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Université de Fribourg

The rise of angiosperms pushed conifers to decline during global cooling

Condamine, Fabien L. ; Silvestro, Daniele ; Koppelhus, Eva B. ; Antonelli, Alexandre

In: Proceedings of the National Academy of Sciences, 2020, vol. 117, no. 46, p. 28867–28875

Competition among species and entire clades can impact species diversification and extinction, which can shape macroevolutionary patterns. The fossil record shows successive biotic turnovers such that a dominant group is replaced by another. One striking example involves the decline of gymnosperms and the rapid diversification and ecological dominance of angiosperms in the Cretaceous. It is...

Université de Fribourg

Tissue-specific isoforms of the single C. elegans Ryanodine receptor gene unc-68 control specific functions

Marques, Filipe ; Thapliyal, Saurabh ; Javer, Avelino ; Shrestha, Priyanka ; Brown, André E. X. ; Glauser, Dominique A.

In: PLOS Genetics, 2020, vol. 16, no. 10, p. e1009102

Ryanodine receptors (RyR) are essential regulators of cellular calcium homeostasis and signaling. Vertebrate genomes contain multiple RyR gene isoforms, expressed in different tissues and executing different functions. In contrast, invertebrate genomes contain a single RyR-encoding gene and it has long been proposed that different transcripts generated by alternative splicing may diversify...

Université de Fribourg

A revision of Ophidiaster davidsoni de Loriol and Pellat 1874 from the Tithonian of Boulogne (France) and its transfer from the Valvatacea to the new forcipulatacean genus Psammaster gen. nov.

Fau, Marine ; Villier, Loïc ; Ewin, Timothy A. M. ; Gale, Andrew S.

In: Fossil Record, 2020, vol. 23, no. 2, p. 141–149

Forcipulatacea is one of the three major groups of extant sea stars (Asteroidea: Echinodermata), composed of 400 extant species, but only known from fewer than 25 fossil species. Despite unequivocal members being recognized in the early Jurassic, the evolutionary history of this group is still the subject of debate. Thus, the identification of any new fossil representatives is significant. We...

Université de Fribourg

Assessing the impact of diagenesis on foraminiferal geochemistry from a low latitude, shallow-water drift deposit

Stainbank, Stephanie ; Spezzaferri, Silvia ; Boever, Eva De ; Bouvier, Anne-Sophie ; Chilcott, Colin ; Leau, Erica S.de ; Foubert, Anneleen ; Kunkelova, Tereza ; Pichevin, Laetitia ; Raddatz, Jacek ; Rüggeberg, Andres ; D.Wright, James ; M.Yu, Siyao ; Zhang, Manlin ; Kroon, Dick

In: Earth and Planetary Science Letters, 2020, vol. 545, p. 116390

Due to their large heat and moisture storage capabilities, the tropics are fundamental in modulating both regional and global climate. Furthermore, their thermal response during past extreme warming periods, such as super interglacials, is not fully resolved. In this regard, we present high-resolution (analytical) foraminiferal geochemical (δ18O and Mg/Ca) records for the last 1800 kyr from...

Université de Fribourg

Living (stained) foraminifera in the Lesser Syrtis (Tunisia): influence of pollution and substratum

El Kateb, Akram ; Beccari, Valentina ; Stainbank, Stephanie ; Spezzaferri, Silvia ; Coletti, Giovanni

In: PeerJ, 2020, p. e8839

Foraminifera are protozoans with biomineralized tests that can be successfully used as a low cost monitoring tool to assess the health status of marine environments. Living benthic foraminiferal assemblages can provide essential information on natural and/or anthropogenic stresses and provide baseline conditions for studies on fossil material. Several studies have highlighted the negative impact...

Université de Fribourg

Foraminiferal-based biotic indices to assess the ecological quality status of the Gulf of Gabes (Tunisia): Present limitations and future perspectives

Kateb, Akram El ; Stalder, Claudio ; Martínez-Colón, Michael ; Mateu-Vicens, Guillem ; Francescangeli, Fabio ; Coletti, Giovanni ; Stainbank, Stephanie ; Spezzaferri, Silvia

In: Ecological Indicators, 2020, vol. 111, p. 105962

Biotic indices are tools to assess the ecological status of marine systems, and can be based on different metrics (such as ecological groups, specific diversity). The present study applies five biotic indices based on living (stained) benthic foraminiferal assemblages to assess ecological conditions in a wide area of the Mediterranean Sea in the heavily polluted Gulf of Gabes and along the...

Université de Fribourg

Alleviating the sign problem in quantum Monte Carlo simulations of spin-orbit-coupled multiorbital Hubbard models

Kim, Aaram J. ; Werner, Philipp ; Valentí, Roser

In: Physical Review B, 2020, vol. 101, no. 4, p. 045108

We present a strategy to alleviate the sign problem in continuous-time quantum Monte Carlo (CTQMC) simulations of the dynamical-mean-field-theory (DMFT) equations for the spin-orbit-coupled multiorbital Hubbard model. We first identify the combinations of rotationally invariant Hund coupling terms present in the relativistic basis which lead to a severe sign problem. Exploiting the fact that...

Université de Fribourg

Subfossil lemur discoveries from the Beanka Protected Area in western Madagascar

Burney, David A. ; Andriamialison, Haingoson ; Andrianaivoarivelo, Radosoa A. ; Bourne, Steven ; Crowley, Brooke E. ; Boer, Erik J. de ; Godfrey, Laurie R. ; Goodman, Steven M. ; Griffiths, Christine ; Griffiths, Owen ; Hume, Julian P. ; Joyce, Walter G. ; Jungers, William L. ; Marciniak, Stephanie ; Middleton, Gregory J. ; Muldoon, Kathleen M. ; Noromalala, Eliette ; Pérez, Ventura R. ; Perry, George H. ; Randalana, Roger ; Wright, Henry T.

In: Quaternary Research, 2020, vol. 93, no. 1, p. 187–203

A new fossil site in a previously unexplored part of western Madagascar (the Beanka Protected Area) has yielded remains of many recently extinct vertebrates, including giant lemurs (Babakotia radofilai, Palaeopropithecus kelyus, Pachylemur sp., and Archaeolemur edwardsi), carnivores (Cryptoprocta spelea), the aardvark-like Plesiorycteropus sp., and giant ground cuckoos (Coua). Many of these...

Université de Fribourg

The fossil record of the genus Varanus from the Southern Caucasus (Armenia, Georgia)

Vasilyan, Davit ; Bukhsianidze, Maia

In: PeerJ, 2020, p. e8322

The Southern Caucasus, with its special geographic position and complex topography, is a well-known biodiversity hotspot. However, the formation of this hotspot remains largely unstudied. To reveal this, a thorough study of the fossil record of the region is necessary. In the present paper, we describe for the first time fossil monitor lizards (Varanus sp.) from two late Miocene localities from...

Université de Fribourg

Assessment of the potential for in-plume sulphur dioxide gas-ash interactions to influence the respiratory toxicity of volcanic ash

Tomašek, Ines ; Damby, David E. ; Horwell, Claire J. ; Ayris, Paul M. ; Delmelle, Pierre ; Ottley, Christopher J. ; Cubillas, Pablo ; Casas, Ana S. ; Bisig, Christoph ; Petri-Fink, Alke ; Dingwell, Donald B. ; Clift, Martin J. D. ; Drasler, Barbara ; Rothen-Rutishauser, Barbara

In: Environmental Research, 2019, vol. 179, p. 108798

Volcanic plumes are complex environments composed of gases and ash particles, where chemical and physical processes occur at different temperature and compositional regimes. Commonly, soluble sulphate- and chloride-bearing salts are formed on ash as gases interact with ash surfaces. Exposure to respirable volcanic ash following an eruption is potentially a significant health concern. The...