Monoterpene Enrichments Have Positive Impacts on Soil Bacterial Communities and the Potential of Application in Bioremediation.

We study here how soil bacterial communities of different ecosystems respond to disturbances caused by enrichments with monoterpenes that are common essential oil constituents. We used fenchone, 1,8-cineol and α-pinene, and soils from phrygana, a typical Mediterranean-type ecosystem where aromatic plants abound, and from another five ecosystem types, focusing on culturable bacteria. Patterns of response were common to all ecosystems, but responses themselves were not always as pronounced in phrygana as in the other ecosystems, suggesting that these enrichments are less of a disturbance there. More specifically, soil respiration and abundance of the bacterial communities increased, becoming from below two up to 16 times as high as in control soils (for both attributes) and remained at high levels as long as these compounds were present. Bacteria that can utilize these three compounds as substrates of growth became dominant members of the bacterial communities in the enriched soils. All changes were readily reversible once monoterpene addition stopped. Bacteria with the ability to utilize these monoterpenes as carbon sources were found in soils from all ecosystems, 15 strains in total, suggesting a rather universal presence; of these, six could also utilize the organic pollutants toluene or p-xylene. These results suggest also potential novel applications of monoterpenes in combating soil pollution.

Climate drives plant-pollinator interactions even along small-scale climate gradients: the case of the Aegean.

Plant-pollinator network structure is the outcome of ecological and evolutionary processes, and although the importance of environmental factors is beyond doubt, our knowledge of how abiotic factors (e.g. climate) shape plant-pollinator networks remains limited. This knowledge gap is critical, as climate change poses a major threat to ecosystems, especially in the Mediterranean. This study focuses on one of the hottest parts of the Mediterranean Basin, the Aegean Archipelago, Greece, and examines how climate affects species richness and network properties (e.g. nestedness, modularity and specialisation) - either directly or indirectly through species richness. We sampled systematically 39 local plant-pollinator networks on eight islands along a north-south climate gradient in the Aegean. All plant-pollinator material used in the analyses was collected in 2012 and identified to species level. Aspects of climate used in the models were expressed as average conditions (mean temperature and annual precipitation) or as seasonal variability (isothermality and temperature seasonality). Structural properties of plant-pollinator networks were found to be strongly associated with species richness, which was in turn affected by climate, implying that pollination network structure is driven indirectly by climate. In addition, climate had a direct effect on network structure, especially on modularity and specialisation. Different aspects of climate affected network properties in different ways. We highlight that even in a relatively narrow latitudinal gradient, such as within the Aegean Sea region, climate constitutes a significant driver of plant-pollinator interactions.

Climate change reduces nectar secretion in two common Mediterranean plants.

Global warming can lead to considerable impacts on natural plant communities, potentially inducing changes in plant physiology and the quantity and quality of floral rewards, especially nectar. Changes in nectar production can in turn strongly affect plant-pollinator interaction networks-pollinators may potentially benefit under moderate warming conditions, but suffer as resources reduce in availability as elevated temperatures become more extreme. Here, we studied the effect of elevated temperatures on nectar secretion of two Mediterranean Lamiaceae species-Ballota acetabulosa and Teucrium divaricatum. We measured nectar production (viz. volume per flower, sugar concentration per flower and sugar content per flower and per plant), number of open and empty flowers per plant, as well as biomass per flower under a range of temperatures selected ad hoc in a fully controlled climate chamber and under natural conditions outdoors. The average temperature in the climate chamber was increased every 3 days in 3 °C increments from 17.5 to 38.5 °C. Both study species showed a unimodal response of nectar production (volume per flower, sugar content per flower and per plant) to temperature. Optimal temperature for sugar content per flower was 25-26 °C for B. acetabulosa and 29-33 °C for T. divaricatum. According to our results, moderate climate warming predicted for the next few decades could benefit nectar secretion in T. divaricatum as long as the plants are not water stressed, but have a moderate negative effect on B. acetabulosa. Nevertheless, strong warming as predicted by climate change models for the end of the 21st century is expected to reduce nectar secretion in both species and can thus significantly reduce available resources for both wild bees and honeybees in Mediterranean systems.