Lago Maggiore oligotrophication as seen from the long-term evolution of its phytoplankton taxonomic size structure

Due to the rapid and common deterioration of aquatic ecosystems, scientists and environmental protection organizations acutely need means capable of producing quantitative estimates for structural deformations of natural communities. Recently, very common biomass size spectra ignore community taxonomic composition, i.e., one of the most important kinds of biological information. Therefore, another very old, but rare in planktonology, method - the traditional taxonomic size spectrum (TTSS) - can be helpful. TTSS, a specific form of size-frequency distribution of taxonomic units, reveals repeating patterns of deep subalpine Lago Maggiore (Italy) phytoplankton taxonomic structure. The general TTSS pattern was safeguarded during 22 annual cycles (1984-2005), when many principal environmental characteristics were changed considerably during the lake oligotrophication. At the same time, the fine structure deformations of this pattern helped us divide the total oligotrophication process into several stages characterized by notable changes of TTSS peaks\u27 proportions. These peak-height alterations were caused by pronounced changes in the species list and overall taxonomic diversity of the lake phytoplankton. The average cell volume decline was found. It was significantly correlated with the total phosphorus descending trend. This cell volume decline was produced by the addition of numerous species into the medium-and-small size fractions. Typical patterns of the stable and transitory stages were differentiated, which could be valuable for environmental protection and diagnostic applications. The central peak height difference between the stable and the transitory periods was statistically significant. Oligotrophication process decomposition into several more homogenous groups of years was supported by quantitative estimators produced by hierarchical cluster analysis. The highest level of the similarity measure (Pearson r) in pairs of annual TTSS was close to the respective estimates found for other lakes. Concomitantly, its minimal level, produced by a specific pair of abnormal years at the beginning and end of the studied process, was found previously only for pairs taken from two different ecosystems (Lakes Kinneret and Tahoe). This way, TTSS can be applied as a quantitative analysis means of the integral natural community structural evolution. Such tools are acutely needed for environmental management, monitoring, and theoretical ecology

Correction to: Landraces of snake melon, an ancient Middle Eastern crop, reveal extensive morphological and DNA diversity for potential genetic improvement

Following publication of the original article [1], the authors reported the need for a more detailed acknowledgement of the source of the samples that were analyzed and their coordinates, which are discussed in the ‘Methods’ section of the article. This Correction provides an addition to the ‘Methods’ section, and a subsequently revised ‘Acknowledgements’ and ‘Availability of data and materials’ section

Landraces of snake melon, an ancient Middle Eastern crop, reveal extensive morphological and DNA diversity for potential genetic improvement

Abstract Background Snake melon (Cucumis melo var. flexuosus, “Faqqous”) is a traditional and ancient vegetable in the Mediterranean area. A collection of landraces from 42 grower fields in Israel and Palestinian territories was grown and characterized in a “Common Garden” rain-fed experiment, at the morphological-horticultural and molecular level using seq-DArT markers. Results The different landraces (“populations”) showed extensive variation in morphology and quantitative traits such as yield and femaleness, and clustered into four horticultural varieties. Yield was assessed by five harvests along the season, with middle harvests producing the highest yields. Yield correlated with early vigor, and with femaleness, but not with late vigor. At the molecular level, 2784 SNP were produced and > 90% were mapped to the melon genome. Populations were very polymorphic (46–72% of the markers biallelic in a 4 individuals sample), and observed heterozygosity was higher than the expected, suggesting gene flow among populations and extensive cross pollination among individuals in the field. Genetic distances between landraces were significantly correlated with the geographical distance between collecting sites, and with long term March precipitation average; variation in yield correlated with April temperature maxima. Conclusions The extensive variation suggests that selection of local snake melon could result in yield improvement. Correlations between traits and climatic variables could suggest local adaptation of landraces to the diverse environment in which they evolved. This study stresses the importance of preserving this germplasm, and its potential for breeding better snake melons as an heirloom crop in our region

Additional file 1: of Landraces of snake melon, an ancient Middle Eastern crop, reveal extensive morphological and DNA diversity for potential genetic improvement

Omari et al. Table S1. Data on landraces used in this study and their respective collection sites. Table provides, for each population (collection site), the full set of geographic and climatic variables, morphological scores, and genetic diversity parameters that were calculated from the molecular data. (XLS 103 kb