Genetic structure in patchy populations of a candidate foundation plant: a case study of Leymus chinensis using genetic and clonal diversity.

Premise: The distribution of genetic diversity on the landscape has critical ecological and evolutionary implications. This may be especially the case on a local scale for foundation plant species because they create and define ecological communities, contributing disproportionately to ecosystem function.

Methods: We examined the distribution of genetic diversity and clones, which we defined first as unique multilocus genotypes (MLG), and then by grouping similar MLGs into multilocus lineages.

Inheritance of DNA methylation differences in the mangrove Rhizophora mangle.

The capacity to respond to environmental challenges ultimately relies on phenotypic variation which manifests from complex interactions of genetic and nongenetic mechanisms through development. While we know something about genetic variation and structure of many species of conservation importance, we know very little about the nongenetic contributions to variation. Rhizophora mangle is a foundation species that occurs in coastal estuarine habitats throughout the neotropics where it provides critical ecosystem functions and is potentially threatened by anthropogenic environmental changes.

Scale-dependent portfolio effects explain growth inflation and volatility reduction in landscape demography.

Population demography is central to fundamental ecology and for predicting range shifts, decline of threatened species, and spread of invasive organisms. There is a mismatch between most demographic work, carried out on few populations and at local scales, and the need to predict dynamics at landscape and regional scales. Inspired by concepts from landscape ecology and Markowitz's portfolio theory, we develop a landscape portfolio platform to quantify and predict the behavior of multiple populations, scaling up the expectation and variance of the dynamics of an ensemble of populations.

Landscape Demography: Population Change and its Drivers Across Spatial Scales.

Demographic studies of plants and animals have a rich history and literature in ecology, and are important for both fundamental and applied ecology and conservation biology. Almost all demographic work has focused on intensive studies in which births, deaths, growth of individuals, and related measures are quantified in a single population or a few populations. This has been for practical reasons due to the high demands of labor required for this work, and because the questions addressed in these studies have been asked at the level of individual populations, with implicit assumptions about generalizing from the results.

Dissolved inorganic carbon uptake in Thiomicrospira crunogena XCL-2 is Δp- and ATP-sensitive and enhances RubisCO-mediated carbon fixation.

The gammaproteobacterium Thiomicrospira crunogena XCL-2 is an aerobic sulfur-oxidizing hydrothermal vent chemolithoautotroph that has a CO2 concentrating mechanism (CCM), which generates intracellular dissolved inorganic carbon (DIC) concentrations much higher than extracellular, thereby providing substrate for carbon fixation at sufficient rate. This CCM presumably requires at least one active DIC transporter to generate the elevated intracellular concentrations of DIC measured in this organism. In this study, the half-saturation constant (K CO2) for purified carboxysomal RubisCO was measured (276 ± 18 µM) which was much greater than the K CO2 of whole cells (1.

Predictors of desaturation in the postoperative anesthesia care unit: an observational study.

Study Objective: To evaluate predictors of desaturation and to identify practice for patient transport following general anesthesia.

Design: Observational quality assurance study.

Setting: Postanesthesia Care Unit (PACU) of a university-affiliated, tertiary-care hospital.

Variation among individuals in cone production in Pinus palustris (Pinaceae).

Premise Of The Study: Reproductive output varies considerably among individuals within plant populations, and this is especially so in cone production of conifers. While this variation can have substantial effects on populations, little is known about its magnitude or causes.

Methods: We studied variation in cone production for 2 years within a population of Pinus palustris Mill.

Demographic heterogeneity, cohort selection, and population growth.

Demographic heterogeneity--variation among individuals in survival and reproduction--is ubiquitous in natural populations. Structured population models address heterogeneity due to age, size, or major developmental stages. However, other important sources of demographic heterogeneity, such as genetic variation, spatial heterogeneity in the environment, maternal effects, and differential exposure to stressors, are often not easily measured and hence are modeled as stochasticity.

Inferring microhabitat preferences of Lilium catesbaei (Liliaceae).

Premise Of The Study: Microhabitat studies use varied statistical methods, some treating site occupancy as a dependent and others as an independent variable. Using the rare Lilium catesbaei as an example, we show why approaches to testing hypotheses of differences between occupied and unoccupied sites can lead to erroneous conclusions about habitat preferences. Predictive approaches like logistic regression can better lead to understanding of habitat requirements.

The statistical mechanics of community assembly and species distribution.

• Theoretically, communities at or near their equilibrium species number resist entry of new species. Such 'biotic resistance' recently has been questioned because of successful entry of alien species into diverse natural communities. • Data on 10,409 naturalizations of 5350 plant species over 16 sites dispersed globally show exponential distributions both for species over sites and for sites over number of species shared.

Measuring isotope fractionation by autotrophic microorganisms and enzymes.

Physical, chemical, and biological processes commonly discriminate among stable isotopes. Therefore, the stable isotope compositions of biomass, growth substrates, and products often carry the isotopic fingerprints of the processes that shape them. Therefore, measuring isotope fractionation by enzymes and cultures of autotrophic microorganisms can provide insights at many levels, from metabolism to ecosystem function.

Consequences of heterogeneity in survival probability in a population of Florida scrub-jays.

1. Using data on breeding birds from a 35-year study of Florida scrub-jays Aphelocoma coerulescens (Bosc 1795), we show that survival probabilities are structured by age, birth cohort, and maternal family, but not by sex. Using both accelerated failure time (AFT) and Cox proportional hazard models, the data are best described by models incorporating variation among birth cohorts and greater mortality hazard with increasing age.

Sources of variation in growth, form, and survival in dwarf and normal-stature pitch pines (Pinus rigida, Pinaceae) in long-term transplant experiments.

Determining the relative contributions of genetic and environmental factors to phenotypic variation is critical for understanding the evolutionary ecology of plant species, but few studies have examined the sources of phenotypic differentiation between nearby populations of woody plants. We conducted reciprocal transplant experiments to examine sources of variation in growth rate, form, survival, and maturation in a globally rare dwarf population of pitch pine (Pinus rigida) and in surrounding populations of normal-stature pitch pines on Long Island, New York. Transplants were monitored over a 6-yr period.

Monitored anesthesia care provided by registered respiratory care practitioners during cataract surgery: a report of 1957 cases.

Objective: To evaluate the safety and feasibility of having monitored anesthesia care during cataract surgery provided by registered respiratory care practitioners (RRCPs).

Design: Retrospective case series.

Participants: One thousand nine hundred fifty-seven consecutive patients undergoing cataract surgery at one surgical center between November 2001 and October 2003.

Limiting relationships between selection and recombination.

It is difficult to directly observe processes like natural selection at the genetic level, but relatively easy to estimate genetic frequencies in populations. As a result, genetic frequency data are widely used to make inferences about the underlying evolutionary processes. However, multiple processes can generate the same patterns of frequency data, making such inferences weak.

Variation among Individuals and Reduced Demographic Stochasticity.

Population viability analysis ( PVA) is a technique that employs stochastic demographic models to predict extinction risk. All else being equal, higher variance in a demographic rate leads to a greater extinction risk. Demographic stochasticity represents variance due to differences among individuals.

Population Numbers Count: Tools for Near-Term Demographic Analysis.

How do unit or proportional changes in vital rates affect populations in the short term? We present a new extension to standard methods of matrix model analysis that allows us to answer this question for the first time. By using the sensitivities of all the eigenvalues/vectors, rather than just the leading eigenvalue/vector pair, we can predict the consequences of unit or proportional changes in vital rates to population size and structure at any arbitrary time, not just when populations have neared their stable distribution. These extensions are particularly important in studying populations subject to frequent disturbance, where stable growth rate and stable distribution do not provide sufficient information about the effects of changes in the vital rates; managed populations in which short-term goals are defined; and the adequacy of the underlying matrix model for either short- or long-term understanding.

COMPONENTS OF FLOWERING TIME VARIATION IN A DESERT ANNUAL.

How much of the variation seen in life histories is consistent with adaptive hypotheses, and how much requires other kinds of explanation? Differences in flowering time between Sonoran (earlier flowering) and Chihuahuan Desert (later flowering) populations of the desert annual Eriogonum abertianum Torr. (Polygonaceae) are significant, repeatable between greenhouse experiments, and persist into a second greenhouse generation. These apparent genetic differences are consistent with a hypothesis of local adaptation: field demographic studies (Fox, 1989b) show that many fewer Sonoran than Chihuahuan Desert plants survive to the summer rainy season, suggesting selection for earlier flowering in the Sonoran Desert.