Persistent millennial-scale climate variability in Southern Europe during Marine Isotope Stage 6

Exploring the mode and tempo of millennial-scale climate variability under evolving boundary conditions can provide insights into tipping points in different parts of the Earth system, and can facilitate a more detailed understanding of climate teleconnections and phase relationships between different Earth system components. Here we use fossil diatom and stable carbon and oxygen isotope analysis of lake sediment deposits (core I-284) from the Ioannina basin, NW Greece, to explore in further detail millennial-scale climate instability in southern Europe during Marine Isotope Stage 6 (MIS 6; ca. 185‒130 ka). This interval correlates with the Vlasian Stage in Greece and the Late Saalian Substage in northern Europe, which were both characterised by extensive glaciations. The new dataset resolves at least 18 discrete warmer/wetter intervals, many of which were associated with strong Asian Monsoon events and North Atlantic interstadials. A number of cooler/drier intervals are also identified in the I-284 record, which are typically associated with weaker Asian Monsoon events and North Atlantic stadials, consistent with a variable Atlantic Meridional Overturning Circulation. Unlike the subdued changes in tree populations that are observed at Ioannina during mid-to-late MIS 6, the diatom record contains frequent high-amplitude oscillations in species assemblages, pointing to its sensitivity at a time when the lake system must have been close to environmental thresholds. Millennial-scale variability in diatom species assemblages continues into late MIS 6 at Ioannina, contributing important evidence for an emerging picture of frequent and persistent climate instability even at times of high global ice volume

Assessment of transcript reconstruction methods for RNA-seq

We evaluated 25 protocol variants of 14 independent computational methods for exon identification, transcript reconstruction and expression-level quantification from RNA-seq data. Our results show that most algorithms are able to identify discrete transcript components with high success rates but that assembly of complete isoform structures poses a major challenge even when all constituent elements are identified. Expression-level estimates also varied widely across methods, even when based on similar transcript models. Consequently, the complexity of higher eukaryotic genomes imposes severe limitations on transcript recall and splice product discrimination that are likely to remain limiting factors for the analysis of current-generation RNA-seq data