Community structure, abundance, and morphology

. 2000. Community structure, abundance, and morphology. -Oikos 88: 48 -56. The role of interspecific competition in structuring communities has been a highly debated issue for the last two decades. The nonrandom nature of morphological patterns within communities has been at the center of this controversy. Null models addressing community-wide dispersions in morphology have produced equivocal results and may be based on assumptions that are too restrictive (e.g., competitive exclusion or displacement). If morphological distinctiveness allows species to escape competitive pressures and exhibit higher densities, then a positive relationship should exist between morphological dissimilarity and abundance. We develop a suite of models that evaluates patterns in abundance that are associated with the morphological proximity of a species to other competitors. We evaluated the relationship between morphological distance and abundance from a variety of morphological perspectives, from those representing strictly diffuse interactions to those representing only interactions between a species and its nearest neighbor in morphological space. These models were sufficiently powerful to detect positive associations between abundance and morphological differences in a nocturnal desert rodent guild for which the effects of competition on structure are well established. Models such as these may be more useful than traditional models evaluating morphological dispersions for many reasons. They do not require that communities reach equilibrium before competitive interactions give rise to deterministic structure. They do not suffer from limitations of potentially inaccurate faunal pools or from phylogenetic constraints. Lastly, they may be used as a diagnostic tool in comparative studies to determine the degree to which competitive interactions structure communities

Experimental decoupling of canopy opening and debris addition on tropical gastropod populations and communities

a b s t r a c t Climate-induced disturbances such as hurricanes affect the structure and functioning of many ecosystems, especially those in the Caribbean Basin, where effects are well documented with regard to biodiversity and biogeochemical dynamics. Because climate change will likely alter the frequency or intensity of such storms, it is increasingly important to understand the mechanistic bases for ecosystem responses. However, this is particularly difficult to do in the absence of manipulative experiments that decouple confounded factors such as canopy opening and debris deposition. To address this issue, we exploited a replicated factorial design to experimentally distinguish the effects of canopy opening and debris deposition on population-and community-level characteristics of gastropods in the Luquillo Experimental Forest of Puerto Rico. Despite considerable spatial variation, abundances of all gastropods (combined) as well as abundances of each of 3 species (i.e., Alcadia striata, Platysuccinea portoricensis, and Polydontes acutangula) responded significantly to canopy opening while abundances of each of 2 species (i.e., Pl. portoricensis, and Po. acutangula) responded significantly to debris deposition within two years of experimental manipulation. In contrast, two species (i.e., Gaeotis nigrolineata and Nenia tridens) did not respond to any experimental manipulations in the short term. Moreover, species composition did not differ between pre-and post-manipulation periods, in part because of considerable variation among replicated blocks. In contrast, canopy removal consistently affected species richness, Shannon diversity, and rarity, while debris deposition consistently affected species richness and Shannon diversity. Neither treatment affected species dominance or evenness. Longer-term responses of the gastropod fauna were more complex. Although considerable interspecific heterogeneity characterized responses of the gastropod fauna, temporal variation in mean abundance for each of the three manipulative treatments was similar to that of the non-manipulated treatment when abundances were combined for all species. In contrast, temporal variation in each of the manipulative treatments was unrelated to temporal variation in the non-manipulated treatment for species richness, evenness, dominance, and rarity. Moreover, temporal variation in abundance generally differed between at least two of the manipulative treatments for most species and temporal variation in components of taxonomic biodiversity generally differed between manipulative treatments as well. Temporal variation in species composition was considerable and comparable for each of the four treatment combinations. Species composition within each treatment combination varied over time in ways unrelated to temporal variation in the other treatment combinations, including the reference treatment (i.e., no canopy trimming and no debris addition). Manipulated treatments were surrounded by large areas of intact forest, and tabonuco forest generally exhibits appreciable spatial and temporal variation. Natural spatiotemporal variation in the study system likely overwhelmed many of the effects of experimental manipulations on gastropod populations or communities via edge effects and recruitment of individuals from nearby less disturbed portions of the landscape

Updating Categorical Soil Maps Using Limited Survey Data by Bayesian Markov Chain Cosimulation

Updating categorical soil maps is necessary for providing current, higher-quality soil data to agricultural and environmental management but may not require a costly thorough field survey because latest legacy maps may only need limited corrections. This study suggests a Markov chain random field (MCRF) sequential cosimulation (Co-MCSS) method for updating categorical soil maps using limited survey data provided that qualified legacy maps are available. A case study using synthetic data demonstrates that Co-MCSS can appreciably improve simulation accuracy of soil types with both contributions from a legacy map and limited sample data. The method indicates the following characteristics: (1) if a soil type indicates no change in an update survey or it has been reclassified into another type that similarly evinces no change, it will be simply reproduced in the updated map; (2) if a soil type has changes in some places, it will be simulated with uncertainty quantified by occurrence probability maps; (3) if a soil type has no change in an area but evinces changes in other distant areas, it still can be captured in the area with unobvious uncertainty. We concluded that Co-MCSS might be a practical method for updating categorical soil maps with limited survey data

What is psychosis? A meta-synthesis of inductive qualitative studies exploring the experience of psychosis

Qualitative studies have played an important role in elucidating the lived experience of psychosis and there has recently been an increase in the number of such studies. There is now an urgent need to draw together the findings of these studies. This paper performed a meta-synthesis of inductive qualitative peer-reviewed research into psychosis. Ninety-eight articles were identified for systematic appraisal. Four themes, ‘Losing’, ‘Identifying a need for, and seeking, help’, ‘Rebuilding and reforging’, and ‘Better than new: gifts from psychosis’, were identified. The important implications these themes for clinicians and future research are examined upon. These findings also highlight that the experience of psychosis is much more than simply just hallucinations and/or delusions

Comparative efficacy versus effectiveness of initial antiretroviral therapy in clinical trials versus routine care

BACKGROUND: The applicability of clinical trial findings (efficacy) to the routine care setting (effectiveness) may be limited because of study eligibility criteria and volunteer bias. Although well-chronicled in many conditions, the efficacy versus effectiveness of antiretroviral therapy (ART) remains understudied. METHODS: A retrospective study of the University of Alabama at Birmingham 1917 Clinic Cohort evaluated ART-naive patients who started ART from 1 January 2000 through 31 December 2006. Patients received ART through clinical trials or routine care. Multivariable logistic and linear regression models were fit to evaluate factors associated with virological failure (virological failure was defined as a viral load \u3e50 copies/mL) and change from baseline CD4+ cell count 6 and 12 months after ART initiation. Sensitivity analyses evaluated the impact of missing data on outcomes. RESULTS: Among 570 patients starting ART during the study period, 121 (21%) enrolled in clinical trials, and 449 (79%) received ART via routine care. ART receipt through routine care was not associated with viral failure at either 6 months (odds ratio [OR], 1.00; 95% confidence interval [CI], 0.54-1.86) or 12 months (OR, 1.56; 95% CI, 0.80-3.05) in primary analyses. No statistically significant differences in CD4+ cell count responses at 6 and 12 months were observed. CONCLUSIONS: Although marked differences in efficacy versus effectiveness have been observed in the therapeutic outcomes of other conditions, our analyses found no evidence of such divergence among our patients who initiated antiretroviral therapy for human immunodeficiency virus infection

Weight gain among treatment-naïve persons with HIV starting integrase inhibitors compared to non-nucleoside reverse transcriptase inhibitors or protease inhibitors in a large observational cohort in the United States and Canada.

IntroductionWeight gain following antiretroviral therapy (ART) initiation is common, potentially predisposing some persons with HIV (PWH) to cardio-metabolic disease. We assessed relationships between ART drug class and weight change among treatment-naïve PWH initiating ART in the North American AIDS Cohort Collaboration on Research and Design (NA-ACCORD).MethodsAdult, treatment-naïve PWH in NA-ACCORD initiating integrase strand transfer inhibitor (INSTI), protease inhibitor (PI) or non-nucleoside reverse-transcriptase inhibitor (NNRTI)-based ART on/after 1 January 2007 were followed through 31 December 2016. Multivariate linear mixed effects models estimated weight up to five years after ART initiation, adjusting for age, sex, race, cohort site, HIV acquisition mode, treatment year, and baseline weight, plasma HIV-1 RNA level and CD4+ cell count. Due to shorter follow-up for PWH receiving newer INSTI drugs, weights for specific INSTIs were estimated at two years. Secondary analyses using logistic regression and all covariates from primary analyses assessed factors associated with >10% weight gain at two and five years.ResultsAmong 22,972 participants, 87% were male, and 41% were white. 49% started NNRTI-, 31% started PI- and 20% started INSTI-based regimens (1624 raltegravir (RAL), 2085 elvitegravir (EVG) and 929 dolutegravir (DTG)). PWH starting INSTI-based regimens had mean estimated five-year weight change of +5.9kg, compared to +3.7kg for NNRTI and +5.5kg for PI. Among PWH starting INSTI drugs, mean estimated two-year weight change was +7.2kg for DTG, +5.8kg for RAL and +4.1kg for EVG. Women, persons with lower baseline CD4+ cell counts, and those initiating INSTI-based regimens had higher odds of >10% body weight increase at two years (adjusted odds ratio = 1.37, 95% confidence interval: 1.20 to 1.56 vs. NNRTI).ConclusionsPWH initiating INSTI-based regimens gained, on average, more weight compared to NNRTI-based regimens. This phenomenon may reflect heterogeneous effects of ART agents on body weight regulation that require further exploration

Mortality after cancer diagnosis in HIV-infected individuals treated with antiretroviral therapy

To evaluate survival and predictors of mortality after cancer diagnosis among HIV-infected persons receiving combination antiretroviral therapy (cART)