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The biota of Sulawesi is noted for its high degree of endemism and for its substantial levels of in situ biological diversification. While the island’s long period of isolation and dynamic tectonic history have been implicated as drivers of the regional diversification, this has rarely been tested in the context of an explicit geological framework. Here, we provide a tectonically informed biogeographical framework that we use to explore the diversification history of Sulawesi flying lizards (the Draco lineatus Group), a radiation that is endemic to Sulawesi and its surrounding islands. We employ a framework for inferring cryptic speciation that involves phylogeographic and genetic clustering analyses as a means of identifying potential species followed by population demographic assessment of divergence-timing and rates of bi-directional migration as means of confirming lineage independence (and thus species status). Using this approach, phylogenetic and population genetic analyses of mitochondrial sequence data obtained for 613 samples, a 50-SNP data set for 370 samples, and a 1249-locus exon-capture data set for 106 samples indicate that the current taxonomy substantially understates the true number of Sulawesi Draco species, that both cryptic and arrested speciations have taken place, and that ancient hybridization confounds phylogenetic analyses that do not explicitly account for reticulation. The Draco lineatus Group appears to comprise 15 species—9 on Sulawesi proper and 6 on peripheral islands. The common ancestor of this group colonized Sulawesi ~11 Ma when proto-Sulawesi was likely composed of two ancestral islands, and began to radiate ~6 Ma as new islands formed and were colonized via overwater dispersal. The enlargement and amalgamation of many of these proto-islands into modern Sulawesi, especially during the past 3 Ma, set in motion dynamic species interactions as once-isolated lineages came into secondary contact, some of which resulted in lineage merger, and others surviving to the present. [Genomics; Indonesia; introgression; mitochondria; phylogenetics; phylogeography; population genetics; reptiles.]

 

Considerable attention is given to absolute nutrient levels in lakes, rivers, and oceans, but less is paid to their relative concentrations, their nitrogen:phosphorus (N:P) stoichiometry, and the consequences of imbalanced stoichiometry. Here, we report 38 y of nutrient dynamics in Flathead Lake, a large oligotrophic lake in Montana, and its inflows. While nutrient levels were low, the lake had sustained high total N: total P ratios (TN:TP: 60 to 90:1 molar) throughout the observation period. N and P loading to the lake as well as loading N:P ratios varied considerably among years but showed no systematic long-term trend. Surprisingly, TN:TP ratios in river inflows were consistently lower than in the lake, suggesting that forms of P in riverine loading are removed preferentially to N. In-lake processes, such as differential sedimentation of P relative to N or accumulation of fixed N in excess of denitrification, likely also operate to maintain the lake’s high TN:TP ratios. Regardless of causes, the lake’s stoichiometric imbalance is manifested in P limitation of phytoplankton growth during early and midsummer, resulting in high C:P and N:P ratios in suspended particulate matter that propagate P limitation to zooplankton. Finally, the lake’s imbalanced N:P stoichiometry appears to raise the potential for aerobic methane production via metabolism of phosphonate compounds by P-limited microbes. These data highlight the importance of not only absolute N and P levels in aquatic ecosystems, but also their stoichiometric balance, and they call attention to potential management implications of high N:P ratios. 

Mean annual temperature and mean annual precipitation drive much of the variation in productivity across Earth's terrestrial ecosystems but do not explain variation in gross primary productivity (GPP) or ecosystem respiration (ER) in flowing waters. We document substantial variation in the magnitude and seasonality of GPP and ER across 222 US rivers. In contrast to their terrestrial counterparts, most river ecosystems respire far more carbon than they fix and have less pronounced and consistent seasonality in their metabolic rates. We find that variation in annual solar energy inputs and stability of flows are the primary drivers of GPP and ER across rivers. A classification schema based on these drivers advances river science and informs management. 

JAMIE LENNEY, BYRON LUTZ, FINN SCHÜLE, and LOUISE SHEINER: "The Sustainability of State and Local Pensions: A Public Finance Approach" Comment by Deborah Lucas Comment by Joshua Rauh General Discussion PANEL on COVID-19 AND ECONOMIC POLICY AFTER ONE YEAR ANDREW ATKESON: "Behavior and the Dynamics of Epidemics" CHRISTINA D. ROMER: "The Fiscal Policy Response to the Pandemic" KRISTA RUFFINI and ABIGAIL WOZNIAK: "Supporting Workers and Families in the Pandemic Recession: Results in 2020 and Suggestions for 2021" General Discussion ANDREW METRICK and DANIEL TARULLO: "Congruent Financial Regulation" Comment by Viral Acharya Comment by Hyun Song Shin General Discussion PANEL on FIFTY YEARS OF BPEA’S CONTRIBUTIONS TO MACROECONOMICS AND POLICY ROBERT E. HALL: "The Brookings Panel’s Contributions to Research on Labor Markets" ROBERT J. GORDON: "Productivity and Growth over the Years at BPEA" ALAN S. BLINDER: "BPEA and Monetary Policy over Fifty Years" WILL DOBBIE and CRYSTAL YANG: "The Economic Costs of Pretrial Detention" Comment by Conrad Miller Comment by Justin Wolfers General Discussion CAROLINE M. HOXBY: "Advanced Cognitive Skill Deserts in the United States: Their Likely Causes and Implications" Comment by Erik Hurst Comment by Brian A. Jacob General Discussion 

JAMIE LENNEY, BYRON LUTZ, FINN SCHÜLE, and LOUISE SHEINER: "The Sustainability of State and Local Pensions: A Public Finance Approach" Comment by Deborah Lucas Comment by Joshua Rauh General Discussion PANEL on COVID-19 AND ECONOMIC POLICY AFTER ONE YEAR ANDREW ATKESON: "Behavior and the Dynamics of Epidemics" CHRISTINA D. ROMER: "The Fiscal Policy Response to the Pandemic" KRISTA RUFFINI and ABIGAIL WOZNIAK: "Supporting Workers and Families in the Pandemic Recession: Results in 2020 and Suggestions for 2021" General Discussion ANDREW METRICK and DANIEL TARULLO: "Congruent Financial Regulation" Comment by Viral Acharya Comment by Hyun Song Shin General Discussion PANEL on FIFTY YEARS OF BPEA’S CONTRIBUTIONS TO MACROECONOMICS AND POLICY ROBERT E. HALL: "The Brookings Panel’s Contributions to Research on Labor Markets" ROBERT J. GORDON: "Productivity and Growth over the Years at BPEA" ALAN S. BLINDER: "BPEA and Monetary Policy over Fifty Years" WILL DOBBIE and CRYSTAL YANG: "The Economic Costs of Pretrial Detention" Comment by Conrad Miller Comment by Justin Wolfers General Discussion CAROLINE M. HOXBY: "Advanced Cognitive Skill Deserts in the United States: Their Likely Causes and Implications" Comment by Erik Hurst Comment by Brian A. Jacob General Discussion 

Abstract The relationship between detritivore diversity and decomposition can provide information on how biogeochemical cycles are affected by ongoing rates of extinction, but such evidence has come mostly from local studies and microcosm experiments. We conducted a globally distributed experiment (38 streams across 23 countries in 6 continents) using standardised methods to test the hypothesis that detritivore diversity enhances litter decomposition in streams, to establish the role of other characteristics of detritivore assemblages (abundance, biomass and body size), and to determine how patterns vary across realms, biomes and climates. We observed a positive relationship between diversity and decomposition, strongest in tropical areas, and a key role of abundance and biomass at higher latitudes. Our results suggest that litter decomposition might be altered by detritivore extinctions, particularly in tropical areas, where detritivore diversity is already relatively low and some environmental stressors particularly prevalent. 

Gene‐editing techniques are currently revolutionizing biology, allowing far greater precision than previous mutagenic and transgenic approaches. They are becoming applicable to a wide range of plant species and biological processes. Gene editing can rapidly improve a range of crop traits, including disease resistance, abiotic stress tolerance, yield, nutritional quality and additional consumer traits. Unlike transgenic approaches, however, it is not facile to forensically detect gene‐editing events at the molecular level, as no foreign DNA exists in the elite line. These limitations in molecular detection approaches are likely to focus more attention on the products generated from the technology than on the process in itself. Rapid advances in sequencing and genome assembly increasingly facilitate genome sequencing as a means of characterizing new varieties generated by gene‐editing techniques. Nevertheless, subtle edits such as single base changes or small deletions may be difficult to distinguish from normal variation within a genotype. Given these emerging scenarios, downstream ‘omics’ technologies reflective of edited affects, such as metabolomics, need to be used in a more prominent manner to fully assess compositional changes in novel foodstuffs. To achieve this goal, metabolomics or ‘non‐targeted metabolite analysis’ needs to make significant advances to deliver greater representation across the metabolome. With the emergence of new edited crop varieties, we advocate: (i) concerted efforts in the advancement of ‘omics’ technologies, such as metabolomics, and (ii) an effort to redress the use of the technology in the regulatory assessment for metabolically engineered biotech crops.