Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title><jats:p>The fossil record of marine invertebrates has long fuelled the debate as to whether or not there are limits to global diversity in the sea<jats:sup>1–5</jats:sup>. Ecological theory states that, as diversity grows and ecological niches are filled, the strengthening of biological interactions imposes limits on diversity<jats:sup>6,7</jats:sup>. However, the extent to which biological interactions have constrained the growth of diversity over evolutionary time remains an open question<jats:sup>1–5,8–11</jats:sup>. Here we present a regional diversification model that reproduces the main Phanerozoic eon trends in the global diversity of marine invertebrates after imposing mass extinctions. We find that the dynamics of global diversity are best described by a diversification model that operates widely within the exponential growth regime of a logistic function. A spatially resolved analysis of the ratio of diversity to carrying capacity reveals that less than 2% of the global flooded continental area throughout the Phanerozoic exhibits diversity levels approaching ecological saturation. We attribute the overall increase in global diversity during the Late Mesozoic and Cenozoic eras to the development of diversity hotspots under prolonged conditions of Earth system stability and maximum continental fragmentation. We call this the ‘diversity hotspots hypothesis’, which we propose as a non-mutually exclusive alternative to the hypothesis that the Mesozoic marine revolution led this macroevolutionary trend<jats:sup>12,13</jats:sup>.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Social-evaluative stressors—experiences in which people feel they could be judged negatively—pose a major threat to adolescent mental health<jats:sup>1–3</jats:sup> and can cause young people to disengage from stressful pursuits, resulting in missed opportunities to acquire valuable skills. Here we show that replicable benefits for the stress responses of adolescents can be achieved with a short (around 30-min), scalable 'synergistic mindsets' intervention. This intervention, which is a self-administered online training module, synergistically targets both growth mindsets<jats:sup>4</jats:sup> (the idea that intelligence can be developed) and stress-can-be-enhancing mindsets<jats:sup>5</jats:sup> (the idea that one’s physiological stress response can fuel optimal performance). In six double-blind, randomized, controlled experiments that were conducted with secondary and post-secondary students in the United States, the synergistic mindsets intervention improved stress-related cognitions (study 1, <jats:italic>n</jats:italic> = 2,717; study 2, <jats:italic>n</jats:italic> = 755), cardiovascular reactivity (study 3, <jats:italic>n</jats:italic> = 160; study 4, <jats:italic>n</jats:italic> = 200), daily cortisol levels (study 5, <jats:italic>n</jats:italic> = 118 students, <jats:italic>n</jats:italic> = 1,213 observations), psychological well-being (studies 4 and 5), academic success (study 5) and anxiety symptoms during the 2020 COVID-19 lockdowns (study 6, <jats:italic>n</jats:italic> = 341). Heterogeneity analyses (studies 3, 5 and 6) and a four-cell experiment (study 4) showed that the benefits of the intervention depended on addressing both mindsets—growth and stress—synergistically. Confidence in these conclusions comes from a conservative, Bayesian machine-learning statistical method for detecting heterogeneous effects<jats:sup>6</jats:sup>. Thus, our research has identified a treatment for adolescent stress that could, in principle, be scaled nationally at low cost.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Gonadal development is a complex process that involves sex determination followed by divergent maturation into either testes or ovaries<jats:sup>1</jats:sup>. Historically, limited tissue accessibility, a lack of reliable in vitro models and critical differences between humans and mice have hampered our knowledge of human gonadogenesis, despite its importance in gonadal conditions and infertility. Here, we generated a comprehensive map of first- and second-trimester human gonads using a combination of single-cell and spatial transcriptomics, chromatin accessibility assays and fluorescent microscopy. We extracted human-specific regulatory programmes that control the development of germline and somatic cell lineages by profiling equivalent developmental stages in mice. In both species, we define the somatic cell states present at the time of sex specification, including the bipotent early supporting population that, in males, upregulates the testis-determining factor <jats:italic>SRY</jats:italic> and sPAX8s, a gonadal lineage located at the gonadal–mesonephric interface. In females, we resolve the cellular and molecular events that give rise to the first and second waves of granulosa cells that compartmentalize the developing ovary to modulate germ cell differentiation. In males, we identify human <jats:italic>SIGLEC15</jats:italic><jats:sup>+</jats:sup> and <jats:italic>TREM2</jats:italic><jats:sup><jats:italic>+</jats:italic></jats:sup> fetal testicular macrophages, which signal to somatic cells outside and inside the developing testis cords, respectively. This study provides a comprehensive spatiotemporal map of human and mouse gonadal differentiation, which can guide in vitro gonadogenesis.</jats:p>