Phyllosphere bacterial assembly in citrus crop under conventional and ecological management

Divergences between agricultural management can result in different types of biological interactions between plants and microorganisms, which may affect food quality and productivity. Conventional practices are well-established in the agroindustry as very efficient and lucrative; however, the increasing demand for sustainable alternatives has turned attention towards agroecological approaches. Here we intend to explore microbial dynamics according to the agricultural management used, based on the composition and structure of these bacterial communities on the most environmentally exposed habitat, the phyllosphere. Leaf samples were collected from a Citrus crop (cultivated Orange) in Mogi-Guaçu (SP, Brazil), where either conventional or ecological management systems were properly applied in two different areas. NGS sequencing analysis and quantitative PCR allowed us to comprehend the phyllosphere behavior and µ-XRF (micro X-ray fluorescence) could provide an insight on agrochemical persistence on foliar tissues. Our results demonstrate that there is considerable variation in the phyllosphere community due to the management practices used in the citrus orchard, and it was possible to quantify most of this variation. Equally, high copper concentrations may have influenced bacterial abundance, having a relevant impact on the differences observed. Moreover, we highlight the intricate relationship microorganisms have with crop production, and presumably with crop yield as well.

Plagiochila xerophila (Plagiochilaceae, Marchantiophyta) – a highly xerophilous new species from the Tibetan Spur (China)

Background and aims – The xeric landscapes of the Tibetan floristic province are adverse habitats for leafy liverworts. Here we report on the occurrence of a population of a species of the genus Plagiochila from exposed high-elevation cliffs in the Sichuan Province, China. We assessed its taxonomic distinctiveness and affinities within a morphological and phylogenetic framework.Results and discussion – The population is accommodated in a new species, Plagiochila xerophila Bakalin & Vilnet – probably the most xerophilous taxon within the genus in Asia – and a new section (sect. Xerophilae Bakalin & Vilnet) based on integrative analyses of molecular and morphological traits. The species is characterized by a greenish colour, unexpected given the highly exposed habitat, rigid texture and stem paraphyllia. The closest morphological relatives from sect. Poeltiae are phylogenetically only distantly related, whereas members of its sister groups, namely of sect. Trabeculatae and sect. Fruticosae are morphologically conspicuously different.

First record of the European Giant File Clam, Acesta excavata (Bivalvia: Pectinoidea: Limidae), in the Northwest Atlantic

Two large bivalve specimens collected in Bay d’Espoir, a deep fjord situated on the south coast of Newfoundland, are described and identified as belonging to the species Acesta excavata (Fabricius 1779). In situ observations onboard the manned submersible PISCES IV and color videos have provided information on the vertical distribution, density and habitat of the species. Maximum abundances of about 15 large individuals/m2 occurred on sheltered rock outcrops at depth ranging from 550 to 775 m, where warm (6°C) continental slope water is found. Differences in shape and thickness between the valves of the two specimens appear to be related to the degree of exposure to rock falls (i.e., sheltered versus exposed habitat). Prior to this account, the European Giant File Clam had never been encountered west of the Azores Islands in the North Atlantic.

The ecology of Rhizocarpon superficielle. I. The rock surface boundary-layer microclimate

The thermal environment of the crustaceous lichen Rhizocarpon superficiale (Schaer.) Vain, is documented for spring and summer conditions using selected data characteristic of a range of thallus hydration conditions. During extended rainfall periods hydrated thallus temperatures largely parallel air temperature, usually remaining below 10 °C. However, quite often periods of shower activity alternate rapidly with intervals of full solar isolation, particularly during summer thundershower activity. This can result in hydrated thallus temperatures, fluctuating from 5 to 20 °C within minutes. An equally wide range of hydrated thallus temperatures is also evident under spring snowmelt conditions. Under the high levels of convective cooling typical of the exposed habitat of Rhizocarpon superficiale, thallus temperatures under maximum solar radiation conditions in midsummer rarely rise above 32 °C. Under still conditions thallus temperatures rapidly reach a potentially stressful level of 45 °C and it is probable that strong convective cooling in summer plays an important role in the ecology of R. superficiale.

Macroinfauna of northern New England marine sand. II. Amphipod-dominated intertidal communities

This is a 5-year study of macroinfaunal communities of moderately exposed to sheltered intertidal sands of New Hampshire and southwestern Maine. Habitats also differed in slope, width, predominant sand grain size, and carbon–nitrogen concentrations. Thirty-one species were recorded. Abundance and dry weight biomass at four intensively studied habitats averaged 5000/m2 and 2.1 g/m2, respectively, during 1971. The most exposed habitat yielded twice this standing crop, correlated with intermediate levels of carbon and nitrogen. Over 90% of seasonal numbers and biomass at more exposed habitats were attributable to six species of relatively short-lived amphipods, mostly Haustoriidae. Between-habit at variation in abundance and biomass of amphipods was in general greater than seasonal variation within habitats. Polychaete species increased at sheltered habitats, and bivalve mollusks were restricted to shelter. The typical community of moderately exposed sands south of Penobscot Bay, Maine, is characterized by a recurrent group of nine species (five amphipods). Community stability is assisted by brooding habits of dominant amphipods. Zonation, subtidal connections, seasonal movements, and patterns of amphipod species dominance are discussed. Structural comparisons are made with boreal European and other Atlantic coast intertidal sand communities.