Global patterns and drivers of ecosystem functioning in rivers and riparian zones

River ecosystems receive and process vast quantities of terrestrial organic carbon, the fate of which depends strongly on microbial activity. Variation in and controls of processing rates, however, are poorly characterized at the global scale. In response, we used a peer-sourced research network and a highly standardized carbon processing assay to conduct a global-scale field experiment in greater than 1000 river and riparian sites. We found that Earth's biomes have distinct carbon processing signatures. Slow processing is evident across latitudes, whereas rapid rates are restricted to lower latitudes. Both the mean rate and variability decline with latitude, suggesting temperature constraints toward the poles and greater roles for other environmental drivers (e.g., nutrient loading) toward the equator. These results and data set the stage for unprecedented "next-generation biomonitoring" by establishing baselines to help quantify environmental impacts to the functioning of ecosystems at a global scale.peerReviewe

Exotic fish in exotic plantations: a multi-scale approach to understand amphibian occurrence in the mediterranean region

Globally, amphibian populations are threatened by a diverse range of factors including habitat destruction and alteration. Forestry practices have been linked with low diversity and abundance of amphibians. The effect of exotic Eucalyptus spp. plantations on amphibian communities has been studied in a number of biodiversity hotspots, but little is known of its impact in the Mediterranean region. Here, we identify the environmental factors influencing the presence of six species of amphibians (the Caudata Pleurodeles waltl, Salamandra salamandra, Lissotriton boscai, Triturus marmoratus and the anurans Pelobates cultripes and Hyla arborea/meridionalis) occupying 88 ponds. The study was conducted in a Mediterranean landscape dominated by eucalypt plantations alternated with traditional use (agricultural, montados and native forest) at three different scales: local (pond), intermediate (400 metres radius buffer) and broad (1000 metres radius buffer). Using the Akaike Information Criterion for small samples (AICc), we selected the top-ranked models for estimating the probability of occurrence of each species at each spatial scale separately and across all three spatial scales, using a combination of covariates from the different magnitudes. Models with a combination of covariates at the different spatial scales had a stronger support than those at individual scales. The presence of predatory fish in a pond had a strong effect on Caudata presence. Permanent ponds were selected by Hyla arborea/meridionalis over temporary ponds. Species occurrence was not increased by a higher density of streams, but the density of ponds impacted negatively on Lissotriton boscai. The proximity of ponds occupied by their conspecifics had a positive effect on the occurrence of Lissotriton boscai and Pleurodeles waltl. Eucalypt plantations had a negative effect on the occurrence of the newt Lissotriton boscai and anurans Hyla arborea/meridionalis, but had a positive effect on the presence of Salamandra salamandra, while no effect on any of the other species was detected. In conclusion, eucalypts had limited effects on the amphibian community at the intermediate and broad scales, but predatory fish had a major impact when considering all the scales combined. The over-riding importance of introduced fish as a negative impact suggests that forest managers should prevent new fish introductions and eradicate fish from already-occupied ponds whenever possible

Effect and analysis of phenolic compounds during somatic embryogenesis induction in Feijoa sellowiana Berg

Summary. The effect of phenolic compounds on somatic embryogenesis in Feijoa sellowiana was analysed. The results showed that caffeic acid (140–560 µM) significantly increased somatic embryogenesis induction compared with the control. The presence of phloridzin, even at lower concentrations (11.5 µM), or caffeic acid or phloroglucinol at concentrations greater than 140.0 and 197.5 µM, respectively, inhibited somatic embryo development beyond the globular stage. When somatic embryos were transferred to the germination medium, the highest rates of germination (81.9%) were obtained with embryos induced in the presence of phloroglucinol (79.0 µM). At all concentrations tested, somatic embryos induced in medium containing phloroglucinol germinated at higher rates than those induced in the presence of caffeic acid. Histological and ultrastructural studies showed that somatic embryos were formed in close association with phenolic-rich cells which, in more advanced stages of development, formed a zone isolating the embryo from the maternal tissue. A comparative analysis of total phenolic content indicated that phenolics reached a peak by the third week of culture, independently of the medium used. However, after that period, the amount of phenolic compounds was significantly higher in explants cultured in the presence of phloroglucinol than in those cultured in the control or in caffeic acid-containing medium. Attempts to identify the type of phenolic compounds showed that flavan-3-ols and gallic acid derivatives were mainly produced in phloroglucinol-containing medium, whereas flavanones and dihydroflavonols were also present in medium containing caffeic acid. Flavones were the main phenols detected in the control. The ways in which phenolic compounds may affect somatic embryogenesis are discussed

In vitro propagation of the wild carrot Daucus carota L. subsp. halophilus (Brot.) A. Pujadas for conservation purposes

Daucus carota subsp. halophilus, is a wild crop relative of domestic carrot. It is an aromatic plant widely used in folk medicine due to recognized therapeutic properties of its essential oils. Experiments were carried out to evaluate the potential of in vitro propagation techniques to the conservation of this endemic and endangered taxon. The results showed that shoot tips of in vitro germinated seeds were able to proliferate in the presence of benzyladenine, with the best results being achieved using 4.4μM, both in the first and second cultures. Shoots rooted after being transferred to 1/2- Murashige and Skoog basal medium. The results indicated that the concentration of benzyladenine used during the multiplication phase did not interfere with the rate of root formation. The obtained plantlets were morphologically and anatomically identical to those obtained by seeds. Some of the in vitro produced shoots developed flowers that produced viable pollen. Plant regeneration was also achieved by somatic embryogenesis induction in cotyledons and root segments cultured in the presence of 4.5μM 2,4-dichlorophenoxyacetic acid. Somatic embryos converted into plantlets in a medium without growth regulators. Plants obtained either by shoot proliferation or somatic embryogenesis were acclimatized and are now growing at the Coimbra Botanical Garden. The first attempts to reintroduce these plants in the original habitat were successful. It can be concluded that the protocols developed are a useful approach to the conservation of this endemic species

Ploidy stability in embryogenic cultures and regenerated plantlets of tamarillo

Ploidy levels of short-term (1 and 2 years) and long-term (7 and 10 years) embryogenic cultures as well as of regenerated plantlets of tamarillo were analyzed by flow cytometry and chromosome counts. Embryogenic cultures were induced from expanding leaves cultured in the presence of Picloram or 2,4-dichlorophenoxyacetic acid (2,4-D) and monthly subcultured on the same media. Embryo development and plantlets were obtained following subculture of the embryogenic tissue in auxin free medium containing gibberellic acid (GA3). Seedlings and rooted shoots from axillary shoot proliferation were used as controls. The results showed that in long-term embryogenic cultures the ability to develop somatic embryos and plantlets was reduced. Embryogenic tissues maintained for 10 years were mostly aneuploids of the tetraploid (2n = 4x = 48) level whereas those kept in culture for 7 years or less were also mostly aneuploids but of the diploid (2n = 2x = 24) level. The results obtained by flow cytometry were, in general, consistent with those obtained by chromosome counts. The chromosome alteration observed in the embryogenic tissues was already present after 1 year of culture and increased with culture age, hence impairing the maintenance of these tissues for long periods without affecting chromosome stability of the regenerated plantlets. However, the occurrence of triploids and tetraploids as well as aneuploids can be useful for breeding purposes. A value around 23 pg/2C was found for the genome size of tamarillo largely exceeding the value previously published (15.50 pg/2C).This work was supported by the Portuguese Foundation for Science and Technology (FCT).publishe