The maintenance and generation of freshwater diversity from the local to the global scale

The distribution of biological diversity is markedly uneven across the world. Despite the seemingly endless variety of forms and adaptations that have evolved and continue to evolve, large differences in the numbers and characteristics of species remain among locales. These differences are often not random; e.g., the Earth\u2019s tropics are disproportionately rich in the diversity of life and large areas harbor more species than small areas. Observations of these general biogeographic patterns are some of the oldest contributions by early naturalists and ecologists, yet explanations for these patterns are a recurring topic of debate. Generality of pattern (with room for exceptions to the rule) has been reached for large-scale gradients in diversity but not generality of the theories that underlie these patterns. Unlike diversity at the biogeographic scale, even the generality of pattern at the local scale of species interactions remains elusive. Although numerous investigations into how potential drivers of local diversity such as productivity, isolation, and disturbance influence diversity have been made, a unifying consensus to describe general patterns of local diversity has not emerged. Today, increasing emphasis is being placed on the importance of the interaction between local and regional scales in influencing local diversity. The thesis first introduces and summarizes attempts to describe and explain biodiversity patterns at both the local and regional scales. Chapter 1 describes a study of the role of dispersal and assembly history in influencing species diversity in natural and experimental pond communities of plankton under the metacommunity framework. A further test of the role of dispersal and assembly history is presented in Chapter 2 using experimental pond mesocosms. This study evaluates the role of ecosystem size on the assembly and structure of a multitrophic community of both plankton and macroinvertebrates while concurrently varying nutrient input rate and initial assembly. Chapter 3 empirically illustrates variation in the dormancy-dispersal strategies used by freshwater zooplankton that can lead to interspecific differences in the degree and type of dispersal limitation. In Chapter 4, I use the distribution of single lake endemic fish in the largest lakes in the world to estimate the relative contributions of lake surface area, age, and latitude on diversification.(Ph. D.)--Michigan State University. Integrative Biology, 2017Includes bibliographical reference

Equivalent roles of marine subsidies and island characteristics in shaping island bird communities

AimSpecies distributions across islands are shaped by dispersal limitations, environmental filters and biotic interactions but the relative influence of each of these processes has rarely been assessed. Here, we examine the relative contributions of island characteristics, marine subsidies, species traits, and species interactions on avian community composition.LocationCentral Coast region of British Columbia, Canada.TaxonTerrestrial breeding birds.MethodsWe observed 3610 individuals of 32 bird species on 89 islands that spanned multiple orders of magnitude in area (0.0002–3 km$^{2}$). We fit a spatially explicit joint species distribution model to estimate the relative contributions of island physical characteristics, island‐specific inputs of marine subsidies, species' traits, and biotic interactions on species distributions. Biogeographic characteristics included island area, isolation, and habitat heterogeneity, while marine influence was represented by forest‐edge soil δ$^{15}$N, wrack biomass, shoreline substrate, and distance to shore. This approach also allowed us to estimate how much variation in distributions resulted from species' biological traits (i.e. body mass, feeding guild, feeding height, and nesting height).ResultsBird species distributions were determined almost equivalently by island biogeographic characteristics (23.5% of variation explained) and marine influence (24.8%). We detected variation in species‐specific responses to both island biogeographic characteristics and marine influence, but no significant effect of any biological trait examined. Additionally, we found evidence that habitat preferences were a more important driver than competitive interactions.Main ConclusionsAlthough most island biogeographic studies focus only on islands' physical characteristics, we found evidence for an equivalent role of marine subsidy in structuring island bird communities. Our study suggests that for small islands, disentangling the effects of island biogeographic characteristics, marine inputs, and biotic interactions is a useful next step in understanding species distributions

Equivalent roles of marine subsidies and island characteristics in shaping island bird communities

Aim: Species distributions across islands are shaped by dispersal limitations, environmental filters and biotic interactions but the relative influence of each of these processes has rarely been assessed. Here, we examine the relative contributions of island characteristics, marine subsidies, species traits, and species interactions on avian community composition. Location: Central Coast region of British Columbia, Canada. Taxon: Terrestrial breeding birds. Methods: We observed 3610 individuals of 32 bird species on 89 islands that spanned multiple orders of magnitude in area (0.0002–3 km2). We fit a spatially explicit joint species distribution model to estimate the relative contributions of island physical characteristics, island-specific inputs of marine subsidies, species' traits, and biotic interactions on species distributions. Biogeographic characteristics included island area, isolation, and habitat heterogeneity, while marine influence was represented by forest-edge soil δ15N, wrack biomass, shoreline substrate, and distance to shore. This approach also allowed us to estimate how much variation in distributions resulted from species' biological traits (i.e. body mass, feeding guild, feeding height, and nesting height). Results: Bird species distributions were determined almost equivalently by island biogeographic characteristics (23.5% of variation explained) and marine influence (24.8%). We detected variation in species-specific responses to both island biogeographic characteristics and marine influence, but no significant effect of any biological trait examined. Additionally, we found evidence that habitat preferences were a more important driver than competitive interactions. Main Conclusions: Although most island biogeographic studies focus only on islands' physical characteristics, we found evidence for an equivalent role of marine subsidy in structuring island bird communities. Our study suggests that for small islands, disentangling the effects of island biogeographic characteristics, marine inputs, and biotic interactions is a useful next step in understanding species distributions

Nocturnal Hypoxia and Loss of Kidney Function

Background: Although obstructive sleep apnea (OSA) is more common in patients with kidney disease, whether nocturnal hypoxia affects kidney function is unknown. Methods: We studied all adult subjects referred for diagnostic testing of sleep apnea between July 2005 and December 31 2007 who had serial measurement of their kidney function. Nocturnal hypoxia was defined as oxygen saturation (SaO2) below 90 % for $12$4 ml/min/1.73 m2 per year. Results: 858 participants were included and followed for a mean study period of 2.1 years. Overall 374 (44%) had nocturnal hypoxia, and 49 (5.7%) had accelerated loss of kidney function. Compared to controls without hypoxia, patients with nocturnal hypoxia had a significant increase in the adjusted risk of accelerated kidney function loss (odds ratio (OR) 2.89, 95 % confidence interval [CI] 1.25, 6.67). Conclusion: Nocturnal hypoxia was independently associated with an increased risk of accelerated kidney function loss. Further studies are required to determine whether treatment and correction of nocturnal hypoxia reduces loss of kidney function

Scale-dependent effects of marine subsidies on the island biogeographic patterns of plants

Although species richness can be determined by different mechanisms at different spatial scales, the role of scale in the effects of marine inputs on island biogeography has not been studied explicitly. Here, we evaluated the potential influence of island characteristics and marine inputs (seaweed wrack biomass and marine-derived nitrogen in the soil) on plant species richness at both a local (plot) and regional (island) scale on 92 islands in British Columbia, Canada. We found that the effects of subsidies on species richness depend strongly on spatial scale. Despite detecting no effects of marine subsidies at the island scale, we found that as plot level subsidies increased, species richness decreased; plots with more marine-derived nitrogen in the soil hosted fewer plant species. We found no effect of seaweed wrack at either scale. To identify potential mechanisms underlying the decrease in diversity, we fit a spatially explicit joint species distribution model to evaluate species level responses to marine subsidies and effects of biotic interactions among species. We found mixed evidence for competition for both light and nutrients, and cannot rule out an alternative mechanism; the observed decrease in species richness may be due to disturbances associated with animal-mediated nutrient deposits, particularly those from North American river otters (Lontra canadensis). By evaluating the scale-dependent effects of marine subsidies on island biogeographic patterns of plants and revealing likely mechanisms that act on community composition, we provide novel insights on the scale dependence of a fundamental ecological theory, and on the rarely examined links between marine and terrestrial ecosystems often bridged by animal vectors

Biogeographic features mediate marine subsidies to island food webs

Although marine subsidies often enrich terrestrial ecosystems, their influence is known to be context-dependent. Additionally, the multitrophic impact of marine subsidies has not been traced through food webs across physically diverse islands. Here, we test predictions about how island characteristics can affect marine enrichment of food web constituents and how nutrients flow through island food webs. To evaluate enrichment and trace marine nutrients across food webs, we used stable isotopes of soil, flora, and fauna (n = 4752 samples) collected from 97 islands in British Columbia, Canada. Island area was the strongest predictor of enrichment across taxa; we found that samples were more 15N-rich on smaller islands. Enrichment declined with distance from shore but less so on small islands, implying a higher per-unit-area subsidy effect. These area and distance-to-shore effects were taxon-specific, and nearly twice as strong in basal food web groups. We also found that increases in δ15N correlated with increases in %N in basal trophic groups, as well as in songbirds, implying biologically relevant uptake of a potentially limiting nutrient. Path analysis demonstrated that subsidies in soil flow through plants and detritivores, and into upper-level consumers. Our results reveal an interplay between island biogeography and marine subsidies in shaping island food webs through bottom-up processes

Electrocardiographic findings in systemic lupus erythematosus: data from an international inception cohort.

To estimate the early prevalence of various electrocardiographic (EKG) abnormalities in patients with systemic lupus erythematosus (SLE) and to evaluate possible associations between repolarization changes (increased corrected QT [QTc] and QT dispersion [QTd]) and clinical and laboratory variables, including the anti-Ro/SSA level and specificity (52 or 60 kd).We studied adult SLE patients from 19 centers participating in the Systemic Lupus International Collaborating Clinics (SLICC) Inception Registry. Demographics, disease activity (Systemic Lupus Erythematosus Disease Activity Index 2000 [SLEDAI-2K]), disease damage (SLICC/American College of Rheumatology Damage Index [SDI]), and laboratory data from the baseline or first followup visit were assessed. Multivariate logistic and linear regression models were used to asses for any cross-sectional associations between anti-Ro/SSA and EKG repolarization abnormalities.For the 779 patients included, mean ± SD age was 35.2 ± 13.8 years, 88.4% were women, and mean ± SD disease duration was 10.5 ± 14.5 months. Mean ± SD SLEDAI-2K score was 5.4 ± 5.6 and mean ± SD SDI score was 0.5 ± 1.0. EKG abnormalities were frequent and included nonspecific ST-T changes (30.9%), possible left ventricular hypertrophy (5.4%), and supraventricular arrhythmias (1.3%). A QTc ≥440 msec was found in 15.3%, while a QTc ≥460 msec was found in 5.3%. Mean ± SD QTd was 34.2 ± 14.7 msec and QTd ≥40 msec was frequent (38.1%). Neither the specificity nor the level of anti-Ro/SSA was associated with QTc duration or QTd, although confidence intervals were wide. Total SDI was significantly associated with a QTc interval exceeding 440 msec (odds ratio 1.38 [95% confidence interval 1.06, 1.79]).A substantial proportion of patients with recent-onset SLE exhibited repolarization abnormalities, although severe abnormalities were rare.VoRSUNY DownstateRheumatologyN/

Code for generating Landsat reflectance time series, water chemistry matchups, and machine learning models to predict water chemistry for US lakes

<p>Code and models associated with the generation of the LAGOS-US LANDSAT extension module, which contains 45,867,023 sets of reflectances from Landsat 5, 7, and 8 as well predicted water quality for chlorophyll, Secchi deph, true water color, dissolved organic carbon, total suspended solids, and turbidity for 136,977 lakes 4+ hectares in the conterminous US based on matchups to in situ data from LAGOS-US LIMNO. Contained here are the following files:</p> <p>GEE_Extraction_Code.txt: code used to extract time series of Landsat reflectances for a list of LAGOS-US lakes using the shapefiles contained within the LAGOS-US LOCUS data module using Google Earth Engine. The code harmonizes among sensors, calculates pixel-specific band ratios, and exports a CSV of the time series for each lake. </p> <p>lagos_us_matchup.R: Creates a matchup dataset for a window of +/- 7 calendar days using LAGOS-US LIMNO data and the compiled CSVs generated by GEE.</p> <p>lagos_us_rs_model.R: Suite of 40 random forest models run for water quality variable predictions, including testing the usage of log10-transformed response, band ratio usage, the removal of scenes with negative median reflectances, and the removal of scenes with >50% cloud cover. The selected final model for each water quality variable is used to make final predictions for the data module.</p> <p>Each of the final model fitted objects is contained within this model and code product in an individual RData file:</p> <p>Colort: true water color (pcu) - log10-transformed</p> <p>CHL: chlorophyll (micrograms/L) - log10-transformed</p> <p>NTU: turbidity (NTU) - log10-transformed</p> <p>TSS: total suspended solids (mg/L) - log10-transformed</p> <p>DOC: dissolved organic carbon (mg/L) - log10-transformed</p> <p>Secchi: Secchi depth (m) - untransformed</p> <p>lagos_us_pred_obs.R: Script that calculates and plots predicted vs in situ output from each of the six water quality variable models and generates plots of mean absolute percentage error (MAPE) by range of each water quality variable.</p&gt