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International audience; The COVID-19 pandemic has led to a resurgence of the debate on whether host-parasite interactions should evolve towards avirulence. In this review, we first show that SARS-CoV-2 virulence is evolving, before explaining why some expect the mortality caused by the epidemic to converge towards that of human seasonal alphacoronaviruses. Leaning on existing theory, we then include viral evolution into the picture and discuss hypotheses explaining why the virulence has increased since the beginning of the pandemic. Finally, we mention some potential scenarios for the future.

The collection of animal position data via GPS tracking devices has increased in quality and usage in recent years. Animal position and movement, although measured discretely, follows the same principles of kinematic motion, and as such, the process is inherently continuous and differentiable. I demonstrate the functionality and visual elegance of smoothing spline models. I discuss the challenges and benefits of implementing such an approach, and I provide an analysis of movement and social interaction of seven jaguars inhabiting the Taiamã Ecological Station, Pantanal, Brazil, a region with the highest known density of jaguars. In the analysis, I derive measures for pairwise distance, cooccurrence, and spatiotemporal association between jaguars, borrowing ideas from density estimation and information theory. These measures are feasible as a result of spline model estimation, and they provide a critical tool for a deeper investigation of cooccurrence duration, frequency, and localized spatio‐temporal relationships between animals. In this work, I characterize a variety of interactive relationships between pairs of jaguars, and I particularly emphasize the relationships in movement of two male–female and two male–male jaguar pairs exhibiting highly associative relationships., I propose the use of smoothing spline models to explore animal movement and social interaction. I propose temporal‐state density estimation and localized mutual information measures to characterize behavior and strength of association between jaguars on a refined and unified time grid. I provide further characterization of time‐dependent male–male and female–male relationships in this region, an important step in determining conservation policy for an endangered neotropical predator.

The cecal appendix had been considered as a useless vestige since Darwin's work, but recent research questioned this idea demonstrating that the cecal appendix appeared among the mammals at least 80 million years ago and has made multiple and independent appearances without any obvious correlation with diet, social life, ecology, or size of the cecum. However, functions and probable selective advantage conferred by this anatomical structure still remain enigmatic. We found, through analyses of data on 258 mammalian species, that cecal appendix presence is correlated with increased maximal observed longevity. This is the first demonstration of a correlation between cecal appendix presence and life history. Interestingly, the classical evolutionary theory of aging that predicts an increased longevity when the extrinsic mortality is reduced has been questioned several times, but recent comparative studies asserted its validity in the taxa, which experience age‐dependent and density‐dependent mortality, as in mammals. Thus, the cecal appendix may contribute to the increase in longevity through a reduction of extrinsic mortality. A lower risk of fatal infectious diarrhea is one of the most plausible hypotheses that could explain it. However, several hypotheses coexist about the possible functions of the cecal appendix, and our results provide new insights about this much‐disputed question. In addition, we show that the cecal appendix arose at least 16 times and was lost only once during the evolutionary history of the considered mammals, an asymmetry that supports the existence of a positive selective of this structure., Most people think about the appendix as a useless and even harmful structure that is removed on emergency in case of appendicitis. This belief harks as far back as Darwin, but it has been questioned by recent works that suggests that the cecal appendix does have a function. In this study, we found that the presence of an appendix is correlated with greater longevity in mammals, even when controlling for the strong positive size effects and for the phylogeny.

International audience; Ionotropic glutamate receptors (iGluRs) are a major class of ligand-gated ion channels that are widespread in the living kingdom. Their critical role in excitatory neurotransmission and brain function of vertebrates has made them a compelling subject of interest for neurophysiologists and pharmacologists. This is particularly true for NMDA receptor (NMDARs), a subclass of iGluRs that act as central drivers of synaptic plasticity in the CNS. How and when the unique properties of NMDARs arose during evolution, and how they relate to the evolution of the nervous system, remain open questions. Recent years have witnessed a boom in both genomic and structural data, such that it is now possible to analyse the evolution of iGluR genes on an unprecedented scale and within a solid molecular framework. In this review, combining insights from phylogeny, atomic structure and physiological and mechanistic data, we discuss how evolution of NMDAR motifs and sequences shaped their architecture and functionalities. We trace differences and commonalities between NMDARs and other iGluRs, emphasizing a few distinctive properties of the former regarding ligand binding and gating, permeation, allosteric modulation and intracellular signalling. Finally, we speculate on how specific molecular properties of iGuRs arose to supply new functions to the evolving structure of the nervous system, from early metazoan to present mammals.