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Claremont, CA, United States

Angielczyk K.D.,Integrative Research Center | Schmitz L.,Pitzer and Scripps Colleges
Proceedings of the Royal Society B: Biological Sciences | Year: 2014

Nocturnality is widespread among extant mammals and often considered the ancestral behavioural pattern for all mammals. However, mammals are nested within a larger clade, Synapsida, and non-mammalian synapsids comprise a rich phylogenetic, morphological and ecological diversity. Even though non-mammalian synapsids potentially could elucidate the early evolution of diel activity patterns and enrich the understanding of synapsid palaeobiology, data on their diel activity are currently unavailable. Using scleral ring and orbit dimensions, we demonstrate that nocturnal activity was not an innovation unique to mammals but a character that appeared much earlier in synapsid history, possibly several times independently. The 24 Carboniferous to Jurassic non-mammalian synapsid species in our sample featured eye morphologies consistent with all major diel activity patterns, with examples of nocturnality as old as the Late Carboniferous (ca 300 Ma). Carnivores such as Sphenacodon ferox and Dimetrodon milleri, but also the herbivorous cynodont Tritylodon longaevus were likely nocturnal, whereas most of the anomodont herbivores are reconstructed as diurnal. Recognizing the complexity of diel activity patterns in non-mammalian synapsids is an important step towards a more nuanced picture of the evolutionary history of behaviour in the synapsid clade. © 2014 The Author(s) Published by the Royal Society. All rights reserved. Source


In eukaryotes, abnormally circularized chromosomes, known as ‘rings,’ can be mitotically unstable. Some rings derived from a compound X-Y chromosome induce mitotic abnormalities during the embryonic cleavage divisions and early death in Drosophila melanogaster, but the underlying basis is poorly understood. We recently demonstrated that a large region of 359-bp satellite DNA, which normally resides on the X chromosome, prevents sister ring chroma-tids from segregating properly during these divisions. Cytogenetic comparisons among 3 different X-Y rings with varying levels of lethality showed that all 3 contain similar amounts of 359-bp DNA, but the repetitive sequences surrounding the 359-bp DNA differ in each case. This finding suggests that ring misbehavior results from novel heterochromatin position effects on the 359-bp satellite. The purpose of this view is to explore possible explanations for these effects with regard to heterochromatin formation and replication of repetitive sequences. Also discussed are similarities of this system to a satellite-based hybrid incompatibility and potential influences on genome evolution. © 2014 Landes Bioscience. Source


Tambara K.,University of Cambridge | Olsen J.-C.,Indiana University Kokomo | Hansen D.E.,Pitzer and Scripps Colleges | Pantos G.D.,University of Bath
Organic and Biomolecular Chemistry | Year: 2014

The mechanism and thermodynamic functions of the self-assembly of a family of covalently linked oligomeric naphthalenediimides (NDIs) were investigated through variable-temperature NMR and CD studies. The NDIs were shown to self-assemble into helical supramolecular nanotubes via an isodesmic polymerisation mechanism, and regardless of the oligomer length a surprising entropy-enthalpy compensation was observed. This journal is © The Royal Society of Chemistry. Source


Brock-Hon A.L.,University of Tennessee at Chattanooga | Robins C.R.,Pitzer and Scripps Colleges | Buck B.J.,University of Nevada, Las Vegas
Geoderma | Year: 2012

Barite crystals are identified in stage VI petrocalcic horizons at Mormon Mesa, Nevada. Their presence is significant because barite is not typically associated with arid soil processes. Barite is identified through backscatter SEM/EDS as bright white crystals with EDS peaks of high Ba, S, and O. Barite crystals are euhedral, tabular to acicular crystals ranging in size from 1 to 50μm in length and 1-20μm in diameter, and as small (2-4μm) tabular-ovoid crystals. Forty-one percent of the barite in SEM images is associated with fibers of palygorskite and/or sepiolite. Barite crystals are also associated with linear voids, circular pores, and within micropores between fibers of silicate clays. The formation of barite at Mormon Mesa is attributed to: (i) The dissolution of Ba and SO 4 ions from detrital minerals and dust that are flushed into the soil profile and precipitate as barite; and/or (ii) Biomineralization of barite in micro-environments suitable for bacteria or other organisms within the petrocalcic horizon. © 2012 Elsevier B.V.. Source


Price S.A.,University of California at Davis | Schmitz L.,Pitzer and Scripps Colleges
Philosophical Transactions of the Royal Society B: Biological Sciences | Year: 2016

Studies into the complex interaction between an organism and changes to its biotic and abiotic environment are fundamental to understanding what regulates biodiversity. These investigations occur at many phylogenetic, temporal and spatial scales and within a variety of biological and geological disciplines but often in relative isolation. This issue focuses on what can be achieved when ecological mechanisms are integrated into analyses of deep-time biodiversity patterns through the union of fossil and extant data and methods. We expand upon this perspective to argue that, given its direct relevance to the current biodiversity crisis, greater integration is needed across biodiversity research.We focus on the need to understand scaling effects, how lower-level ecological and evolutionary processes scale up and vice versa, and the importance of incorporating functional biology. Placing function at the core of biodiversity research is fundamental, as it establishes how an organism interacts with its abiotic and biotic environment and it is functional diversity that ultimately determines important ecosystem processes. To achieve full integration, concerted and ongoing efforts are needed to build a united and interactive community of biodiversity researchers, with education and interdisciplinary training at its heart. © 2016 The Author(s) Published by the Royal Society. All rights reserved. Source

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