Isotopic evidence for massive oxidation of organic matter following the great oxidation event

The stable isotope record of marine carbon indicates that the Proterozoic Eon began and ended with extreme fluctuations in the carbon cycle. In both the Paleoproterozoic [2500 to 1600 million years ago (Ma)] and Neoproterozoic (1000 to 542 Ma), extended intervals of anomalously high carbon isotope ratios (δ(13)C) indicate high rates of organic matter burial and release of oxygen to the atmosphere; in the Neoproterozoic, the high δ(13)C interval was punctuated by abrupt swings to low δ(13)C, indicating massive oxidation of organic matter. We report a Paleoproterozoic negative δ(13)C excursion that is similar in magnitude and apparent duration to the Neoproterozoic anomaly. This Shunga-Francevillian anomaly may reflect intense oxidative weathering of rocks as the result of the initial establishment of an oxygen-rich atmosphere.     

Genetic diversity and relationships among cultivated and wild accessions of tartary buckwheat (Fagopyrum tataricum Gaertn.) as revealed by RAPD markers

The methodology of sampling and the selection of a proper marker systemfor the analysis of accessions are major concerns in the evaluation of gene bank material. In our study the RAPD analysis of bulked DNA samples and single seedsDNA was successfully employed to evaluate intra- and inter-population geneticvariability of cultivated and wild tartary buckwheat accessions. The bulkingapproach enabled the distinction of all 40 analysed accessions and theirseparation into geographically well defined clusters. Three wild populations,two from Sichuan and one from Qinghai, formed a group that was geneticallyrelatively distant from wild populations from Tibet and all cultivatedlandraces which, on the other hand, exhibited very close relationships. Thesingle seed study that was used after bulked DNA analysis provided detailedinformation of the genetic variation present within some accessions of specialinterest. A moderate level of genetic variability was detected betweenaccessions and the variability was partitioned into between- andwithin-population components. On average, most of the detected variation ispresent between F. tataricumpopulations. The genetic and geographic distribution of variability is furtherdiscussed. We demonstrated the usefulness of combining bulking and single seedstudy approaches for the effective evaluation of genetic variability inF. tataricum accessions that couldalso have wider applicability in the management of plant genetic resources andphylogenetic studies.     

38–48 kDa subunits of buckwheat 13S globulins are controlled by a single locus

The inheritance of buckwheat (Fagopyrum esculentum Moench) seed storage proteins was investigated by control crosses between accessions containing different SDS‐PAGE protein patterns in the range of 38–48 kDa. Analysis of segregation of individual F₁ and F₂ seeds obtained by 17 crosses showed segregation of eight electrophoretic bands, from which 12‐banding variants were inferred. Two variants contained one band, nine contained two bands and one variant contained three bands and behaved as a single co‐dominant unit. The segregation of banding variants fits the expected ratios and thus supports the hypothesis of single Mendelian gene inheritance and that alleles are co‐dominant. The results therefore suggest that the genes controlling globulin subunits are tightly linked and inherited as a single locus. The locus was designated Glob‐1 and the twelve segregated protein variants as alleles a‐l. This is the first buckwheat globulin locus identified with multiple alleles, phenotypically expressed as groups of protein bands and thus applicable as a functional marker in buckwheat genomic studies.     

Carbon and nitrogen natural stable isotopes in Slovene honey: adulteration and botanical and geographical aspects

Isotope parameters (δ(13)C(honey), δ(13)C(protein), δ(15)N) were determined for 271 honey samples of 7 types (black locust, multifloral, lime, chestnut, forest, spruce, and fir honeys) from 4 natural geographical regions of Slovenia. Carbon and nitrogen stable isotope ratios were measured to elucidate the applicability of this method in the identification of the botanical and geographical origin of honey and in honey adulteration. Only 2.2% of the samples were adulterated according to the internal standard carbon isotope ratio analysis method. Botanical origin did not have any major influence on the honey isotope profiles; only black locust honey showed higher δ(13)C values. Some differences were seen across different production years, indicating that the influence of season should be further tested. Statistical and multivariate analyses demonstrated differences among honeys of various geographical origins. Those from the Alpine region had low δ(13)C (-26.0‰) and δ(15)N values (1.1‰); those from the Mediterranean region, high δ(13)C (-24.6‰) and medium δ(15)N values (2.2‰); those from the Pannonian region, medium δ(13)C (-25.6‰) and high δ(15)N value (3.0‰); and those from the Dinaric region, medium δ(13)C (-25.7‰) and low δ(15)N values (1.4‰).     

Amplification of Cretaceous warmth by biological cloud feedbacks

The extreme warmth of particular intervals of geologic history cannot be simulated with climate models, which are constrained by the geologic proxy record to relatively modest increases in atmospheric carbon dioxide levels. Recent recognition that biological productivity controls the abundance of cloud condensation nuclei (CCN) in the unpolluted atmosphere provides a solution to this problem. Our climate simulations show that reduced biological productivity (low CCN abundance) provides a substantial amplification of CO2-induced warming by reducing cloud lifetimes and reflectivity. If the stress of elevated temperatures did indeed suppress marine and terrestrial ecosystems during these times, this long-standing climate enigma may be solved.     

The geological record of ocean acidification

Ocean acidification may have severe consequences for marine ecosystems; however, assessing its future impact is difficult because laboratory experiments and field observations are limited by their reduced ecologic complexity and sample period, respectively. In contrast, the geological record contains long-term evidence for a variety of global environmental perturbations, including ocean acidification plus their associated biotic responses. We review events exhibiting evidence for elevated atmospheric CO(2), global warming, and ocean acidification over the past ~300 million years of Earth's history, some with contemporaneous extinction or evolutionary turnover among marine calcifiers. Although similarities exist, no past event perfectly parallels future projections in terms of disrupting the balance of ocean carbonate chemistry-a consequence of the unprecedented rapidity of CO(2) release currently taking place.     

Ophiostomatoid fungi associated with three spruce-infesting bark beetles in Slovenia

Context

Ophiostomatoid fungi can severely affect the health and economic value of Norway spruce trees (Picea abies). Although the diversity of ophiostomatoid species and their associations with insects have been well-investigated in central and northern Europe, little is known about the conditions in south-eastern Europe.

Aim

This study aims to study the assemblages of ophiostomatoid fungi associated with three bark beetle species (Ips typographus, Ips amitinus, and Pityogenes chalcographus) that infect Norway spruce in Slovenia.

Methods

Bark beetles were sampled in four phytogeographic regions in Slovenia. The fungi found on the bark beetles were identified based on morphology, DNA sequence comparisons of ITS regions and phylogenetic analysis. The species compositions of the fungal associates of the three insect species were compared and the pairwise associations of the occurrence of the fungal species were analysed.

Results

Thirteen different species were found. The most commonly encountered fungal associates of the beetles were Ophiostoma bicolor, Ophiostoma brunneo-ciliatum, Grosmannia piceiperda, Ophiostoma ainoae, Ceratocystiopsis minuta, and Grosmannia penicillata. The composition of the fungal associates differed among the bark beetle species, but not among the phytogeographic regions.

Conclusions

This study confirms that ophiostomatoid species are common associates of the investigated bark beetle species. Many ophiostomatoid species have strong host associations. I. typographus and P. chalcographus can act as effective vectors for O. bicolor, O. ainoae, G. piceiperda and O. brunneo-ciliatum, whereas I. amitinus often carries G. piceiperda and C. minuta in Slovenian forests.