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Shovon TA, Auge H, Haase J, Nock CA. Positive effects of tree species diversity on productivity switch to negative after severe drought mortality in a temperate forest experiment. Glob Chang Biol 2024; 30:e17252. [PMID: 38501719 DOI: 10.1111/gcb.17252] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Revised: 12/20/2023] [Accepted: 12/27/2023] [Indexed: 03/20/2024]
Abstract
The synthesis of a large body of evidence from field experiments suggests more diverse plant communities are more productive as well as more resistant to the effects of climatic extremes like drought. However, this view is strongly based on data from grasslands due to the limited empirical evidence from tree diversity experiments. Here we report on the relationship between tree diversity and productivity over 10 years in a field experiment established in 2005 that was then affected by the 2018 mega-drought in central Europe. Across a number of years, tree species diversity and productivity were significantly positively related; however, the slope switched to negative in the year of the drought. Net diversity effects increased through time, with complementarity effects making greater contributions to the net diversity effect than selection effects. Complementarity effects were clearly positive in three- and five-species mixtures before the drought (2012-2016) but were found to decrease in the year of the drought. Selection effects were clearly positive in 2016 and remained positive in the drought year 2018 in two-, three-, and five-species mixtures. The survival of Norway spruce (Picea abies) plummeted in response to the drought, and a negative relationship between species diversity and spruce survival was found. Taken together, our findings suggest that tree diversity per se may not buffer communities against the impacts of extreme drought and that tree species composition and the drought tolerance of tree species (i.e., species identity) will be important determinants of community productivity as the prevalence of drought increases.
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Affiliation(s)
- Tanvir Ahmed Shovon
- Department of Renewable Resources, Faculty of Agricultural, Life and Environmental Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Harald Auge
- Department of Community Ecology, Helmholtz-Centre for Environmental Research-UFZ, Halle (Saale), Germany
- German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Leipzig, Germany
| | - Josephine Haase
- Department of Community Ecology, Helmholtz-Centre for Environmental Research-UFZ, Halle (Saale), Germany
- Department of Aquatic Ecology, Eawag-Swiss Federal Institute of Aquatic Science and Technology, Dübendorf, Switzerland
| | - Charles A Nock
- Department of Renewable Resources, Faculty of Agricultural, Life and Environmental Sciences, University of Alberta, Edmonton, Alberta, Canada
- Geobotany, Faculty of Biology, University of Freiburg, Freiburg, Germany
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Wu B, Guan X, Deng T, Yang X, Li J, Zhou M, Wang C, Wang S, Yan Q, Shu L, He Q, He Z. Synthetic Denitrifying Communities Reveal a Positive and Dynamic Biodiversity-Ecosystem Functioning Relationship during Experimental Evolution. Microbiol Spectr 2023; 11:e0452822. [PMID: 37154752 PMCID: PMC10269844 DOI: 10.1128/spectrum.04528-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Accepted: 04/04/2023] [Indexed: 05/10/2023] Open
Abstract
Biodiversity is vital for ecosystem functions and services, and many studies have reported positive, negative, or neutral biodiversity-ecosystem functioning (BEF) relationships in plant and animal systems. However, if the BEF relationship exists and how it evolves remains elusive in microbial systems. Here, we selected 12 Shewanella denitrifiers to construct synthetic denitrifying communities (SDCs) with a richness gradient spanning 1 to 12 species, which were subjected to approximately 180 days (with 60 transfers) of experimental evolution with generational changes in community functions continuously tracked. A significant positive correlation was observed between community richness and functions, represented by productivity (biomass) and denitrification rate, however, such a positive correlation was transient, only significant in earlier days (0 to 60) during the evolution experiment (180 days). Also, we found that community functions generally increased throughout the evolution experiment. Furthermore, microbial community functions with lower richness exhibited greater increases than those with higher richness. Biodiversity effect analysis revealed positive BEF relationships largely attributable to complementary effects, which were more pronounced in communities with lower richness than those with higher richness. This study is one of the first studies that advances our understanding of BEF relationships and their evolutionary mechanisms in microbial systems, highlighting the crucial role of evolution in predicting the BEF relationship in microbial systems. IMPORTANCE Despite the consensus that biodiversity supports ecosystem functioning, not all experimental models of macro-organisms support this notion with positive, negative, or neutral biodiversity-ecosystem functioning (BEF) relationships reported. The fast-growing, metabolically versatile, and easy manipulation nature of microbial communities allows us to explore well the BEF relationship and further interrogate if the BEF relationship remains constant during long-term community evolution. Here, we constructed multiple synthetic denitrifying communities (SDCs) by randomly selecting species from a candidate pool of 12 Shewanella denitrifiers. These SDCs differ in species richness, spanning 1 to 12 species, and were monitored continuously for community functional shifts during approximately 180-day parallel cultivation. We demonstrated that the BEF relationship was dynamic with initially (day 0 to 60) greater productivity and denitrification among SDCs of higher richness. However, such pattern was reversed thereafter with greater productivity and denitrification increments in lower-richness SDCs, likely due to a greater accumulation of beneficial mutations during the experimental evolution.
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Affiliation(s)
- Bo Wu
- Environmental Microbiomics Research Center, School of Environmental Science and Engineering, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Sun Yat-sen University, Guangzhou, China
| | - Xiaotong Guan
- Environmental Microbiomics Research Center, School of Environmental Science and Engineering, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Sun Yat-sen University, Guangzhou, China
| | - Ting Deng
- Environmental Microbiomics Research Center, School of Environmental Science and Engineering, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Sun Yat-sen University, Guangzhou, China
| | - Xueqin Yang
- Environmental Microbiomics Research Center, School of Environmental Science and Engineering, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Sun Yat-sen University, Guangzhou, China
| | - Juan Li
- College of Agronomy, Hunan Agricultural University, Changsha, China
| | - Min Zhou
- Environmental Microbiomics Research Center, School of Environmental Science and Engineering, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Sun Yat-sen University, Guangzhou, China
| | - Cheng Wang
- Environmental Microbiomics Research Center, School of Environmental Science and Engineering, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Sun Yat-sen University, Guangzhou, China
| | - Shanquan Wang
- Environmental Microbiomics Research Center, School of Environmental Science and Engineering, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Sun Yat-sen University, Guangzhou, China
| | - Qingyun Yan
- Environmental Microbiomics Research Center, School of Environmental Science and Engineering, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Sun Yat-sen University, Guangzhou, China
| | - Longfei Shu
- Environmental Microbiomics Research Center, School of Environmental Science and Engineering, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Sun Yat-sen University, Guangzhou, China
| | - Qiang He
- Department of Civil and Environmental Engineering, The University of Tennessee, Knoxville, Tennessee, USA
| | - Zhili He
- Environmental Microbiomics Research Center, School of Environmental Science and Engineering, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Sun Yat-sen University, Guangzhou, China
- College of Agronomy, Hunan Agricultural University, Changsha, China
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3
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Kim J, Shin YJ, Park D. Peer network in math anxiety: A longitudinal social network approach. J Exp Child Psychol 2023; 232:105672. [PMID: 37003154 DOI: 10.1016/j.jecp.2023.105672] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Revised: 02/28/2023] [Accepted: 02/28/2023] [Indexed: 04/03/2023]
Abstract
Regardless of age, math anxiety (i.e., adverse affective reactions in situations involving math) is associated with lower math achievement. Previous studies have investigated the role of adult figures (e.g., parents, teachers) in the development of children's math anxiety. However, given the importance of peer relationships during adolescence, we examined friendship selection and social influence on children's math anxiety using longitudinal peer network analyses. Throughout the academic semester, we found that children became more similar to their peers in math anxiety levels but did not form new peer networks based on their levels of math anxiety. These findings highlight the importance of peers' emotional reactions to math, which could influence future academic achievement and career aspirations considerably.
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Affiliation(s)
- Jingu Kim
- Radboud University, 6525 XZ Nijmegen, The Netherlands; Busan National University of Education, Yeonje-gu, Busan 47503, South Korea
| | - Yun-Jeong Shin
- Seoul National University, Gwanak-gu, Seoul 08826, South Korea
| | - Daeun Park
- Sungkyunkwan University, Jongno-gu, Seoul 03063, South Korea.
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Wang Y, Shahid MQ. Genome sequencing and resequencing identified three horizontal gene transfers and uncovered the genetic mechanism on the intraspecies adaptive evolution of Gastrodia elata Blume. Front Plant Sci 2023; 13:1035157. [PMID: 36684780 PMCID: PMC9848658 DOI: 10.3389/fpls.2022.1035157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Accepted: 12/13/2022] [Indexed: 06/17/2023]
Abstract
Horizontal gene transfer is a rare and useful genetic mechanism in higher plants. Gastrodia elata Blume (GE) (Orchidaceae), well known as traditional medicinal material in East Asia, adopts a heterotrophic lifestyle, thus being considered to be more prone to horizontal gene transfer (HGT). GE is a "polytypic species" that currently comprised of five recognized forms according to the plant morphology. G. elata Blume forma elata (GEE) and G. elata Bl.f.glauca (GEG) are two common forms that naturally grow in different habitats with difference in altitude and latitude. G. elata Bl.f.viridis (GEV) often occurs sporadically in cultivated populations of GEE and GEG. However, the genetic relationships and genetic mechanism underpinned the divergent ecological adaptations of GEE and GEG have not been revealed. Here, we assembled a chromosome-level draft genome of GEE with 1.04 Gb. Among predicted 17,895 protein coding genes, we identified three HGTs. Meanwhile, we resequenced 10 GEE accessions, nine GEG accessions, and 10 GEV accessions, and identified two independent genetic lineages: GEG_pedigree (GEG individuals and GEV individuals collected from GEG populations) and GEE_pedigree (GEE individuals and GEV individuals collected from GEE populations), which strongly support the taxonomic status of GEE and GEG as subspecies, not as different forms. In highly differentiated genomic regions of GEE_pedigree and GEG_pedigree, three chalcone synthase-encoding genes and one Phox/Bem1p (PB1) domain of encoding Auxin (AUX)/Indoleacetic acid (IAA) were identified in selection sweeping genome regions, which suggested that differentiation between GEE_pedigree and GEG_pedigree was promoted by the selection of genes related to photoresponse and growth and development. Overall, this new genome would be helpful for breeding and utilization of GE and the new findings would deepen the understanding about ecological adaptation and evolution of GE.
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Affiliation(s)
- Yunsheng Wang
- School of Health and Life Science, Kaili University, Kaili, Guizhou, China
| | - Muhammad Qasim Shahid
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, South China Agricultural University, Guangzhou, China
- Guangdong Provincial Key Laboratory of Plant Molecular Breeding, South China Agricultural University, Guangzhou, China
- College of Agriculture, South China Agricultural University, Guangzhou, Guangdong, China
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Metts A, Yarrington J, Enders C, Hammen C, Mineka S, Zinbarg R, Craske MG. Reciprocal effects of neuroticism and life stress in adolescence. J Affect Disord 2021; 281:247-255. [PMID: 33338843 PMCID: PMC7855753 DOI: 10.1016/j.jad.2020.12.016] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Revised: 11/24/2020] [Accepted: 12/05/2020] [Indexed: 12/15/2022]
Abstract
BACKGROUND Stressful life experiences and personality can influence one another. Personality may contribute to the amount and type of stress individuals experience, which is referred to as a selection effect. Life stress may also impact one's personality, which is referred to as a socialization effect. It was hypothesized that neuroticism would predict increased chronic and episodic stress (selection effect) and that chronic and episodic stress would predict increased neuroticism (socialization effect). METHODS The current study investigated selection and socialization effects of neuroticism and life stress over a three-year period in 627 adolescents. Life stress data were examined in terms of duration (chronic versus episodic) and type (interpersonal versus non-interpersonal). Episodic stress data were examined as dependent or independent. RESULTS The results from ten cross-lagged panel models provided some evidence for significant selection and socialization effects depending on stress type. Over three years, we observed that neuroticism increases interpersonal chronic stress and non-interpersonal stressful events (selection effects) and that dependent non-interpersonal stressful events and chronic stress increase neuroticism (socialization effects). LIMITATIONS Study limitations include a lack of a lifespan perspective and a statistical approach that does not differentiate between- from within-person variance. CONCLUSIONS Findings suggest the value of attending to stress response as well as targeting neuroticism in prevention and intervention approaches in adolescents.
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Affiliation(s)
- Allison Metts
- University of California, Los Angeles, Department of Psychology, 1285 Franz Hall, Los Angeles, CA 90025, USA
| | - Julia Yarrington
- University of California, Los Angeles, Department of Psychology, 1285 Franz Hall, Los Angeles, CA 90025, USA
| | - Craig Enders
- University of California, Los Angeles, Department of Psychology, 1285 Franz Hall, Los Angeles, CA 90025, USA
| | - Constance Hammen
- University of California, Los Angeles, Department of Psychology, 1285 Franz Hall, Los Angeles, CA 90025, USA
| | - Susan Mineka
- Northwestern University, Department of Psychology, 2029 Sheridan Road, Swift Hall 102, Evanston, IL 60208, US
| | - Richard Zinbarg
- Northwestern University, Department of Psychology, 2029 Sheridan Road, Swift Hall 102, Evanston, IL 60208, US
| | - Michelle G. Craske
- University of California, Los Angeles, Department of Psychology, 1285 Franz Hall, Los Angeles, CA 90025, USA,Correspondence to: Department of Psychology, University of California, Los Angeles, 1285 Franz Hall, Los Angeles, CA 90095,
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Pillai P, Gouhier TC. Not even wrong: the spurious measurement of biodiversity's effects on ecosystem functioning. Ecology 2019; 100:e02645. [PMID: 30719717 DOI: 10.1002/ecy.2645] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/28/2018] [Revised: 12/27/2018] [Accepted: 01/03/2019] [Indexed: 11/10/2022]
Abstract
Understanding how biodiversity influences ecosystem functioning is one of the central goals of modern ecology. The early and often acrimonious debates about the relationship between biodiversity and ecosystem functioning were largely resolved following the advent of a statistical partitioning scheme that decomposed the net effect of biodiversity on ecosystem functioning into a "selection" effect and a "complementarity" effect. Here we show that both the biodiversity effect and its statistical decomposition into selection and complementarity are fundamentally flawed because these methods use a naïve null expectation based on neutrality, likely leading to an overestimate of the net biodiversity effect, and because they fail to account for the nonlinear abundance-ecosystem-functioning relationships widely observed in nature. Furthermore, under nonlinearity no such statistical scheme can be devised to partition the biodiversity effect. We also present an alternative approach that provides a more reasonable starting point for estimating biodiversity effects. Overall, our results suggest that all studies conducted since the early 1990s are likely to have overestimated the positive effects of biodiversity on ecosystem functioning.
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Affiliation(s)
- Pradeep Pillai
- Marine Science Center, Northeastern University, 430 Nahant Road, Nahant, Massachusetts, 01908, USA
| | - Tarik C Gouhier
- Marine Science Center, Northeastern University, 430 Nahant Road, Nahant, Massachusetts, 01908, USA
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7
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Hannuschke M, Gollwitzer M, Geukes K, Nestler S, Back M. Neuroticism and interpersonal perception: Evidence for positive, but not negative, biases. J Pers 2019; 88:217-236. [PMID: 30985001 DOI: 10.1111/jopy.12480] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2018] [Revised: 03/28/2019] [Accepted: 04/03/2019] [Indexed: 11/29/2022]
Abstract
OBJECTIVE Personality dispositions predict how individuals perceive, interpret, and react to social interactions with others. A still unresolved question is (a) whether these personality-congruent interpersonal perceptions reflect perception biases, which occur when perceivers' dispositions systematically predict deviations between perceivers' and other people's perceptions of the same interaction, and/or selection effects, which occur when perceivers' dispositions predict their selection of interaction partners, and (b) whether these effects feed back into perceivers' personality. METHOD Data from 110 psychology freshmen involving repeated assessments of Neuroticism and repeated interpersonal perceptions of social interactions with fellow students were analyzed to address these questions, focusing on Neuroticism. RESULTS There is evidence for a Neuroticism-related positivity bias in interpersonal perceptions (i.e., perceivers high in Neuroticism tended to make more positive judgments of others' sociability and warmth), but little evidence for personality-congruent selection effects (i.e., Neuroticism-related preferences for interaction partners). The positivity bias did not predict intrapersonal changes in Neuroticism over time, but the selection of specific interaction partners did. CONCLUSIONS These findings help to shed light on the interpersonal perception dynamics of Neuroticism in a real-life context and add to our understanding of the psychological mechanisms underlying the interplay of personality and interpersonal perceptions.
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Affiliation(s)
| | - Mario Gollwitzer
- Department of Psychology, Ludwig-Maximilians-Universität München, München, Germany
| | - Katharina Geukes
- Department of Psychology, Westfälische Wilhelms-Universität Münster, Münster, Germany
| | - Steffen Nestler
- Department of Psychology, Westfälische Wilhelms-Universität Münster, Münster, Germany
| | - Mitja Back
- Department of Psychology, Westfälische Wilhelms-Universität Münster, Münster, Germany
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Abstract
Contents Summary 50 I. Introduction 50 II. Drivers of the diversity-productivity relationship 51 III. Patterns of the diversity-productivity relationship 55 IV. Responses of mixed stands to climate change 57 V. Conclusions 60 Acknowledgements 61 References 61 SUMMARY: Although the relationship between species diversity and biomass productivity has been extensively studied in grasslands, the impact of tree species diversity on forest productivity, as well as the main drivers of this relationship, are still under discussion. It is widely accepted that the magnitude of the relationship between tree diversity and forest stand productivity is context specific and depends on environmental conditions, but the underlying mechanisms of this relationship are still not fully understood. Competition reduction and facilitation have been identified as key mechanisms driving the diversity-productivity relationship. However, contrasting results have been reported with respect to the extent to which competition reduction and facilitation determine the diversity-productivity relationship. They appear to depend on regional climate, soil fertility, functional diversity of the tree species involved, and developmental stage of the forest. The purpose of this review is to summarize current knowledge and to suggest a conceptual framework to explain the various processes leading to higher productivity of species-rich forests compared with average yields of their respective monocultures. This framework provides three pathways for possible development of the diversity-productivity relationship under a changing climate.
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Affiliation(s)
- Christian Ammer
- Silviculture and Forest Ecology of the Temperate Zones, Faculty of Forest Sciences, University of Göttingen, Büsgenweg 1, D-37077, Göttingen, Germany
- Centre of Biodiversity and Sustainable Land-use, University of Göttingen, Büsgenweg 1, D-37077, Göttingen, Germany
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Isbell F, Cowles J, Dee LE, Loreau M, Reich PB, Gonzalez A, Hector A, Schmid B. Quantifying effects of biodiversity on ecosystem functioning across times and places. Ecol Lett 2018; 21:763-778. [PMID: 29493062 DOI: 10.1111/ele.12928] [Citation(s) in RCA: 85] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Revised: 12/08/2017] [Accepted: 01/25/2018] [Indexed: 11/30/2022]
Abstract
Biodiversity loss decreases ecosystem functioning at the local scales at which species interact, but it remains unclear how biodiversity loss affects ecosystem functioning at the larger scales of space and time that are most relevant to biodiversity conservation and policy. Theory predicts that additional insurance effects of biodiversity on ecosystem functioning could emerge across time and space if species respond asynchronously to environmental variation and if species become increasingly dominant when and where they are most productive. Even if only a few dominant species maintain ecosystem functioning within a particular time and place, ecosystem functioning may be enhanced by many different species across many times and places (β-diversity). Here, we develop and apply a new approach to estimate these previously unquantified insurance effects of biodiversity on ecosystem functioning that arise due to species turnover across times and places. In a long-term (18-year) grassland plant diversity experiment, we find that total insurance effects are positive in sign and substantial in magnitude, amounting to 19% of the net biodiversity effect, mostly due to temporal insurance effects. Species loss can therefore reduce ecosystem functioning both locally and by eliminating species that would otherwise enhance ecosystem functioning across temporally fluctuating and spatially heterogeneous environments.
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Affiliation(s)
- Forest Isbell
- Department of Ecology, Evolution, and Behavior, University of Minnesota Twin Cities, Saint Paul, MN, 55108, USA
| | - Jane Cowles
- Department of Ecology, Evolution, and Behavior, University of Minnesota Twin Cities, Saint Paul, MN, 55108, USA
| | - Laura E Dee
- Department of Fisheries, Wildlife, and Conservation Biology, University of Minnesota Twin Cities, Saint Paul, MN, 55108, USA
| | - Michel Loreau
- Centre for Biodiversity Theory and Modelling, Theoretical and Experimental Ecology Station, CNRS and Paul Sabatier University, 09200, Moulis, France
| | - Peter B Reich
- Department of Forest Resources, University of Minnesota Twin Cities, Saint Paul, MN, 55108, USA.,Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW, 2753, Australia
| | - Andrew Gonzalez
- Department of Biology, McGill University, Montreal, QC, H3A 1B1, Canada
| | - Andy Hector
- Department of Plant Sciences, University of Oxford, Oxford, OX1 3RB, UK
| | - Bernhard Schmid
- URPP Global Change and Biodiversity, Department of Evolutionary Biology and Environmental Studies, University of Zürich, Winterthurerstrasse 190, 8057, Zürich, Switzerland
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10
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Rosenberg M, Pettifor A, Twine R, Hughes JP, Gomez-Olive FX, Wagner RG, Sulaimon A, Tollman S, Selin A, MacPhail C, Kahn K. Evidence for sample selection effect and Hawthorne effect in behavioural HIV prevention trial among young women in a rural South African community. BMJ Open 2018; 8:e019167. [PMID: 29326192 PMCID: PMC5781067 DOI: 10.1136/bmjopen-2017-019167] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
OBJECTIVES We examined the potential influence of both sample selection effects and Hawthorne effects in the behavioural HIV Prevention Trial Network 068 study, designed to examine whether cash transfers conditional on school attendance reduce HIV acquisition in young South African women. We explored whether school enrolment among study participants differed from the underlying population, and whether differences existed at baseline (sample selection effect) or arose during study participation (Hawthorne effect). METHODS We constructed a cohort of 3889 young women aged 11-20 years using data from the Agincourt Health and socio-Demographic Surveillance System. We compared school enrolment in 2011 (trial start) and 2015 (trial end) between those who did (n=1720) and did not (n=2169) enrol in the trial. To isolate the Hawthorne effect, we restricted the cohort to those enrolled in school in 2011. RESULTS In 2011, trial participants were already more likely to be enrolled in school (99%) compared with non-participants (93%). However, this association was attenuated with covariate adjustment (adjusted risk difference (aRD) (95% CI): 2.9 (- 0.7 to 6.5)). Restricting to those enrolled in school in 2011, trial participants were also more likely to be enrolled in school in 2015 (aRD (95% CI): 4.9 (1.5 to 8.3)). The strength of associations increased with age. CONCLUSIONS Trial participants across both study arms were more likely to be enrolled in school than non-participants. Our findings suggest that both sample selection and Hawthorne effects may have diminished the differences in school enrolment between study arms, a plausible explanation for the null trial findings. The Hawthorne-specific findings generate hypotheses for how to structure school retention interventions to prevent HIV.
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Affiliation(s)
- Molly Rosenberg
- Department of Epidemiology and Biostatistics, Indiana University School of Public Health, Bloomington, Indiana, USA
| | - Audrey Pettifor
- Department of Epidemiology, University of North Carolina, Chapel Hill, North Carolina, USA
- Carolina Population Center, University of North Carolina, Chapel Hill, North Carolina, USA
- MRC/Wits Rural Public Health and Health Transitions Research Unit (Agincourt), Faculty of Health Sciences, School of Public Health, University of the Witwatersrand, Johannesburg, South Africa
| | - Rhian Twine
- MRC/Wits Rural Public Health and Health Transitions Research Unit (Agincourt), Faculty of Health Sciences, School of Public Health, University of the Witwatersrand, Johannesburg, South Africa
| | - James P Hughes
- Department of Biostatistics, University of Washington, Seattle, Washington, USA
| | - F Xavier Gomez-Olive
- MRC/Wits Rural Public Health and Health Transitions Research Unit (Agincourt), Faculty of Health Sciences, School of Public Health, University of the Witwatersrand, Johannesburg, South Africa
- Center for Population and Development Studies, Harvard University, Cambridge, Massachusetts, USA
- INDEPTH Network, Accra, Ghana
| | - Ryan G Wagner
- MRC/Wits Rural Public Health and Health Transitions Research Unit (Agincourt), Faculty of Health Sciences, School of Public Health, University of the Witwatersrand, Johannesburg, South Africa
- Division of Epidemiology and Global Health, Department of Public Health and Clinical Medicine, Umeå Centre for Global Health Research, Umeå University, Umeå, Sweden
| | - Afolabi Sulaimon
- MRC/Wits Rural Public Health and Health Transitions Research Unit (Agincourt), Faculty of Health Sciences, School of Public Health, University of the Witwatersrand, Johannesburg, South Africa
| | - Stephen Tollman
- MRC/Wits Rural Public Health and Health Transitions Research Unit (Agincourt), Faculty of Health Sciences, School of Public Health, University of the Witwatersrand, Johannesburg, South Africa
- INDEPTH Network, Accra, Ghana
- Division of Epidemiology and Global Health, Department of Public Health and Clinical Medicine, Umeå Centre for Global Health Research, Umeå University, Umeå, Sweden
| | - Amanda Selin
- Carolina Population Center, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Catherine MacPhail
- MRC/Wits Rural Public Health and Health Transitions Research Unit (Agincourt), Faculty of Health Sciences, School of Public Health, University of the Witwatersrand, Johannesburg, South Africa
- School of Health and Society, University of Wollongong, Wollongong, New South Wales, Australia
- Wits Reproductive Health and HIV Institute, University of the Witwatersrand, Johannesburg, South Africa
| | - Kathleen Kahn
- MRC/Wits Rural Public Health and Health Transitions Research Unit (Agincourt), Faculty of Health Sciences, School of Public Health, University of the Witwatersrand, Johannesburg, South Africa
- INDEPTH Network, Accra, Ghana
- Division of Epidemiology and Global Health, Department of Public Health and Clinical Medicine, Umeå Centre for Global Health Research, Umeå University, Umeå, Sweden
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Hu XF, Liu GG, Fan M. Long-Term Effects of Famine on Chronic Diseases: Evidence from China's Great Leap Forward Famine. Health Econ 2017; 26:922-936. [PMID: 27311596 DOI: 10.1002/hec.3371] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2015] [Revised: 04/28/2016] [Accepted: 05/19/2016] [Indexed: 06/06/2023]
Abstract
We evaluate the long-term effects of famine on chronic diseases using China's Great Leap Forward Famine as a natural experiment. Using a unique health survey, we explore the heterogeneity of famine intensity across regions and find strong evidence supporting both the adverse effect and the selection effect. The two offsetting effects co-exist and their magnitudes vary in different age cohorts at the onset of famine. The selection effect is dominant among the prenatal/infant famine-exposed cohort, while the adverse effect appears dominant among the childhood/puberty famine-exposed cohort. The net famine effects are more salient in rural residents and non-migrants subsamples. Gender differences are also found, and are sensitive to smoking and drinking behaviors. Our conclusion is robust to various specifications. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- Xue Feng Hu
- Department of Biology, University of Ottawa, Canada
| | - Gordon G Liu
- National School of Development, Beijing University, China
| | - Maoyong Fan
- Department of Economics, Ball State University, USA
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12
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Zhang Q, Buyantuev A, Li FY, Jiang L, Niu J, Ding Y, Kang S, Ma W. Functional dominance rather than taxonomic diversity and functional diversity mainly affects community aboveground biomass in the Inner Mongolia grassland. Ecol Evol 2017; 7:1605-1615. [PMID: 28261469 PMCID: PMC5330864 DOI: 10.1002/ece3.2778] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Revised: 12/23/2016] [Accepted: 01/05/2017] [Indexed: 11/17/2022] Open
Abstract
The relationship between biodiversity and productivity has been a hot topic in ecology. However, the relative importance of taxonomic diversity and functional characteristics (including functional dominance and functional diversity) in maintaining community productivity and the underlying mechanisms (including selection and complementarity effects) of the relationship between diversity and community productivity have been widely controversial. In this study, 194 sites were surveyed in five grassland types along a precipitation gradient in the Inner Mongolia grassland of China. The relationships between taxonomic diversity (species richness and the Shannon-Weaver index), functional dominance (the community-weighted mean of four plant traits), functional diversity (Rao's quadratic entropy), and community aboveground biomass were analyzed. The results showed that (1) taxonomic diversity, functional dominance, functional diversity, and community aboveground biomass all increased from low to high precipitation grassland types; (2) there were significant positive linear relationships between taxonomic diversity, functional dominance, functional diversity, and community aboveground biomass; (3) the effect of functional characteristics on community aboveground biomass is greater than that of taxonomic diversity; and (4) community aboveground biomass depends on the community-weighted mean plant height, which explained 57.1% of the variation in the community aboveground biomass. Our results suggested that functional dominance rather than taxonomic diversity and functional diversity mainly determines community productivity and that the selection effect plays a dominant role in maintaining the relationship between biodiversity and community productivity in the Inner Mongolia grassland.
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Affiliation(s)
- Qing Zhang
- School of Ecology and EnvironmentInner Mongolia UniversityHohhotChina
| | - Alexander Buyantuev
- Department of Geography and PlanningUniversity at AlbanyState University of New YorkAlbanyNYUSA
| | - Frank Yonghong Li
- School of Ecology and EnvironmentInner Mongolia UniversityHohhotChina
| | - Lin Jiang
- School of BiologyGeorgia Institute of TechnologyAtlantaGAUSA
| | - Jianming Niu
- School of Ecology and EnvironmentInner Mongolia UniversityHohhotChina
| | - Yong Ding
- Grassland Research Institute of Chinese Academy of Agricultural SciencesHohhotChina
| | - Sarula Kang
- School of Ecology and EnvironmentInner Mongolia UniversityHohhotChina
| | - Wenjing Ma
- School of Ecology and EnvironmentInner Mongolia UniversityHohhotChina
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13
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Gianuca AT, Pantel JH, De Meester L. Disentangling the effect of body size and phylogenetic distances on zooplankton top-down control of algae. Proc Biol Sci 2016; 283:rspb.2016.0487. [PMID: 27075258 DOI: 10.1098/rspb.2016.0487] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Accepted: 03/21/2016] [Indexed: 12/12/2022] Open
Abstract
A negative consequence of biodiversity loss is reduced rates of ecosystem functions. Phylogenetic-based biodiversity indices have been claimed to provide more accurate predictions of ecosystem functioning than species diversity alone. This approach assumes that the most relevant traits for ecosystem functioning present a phylogenetic signal. Yet, traits-mediating niche partitioning and resource uptake efficiency in animals can be labile. To assess the relative power of a key trait (body size) and phylogeny to predict zooplankton top-down control on phytoplankton, we manipulated trait and phylogenetic distances independently in microcosms while holding species richness constant. We found that body size provided strong predictions of top-down control. In contrast, phylogeny was a poor predictor of grazing rates. Size-related grazing efficiency asymmetry was mechanistically more important than niche differences in mediating ecosystem function in our experimental settings. Our study demonstrates a strong link between a single functional trait (i.e. body size) in zooplankton and trophic interactions, and urges for a cautionary use of phylogenetic information and taxonomic diversity as substitutes for trait information to predict and understand ecosystem functions.
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Affiliation(s)
- Andros T Gianuca
- Laboratory of Aquatic Ecology, Evolution and Conservation, KU Leuven, Charles Deberiotstraat 32, 3000 Leuven, Belgium
| | - Jelena H Pantel
- Centre d'Ecologie fonctionnelle et Evolutive, UMR 5175 CNRS-Université de Montpellier-EPHE, Campus CNRS, 1919 route de Mende 34293, Montpellier, Cedex 05, France
| | - Luc De Meester
- Laboratory of Aquatic Ecology, Evolution and Conservation, KU Leuven, Charles Deberiotstraat 32, 3000 Leuven, Belgium
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McKenna TP, Yurkonis KA. Across species-pool aggregation alters grassland productivity and diversity. Ecol Evol 2016; 6:5788-95. [PMID: 27547354 PMCID: PMC4983591 DOI: 10.1002/ece3.2325] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Revised: 06/17/2016] [Accepted: 06/23/2016] [Indexed: 11/08/2022] Open
Abstract
Plant performance is determined by the balance of intra- and interspecific neighbors within an individual's zone of influence. If individuals interact over smaller scales than the scales at which communities are measured, then altering neighborhood interactions may fundamentally affect community responses. These interactions can be altered by changing the number (species richness), abundances (species evenness), and positions (species pattern) of the resident plant species, and we aimed to test whether aggregating species at planting would alter effects of species richness and evenness on biomass production at a common scale of observation in grasslands. We varied plant species richness (2, 4, or 8 species and monocultures), evenness (0.64, 0.8, or 1.0), and pattern (planted randomly or aggregated in groups of four individuals) within 1 × 1 m plots established with transplants from a pool of 16 tallgrass prairie species and assessed plot-scale biomass production and diversity over the first three growing seasons. As expected, more species-rich plots produced more biomass by the end of the third growing season, an effect associated with a shift from selection to complementarity effects over time. Aggregating conspecifics at a 0.25-m scale marginally reduced biomass production across all treatments and increased diversity in the most even plots, but did not alter biodiversity effects or richness-productivity relationships. Results support the hypothesis that fine-scale species aggregation affects diversity by promoting species coexistence in this system. However, results indicate that inherent changes in species neighborhood relationships along grassland diversity gradients may only minimally affect community (meter) - scale responses among similarly designed biodiversity-ecosystem function studies. Given that species varied in their responses to local aggregation, it may be possible to use such species-specific results to spatially design larger-scale grassland communities to achieve desired diversity and productivity responses.
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Affiliation(s)
- Thomas P McKenna
- Department of Biology University of North Dakota 10 Cornell Street Stop 9019 Grand Forks North Dakota 58202
| | - Kathryn A Yurkonis
- Department of Biology University of North Dakota 10 Cornell Street Stop 9019 Grand Forks North Dakota 58202
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15
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Kuebbing SE, Classen AT, Sanders NJ, Simberloff D. Above- and below-ground effects of plant diversity depend on species origin: an experimental test with multiple invaders. New Phytol 2015; 208:727-35. [PMID: 26053089 DOI: 10.1111/nph.13488] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2015] [Accepted: 04/27/2015] [Indexed: 05/26/2023]
Abstract
Although many plant communities are invaded by multiple nonnative species, we have limited information on how a species' origin affects ecosystem function. We tested how differences in species richness and origin affect productivity and seedling establishment. We created phylogenetically paired native and nonnative plant communities in a glasshouse experiment to test diversity-productivity relationships and responsible mechanisms (i.e. selection or complementarity effects). Additionally, we tested how productivity and associated mechanisms influenced seedling establishment. We used diversity-interaction models to describe how species' interactions influenced diversity-productivity relationships. Communities with more species had higher total biomass than did monoculture communities, but native and nonnative communities diverged in root : shoot ratios and the mechanism responsible for increased productivity: positive selection effect in nonnative communities and positive complementarity effect in native communities. Seedling establishment was 46% lower in nonnative than in native communities and was correlated with the average selection effect. Interspecific interactions contributed to productivity patterns, but the specific types of interactions differed between native and nonnative communities. These results reinforce findings that the diversity-productivity mechanisms in native and nonnative communities differ and are the first to show that these mechanisms can influence seedling establishment and that different types of interactions influence diversity-productivity relationships.
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Affiliation(s)
- Sara E Kuebbing
- Department of Ecology and Evolutionary Biology, University of Tennessee, 569 Dabney Hall, Knoxville, TN, 37996-1610, USA
| | - Aimée T Classen
- Department of Ecology and Evolutionary Biology, University of Tennessee, 569 Dabney Hall, Knoxville, TN, 37996-1610, USA
- Natural History Museum of Denmark, University of Copenhagen, DK-2100, Copenhagen, Denmark
| | - Nathan J Sanders
- Department of Ecology and Evolutionary Biology, University of Tennessee, 569 Dabney Hall, Knoxville, TN, 37996-1610, USA
- Center for Macroecology, Evolution and Climate, University of Copenhagen, DK-2100, Copenhagen, Denmark
| | - Daniel Simberloff
- Department of Ecology and Evolutionary Biology, University of Tennessee, 569 Dabney Hall, Knoxville, TN, 37996-1610, USA
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Lübbe T, Schuldt B, Leuschner C. Species identity and neighbor size surpass the impact of tree species diversity on productivity in experimental broad-leaved tree sapling assemblages under dry and moist conditions. Front Plant Sci 2015; 6:857. [PMID: 26579136 PMCID: PMC4620412 DOI: 10.3389/fpls.2015.00857] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Accepted: 09/28/2015] [Indexed: 05/22/2023]
Abstract
Species diversity may increase the productivity of tree communities through complementarity (CE) and/or selection effects (SE), but it is not well known how this relationship changes under water limitation. We tested the stress-gradient hypothesis, which predicts that resource use complementarity and facilitation are more important under water-limited conditions. We conducted a growth experiment with saplings of five temperate broad-leaved tree species that were grown in assemblages of variable diversity (1, 3, or 5 species) and species composition under ample and limited water supply to examine effects of species richness and species identity on stand- and tree-level productivity. Special attention was paid to effects of neighbor identity on the growth of target trees in mixture as compared to growth in monoculture. Stand productivity was strongly influenced by species identity while a net biodiversity effect (NE) was significant in the moist treatment (mostly assignable to CE) but of minor importance. The growth performance of some of the species in the mixtures was affected by tree neighborhood characteristics with neighbor size likely being more important than neighbor species identity. Diversity and neighbor identity effects visible in the moist treatment mostly disappeared in the dry treatment, disproving the stress-gradient hypothesis. The mixtures were similarly sensitive to drought-induced growth reduction as the monocultures, which may relate to the decreased CE on growth upon drought in the mixtures.
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Affiliation(s)
- Torben Lübbe
- Plant Ecology and Ecosystems Research, Albrecht von Haller Institute for Plant Sciences, University of GöttingenGöttingen, Germany
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Larson AR, Rothschild B, Walls AC, Granter SR, Qureshi AA, Murphy GF, Laga AC. Impact of the 2009 AJCC staging guidelines for melanoma on the number of mitotic figures reported by dermatopathologists at one institution. J Cutan Pathol 2015; 42:536-41. [PMID: 25929156 DOI: 10.1111/cup.12517] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Revised: 12/30/2014] [Accepted: 02/21/2015] [Indexed: 12/16/2023]
Abstract
BACKGROUND In 2009 the revised seventh staging system for melanoma recommended the use of mitotic count to separate stage T1a from T1b. However, careful scrutiny of cases may lead to an inadvertent selection effect, with consequent increased reporting of mitotic counts. METHODS We investigated whether there is a significant increase in mitotic counts reported since 2009 for melanomas with a Breslow thickness of 1.0 mm or less. We conducted a retrospective, case-controlled study examining invasive melanoma cases at a large academic center. Mitotic counts were compared between pathology reports before 2009 (n = 61) and after 2009 (n = 125), with a subset of slides re-examined in a blinded fashion. RESULTS Before the 2009 staging guidelines, 51% of cases had one or more mitosis reported compared to 38% after 2009 (p = 0.113). Blinded re-counting did not yield a significant difference when compared with the original pathology reports in either group. CONCLUSIONS There was not a significant difference in the number of mitoses reported after the implementation of the new guidelines.
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Affiliation(s)
- Allison R Larson
- Division of Dermatopathology, Department of Pathology, Brigham and Women's, Hospital, Harvard Medical School, Boston, MA, USA
- Department of Dermatology, Boston Medical Center, Boston, MA, USA
| | - Brian Rothschild
- Department of Dermatology, Colorado Permanente Medical Group, Denver, CO, USA
- Harvard Combined Dermatology Residency Program, Boston, MA, USA
| | - Andrew C Walls
- Harvard Combined Dermatology Residency Program, Boston, MA, USA
| | - Scott R Granter
- Division of Dermatopathology, Department of Pathology, Brigham and Women's, Hospital, Harvard Medical School, Boston, MA, USA
| | - Abrar A Qureshi
- Department of Dermatology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | - George F Murphy
- Division of Dermatopathology, Department of Pathology, Brigham and Women's, Hospital, Harvard Medical School, Boston, MA, USA
| | - Alvaro C Laga
- Division of Dermatopathology, Department of Pathology, Brigham and Women's, Hospital, Harvard Medical School, Boston, MA, USA
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Abstract
OBJECTIVE To examine private insurance coverage and its impact on use of Veterans Health Administration (VA) care among VA enrollees without Medicare coverage. DATA SOURCES The 1999 National Health Survey of Veteran Enrollees merged with VA administrative data, with other information drawn from American Hospital Association data and the Area Resource File. STUDY DESIGN We modeled VA enrollees' decision of having private insurance coverage and its impact on use of VA care controlling for sociodemographic information, patients' health status, VA priority status and access to VA and non-VA alternatives. We estimated the true impact of insurance on the use of VA care by teasing out potential selection bias. Bias came from two sources: a security selection effect (sicker enrollees purchase private insurance for extra security and use more VA and non-VA care) and a preference selection effect (VA enrollees who prefer non-VA care may purchase private insurance and use less VA care). PRINCIPAL FINDINGS VA enrollees with private insurance coverage were less likely to use VA care. Security selection dominated preference selection and naïve models that did not control for selection effects consistently underestimated the insurance effect. CONCLUSIONS Our results indicate that prior research, which has not controlled for insurance selection effects, may have underestimated the potential impact of any private insurance policy change, which may in turn affect VA enrollees' private insurance coverage and consequently their use of VA care. From the decline in private insurance coverage from 1999 to 2002, we projected an increase of 29,400 patients and 158 million dollars for VA health care services.
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Affiliation(s)
- Yujing Shen
- VA New Jersey Healthcare System Center for Healthcare Knowledge Management, East Orange VA Medical Center, 385 Tremont Avenue, Mailstop 129, East Orange, NJ 07018-1095, USA
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