Crime, Income Inequality, and Density at the Neighborhood Level

An economic model of crime gives policymakers a basis to understand how income inequality and population density relate to crime at the neighborhood level. This study reveals a negative and significant relationship between population density in Census tracts and both property and violent crime rates. It finds ambiguous results that vary by city for income inequality. This cross-sectional analysis of Census tracts in Chicago, Los Angeles, Houston, and Dallas uses crime and demographic data from the National Neighborhood Crime Study. This study also yields interesting results about the importance of residential stability for crime prevention and comments on possible urban design tools for crime reduction

A Multidecade Experiment Shows that Fertilization by Salmon Carcasses Enhanced Tree Growth in the Riparian Zone

As they return to spawn and die in their natal streams, anadromous, semelparous fishes such as Pacific salmon import marine‐derived nutrients to otherwise nutrient‐poor freshwater and riparian ecosystems. Diverse organisms exploit this resource, and previous studies have indicated that riparian tree growth may be enhanced by such marine‐derived nutrients. However, these studies were largely inferential and did not account for all factors affecting tree growth. As an experimental test of the contribution of carcasses to tree growth, for 20 yr, we systematically deposited all sockeye salmon (Oncorhynchus nerka) carcasses (217,055 individual salmon) in the riparian zone on one bank of a 2‐km‐long stream in southwestern Alaska, reducing carcass accumulation on one bank and enhancing it on the other. After accounting for partial consumption and movement of carcasses by brown bears (Ursus arctos) and variation in salmon abundance and body size, we estimated that 267,620 kg of salmon were deposited on the enhanced bank and 45,200 kg on the depleted bank over the 20 yr, for a 5.9‐fold difference in total mass. In 2016, we sampled needles of 84 white spruce trees (Picea glauca) the dominant riparian tree species, for foliar nitrogen (N) content and stable isotope ratios (δ15N), and took core samples for annual growth increments. Stable isotope analysis indicated that marine‐derived N was incorporated into the new growth of the trees on the enhanced bank. Analysis of tree cores indicated that in the two decades prior to our enhancement experiment, trees on the south‐facing (subsequently the depleted) bank grew faster than those on the north‐facing (later enhanced) bank. This difference was reduced significantly during the two decades of fertilization, indicating an effect of the carcass transfer experiment against the background of other factors affecting tree growth

Climate drives the geography of marine consumption by changing predator communities

Este artículo contiene 7 páginas, 3 figuras, 1 tabla.The global distribution of primary production and consumption by humans (fisheries) is well-documented, but we have no map linking the central ecological process of consumption within food webs to temperature and other ecological drivers. Using standardized assays that span 105° of latitude on four continents, we show that rates of bait consumption by generalist predators in shallow marine ecosystems are tightly linked to both temperature and the composition of consumer assemblages. Unexpectedly, rates of consumption peaked at midlatitudes (25 to 35°) in both Northern and Southern Hemispheres across both seagrass and unvegetated sediment habitats. This pattern contrasts with terrestrial systems, where biotic interactions reportedly weaken away from the equator, but it parallels an emerging pattern of a subtropical peak in marine biodiversity. The higher consumption at midlatitudes was closely related to the type of consumers present, which explained rates of consumption better than consumer density, biomass, species diversity, or habitat. Indeed, the apparent effect of temperature on consumption was mostly driven by temperature-associated turnover in consumer community composition. Our findings reinforce the key influence of climate warming on altered species composition and highlight its implications for the functioning of Earth’s ecosystems.We acknowledge funding from the Smithsonian Institution and the Tula Foundation.Peer reviewe

3D genomics across the tree of life reveals condensin II as a determinant of architecture type

We investigated genome folding across the eukaryotic tree of life. We find two types of three-dimensional (3D) genome architectures at the chromosome scale. Each type appears and disappears repeatedly during eukaryotic evolution. The type of genome architecture that an organism exhibits correlates with the absence of condensin II subunits. Moreover, condensin II depletion converts the architecture of the human genome to a state resembling that seen in organisms such as fungi or mosquitoes. In this state, centromeres cluster together at nucleoli, and heterochromatin domains merge. We propose a physical model in which lengthwise compaction of chromosomes by condensin II during mitosis determines chromosome-scale genome architecture, with effects that are retained during the subsequent interphase. This mechanism likely has been conserved since the last common ancestor of all eukaryotes

The structure of a conserved telomeric region associated with variant antigen loci in the blood parasite Trypanosoma congolense

African trypanosomiasis is a vector-borne disease of humans and livestock caused by African trypanosomes (Trypanosoma spp.). Survival in the vertebrate bloodstream depends on antigenic variation of Variant Surface Glycoproteins (VSGs) coating the parasite surface. In T. brucei, a model for antigenic variation, monoallelic VSG expression originates from dedicated VSG expression sites (VES). Trypanosoma brucei VES have a conserved structure consisting of a telomeric VSG locus downstream of unique, repeat sequences, and an independent promoter. Additional protein-coding sequences, known as “Expression Site Associated Genes (ESAGs)”, are also often present and are implicated in diverse, bloodstream-stage functions. Trypanosoma congolense is a related veterinary pathogen, also displaying VSG-mediated antigenic variation. A T. congolense VES has not been described, making it unclear if regulation of VSG expression is conserved between species. Here, we describe a conserved telomeric region associated with VSG loci from long-read DNA sequencing of two T. congolense strains, which consists of a distal repeat, conserved noncoding elements and other genes besides the VSG; although these are not orthologous to T. brucei ESAGs. Most conserved telomeric regions are associated with accessory minichromosomes, but the same structure may also be associated with megabase chromosomes. We propose that this region represents the T. congolense VES, and through comparison with T. brucei, we discuss the parallel evolution of antigenic switching mechanisms, and unique adaptation of the T. brucei VES for developmental regulation of bloodstream-stage genes. Hence, we provide a basis for understanding antigenic switching in T. congolense and the origins of the African trypanosome VES

Data from: A multi-decade experiment shows that fertilization by salmon carcasses enhanced tree growth in the riparian zone

As they return to spawn and die in their natal streams, anadromous, semelparous fishes such as Pacific salmon import marine‐derived nutrients to otherwise nutrient‐poor freshwater and riparian ecosystems. Diverse organisms exploit this resource, and previous studies have indicated that riparian tree growth may be enhanced by such marine‐derived nutrients. However, these studies were largely inferential and did not account for all factors affecting tree growth. As an experimental test of the contribution of carcasses to tree growth, for 20 yr, we systematically deposited all sockeye salmon (Oncorhynchus nerka) carcasses (217,055 individual salmon) in the riparian zone on one bank of a 2‐km‐long stream in southwestern Alaska, reducing carcass accumulation on one bank and enhancing it on the other. After accounting for partial consumption and movement of carcasses by brown bears (Ursus arctos) and variation in salmon abundance and body size, we estimated that 267,620 kg of salmon were deposited on the enhanced bank and 45,200 kg on the depleted bank over the 20 yr, for a 5.9‐fold difference in total mass. In 2016, we sampled needles of 84 white spruce trees (Picea glauca) the dominant riparian tree species, for foliar nitrogen (N) content and stable isotope ratios (δ15N), and took core samples for annual growth increments. Stable isotope analysis indicated that marine‐derived N was incorporated into the new growth of the trees on the enhanced bank. Analysis of tree cores indicated that in the two decades prior to our enhancement experiment, trees on the south‐facing (subsequently the depleted) bank grew faster than those on the north‐facing (later enhanced) bank. This difference was reduced significantly during the two decades of fertilization, indicating an effect of the carcass transfer experiment against the background of other factors affecting tree growth

White spruce N and C isotope data

Spruce tree location, date, historic stream sampling reach, side of stream, distance from bank (cm), diameter at breast height (cm), number of stems, distance to a heavily used "bear kitchen" (cm), and nitrogen and carbon isotope values from August 2016 sampling from Hansen Creek, Alaska, USA