Area Of Ecological Research Research Articles

A quantitative framework for analysis of regime shifts in a Galápagos coastal lagoon

Regime shifts are often used to describe sharp changes between two or more ecological states, each characterized by their own dynamics, stochastic fluctuations, or cycles. Ecological theory indicates they can occur either as a result of an abrupt environmental forcing (extrinsic regime shift), or be indicative of complex responses to local‐scale dynamics and thresholds (intrinsic regime shift). One important area of ecological research is to develop quantitative tools to analyze regime shifts, but there are few studies that have applied these methods to the long‐term ecological record. In this study, we introduce a framework to investigate regime shifts in diatom assemblages and mangrove ecosystem dynamics in a coastal lagoon from the Galápagos Islands over the past 2600 years. The framework integrates a set of established statistical methodologies for investigating regime shift dynamics in long‐term ecological records. We use these methods to (1) identify the presence of regime shifts; (2) test for a series of hypothetical relationships (i.e., linear through to threshold) between ecological response and environment using nonlinear regression; and (3) investigate the relative importance of intrinsic and extrinsic dynamics in response to environmental perturbations. The transitions in the diatoms closely track the sequence of disturbance, recovery, and habitat shifts that have occurred in the lagoon over the past 2600 years, demonstrating extrinsic responses to environmental forcing. In contrast, the shift from a mangrove‐ to a microbial mat‐dominated system ∼945 cal yr BP provides potential evidence of an intrinsic regime shift. Our framework enables robust interpretations into the underlying dynamics of regime shifts in the paleoecological record and is widely applicable for investigating abrupt ecological changes in a range of systems.

Habitat prioritization across large landscapes, multiple seasons, and novel areas: An example using greater sage‐grouse in Wyoming

ABSTRACTAnimal habitat selection is an important and expansive area of research in ecology. In particular, the study of habitat selection is critical in habitat prioritization efforts for species of conservation concern. Landscape planning for species is happening at ever‐increasing extents because of the appreciation for the role of landscape‐scale patterns in species persistence coupled to improved datasets for species and habitats, and the expanding and intensifying footprint of human land uses on the landscape. We present a large‐scale collaborative effort to develop habitat selection models across large landscapes and multiple seasons for prioritizing habitat for a species of conservation concern. Greater sage‐grouse (Centrocercus urophasianus, hereafter sage‐grouse) occur in western semi‐arid landscapes in North America. Range‐wide population declines of this species have been documented, and it is currently considered as “warranted but precluded” from listing under the United States Endangered Species Act. Wyoming is predicted to remain a stronghold for sage‐grouse populations and contains approximately 37% of remaining birds. We compiled location data from 14 unique radiotelemetry studies (data collected 1994–2010) and habitat data from high‐quality, biologically relevant, geographic information system (GIS) layers across Wyoming. We developed habitat selection models for greater sage‐grouse across Wyoming for 3 distinct life stages: 1) nesting, 2) summer, and 3) winter. We developed patch and landscape models across 4 extents, producing statewide and regional (southwest, central, northeast) models for Wyoming. Habitat selection varied among regions and seasons, yet preferred habitat attributes generally matched the extensive literature on sage‐grouse seasonal habitat requirements. Across seasons and regions, birds preferred areas with greater percentage sagebrush cover and avoided paved roads, agriculture, and forested areas. Birds consistently preferred areas with higher precipitation in the summer and avoided rugged terrain in the winter. Selection for sagebrush cover varied regionally with stronger selection in the Northeast region, likely because of limited availability, whereas avoidance of paved roads was fairly consistent across regions. We chose resource selection function (RSF) thresholds for each model set (seasonal × regional combination) that delineated important seasonal habitats for sage‐grouse. Each model set showed good validation and discriminatory capabilities within study‐site boundaries. We applied the nesting‐season models to a novel area not included in model development. The percentage of independent nest locations that fell directly within identified important habitat was not overly impressive in the novel area (49%); however, including a 500‐m buffer around important habitat captured 98% of independent nest locations within the novel area. We also used leks and associated peak male counts as a proxy for nesting habitat outside of the study sites used to develop the models. A 1.5‐km buffer around the important nesting habitat boundaries included 77% of males counted at leks in Wyoming outside of the study sites. Data were not available to quantitatively test the performance of the summer and winter models outside our study sites. The collection of models presented here represents large‐scale resource‐management planning tools that are a significant advancement to previous tools in terms of spatial and temporal resolution. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.

Functional correlates of allelopathic potential in a successional plant community

Allelopathy, plant–plant interactions mediated through chemical production, is an active area of ecological research. Despite this widespread interest, we still lack community scale information on the prevalence of this interaction and the types of species that may be expected to be allelopathic. To address this research need, the allelopathic potential of 65 plant species from all stages of succession in the Piedmont region of New Jersey, USA, was determined with laboratory bioassays. The strength of each species’ allelopathic activity was then related to life form, origin, and fundamental plant traits. The vast majority of species tested exhibited significant allelopathic effects in the bioassays, with many of these having fairly strong effects. Overall, the allelopathic potential of species decreased with life span, roughly following the successional transitions from short-lived to long-lived herbs and to woody species. Herbaceous species on average were more allelopathic than woody species, but there was no difference between native and non-native species once life form was accounted for. In a principal components analysis, allelopathy was associated with other plant traits, but these relationships differed between woody and herbaceous species. Allelopathic potential was positively associated with plant height in herbaceous species, but negatively associated with height, leaf mass, and seed mass in woody species. These results indicate that allelopathy may be a quite common ecological strategy in plants and is equally common in both native and non-native species. The linkage of allelopathy with other plant functional traits suggests that allelopathy can and should be integrated into the broader suite of plant strategies that are studied.

Microbial regulation of global biogeochemical cycles.

Microbial regulation of global biogeochemical cycles.

Early warning signals of stochastic switching

The development of statistical signals for anticipating changes of state (‘regime shifts’) is an active area of research in ecology [[1][1],[2][2]], earth and atmospheric science [[3][3]], and biology [[4][4],[5][5]]. Causes of regime shifts include noise-induced transitions [[6][6]],

Stress intensity and fitness in the parasitoid Aphidius ervi (Hymenoptera: Braconidae): temperature below the development threshold combined with a fluctuating thermal regime is a must

Abstract An increasing intensity of stress is expected to affect the fitness traits of an organism more and more negatively, but in particular cases, extremely resistant individuals have been observed. The present study was undertaken to determine the effects of different stress intensities on fitness traits of the parasitoid wasp Aphidius ervi Haliday. We exposed 1‐day‐old mummies (dead aphids containing the parasitoid pupa) for 4 weeks to combinations of two low temperatures (4 and 0 °C, 0 °C being the most stressful) and two thermal regimes (constant and fluctuating, constant being the most stressful), representing four stress levels. The present results showed that resistant individuals occurred only in the most stressful treatment (0 °C, constant temperature), which induced a higher mortality rate. These resistant individuals performed almost as well as those of the control, but showed a reduction in their size. The fluctuating regimes, at both temperatures, presented a high emergence rate, but at the expense of higher lipid consumption. Unexpectedly, the fluctuating regime associated with the presumably more stressful temperature (0 °C) produced individuals without any decrease in the measured fitness traits, in contrast to the treatment expected to be less stressful (4 °C, fluctuating temperature). This result opens a new area of research in stress ecology and could modify the practice of cold storage in biological control.

Avian brood parasitism — a growing research area in behavioral ecology (part II)

正We are pleased to publish the second special issue on avian brood parasitism and to be responsible guest editors for the two special issues of Chinese Birds (Vol. 3, No. 4, 2012 and Vol. 4, No. 1, 2013), entitled Avian Brood Parasitism - A Growing Research Area in Behavioral Ecology. The first issue was published in December 2012. The goal of the two special issues is to publish accumulated knowledge and some of the recent developments in

Beyond global change: lessons from 25 years of CO2 research

Over the past 25 years, countless experiments have been conducted on the impact of increased atmospheric CO2 concentration on various plants and ecosystems. While this research was motivated to better understand and predict how rising CO2 will affect the structure and function of ecosystems in the future, it also shed light on some general, CO2-research independent, aspects in ecological research. Interestingly, it is these general aspects that continue to create confusion and lead to misinterpretation. Here, we focus on seven interrelated key issues including (1) the confusion between fluxes and pools, (2) the stoichiometric aspects of growth and biomass production, (3) resource allocation within organisms, (4) data scaling and the choice of a reference metric, (5) the consideration of time and timing (experimental duration, ontogenetic shifts), (6) confounding and second-order (indirect or feedback) effects, and (7) the key role of biodiversity. The principles deriving from addressing these issues relate strongly to each other. Their concurrent consideration requires experimenters and modellers to likewise maintain a broad, holistic perspective. In this synthesis, we attempt to show how appropriate consideration of these principles can greatly enhance the assessment of the validity, plausibility and generality of experimental and modelling results. We conclude that neglecting to adequately address these key issues in ecological research may lead to overestimations of measured responses and/or simplistic interpretations. Our examples mostly originate from research on plant responses to elevated atmospheric CO2, but are also applicable to other areas of ecological research. We provide a checklist for the planning of ecological field experiments and the interpretation of their results that may help in avoiding common pitfalls.

Avian brood parasitism — a growing research area in behavioral ecology

正We are pleased to be responsible guest editors for the two special issues of Chinese Birds(Vol.3,No.4,2012 and Vol.4,No.1,2013),entitled Avian Brood Parasitism — a Growing Research Area in Behavioral Ecology.The goal of the two special issues is to publish accumulated knowledge and some of the recent developments in the fascinating research occurring in avian

난류가 플랑크톤의 거동에 미치는 영향: 역학적 관점에서 본 얇은 층의 형성과정

본 연구에서는 최근 물리적 관측 방법으로 그 존재가 확인된 얇은 층(thin layer)의 형성 메커니즘에 대하여 검토하였다. 기존의 연구들에서는 성층과 전단응력의 상대적 크기인 Richardson수가 얇은 층의 중요한 결정요인인 것으로 밝혀졌다. 성층이 없는 조건하에서의 물리적 수치 실험은 미세 난류(micro-structure turbulence)가 플랑크톤의 거동에 변화를 주어 성장과 재생산 등에 영향줄 수 있음을 설명하였다. 기존의 플랑크톤 거동에 성층과 전단응력의 효과를 고려하여 최근 Gyrotaxis의 메커니즘으로 얇은 층이 형성되는 과정을 설명하였다. 이러한 생태학적 문제에 물리학적 연구방법론의 적용이라는 최근의 연구경향은 현재 및 향후에 해양생태학에서 중요한 접근방법이라고 할 수 있다. The present work reviews some mechanism explaining how thin layer can develop in the near coastal zone. The existence of thin layer was observed by physical research methods later than classical biological approaches. The Richardson number, which is a ratio between the stratification and shear stress is crucial factor determining the occurrence of thin layer. Micro-structure turbulence seems to affect the plankton behavior, in particular the encountering rate. Encountering rate affects significantly feeding, reproduction etc. and this fact was proved by the mechanical simulation methods. Recently the Gyrotaxis was introduced to explain how thin layer occurs in the mixing layer. Such physical approaches to explain ecological problem will be prominent methods for marine ecological research area.

HOW IS THE RATE OF CLIMATIC-NICHE EVOLUTION RELATED TO CLIMATIC-NICHE BREADTH?

The rate of climatic-niche evolution is important to many research areas in ecology, evolution, and conservation biology, including responses of species to global climate change, spread of invasive species, speciation, biogeography, and patterns of species richness. Previous studies have implied that clades with higher rates of climatic-niche evolution among species should have species with narrower niche breadths, but there is also evidence suggesting the opposite pattern. However, the relationships between rate and breadth have not been explicitly analyzed. Here, we examine the relationships between the rate of climatic-niche evolution and climatic-niche breadth using phylogenetic and climatic data for 250 species in the salamander family Plethodontidae, a group showing considerable variation in both rates of climatic-niche evolution and climatic-niche breadths. Contrary to some expectations, we find no general relationship between climatic-niche breadth and the rate of climatic-niche evolution. Climatic-niche breadths for some ecologically important climatic variables considered separately (temperature seasonality and annual precipitation) do show significant relationships with the rate of climatic-niche evolution, but rates are faster in clades in which species have broader (not narrower) niche breadths. In summary, our results show that narrower niche breadths are not necessarily associated with faster rates of niche evolution.

How to measure and test phylogenetic signal

Summary1. Phylogenetic signal is the tendency of related species to resemble each other more than species drawn at random from the same tree. This pattern is of considerable interest in a range of ecological and evolutionary research areas, and various indices have been proposed for quantifying it. Unfortunately, these indices often lead to contrasting results, and guidelines for choosing the most appropriate index are lacking.2. Here, we compare the performance of four commonly used indices using simulated data. Data were generated with numerical simulations of trait evolution along phylogenetic trees under a variety of evolutionary models. We investigated the sensitivity of the approaches to the size of phylogenies, the resolution of tree structure and the availability of branch length information, examining both the response of the selected indices and the power of the associated statistical tests.3. We found that under a Brownian motion (BM) model of trait evolution, Abouheif’sCmeanand Pagel’s λ performed well and substantially better than Moran’sIand Blomberg’sK. Pagel’sλprovided a reliable effect size measure and performed better for discriminating between more complex models of trait evolution, but was computationally more demanding than Abouheif’sCmean. Blomberg’sKwas most suitable to capture the effects of changing evolutionary rates in simulation experiments.4. Interestingly, sample size influenced not only the uncertainty but also the expected values of most indices, while polytomies and missing branch length information had only negligible impacts.5. We propose guidelines for choosing among indices, depending on (a) their sensitivity to true underlying patterns of phylogenetic signal, (b) whether a test or a quantitative measure is required and (c) their sensitivities to different topologies of phylogenies.6. These guidelines aim to better assess phylogenetic signal and distinguish it from random trait distributions. They were developed under the assumption of BM, and additional simulations with more complex trait evolution models show that they are to a certain degree generalizable. They are particularly useful in comparative analyses, when requiring a proxy for niche similarity, and in conservation studies that explore phylogenetic loss associated with extinction risks of specific clades.

Variation in monsoon precipitation drives spatial and temporal patterns of Larrea tridentata growth in the Sonoran Desert

Summary 1. Broad-scale patterns of above-ground net primary production (ANPP) are closely coupled to climate features, particularly the distribution and magnitude of rainfall. In arid and semi-arid regions, however, the precipitation regime, together with local geomorphology and plant life history traits, combine to regulate soil water availability and patterns of growth, complicating simple correlations with climatic variables. 2. To better understand the drivers of plant growth in desert ecosystems, we characterized the rates and spatial heterogeneity of stem elongation by the dominant perennial shrub, creosote bush (Larrea tridentata) in the northern Sonoran Desert of Arizona (USA). Estimates of stem growth were made over a 5-year period (2006–2010) from 60 plots at 15 sites spanning c. 120 km across the Central Arizona–Phoenix (CAP) Long-term Ecological Research (LTER) area. 3. We observed both the highest and lowest rates of stem growth during summer, and these patterns were related to the amount of monsoon rainfall and local rates of water infiltration. The relationship between growth and precipitation in the summer was nonlinear, with rates increasing more than eightfold at plots receiving more than 100 mm of seasonal rainfall. Conversely, growth during the winter/spring was intermediate in magnitude, similar among years and poorly correlated with seasonal precipitation. 4. The spatial heterogeneity of stem growth also differed markedly between seasons and was greater both within and among sites during summer compared to winter/spring growing periods. At broad scales, spatial heterogeneity of shrub growth was correlated with seasonal changes in the spatial variability of rainfall across the study area. At small spatial scales, greater heterogeneity during the summer appears linked to local soil properties that influence infiltration and water availability following monsoon storms. 5. Overall, the strong, nonlinear growth response by L. tridentata to monsoon rainfall suggests that the recurrence interval of wet summer seasons is an important driver of ANPP for this long-lived shrub. More generally, our results illustrate how regional climate variability and local soil properties can interact to influence the rates and heterogeneity of desert plant growth at multiple scales.

Dendrochronological Potential of Quercus garryana, Saltspring Island, British Columbia

Garry oak (Quercus garryana Dougl.) is the cornerstone tree species of one of the most biologically diverse yet threatened ecosystems in Canada. The Canadian Garry oak ecosystem is located only in southern coastal British Columbia and is home to numerous endangered species. This study tests the dendrochronological potential of Garry oak trees near their northern range limit by successfully crossdating a sample from the Crow's Nest Ecological Research Area (CNERA) on Saltspring Island, British Columbia. Forty-five samples were collected from 39 trees to determine accurate age estimates and develop a crossdated tree-ring chronology that spans 180 years (A.D. 1825–2005). Wood anatomy and periodic growth suppression made crossdating challenging. However, distinct marker rings were readily identified on nearly all cores showing a synchronous response among trees to a common radial growth signal. The majority of trees sampled were established during 1860–1880 and 1947–1967. Correlation analyses show that radial growth of Garry oak at CNERA is influenced by both temperature and moisture availability. Our study demonstrates that extraction of high-quality dendrochronological data from Garry oak trees near their northern range limit is possible, so this species should be recognized as having good dendrochronological potential.

Co-occurrence of small mammals in a tropical dry deciduous forest: comparisons of communities and individual species in Colima, Mexico

Abstract:Species co-occurrence is an important ecological research area. Mark-and-recapture studies of mammals allow identification of coexisting species, a necessary step in determining mechanisms enabling habitat sharing. Using data from five 1-ha grids in January 2004 in tropical dry deciduous forest of coastal Colima, Mexico, we detected significantly more interspecific overlap than expected between seven species pairs. Oryzomys couesi shared more stations than expected with Sigmodon mascotensis, Baiomys musculus and Peromyscus perfulvus. Baiomys musculus was associated positively with S. mascotensis and Reithrodontomys fulvescens. Heteromys pictus shared fewer stations than expected with O. couesi and S. mascotensis. For species collectively, there was non-random community structuring, with two grids displaying more species aggregation than expected. While two grids had non-random co-occurrence patterns, three grids did not differ from random, which differs from that reported for mammalian taxa on average. Other small-mammal studies have documented species segregation, while this study detected more positive than negative associations. Similarities in preference and habitat use (or diet) are likely explanations for interspecific overlap patterns at stations and co-occurrence patterns among grids. Simultaneously evaluating associations of species pairs and all species on a grid collectively is novel methodology as applied to mammals, adding to understanding of species co-occurrence.

Cascading effects of host size and host plant species on parasitoid resource allocation

1. The bottom-up factors that determine parasitoid host use are an important area of research in insect ecology. Host size is likely to be a primary cue for foraging parasitoids due to its potential influence on offspring development time, the risk of multiparasitism, and host immunocompetence. Host size is mediated in part by host-plant traits that influence herbivore growth and potentially affect a herbivore's quality as a host for parasitoids. 2. Here, we tested how caterpillar host size and host plant species influence adult fly parasitoid size and whether host size influences wasp parasitoid sex allocation. We measured the hind tibia lengths and determined the sex of wasp and fly parasitoids reared from 11 common host species of polyphagous caterpillars (Limacodidae) that were in turn reared on foliage of seven different host plant species. 3. We also tested how host caterpillar species, host caterpillar size, and host and parasitoid phenology affect how the parasitoid community partitions host resources. We found evidence that parasitoids primarily partition their shared hosts based on size, but not by host species or phenology. One index of specialisation (d′) supports our observation that these parasitoids are quite generalised within the Limacodidae. In general, wasps were reared from caterpillars collected in early instars, while flies were reared from caterpillars collected in late instars. Furthermore, for at least one species of solitary wasp, host size influenced sex allocation of offspring by ovipositing females. 4. Host-plant quality indirectly affected the size attained by a tachinid fly parasitoid through its direct effects on the size and performance of the caterpillar host. The host plants that resulted in the highest caterpillar host performance in the absence of enemies also yielded the largest parasitoid flies, which suggests that host plant quality can cascade up to influence the third trophic level.

Intrusion experiments to measure territory size: development of the method, tests through simulations, and application in the frog Allobates femoralis.

Territoriality is a widespread behaviour in animals and its analysis is crucial in several areas of behavioural, ecological and evolutionary research. Commonly, territory size is assessed through territory mapping and the application of simple area estimators such as minimum convex polygons. In the present study we demonstrate that territory size can be determined adequately with an active approach through intrusion experiments, a technique that is commonly used in behavioural research in other contexts. Tests with simulated data indicate that a minimum of twelve trials needs to be performed to establish reliable orders of relative territory size. To estimate absolute territory size, detailed hull techniques are most appropriate when analyzing point patterns of intrusion experiments, while the local convex hull estimator enables the construction of internal utilization distributions based on such point patterns. Additionally we suggest a ‘stretch the centre’ approach to emphasize the actual process of intrusion experiments in the construction of internal utilization distributions. To demonstrate the utility of the method, we apply all findings from the simulations to data from fieldwork with the model species Allobates femoralis, a territorial aromobatid frog from the lowland rainforest of French Guiana.

Landscape ecology: Coupling of pattern, process, and scale

Landscape ecology provides new theoretical frameworks and methodologies for understanding complex ecological phenomena at multiple scales. Studies of landscape ecology focus on understanding the dynamics of ecological patterns and processes, and highlight the integration of multiple disciplines. In this paper, we discussed the problems and challenges that landscape ecology is currently facing, emphasizing the limitations of current methods used to describe dynamic landscape patterns and processes. We suggested that the focus should be on the integration of ground-based observation, mobile monitoring, transect survey, and remote-sensing monitoring, as well as improved coupling of experimental and model simulations. In addition, we outlined the research frontiers in landscape ecology, including scaling, integrated pattern and process modeling, and regional synthesis. Lastly, a brief review of pattern-process-scale coupling studies in China was provided. We concluded by pointing out that pattern-process-scale interactions, correlations between natural, economic, and social processes, and the coupling of human and natural systems will be major research areas in landscape ecology in the future.

Losing the Culture of Ecology

1) Long-term declines in fundamental fields like taxonomy and natural history (e.g., Noss 1996, Uniyal 2011) and increasing emphasis on meta-analysis, data-mining, and modeling. Even though these latter approaches can be quite powerful, they tend to be cheaper and quicker to complete, and generate publications more rapidly than traditional field-based, empirical ecology. This situation makes it difficult for early-career field ecologists to compete, particularly when funding success is based primarily on metrics like publication numbers. 2) Increasing difficulty in publishing empirical and place-based studies compared with modeling, meta-analysis, and data mining in some areas of ecological research. For example, our recent review of Adaptive Management (Lindenmayer and Likens 2010, Westgate et al., in review) revealed that quantitative studies were significantly less common and less cited than qualitative thought and opinion pieces (β = −0.68 ± 0.09, P < 0.001). 3) Increasing emphasis on articles with significant word and citation limits, which often conspires against field-based studies. These trends have major implications for ecology, such as impeding progress in ecological modeling and theory testing. Meta-analyses and systematic reviews, which underpin evidence-based environmental policy and management (Collaboration for Environmental Evidence 2011), eventually will not be possible without the data from field-based studies (e.g., Whittaker 2010). To balance these cultural changes and to advance ecology, we believe it is important to maintain outlets for empirical and often descriptive field-based ecology, develop new metrics which reward empirical ecologists for the use of their data by others (e.g., Likens and Lindenmayer 2011, Reichman et al. 2011), and re-craft funding schemes to emphasize collaborative partnerships among empirical, field-based ecologists, theoreticians, and modelers.

Techniques to Promote Garry Oak Seedling Growth and Survival in Areas with High Levels of Herbivory and Competition

Though regeneration of Garry oak (Quercus garryana) seedlings within Garry oak ecosystems is important to maintain this threatened habitat, seedling regeneration is often poor. Two independent studies were initiated in the early 2000s to examine questions surrounding Garry oak recruitment: one at the Crow's Nest Ecological Research Area (CNERA) on Salt Spring Island, BC, and another at the Pacific Rim Institute for Environmental Stewardship (PRI) on Whidbey Island, WA. In both areas, Garry oak seedlings were caged and monitored for growth and relative health. Over 8 years at CNERA, growth of caged plants outpaced growth of controls, which was indicative of high browsing pressure and relatively high palatability of Garry oak seedlings to black-tailed deer and feral sheep. The PRI oaks grew more slowly and at four PRI sites survival was 30–50% over 5–6 years as compared to 90% survival at CNERA over 8 years. The mortality at PRI was likely due to a combination of dry summer conditions and large numbers of voles, which took advantage of the cages for protection from predators; furthermore, lack of mycorrhizal hosts could have inhibited seedling establishment. Weed block inside exclosure cages provided ideal nesting conditions for voles. This study demonstrated that the caging of Garry oak seedlings, although labor-intensive and requiring frequent maintenance, provides valuable protection from large ungulate browsers and can be maintained as a relatively long-term measure, but vigilance is required to protect young seedlings from other threats such as voles or competing vegetation.