Publications by authors named "Melissa McCormick"

19 Publications

  • Page 1 of 1

Litter quality, dispersal and invasion drive earthworm community dynamics and forest soil development.

Oecologia 2018 Sep 12;188(1):237-250. Epub 2018 Jun 12.

Department of Zoology, Eszterházy Károly University, Eger, Hungary.

In temperate deciduous forests of eastern USA, most earthworm communities are dominated by invasive species. Their structure and functional group composition have critical impacts on ecological properties and processes. However, the factors determining their community structure are still poorly understood, and little is known regarding their dynamics during forest succession and the mechanisms leading to these changes. Earthworm communities are usually assumed to be stable and driven by vegetation. In contrast, the importance of dispersal and ecological drift is seldom acknowledged. By analyzing a 19-year dataset collected from forest stands in eastern USA, we demonstrated that on a decadal timescale, earthworm community dynamics are shaped by the interplay of selection, dispersal, and ecological drift. We highlighted that forests at different successional stages have distinct earthworm species and functional groups as a result of environmental filtering through leaf litter quality. Specifically, young forests are characterized by soil-feeding species that rely on relatively fresh soil organic matter derived from fast-decomposing litter, whereas old forests are characterized by those feeding on highly processed soil organic matter derived from slow-decomposing litter. In addition, year-to-year species gains and losses are primarily driven by dispersal from regional to local species pools, and by local extinction resulted from competition and ecological drift. We concluded that with continued dispersal of European species and the recent "second wave" of earthworm invasion by Asian species from the surrounding landscape, earthworms at the investigated forests are well-established, and will remain as the major drivers of soil development for the foreseeable future.
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http://dx.doi.org/10.1007/s00442-018-4205-4DOI Listing
September 2018

Mycorrhizal fungi affect orchid distribution and population dynamics.

New Phytol 2018 09 23;219(4):1207-1215. Epub 2018 May 23.

Smithsonian Environmental Research Center, 647 Contees Wharf Rd, Edgewater, MD, 21037, USA.

Symbioses are ubiquitous in nature and influence individual plants and populations. Orchids have life history stages that depend fully or partially on fungi for carbon and other essential resources. As a result, orchid populations depend on the distribution of orchid mycorrhizal fungi (OMFs). We focused on evidence that local-scale distribution and population dynamics of orchids can be limited by the patchy distribution and abundance of OMFs, after an update of an earlier review confirmed that orchids are rarely limited by OMF distribution at geographic scales. Recent evidence points to a relationship between OMF abundance and orchid density and dormancy, which results in apparent density differences. Orchids were more abundant, less likely to enter dormancy, and more likely to re-emerge when OMF were abundant. We highlight the need for additional studies on OMF quantity, more emphasis on tropical species, and development and application of next-generation sequencing techniques to quantify OMF abundance in substrates and determine their function in association with orchids. Research is also needed to distinguish between OMFs and endophytic fungi and to determine the function of nonmycorrhizal endophytes in orchid roots. These studies will be especially important if we are to link orchids and OMFs in efforts to inform conservation.
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http://dx.doi.org/10.1111/nph.15223DOI Listing
September 2018

Phylotranscriptomic analysis and genome evolution of the Cypripedioideae (Orchidaceae).

Am J Bot 2018 04 2;105(4):631-640. Epub 2018 Apr 2.

Division of Biological Sciences, University of Missouri, Columbia, MO, 65211, USA.

Premise Of The Study: The slipper orchids (Cypripedioideae) are a morphologically distinct subfamily of Orchidaceae. They also have some of the largest genomes in the orchids, which may be due to polyploidy or some other mechanism of genome evolution. We generated 10 transcriptomes and incorporated existing RNA-seq data to infer a multilocus nuclear phylogeny of the Cypripedioideae and to determine whether a whole-genome duplication event (WGD) correlated with the large genome size of this subfamily. Knowing more about timing of ancient polyploidy events can help us understand the evolution of one of the most species-rich plant families.

Methods: Transcriptome data were used to identify low-copy orthologous genes to infer a phylogeny of Orchidaceae and to identify paralogs to place any WGD events on the species tree.

Key Results: Our transcriptome phylogeny confirmed relationships published in previous studies that used fewer markers but incorporated more taxa. We did not find a WGD event at the base of the slipper orchids; however, we did identify one on the Orchidaceae stem lineage. We also confirmed the presence of a previously identified WGD event deeper in the monocot phylogeny.

Conclusions: Although WGD has played a role in the evolution of Orchidaceae, polyploidy does not appear to be responsible for the large genome size of slipper orchids. The conserved set of 775 largely single-copy nuclear genes identified in this study should prove useful in future studies of orchid evolution.
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http://dx.doi.org/10.1002/ajb2.1047DOI Listing
April 2018

Drivers of vegetative dormancy across herbaceous perennial plant species.

Ecol Lett 2018 05 25;21(5):724-733. Epub 2018 Mar 25.

Department of Ecology and Genetics, Uppsala University, Uppsala, Sweden.

Vegetative dormancy, that is the temporary absence of aboveground growth for ≥ 1 year, is paradoxical, because plants cannot photosynthesise or flower during dormant periods. We test ecological and evolutionary hypotheses for its widespread persistence. We show that dormancy has evolved numerous times. Most species displaying dormancy exhibit life-history costs of sprouting, and of dormancy. Short-lived and mycoheterotrophic species have higher proportions of dormant plants than long-lived species and species with other nutritional modes. Foliage loss is associated with higher future dormancy levels, suggesting that carbon limitation promotes dormancy. Maximum dormancy duration is shorter under higher precipitation and at higher latitudes, the latter suggesting an important role for competition or herbivory. Study length affects estimates of some demographic parameters. Our results identify life historical and environmental drivers of dormancy. We also highlight the evolutionary importance of the little understood costs of sprouting and growth, latitudinal stress gradients and mixed nutritional modes.
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http://dx.doi.org/10.1111/ele.12940DOI Listing
May 2018

Cosmopolitan Species As Models for Ecophysiological Responses to Global Change: The Common Reed .

Front Plant Sci 2017 16;8:1833. Epub 2017 Nov 16.

Aquatic Biology, Department of Bioscience, Aarhus University, Aarhus, Denmark.

is a cosmopolitan grass and often the dominant species in the ecosystems it inhabits. Due to high intraspecific diversity and phenotypic plasticity, has an extensive ecological amplitude and a great capacity to acclimate to adverse environmental conditions; it can therefore offer valuable insights into plant responses to global change. Here we review the ecology and ecophysiology of prominent lineages and their responses to multiple forms of global change. Key findings of our review are that: (1) lineages are well-adapted to regions of their phylogeographic origin and therefore respond differently to changes in climatic conditions such as temperature or atmospheric CO; (2) each lineage consists of populations that may occur in geographically different habitats and contain multiple genotypes; (3) the phenotypic plasticity of functional and fitness-related traits of a genotype determine the responses to global change factors; (4) genotypes with high plasticity to environmental drivers may acclimate or even vastly expand their ranges, genotypes of medium plasticity must acclimate or experience range-shifts, and those with low plasticity may face local extinction; (5) responses to ancillary types of global change, like shifting levels of soil salinity, flooding, and drought, are not consistent within lineages and depend on adaptation of individual genotypes. These patterns suggest that the diverse lineages of will undergo intense selective pressure in the face of global change such that the distributions and interactions of co-occurring lineages, as well as those of genotypes within-lineages, are very likely to be altered. We propose that the strong latitudinal clines within and between lineages can be a useful tool for predicting plant responses to climate change in general and present a conceptual framework for using lineages to predict plant responses to global change and its consequences.
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http://dx.doi.org/10.3389/fpls.2017.01833DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5715336PMC
November 2017

Human Gut Microbiota: Toward an Ecology of Disease.

Front Microbiol 2017 17;8:1265. Epub 2017 Jul 17.

Department of Biology, Concordia UniversityMontréal, QC, Canada.

Composed of trillions of individual microbes, the human gut microbiota has adapted to the uniquely diverse environments found in the human intestine. Quickly responding to the variances in the ingested food, the microbiota interacts with the host via reciprocal biochemical signaling to coordinate the exchange of nutrients and proper immune function. Host and microbiota function as a unit which guards its balance against invasion by potential pathogens and which undergoes natural selection. Disturbance of the microbiota composition, or dysbiosis, is often associated with human disease, indicating that, while there seems to be no unique optimal composition of the gut microbiota, a balanced community is crucial for human health. Emerging knowledge of the ecology of the microbiota-host synergy will have an impact on how we implement antibiotic treatment in therapeutics and prophylaxis and how we will consider alternative strategies of global remodeling of the microbiota such as fecal transplants. Here we examine the microbiota-human host relationship from the perspective of the microbial community dynamics.
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http://dx.doi.org/10.3389/fmicb.2017.01265DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5511848PMC
July 2017

Symbiont abundance can affect host plant population dynamics.

Am J Bot 2017 Jan 6;104(1):72-82. Epub 2017 Jan 6.

Smithsonian Environmental Research Center, P. O. Box 28, Edgewater, Maryland 21037 USA.

Premise Of The Study: Symbioses are almost universal, but little is known about how symbiont abundance can affect host performance. Many orchids undergo vegetative dormancy and frequent and protracted dormancy have been associated with population declines. If mycorrhizal fungi affect host plant performance, those effects are likely to alter patterns of vegetative dormancy. The goal of this study was to determine whether the abundance of mycorrhizal fungi is related to the likelihood of entering dormancy and whether fungal abundance varied with dormancy duration in the federally listed threatened orchid Isotria medeoloides.

Methods: We studied three populations of the threatened North American terrestrial orchid Isotria medeoloides using long-term emergence data and evaluated the relationship between the abundance of associated mycorrhizal fungi (Russulaceae) and orchid dormancy and emergence. Mycorrhizal fungi in soil adjacent to orchids were quantified in two ways. First, ectomycorrhizal (ECM) fungi on adjacent root tips were identified using DNA sequencing to determine their phylogenetic relationship to fungi that are known to form mycorrhizae with I. medeoloides. Second, we extracted DNA from soil samples and used quantitative real-time PCR to estimate the abundance of Russulaceae hyphae adjacent to each orchid.

Key Results: We found that the abundance of Russulaceae, both in the soil and on nearby ECM root tips, was significantly related to orchid prior emergence. Both abundance and prior emergence history were predictive of future emergence.

Conclusions: These results suggest that the abundance of mycorrhizal fungi can influence orchid population dynamics and is an essential component of orchid conservation.
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http://dx.doi.org/10.3732/ajb.1600334DOI Listing
January 2017

Microbial Community and Greenhouse Gas Fluxes from Abandoned Rice Paddies with Different Vegetation.

Microb Ecol 2016 10 28;72(3):692-703. Epub 2016 Jun 28.

School of Civil and Environmental Engineering, Yonsei University, Seoul, Korea.

The area of rice paddy fields has declined continuously in East Asian countries due to abandonment of agriculture and concurrent socioeconomic changes. When they are abandoned, rice paddy fields generally transform into wetlands by natural succession. While previous studies have mainly focused on vegetation shifts in abandoned rice paddies, little information is available about how these changes may affect their contribution to wetland functions. As newly abandoned fields proceed through succession, their hydrology and plant communities often change. Moreover, the relationships between these changes, soil microbial characteristics, and emissions of greenhouse gasses are poorly understood. In this study, we examined changes over the course of secondary succession of abandoned rice paddies to wetlands and investigated their ecological functions through changes in greenhouse gas fluxes and microbial characteristics. We collected gas and soil samples in summer and winter from areas dominated by Cyperaceae, Phragmites, and Sphagnum in each site. We found that CO2 emissions in summer were significantly higher than those in winter, but CH4 and N2O emission fluxes were consistently at very low levels and were similar among seasons and locations, due to their low nutrient conditions. These results suggest that microbial activity and abundance increased in summer. Greenhouse gas flux, soil properties, and microbial abundance were not affected by plant species, although the microbial community composition was changed by plant species. This information adds to our basic understanding of the contribution of wetlands that are transformed from abandoned rice paddy systems.
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http://dx.doi.org/10.1007/s00248-016-0801-1DOI Listing
October 2016

Belowground interactions with aboveground consequences: Invasive earthworms and arbuscular mycorrhizal fungi.

Ecology 2016 Mar;97(3):605-14

A mounting body of research suggests that invasive nonnative earthworms substantially alter microbial communities, including arbuscular mycorrhizal fungi (AMF). These changes to AMF can cascade to affect plant communities and vertebrate populations. Despite these research advances, relatively little is known about (1) the mechanisms behind earthworms' effects on AMF and (2) the factors that determine the outcomes of earthworm-AMF interactions (i.e., whether AMF abundance is increased or decreased and subsequent effects on plants). We predict that AMF-mediated effects of nonnative earthworms on ecosystems are nearly universal because (1) AMF are important components of most terrestrial ecosystems, (2) nonnative earthworms have become established in nearly every type of terrestrial ecosystem, and (3) nonnative earthworms, due to their burrowing and feeding behavior, greatly affect AMF with potentially profound concomitant effects on plant communities. We highlight the multiple direct and indirect effects of nonnative earthworms on plants and review what is currently known about the interaction between earthworms and AMF. We also illustrate how the effects of nonnative earthworms on plant-AMF mutualisms can alter the structure and stability of aboveground plant communities, as well as the vertebrate communities relying on these habitats. Integrative studies that assess the interactive effects of earthworms and AMF can provide new insights into the role that belowground ecosystem engineers play in altering aboveground ecological processes. Understanding these processes may improve our ability to predict the structure of plant and animal communities in earthworm-invaded regions and to develop management strategies that limit the numerous undesired impacts of earthworms.
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http://dx.doi.org/10.1890/15-1085DOI Listing
March 2016

Advancing the science of microbial symbiosis to support invasive species management: a case study on Phragmites in the Great Lakes.

Front Microbiol 2015 19;6:95. Epub 2015 Feb 19.

Department of Environmental Science and Biology, The College at Brockport, State University of New York Brockport, NY, USA.

A growing body of literature supports microbial symbiosis as a foundational principle for the competitive success of invasive plant species. Further exploration of the relationships between invasive species and their associated microbiomes, as well as the interactions with the microbiomes of native species, can lead to key new insights into invasive success and potentially new and effective control approaches. In this manuscript, we review microbial relationships with plants, outline steps necessary to develop invasive species control strategies that are based on those relationships, and use the invasive plant species Phragmites australis (common reed) as an example of how development of microbial-based control strategies can be enhanced using a collective impact approach. The proposed science agenda, developed by the Collaborative for Microbial Symbiosis and Phragmites Management, contains a foundation of sequential steps and mutually-reinforcing tasks to guide the development of microbial-based control strategies for Phragmites and other invasive species. Just as the science of plant-microbial symbiosis can be transferred for use in other invasive species, so too can the model of collective impact be applied to other avenues of research and management.
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http://dx.doi.org/10.3389/fmicb.2015.00095DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4333861PMC
March 2015

Limitations on orchid recruitment: not a simple picture.

Mol Ecol 2012 Mar 24;21(6):1511-23. Epub 2012 Jan 24.

Smithsonian Environmental Research Center, Edgewater, MD 21037, USA.

Mycorrhizal fungi have substantial potential to influence plant distribution, especially in specialized orchids and mycoheterotrophic plants. However, little is known about environmental factors that influence the distribution of mycorrhizal fungi. Previous studies using seed packets have been unable to distinguish whether germination patterns resulted from the distribution of appropriate edaphic conditions or the distribution of host fungi, as these cannot be separated using seed packets alone. We used a combination of organic amendments, seed packets and molecular assessment of soil fungi required by three terrestrial orchid species to separate direct and indirect effects of fungi and environmental conditions on both seed germination and subsequent protocorm development. We found that locations with abundant mycorrhizal fungi were most likely to support seed germination and greater growth for all three orchids. Organic amendments affected germination primarily by affecting the abundance of appropriate mycorrhizal fungi. However, fungi associated with the three orchid species were affected differently by the organic amendments and by forest successional stage. The results of this study help contextualize the importance of fungal distribution and abundance to the population dynamics of plants with specific mycorrhizal requirements. Such phenomena may also be important for plants with more general mycorrhizal associations.
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http://dx.doi.org/10.1111/j.1365-294X.2012.05468.xDOI Listing
March 2012

Evolution of host breadth in broad interactions: mycorrhizal specificity in East Asian and North American rattlesnake plantains (Goodyera spp.) and their fungal hosts.

Mol Ecol 2010 Jul 24;19(14):3008-17. Epub 2010 Jun 24.

Odum School of Ecology, University of Georgia, 140 E. Green St., GA 30602, USA.

Host breadth is often assumed to have no evolutionary significance in broad interactions because of the lack of cophylogenetic patterns between interacting species. Nonetheless, the breadth and suite of hosts utilized by one species may have adaptive value, particularly if it underlies a common ecological niche among hosts. Here, we present a preliminary assessment of the evolution of mycorrhizal specificity in 12 closely related orchid species (genera Goodyera and Hetaeria) using DNA-based methods. We mapped specificity onto a plant phylogeny that we estimated to infer the evolutionary history of the mycorrhiza from the plant perspective, and hypothesized that phylogeny would explain a significant portion of the variance in specificity of plants on their host fungi. Sampled plants overwhelmingly associated with genus Ceratobasidium, but also occasionally with some ascomycetes. Ancestral mycorrhizal specificity was narrow in the orchids, and broadened rarely as Goodyera speciated. Statistical tests of phylogenetic inertia suggested some support for specificity varying with increasing phylogenetic distance, though only when the phylogenetic distance between suites of fungi interacting with each plant taxon were taken into account. These patterns suggest a role for phylogenetic conservatism in maintaining suits of fungal hosts among plants. We stress the evolutionary importance of host breadth in these organisms, and suggest that even generalists are likely to be constrained evolutionarily to maintaining associations with their symbionts.
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http://dx.doi.org/10.1111/j.1365-294X.2010.04693.xDOI Listing
July 2010

Issues and challenges for development of a sustainable service model for people with spinal cord injury living in rural regions.

Arch Phys Med Rehabil 2008 Oct;89(10):1941-7

Rehabilitation Studies Unit, Faculty of Medicine, University of Sydney, Sydney, Australia.

Objective: To develop and implement a service model for people with spinal cord injury (SCI) living in rural regions.

Design: Service development, pilot evaluation study.

Setting: Regional and remote areas of the state of New South Wales, Australia.

Participants: Persons with SCI, caregivers, and health professionals.

Intervention: Phase 1 included initial needs analysis, followed by education and resource development tailored to needs of rural health professionals, caregivers, and persons with SCI. Phase 2 included coordination, professional support, and network development by part-time rural key worker and metropolitan-based project officer, documenting health- and service-related issues.

Main Outcome Measures: Self-perception of confidence as a result of education as well as reported issues, adverse health events, and barriers to service provision.

Results: Clinician confidence in managing people with SCI improved after education. Various health-related, environmental, and psychosocial issues were reported. Limited availability of resources and health infrastructure, particularly in more isolated or smaller towns, challenged service provision. Rural key workers played a central role in supporting local clinicians and service providers, improving communication and service coordination between rural health professionals and metropolitan SCI services.

Conclusion: Education and support for rural workforce that may be limited in numbers and capacity, and a model facilitating communication and coordination between services, are essential for improving health outcomes of rural people with SCI.
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http://dx.doi.org/10.1016/j.apmr.2008.04.011DOI Listing
October 2008

Internal transcribed spacer primers and sequences for improved characterization of basidiomycetous orchid mycorrhizas.

New Phytol 2008 8;177(4):1020-1033. Epub 2007 Dec 8.

Smithsonian Environmental Research Center, Edgewater, MD 21037, USA.

Despite advances owing to molecular approaches, several hurdles still obstruct the identification of fungi forming orchid mycorrhizas. The Tulasnellaceae exhibit accelerated evolution of the nuclear ribosomal operon, causing most standard primers to fail in polymerase chain reaction (PCR) trials. Insufficient sequences are available from well characterized isolates and fruitbodies. Lastly, taxon-specific PCR primers are needed in order to explore the ecology of the fungi outside of the orchid root. Here, progress in overcoming these hurdles is reported. Broad-spectrum basidiomycete internal transcribed spacer (ITS) primers that do not exclude most known Tulasnellaceae are presented. blast searches and empirical PCR tests support their wide utility within the Basidiomycota. Taxon-specific ITS primers are presented targeted to orchid-associated Tulasnella, and a core component of the Thelephora-Tomentella complex. The efficiency and selectivity of these primer sets are again supported by blast searches and empirical tests. Lastly, ITS DNA sequences are presented from several strains of Epulorhiza, Ceratorhiza, Ceratobasidium, Sistotrema, Thanatephorus and Tulasnella that were originally described in the landmark mycorrhizal studies of Currah and Warcup. Detailed phylogenetic analyses reveal some inconsistencies in species concepts in these taxonomically challenging resupinate basidiomycetes, but also help to place several sequences from environmental samples.
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http://dx.doi.org/10.1111/j.1469-8137.2007.02320.xDOI Listing
April 2008

Inpatient hospital utilization among the uninsured near elderly: data and policy implications for West Virginia.

Health Serv Res 2007 Dec;42(6 Pt 2):2442-57

University of Minnesota School of Public Health, State Health Access Data Assistance Center, 2221 University Avenue, Suite 345, Minneapolis, MN 55414-3164, USA.

Objective: To inform state policy discussions about the insurance coverage of the near elderly in West Virginia (WV) and the impact of the uninsured near elderly on hospitals in the state.

Data Sources: 2003 West Virginia Uniform Bill (UB) hospital discharge data. The data represent all adult inpatient discharges in the state during the year.

Study Design: We compare the near elderly with other adults and examine differences by insurance status. Key variables include volume of discharges, health insurance coverage, patient characteristics, and charges incurred.

Findings: The near elderly constitute the largest group of nonelderly adult inpatient hospital discharges. They are more likely than younger adults to be admitted for emergency conditions; have comorbidities and complications; have longer hospital stays; and incur higher charges on average. Although the near elderly are least likely to be uninsured, they represent the second largest group of uninsured discharges and incur the most in uninsured charges.

Conclusions: The specific needs of the near elderly warrant consideration in WV's (and other states') ongoing development and evaluation of policies aimed at reducing uncompensated care costs, including programs to expand access to health insurance and primary and mental health care among the uninsured.
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http://dx.doi.org/10.1111/j.1475-6773.2007.00765.xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2151320PMC
December 2007

The evolutionary history of mycorrhizal specificity among lady's slipper orchids.

Evolution 2007 Jun;61(6):1380-90

Forestry and Forest Products Research Institute, Tsukuba, Ibaraki, Japan.

Although coevolution is acknowledged to occur in nature, coevolutionary patterns in symbioses not involving species-to-species relationships are poorly understood. Mycorrhizal plants are thought to be too generalist to coevolve with their symbiotic fungi; yet some plants, including some orchids, exhibit strikingly narrow mycorrhizal specificity. Here, we assess the evolutionary history of mycorrhizal specificity in the lady's slipper orchid genus, Cypripedium. We sampled 90 populations of 15 taxa across three continents, using DNA methods to identify fungal symbionts and quantify mycorrhizal specificity. We assessed phylogenetic relationships among sampled Cypripedium taxa, onto which we mapped mycorrhizal specificity. Cypripedium taxa associated almost exclusively with fungi within family Tulasnellaceae. Ancestral specificity appears to have been narrow, followed by a broadening after the divergence of C. debile. Specificity then narrowed, resulting in strikingly narrow specificity in most of the taxa in this study, with no taxon rewidening to the same extant as basal members of the genus. Sympatric taxa generally associated with different sets of fungi, and most clades of Cypripedium-mycorrhizal fungi were found throughout much of the northern hemisphere, suggesting that these evolutionary patterns in specificity are not the result of biogeographic lack of opportunity to associate with potential partners. Mycorrhizal specificity in genus Cypripedium appears to be an evolvable trait, and associations with particular fungi are phylogenetically conserved.
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http://dx.doi.org/10.1111/j.1558-5646.2007.00112.xDOI Listing
June 2007

Patient bypass behavior and critical access hospitals: implications for patient retention.

J Rural Health 2007 ;23(1):17-24

West Virginia University Institute for Health Policy Research, Charleston, WVA, USA.

Purpose: To assess the extent of bypass for inpatient care among patients living in Critical Access Hospital (CAH) service areas, and to determine factors associated with bypass, the reasons for bypass, and what CAHs can do to retain patients locally.

Methods: Six hundred and forty-seven subjects, aged 18 years and older, who had been admitted to a hospital for inpatient care in the past 12 months and lived within 15-20 miles of 25 randomly selected CAHs were surveyed by phone during the period from early February through late July 2005. Survey questions included demographic characteristics, general health status, travel time/distance to health care, questions on satisfaction with local health services, bypass behavior, and solicited suggestions on how local hospitals could retain patients locally.

Findings: About 60% of surveyed patients bypassed their local CAHs for inpatient care including 16% who were referred to another facility by the local CAH/health care providers and would use the local hospital if needed services were available. Bypass rates ranged from 16% to 70% across the sampled CAHs. Factors associated with bypass included age, income, satisfaction with the local hospital, and traveling distance/time. Lack of specialty care, limited services, and the quality/reputation of local services/doctors were most frequently mentioned as reasons why patients bypass local CAHs.

Conclusions: The bypass rate for sampled CAHs is considerably higher than the 20%-50% bypass rates documented in the literature for all hospitals in general using discharge/administrative data. The sizeable variation in bypass rates across CAHs suggests that the appropriate response/fix should come from the facility/community levels.
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http://dx.doi.org/10.1111/j.1748-0361.2006.00063.xDOI Listing
April 2007

Orchid-fungus fidelity: a marriage meant to last?

Ecology 2006 Apr;87(4):903-11

Smithsonian Environmental Research Center, P.O. Box 28, Edgewater, Maryland 21037, USA.

The characteristics of plant-mycorrhizae associations are known to vary in both time and space, but the ecological consequences of variation in the dynamics of plant-fungus interactions are poorly understood. For example, do plants associate with single fungi or multiple fungi simultaneously, and do the associations persist through a plant's lifetime or do plants support a succession of different fungi? We investigated these and other questions related to plant-fungus interactions in Goodyera pubescens, an evergreen terrestrial orchid of the eastern United States, that interacts with closely related fungi in the genus Tulasnella. Unlike the mycorrhizal associations of other plants, orchid-mycorrhizal associations only benefit the orchid, based on current evidence. Many terrestrial orchids have been found to associate with specific groups of fungi. This characteristic could potentially limit orchids to relatively narrow ranges of environmental conditions and may be a contributing factor in the decline of many orchids in the face of changing environmental conditions. We found that G. pubescens protocorms (developing embryos prior to leaf production) and adults associated with only one fungal individual at a time. The orchid-fungus association persists for years, but during a drought period that was associated with the death of many plants, surviving plants were able to switch to new fungal individuals. These results suggest that G. pubescens interacts with the same fungal partner during periods of modest environmental variation but is able to switch to a different fungal partner. We hypothesize that the ability to switch fungi allows G. pubescens to survive more extreme environmental perturbations. However, laboratory experiments suggest that switching fungi has potential costs, as it increases the risk of mortality, especially for smaller individuals. Our findings indicate that it is unlikely that switching fungi is a common way to improve tolerance of less severe environmental fluctuations and disturbances. These findings may have important implications for plant responses to severe climatic events or to more gradual environmental changes such as global warming.
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http://dx.doi.org/10.1890/0012-9658(2006)87[903:ofammt]2.0.co;2DOI Listing
April 2006

Solid-state NMR investigation of the selective perturbation of lipid bilayers by the cyclic antimicrobial peptide RTD-1.

Biochemistry 2004 Aug;43(30):9800-12

Department of Chemistry, Iowa State University, Ames, Iowa 50011, USA.

RTD-1 is a cyclic beta-hairpin antimicrobial peptide isolated from rhesus macaque leukocytes. Using (31)P, (2)H, (13)C, and (15)N solid-state NMR, we investigated the interaction of RTD-1 with lipid bilayers of different compositions. (31)P and (2)H NMR of uniaxially oriented membranes provided valuable information about how RTD-1 affects the static and dynamic disorder of the bilayer. Toward phosphatidylcholine (PC) bilayers, RTD-1 causes moderate orientational disorder independent of the bilayer thickness, suggesting that RTD-1 binds to the surface of PC bilayers without perturbing its hydrophobic core. Addition of cholesterol to the POPC membrane does not affect the orientational disorder. In contrast, binding of RTD-1 to anionic bilayers containing PC and phosphatidylglycerol lipids induces much greater orientational disorder without affecting the dynamic disorder of the membrane. These correlate with the selectivity of RTD-1 for anionic bacterial membranes as opposed to cholesterol-rich zwitterionic mammalian membranes. Line shape simulations indicate that RTD-1 induces the formation of micrometer-diameter lipid cylinders in anionic membranes. The curvature stress induced by RTD-1 may underlie the antimicrobial activity of RTD-1. (13)C and (15)N anisotropic chemical shifts of RTD-1 in oriented PC bilayers indicate that the peptide adopts a distribution of orientations relative to the magnetic field. This is most likely due to a small fraction of lipid cylinders that change the RTD-1 orientation with respect to the magnetic field. Membrane-bound RTD-1 exhibits narrow line widths in magic-angle spinning spectra, but the sideband intensities indicate rigid-limit anisotropies. These suggest that RTD-1 has a well-defined secondary structure and is likely aggregated in the membrane. These structural and dynamical features of RTD-1 differ significantly from those of PG-1, a related beta-hairpin antimicrobial peptide.
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http://dx.doi.org/10.1021/bi036243wDOI Listing
August 2004