. We then determined the degree of overlap with existing protected areas and evaluated whether this PD-based prioritisation of areas provides adequate protection for threatened phylogenetically distinctive species (EDGE). The cost-effective procedure identified as priority for conservation 12% of the study territory, while achieving over 90% of conservation targets (total PD). We showed that priority areas and protected areas are moderately spatially mismatched. We also showed that not all top-EDGE species were met by the procedure applied, hence we conclude that the PD-based model indicated key areas for protection, but nevertheless additional attention is needed to protect top-EDGE species. This study represents one of the most comprehensive analyses, to date, for the conservation of the native flora in the Mediterranean, incorporating both spatial distribution and evolutionary relationships. Our work on the prioritisation of threatened plant species across Italy can serve as a guide for future conservation applications.

Effect of Soil pH on the Growth, Reproductive Investment and Pollen Allergenicity of Ambrosia artemisiifolia L.

Despite the importance of soil reaction for alien plant establishment, few and incomplete studies have included this key factor so far. In this study, we investigated the effects of soil pH on the germination, growth (plant height, width, dry weight, etc.) and reproductive investment (inflorescence size and n° of flowers) of Ambrosia artemisiifolia (common ragweed), an allergenic species that is highly invasive and alien in Europe, through a replicated experiment in controlled conditions. In addition, we determined if soil pH has an effect on the total pollen allergenicity of the species. After preliminary germination tests on agar at different pH (from pH4 to pH8), plants were grown in natural soils with pH values of 5 (acid), 6 (sub-acid) and 7 (neutral) obtained by modifying a natural soil by liming methods (calcium hydroxide solution). Results showed that plants grown at pH7 were shorter and developed leaves at a slower rate than those grown at pH5 and pH6; plants grown at pH7 did not produce flowers and pollen. We also observed that, at pH5 and pH6, larger plants (as assessed by the dry weight of the aerial biomass) had both larger and more numerous inflorescences and emitted pollen earlier. Finally, the IgE-binding signal was higher in pollen samples collected from plants grown at pH5 (Integrated Optical Density, IOD, range: 1.12-1.25) than in those grown at pH6 (IOD range: 0.86 -1.03). Although we acknowledge the limitations of only testing the effects of pH in controlled conditions, this study suggests that soil pH greatly affects the growth and development of A. artemisiifolia and indicates that it may have a role in limiting the distribution and hazardousness of this plant. Future field tests should therefore assess the effectiveness of liming in the management and control of ragweed and other alien species.