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The cultivated strawberry, Fragaria xananassa, is one of the youngest domesticated plants. Its 18th century origin via hybridization in Europe between the North American F. virginiana and the South American F. chiloensis was documented by the botanist Antoine Nicolas Duchesne. His 1766 "Natural History of Strawberries" is an extraordinary work that integrates fundamental discoveries on the biology, ecology, and phylogeny of Fragaria with applied information on cultivation and ethnobotanical uses, serving as an inspiration for current research in the genus. Fragaria species exhibit the full range of sexual systems in the gynodioecy pathway from hermaphroditism to dioecy (and back again), as well as variation in self-compatibility, and evidence of sex chromosomes with female heterogamety. The genus is also characterized by interspecific hybridization and polyploidy, with a natural range of ploidy levels from diploids to decaploids. This biological diversity, combined with the availability of genomic resources and the ease of growing and experimenting with the plants, makes Fragaria a very attractive system for ecological and evolutionary genomics. The goal of this review is to introduce Fragaria as a model genus and to provide a roadmap for future integrative research. These research directions will deepen our understanding of the ecological and evolutionary context that shaped the ancestors of the cultivated strawberry, not only providing information that can be applied to efforts to shape the future of this important fruit crop but also our understanding of key transitions in plant evolution. [ABSTRACT FROM AUTHOR]

Conducting science for practical ends implicates scientists, whether they wish it or not, as agents in social-ecological systems, raising ethical, economic, environmental, and political issues. Considering these issues helps scientists to increase the relevance and sustainability of research outcomes. As we rise to the worthy call to connect basic research with food production, scientists have the opportunity to evaluate alternative food production paradigms and consider how our research funds and efforts are best employed. In this contribution, we review some of the problems produced by science conducted in service of industrial agriculture and its associated economic growth paradigm. We discuss whether the new concept of "ecological intensification" can rescue the industrial agriculture/growth paradigm and present an emerging alternative paradigm of decentralized, localized, biodiversity-promoting agriculture for a steady-state economy. This "custom fit" agriculture engages constructively with complex and highly localized ecosystems, and we draw from examples of published work to demonstrate how ecologists can contribute by using approaches that acknowledge local agricultural practices and draw on community participation. [ABSTRACT FROM AUTHOR]

Metabolomics may be defined as the analysis of thousands of naturally occurring small molecules (metabolites) such as sugars, organic acids, amino acids and nucleotides that are the products of cellular metabolism. As such, it is essentially the study of the complete biochemical phenotype (or metabotype) of any biofluid, cell, tissue or indeed organism, at both the qualitative and quantitative level. Metabolic profiles are context dependent, and will change in response to environmental circumstances. Therefore, while the technique has primarily been used in biomedical research to date, it is also applicable to ecological investigations and shows great promise in measuring the impact of factors such as climate change, disease, food restriction, infection and parasite load. In this review we detail the history and background of metabolomics and discuss examples of previous and potential future metabolic studies and applications in ecological science. [ABSTRACT FROM AUTHOR]

The practice of ecological restoration is a primary option for increasing levels of biodiversity by modifying human-altered ecosystems. The scientific discipline of restoration ecology provides conceptual guidance and tests of restoration strategies, with the ultimate goal of predictive landscape restoration. I construct a conceptual model for restoration of biodiversity, based on site-level (e.g., biotic and abiotic) conditions, landscape (e.g, interpatch connectivity and patch geometry), and historical factors (e.g., species arrival order and land-use legacies). I then ask how well restoration ecology has addressed the various components of this model. During the past decade, restoration research has focused largely on how the restoration of site-level factors promotes species diversity--primarily of plants. Relatively little attention has been paid to how landscape or historical factors interplay with restoration, how restoration influences functional and genetic components of biodiversity, or how a suite of less-studied taxa might be restored. I suggest that the high level of variation seen in restoration outcomes might be explained, at least in part, by the contingencies placed on site-level restoration by landscape and historical factors and then present a number of avenues for future research to address these often ignored linkages in the biodiversity restoration model. Such work will require carefully conducted restoration experiments set across multiple sites and many years. It is my hope that by considering how space and time influence restoration, we might move restoration ecology in a direction of stronger prediction, conducted across landscapes, thus providing feasible restoration strategies that work at scales over which biodiversity conservation occurs. [ABSTRACT FROM AUTHOR]

Copyright of Conservation Biology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Conservation Biology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

1. Linking the movement and behaviour of animals to their environment is a central problem in ecology. Through the use of electronic tagging and tracking (ETT), collection of in situ data from free-roaming animals is now commonplace, yet statistical approaches enabling direct relation of movement observations to environmental conditions are still in development. 2. In this study, we examine the hidden Markov model (HMM) for behavioural analysis of tracking data. HMMs allow for prediction of latent behavioural states while directly accounting for the serial dependence prevalent in ETT data. Updating the probability of behavioural switches with tag or remote-sensing data provides a statistical method that links environmental data to behaviour in a direct and integrated manner. 3. It is important to assess the reliability of state categorization over the range of time-series lengths typically collected from field instruments and when movement behaviours are similar between movement states. Simulation with varying lengths of times series data and contrast between average movements within each state was used to test the HMMs ability to estimate movement parameters. 4. To demonstrate the methods in a realistic setting, the HMMs were used to categorize resident and migratory phases and the relationship between movement behaviour and ocean temperature using electronic tagging data from southern bluefin tuna ( Thunnus maccoyii). Diagnostic tools to evaluate the suitability of different models and inferential methods for investigating differences in behaviour between individuals are also demonstrated. [ABSTRACT FROM AUTHOR]

A component of metabolic scaling theory has worked towards understanding the influence of metabolism over the generation and maintenance of biodiversity. Specific models within this ‘metabolic theory of biodiversity’ (MTB) have addressed temperature gradients in speciation rate and species richness, but the scope of MTB has been questioned because of empirical departures from model predictions. In this study, we first show that a generalized MTB is not inconsistent with empirical patterns and subsequently implement an eco-evolutionary MTB which has thus far only been discussed qualitatively. More specifically, we combine a functional trait (body mass) approach and an environmental gradient (temperature) with a dynamic eco-evolutionary model that builds on the current MTB. Our approach uniquely accounts for feedbacks between ecological interactions (size-dependent competition and predation) and evolutionary rates (speciation and extinction). We investigate a simple example in which temperature influences mutation rate, and show that this single effect leads to dynamic temperature gradients in macroevolutionary rates and community structure. Early in community evolution, temperature strongly influences speciation and both speciation and extinction strongly influence species richness. Through time, niche structure evolves, speciation and extinction rates fall, and species richness becomes increasingly independent of temperature. However, significant temperature-richness gradients may persist within emergent functional (trophic) groups, especially when niche breadths are wide. Thus, there is a strong signal of both history and ecological interactions on patterns of species richness across temperature gradients. More generally, the successful implementation of an eco-evolutionary MTB opens the perspective that a process-based MTB can continue to emerge through further development of metabolic models that are explicit in terms of functional traits and environmental gradients. [ABSTRACT FROM AUTHOR]

1. Movement behaviour has become increasingly important in dispersal ecology and dispersal is central to the development of spatially explicit population ecology. The ways in which the elements have been brought together are reviewed with particular emphasis on dispersal distance distributions and the value of mechanistic models. 2. There is a continuous range of movement behaviours and in some species, dispersal is a clearly delineated event but not in others. The biological complexities restrict conclusions to high-level generalizations but there may be principles that are common to dispersal and other movements. 3. Random walk and diffusion models when appropriately elaborated can provide an understanding of dispersal distance relationships on spatial and temporal scales relevant to dispersal. Leptokurtosis in the relationships may be the result of a combination of factors including population heterogeneity, correlation, landscape features, time integration and density dependence. The inclusion in diffusion models of individual variation appears to be a useful elaboration. The limitations of the negative exponential and other phenomenological models are discussed. 4. The dynamics of metapopulation models are sensitive to what appears to be small differences in the assumptions about dispersal. In order to represent dispersal realistically in population models, it is suggested that phenomenological models should be replaced by those based on movement behaviour incorporating individual variation. 5. The conclusions are presented as a set of candidate principles for evaluation. The main features of the principles are that uncorrelated or correlated random walk, not linear movement, is expected where the directions of habitat patches are unpredictable and more complex behaviour when organisms have the ability to orientate or navigate. Individuals within populations vary in their movement behaviour and dispersal; part of this variation is a product of random elements in movement behaviour and some of it is heritable. Local and metapopulation dynamics are influenced by population heterogeneity in dispersal characteristics and heritable changes in dispersal propensity occur on time-scales short enough to impact population dynamics. [ABSTRACT FROM AUTHOR]

Duplication is a prominent feature of plant genomic architecture. This has led many researchers to speculate that gene duplication may have played an important role in the evolution of phenotypic novelty within plants. Until recently, however, it was difficult to make this connection. We are now beginning to understand how duplication has contributed to adaptive evolution in plants. In this review we introduce the sources of gene duplication and predictions of the various fates of duplicates. We also highlight several recent and pertinent examples from the literature. These examples demonstrate the importance of the functional characteristics of genes and the source of duplication in influencing evolutionary outcome. [ABSTRACT FROM AUTHOR]

• To better understand invasion dynamics, it is essential to determine the influence of genetics and ecology in species persistence in both native and nonnative habitats. One approach is to assess patterns of selection on floral and growth traits of individuals in both habitats. • Mimulus guttatus (Phrymaceae) has a mixed mating system and grows under variable water conditions across its native and nonnative range in North America. Field investigations of patterns of selection of floral and plant size traits were conducted in two native and two nonnative populations. Field-collected seed was grown and crossed in the glasshouse using a paternal half-sib design. The resulting offspring were grown in saturated and dry-down low-water conditions and the same traits were measured in both environments. • Patterns of selection varied across years in the native range. Nonnative populations exhibited selection for increased floral size, consistent with the hypothesis that selection favors larger size in nonnative habitats. In the glasshouse, we detected genetic variation for traits across population/treatment combinations. However, size hierarchy in the glasshouse was dependent on water conditions. • Our results suggest that both variable selection pressures and local adaptation probably influence the persistence of both native and nonnative populations. [ABSTRACT FROM AUTHOR]

• The repeated, independent evolution of phenotypic traits reflects adaptation to similar selective pressures. In some circumstances, parallel phenotypic evolution has a common genetic basis. Here, we investigate the types of genetic change responsible for the repeated evolution of red flowers among Ipomoea species. • We identified three independent transitions from cyanidin- (blue/purple) to pelargonidin-type (red) anthocyanin pigments among Ipomoea species. The genetic basis for these transitions was examined using transgenics and gene expression assays. Using a literature survey to estimate the expected spectrum of mutation types capable of producing red flowers, we evaluated whether the observed distribution of mutation types differed from expectation. • In these species, red floral pigmentation appears to be caused by the disruption of flux through the anthocyanin pathway at the same position. Results implicate tissue-specific regulatory changes in the same gene, which suggests the possibility that flower color evolved independently via the same genetic mechanism. • Although multiple molecular mechanisms are capable of producing red flowers, we found a deviation between the distributions of observed and expected mutation types responsible for these evolutionary transitions. Regulatory mutations thus appear to be preferentially targeted during evolutionary change between species. We discuss possible explanations for this apparent bias. [ABSTRACT FROM AUTHOR]

Despite the global network of protected areas covers 12% of the world's land surface, its performance is still unsatisfactory. Although political and scientifically sound conservation targets usually portray different pictures of the task ahead, we show that in terms of priority areas for expanding the global network of reserves, there is much agreement between the political targets of the Convention on Biological Diversity (CBD), and the scientifically derived goals endorsed by international conservation organizations. Here we analyse four global databases to identify priority areas for fulfilling the CBD target of representing 10% of every ecological region within protected areas, and compare the distribution of priority regions for fulfilling that political target, with the distribution of the priority areas for global biodiversity conservation identified by Conservation International, the WWF, and the Wildlife Conservation Society on scientific basis. For 63% (549) of the world's terrestrial ecoregions the CBD 10% target is still not met; fulfilling it requires protecting another 4.6% of the Earth's land surface (6,239,894 km2). Yet, at least 78% of the priority regions for fulfilling that target lay within priority regions for the main global conservation strategies. By pursuing the political target set by the CBD much ancillary gains in terms of other global conservation objectives can be obtained. [ABSTRACT FROM AUTHOR]

Aim To demonstrate that parsimony analysis of endemicity (PAE) is not analogous to a cladistic biogeographical analysis. Location We used six data sets from previously published studies from around the world. Methods In order to test the efficiency of PAE in recovering historical relationships among areas, we performed an empirical comparison of nodes recovered with PAE, primary Brooks parsimony analysis (BPA), and an event-based method using three models (maximum codivergence, reconciled trees, and the default model of thetreefitter program) for six data sets. We measured the performance of PAE in recovering historical area relationships by counting the number and examining the content of nodes recovered by PAE and by historical methods. The dispersal/vicariance ratio was calculated to assess the prevalence of dispersal or vicariance in each reconstruction and its relationship to the performance of PAE. Results Our results show that PAE recovers an average of 17.25% of historical nodes. PAE and BPA tend to provide similar results; however, in relation to the event-based models, PAE performance was poor under all the tested scenarios. Although in some cases PAE reconstructions are more resolved than historical reconstructions, this does not necessarily mean that PAE produces more informative answers. These additional nodes correspond to unsupported statements that are based solely on the distributional data of taxa and not on their phylogenetic history. In other words, these nodes were not found by the historical methods, which take phylogenetics into account. The number of historical nodes recovered using PAE was in general negatively correlated with the dispersal/vicariance ratio. Main conclusions Our results show that PAE is unable to recover historical patterns and therefore does not fit into the current paradigm of historical biogeography. These findings raise doubts regarding conclusions derived from biogeographical studies that interpret PAE trees as area cladograms. We acknowledge that PAE aims to describe but does not explain the current distribution of organisms. It is therefore a useful tool in other biogeographical or ecological analyses for exploring the distribution of taxa or for establishing hypotheses of primary homology between areas. [ABSTRACT FROM AUTHOR]

Animal movement receives widespread attention within ecology and behavior. However, much research is restricted within isolated sub-disciplines focusing on single phenomena such as navigation (e.g. homing behavior), search strategies (e.g. Levy flights) or theoretical considerations of optimal population dispersion (e.g. ideal free distribution). To help synthesize existing research, we outline a unifying conceptual framework that integrates individual-level behaviors and population-level spatial distributions with respect to spatio-temporal resource dynamics. We distinguish among (1) non-oriented movements based on diffusion and kinesis in response to proximate stimuli, (2) oriented movements utilizing perceptual cues of distant targets, and (3) memory mechanisms that assume prior knowledge of a target's location. Species’ use of these mechanisms depends on life-history traits and resource dynamics, which together shape population-level patterns. Resources with little spatial variability should facilitate sedentary ranges, whereas resources with predictable seasonal variation in spatial distributions should generate migratory patterns. A third pattern, ‘nomadism’, should emerge when resource distributions are unpredictable in both space and time. We summarize recent advances in analyses of animal trajectories and outline three major components on which future studies should focus: (1) integration across alternative movement mechanisms involving links between state variables and specific mechanisms, (2) consideration of dynamics in resource landscapes or environments that include resource gradients in predictability, variability, scale, and abundance, and finally (3) quantitative methods to distinguish among population distributions. We suggest that combining techniques such as evolutionary programming and pattern oriented modeling will help to build strong links between underlying movement mechanisms and broad-scale population distributions. [ABSTRACT FROM AUTHOR]

Aim To explore variation in the number of vertebrae in fishes in the context of Jordan’s rule and other ecogeographical rules. Location Global. Methods The study is based on literature review. Results The number of vertebrae varies very widely across the diversity of fishes. Jordan’s rule states that vertebral number increases with latitude, and this is widely attributed to ambient temperatures during ontogeny of individual fishes. However, the number of vertebrae may depend on both the ontogenetic environment and inheritance. Diverse other aspects of fish development and ecology are suggested as influencing vertebral number, including fish size, phyletic position, body shape and swimming mode. Main conclusions The number of different factors that influence the number of vertebrae in fishes makes for highly complex patterns of variation, and means that unravelling causes is difficult. The question needs to be addressed at the population/species/species group scale; moreover, the lack of discrimination between environmental and inherited causes of variation adds to the complexity. [ABSTRACT FROM AUTHOR]

Using a bioenergetic model we show that the pattern of foraging preferences greatly determines the complexity of the resulting food webs. By complexity we refer to the degree of richness of food-web architecture, measured in terms of some topological indicators (number of persistent species and links, connectance, link density, number of trophic levels, and frequency of weak links). The poorest food-web architecture is found for a mean-field scenario where all foraging preferences are assumed to be the same. Richer food webs appear when foraging preferences depend on the trophic position of species. Food-web complexity increases with the number of basal species. We also find a strong correlation between the complexity of a trophic module and the complexity of entire food webs with the same pattern of foraging preferences. [ABSTRACT FROM AUTHOR]

The Madagascar spider tortoise Pyxis arachnoides is facing pressure from habitat destruction, hunting for food and collection for the exotic pet-trade. Very little is known of the biology and ecology of P. arachnoides. This study centres on a subspecies population of P. arachnoides arachnoides, within the southern dry forests of the Anakao region of southwest Madagascar . Surveys were carried out across 83, one hectare, quadrants over 12 months, during both the wet and dry seasons, with respective seasonal mean population densities recorded at 4.63 and 2.08 individuals per ha. This significant variation was accompanied by a variation in micro habitat preference between the seasons, with P. a. arachnoides moving to areas of greater vegetation cover during the warmer wet season. P. a. arachnoides was only recorded as feeding during the wet months, a period of increased activity. The subspecies became less active during the dry season, with some individuals entering a dormant phase. There was generally a greater abundance of females encountered throughout the year, usually weighing less than males. Juvenile abundance peaked during February and March. Six-year-old specimens were the most regularly encountered individuals and a mean age throughout the survey was recorded at 11.25 years. Résumé La Pyxide arachnoïde de Madagascar, Pyxis arachnoides, subit des pressions comprenant la destruction de son habitat, la chasse alimentaire et le prélèvement destiné au commerce d’animaux exotiques. On connaît très peu de la biologie et de l’écologie de P. arachnoides. Cette étude se focalise sur une population de la sous-espèce P. arachnoides arachnoides vivant dans la forêt sèche du sud, dans la région de l’Anakao au sud ouest de Madagascar. Des reconnaissances ont été menées dans 83 quadrats d’un hectare, durant 12 mois au cours des saisons sèche et humide, où l’on a relevé des densités moyennes saisonnières de respectivement 4,63 et 2,08 individus à l’hectare. Cette variation significative était assortie d’une variation dans la préférence de micro habitat entre les saisons, où P. a. arachnoides se déplace vers des zones à couvert végétal plus étendu durant la saison humide plus chaude. On n’a observé P. a. arachnoides s’alimenter que durant les mois humides durant laquelle son activité est plus importante. Cette sous-espèce devient moins active au cours de la saison sèche, où certains individus entrent en phase dormante. On a généralement constaté tout au long de l’année une plus grande abondance de femelles, qui pèsent habituellement moins que les mâles. L’abondance maximale de juvéniles se situe en février et mars. Les individus rencontrés le plus régulièrement étaient des spécimens âgés de six ans, et l’âge moyen enregistré tout au long de l’étude était de 11,25 ans. [ABSTRACT FROM AUTHOR]

1. Invading species typically need to overcome multiple limiting factors simultaneously in order to become established, and understanding how such factors interact to regulate the invasion process remains a major challenge in ecology. 2. We used the invasion of marine algal communities by the seaweed Sargassum muticum as a study system to experimentally investigate the independent and interactive effects of disturbance and propagule pressure in the short term. Based on our experimental results, we parameterized an integrodifference equation model, which we used to examine how disturbances created by different benthic herbivores influence the longer term invasion success of S. muticum. 3. Our experimental results demonstrate that in this system neither disturbance nor propagule input alone was sufficient to maximize invasion success. Rather, the interaction between these processes was critical for understanding how the S. muticum invasion is regulated in the short term. 4. The model showed that both the size and spatial arrangement of herbivore disturbances had a major impact on how disturbance facilitated the invasion, by jointly determining how much space-limitation was alleviated and how readily disturbed areas could be reached by dispersing propagules. 5. Synthesis. Both the short-term experiment and the long-term model show that S. muticum invasion success is co-regulated by disturbance and propagule pressure. Our results underscore the importance of considering interactive effects when making predictions about invasion success. [ABSTRACT FROM AUTHOR]

Understanding how climate regulates trophic control may help to elucidate the causes of transitions between alternate ecosystem states following climate regime shifts. We used a 34-year time series of the abundance of Pacific cod ( Gadus macrocephalus) and five prey species to show that the nature of trophic control in a North Pacific ecosystem depends on climate state. Rapid warming in the 1970s caused an oscillation between bottom–up and top–down control. This shift to top–down control apparently contributed to the transition from an initial, prey-rich ecosystem state to the final, prey-poor state. However, top–down control could not be detected in the final state without reference to the initial state and transition period. Complete understanding of trophic control in ecosystems capable of transitions between alternate states may therefore require observations spanning more than one state. [ABSTRACT FROM AUTHOR]

How does life history affects the short-term elasticities of population growth rate? We decompose short-term elasticity as a sum of (i) the effect of the perturbation in rates on the unperturbed population structure and (ii) the effect of the original vital rates on the difference in structure between the original and the perturbed population. We provide exact analytical formulas for these components. In a population at its stable stage distribution (SSD), short-term elasticity is determined mainly by the SSD and reproductive value. In a non-stable population, short-term elasticity depends also on the projection of initial structure on the SSD, equal to population momentum. Non-stable stage structures matter most to elasticity if stages are missing that take time to fill in. We show how the demographic damping rate of the original population determines the rate at which short-term elasticity converges to its limiting values. [ABSTRACT FROM AUTHOR]

The pattern of species abundances is central to ecology. But direct measurements of species abundances at ecologically relevant scales are typically unfeasible. This limitation has motivated a long-standing interest in the relationship between the abundance distribution in a large, regional community and the distribution observed in a small sample from the community. Here, we develop a statistical sampling theory to describe how observed patterns of species abundances are influenced by the spatial distributions of populations. For a wide range of regional-scale abundance distributions we derive exact expressions for the sampled abundance distributions, as a function of sample size and the degree of conspecific spatial aggregation. We show that if populations are randomly distributed in space then the sampled and regional-scale species-abundance distribution typically have the same functional form: sampling can be expressed by a simple scaling relationship. In the case of aggregated spatial distributions, however, the shape of a sampled species-abundance distribution diverges from the regional-scale distribution. Conspecific aggregation results in sampled distributions that are skewed towards both rare and common species. We discuss our findings in light of recent results from neutral community theory, and in the context of estimating biodiversity. [ABSTRACT FROM AUTHOR]

1. Contrasting results of relations between standard metabolic rate, behaviour and performance suggest that the evolutionary trade-offs in energy allocation between metabolisms and other parts of the energy budget depend on environmental conditions. Here, we show how habitat complexity changes the relationship between standard metabolic rate, behaviour and performance (winter energy loss-rates) in juvenile Atlantic salmon ( Salmo salar L.). 2. Juvenile Salmon, individually screened for standard metabolic rate, were stocked in replicated semi-natural stream channels with and without sheltering possibilities under ledge cover. We recorded the use of ledged areas, energy-loss rates and feeding activity during a 61-day period. 3. In the channels with ledge cover, individuals with relatively higher standard metabolic rates used areas outside of the cover more frequently and had higher feeding frequency than individuals with lower standard metabolic rates. No relationship was apparent between areas used, feeding and standard metabolic rate for the individuals within the no-cover treatments. In channels without cover, there was a negative relationship between standard metabolic rate and performance (energy balance), whereas standard metabolic rate did not affect performance in channels with ledge cover. 4. The effect of standard metabolic rate on performance depended on habitat complexity expressed through differences in behaviour. In channels with ledge cover, individuals with higher standard metabolic rates were apparently able to compensate for higher metabolic costs by utilizing a riskier habitat outside the cover and attaining a higher feeding success. 5. The present study demonstrates that the relationship between standard metabolic rate and performance may be dependent on habitat complexity and vary on small spatial scales, contributing to the persistence of large variation in standard metabolic rate within populations. [ABSTRACT FROM AUTHOR]

1. Plants that display many open flowers usually receive higher pollinator visitation rates, but it is unclear whether pollinators select plants to visit based on the size of floral display (apparent size) or the value of the floral rewards (reward size). To examine how pollinators respond to apparent size and reward size, we observed bumble bees foraging among arrays of artificial plants. 2. We constructed two kinds of artificial flower: (i) rewarding flowers that produced nectar constantly; and (ii) unrewarding flowers that produced only water. Thus, we could construct plants that varied both in numbers of flowers (apparent size) and in numbers of rewarding flowers (reward size). 3. At the beginning of the experiments, bees made more visits to the plants with the most flowers, irrespective of the rewards they contained. However, after several hours of foraging, bees returned selectively to plants with the greater number of rewarding flowers, irrespective of the number of flowers the plant presented. After we replaced rewarding plants with non-rewarding plants, bees continued visiting plants at formerly-profitable locations for a while. 4. Our results demonstrate that bees initially showed preferences for plants with larger floral displays, but eventually bees were able to discriminate between rewarding and less-rewarding plants of equal display size by associating a plant's location with its reward size. Our results suggest that plants with many flowers can achieve higher visitation rates from pollinators in two ways: (i) by attracting inexperienced pollinators with large displays; and (ii) by encouraging experienced pollinators to return with the promise of greater rewards. [ABSTRACT FROM AUTHOR]

1. Identifying how selection shapes life-history traits by causally relating environment to phenotype, performance and fitness has often proven elusive due to limitations of classical analysis methods, which only identify covariance in traits, and to the difficulties in experimentally manipulating environment to expose cause and effect in wild populations. 2. In an approach resembling the experimental method common to all modern research, structural equation modelling can not only identify covariance in traits, but also test hypotheses of direct and indirect causal paths that tie environment to phenotypes and fitness through natural selection. Here, we use novel confirmatory path analyses and a long-term study of Corsican blue tits to analyse the interactions between environmental variables (prey abundance and ectoparasite load), phenotypic traits (mass and haematocrit), physiological performance (aerobic capacity) and nestling recruitment. 3. Our analyses show that an antagonistic interaction between ectoparasites and food abundance sets tissue development and oxygen carrying capacity of blood at fledging, and that identical paths link these variables to physiological performance and recruitment. 4. This study suggests that metabolic capacity at fledging may be important in determining subsequent recruitment and unmasks subtle fitness costs of an ectoparasite. [ABSTRACT FROM AUTHOR]

1. In generalist nectar-feeding insects such as butterflies, body size and proboscis length show an allometric relationship. Butterflies that deviate from this relationship and have disproportionately long proboscides can access nectar from deep flowers, which is inaccessible to species of similar or larger body size but with shorter proboscides. 2. Despite this selective advantage, few species possess disproportionately long proboscides for their body size, which indicates that there may be developmental, functional or other ecological constraints on very long proboscides. I hypothesized that species with disproportionately long proboscides had a functional cost in terms of higher handling time (amount of time spent per flower); therefore, they were at a competitive disadvantage compared to butterflies that had shorter proboscides and lower handling times. 3. I tested this hypothesis using Costa Rican butterflies. I measured body length, proboscis length and handling time on Lantana and Wedelia, two nectar plants with generalist pollination systems which attract large numbers of nectar-feeding butterfly species. 4. There was a strong positive relationship between ‘relative proboscis length’ (proboscis length in relation to body size) and handling time per flower on both nectar plants. Species with greater relative proboscis length had up to three times longer handling time per flower. Thus, butterflies with relatively long proboscides should harvest less nectar per unit time from the same flower than butterflies with normal proboscides. 5. Reduced foraging efficiency in the face of competition from other nectarivores may thus be a functional constraint that limits the evolution of disproportionately long proboscides in generalist nectar-feeding butterflies. [ABSTRACT FROM AUTHOR]

The article addresses criticisms of the BIODEPTH project, a biodiversity and ecosystem functioning research in Great Britain. It shows that patterns for legume species are not generally consistent with the multispecies sampling effect for legumes proposed by Huston & McBride in 2002. The BIODEPTH results are not also consistent with transient biodiversity effects. Researchers propose that the conflict in the results of biodiversity experiments and observational biodiversity studies arises because they use different approaches to address different questions.

Pieris napi females have different heritable reproductive tactics. Polyandrous females have higher lifetime fecundity, whereas monandrous ones start to reproduce at a faster rate. Butterfly larvae are time-constrained in seasonal environments. Thus, polyandry is expected to be associated with fast juvenile development, which may result in biased mortality due to physiological costs. We compared how females with varying degrees of polyandry allocate between duration of larval period and achievable size in directly developing and over-wintering generations. Offspring survival and growth were monitored under a high density and low quality diet. Polyandrous females developed at a faster rate than monandrous ones, regardless of developmental pathway. The growth rate of female offspring correlated with their mothers’ degree of polyandry, which underpins polyandry and monandry as distinct strategies with life history differences reaching beyond mating frequency. The high growth rate of polyandrous females resulted in a short larval period among directly developing females, and in large size within an over-wintering cohort. A change in either the duration of the larval period or pupal mass had no significant effect on the other, emphasising that growth rate is not necessarily a simple outcome of the tradeoff between development time and size at maturity. The correlation between the degree of polyandry and juvenile growth rate diminished when larvae were exposed to environmental stress, which offers an explanation why juvenile mortality was decoupled from mating tactic. We conclude that polyandry is a strategy that allows larvae to utilise optimal conditions in a more effective way than monandry. As a consequence, polyandrous females either achieve larger size or they mature faster. This gives them a double advantage over monandrous ones within an over-wintering generation or diminishes the effects of asynchronous hatching of offspring within a directly developing generation. Possible costs of high growth rate are discussed. [ABSTRACT FROM AUTHOR]

The relationship between above and belowground species composition has been researched in forests, grasslands, and wetlands to understand what mechanisms control community composition. I thoroughly reviewed 108 articles published between 1945 and 2006 that summarized and provided specific values on similarities between above and belowground communities to identify common trends among ecosystems. Using Sørenson's index of similarity, I found that standing vegetation and its associated seed bank was the least similar in forest ecosystems, most similar in grasslands, and of intermediate similarity in wetlands. I also discovered that species richness was not related to seed bank – vegetation similarity in any of the three ecosystems. Disturbances were a common mechanism driving community composition in all ecosystems, where similarity decreased with time since disturbance in forest and wetland ecosystems and increased with time since disturbance in grasslands. Knowing the relationships between seed bank and standing vegetation may help conservationists to manage against exotic species, plan for community responses to disturbances, restore diversity, and better understand the resilience of an ecosystem. [ABSTRACT FROM AUTHOR]

The article reports on the significance of individual foraging specialization towards ecology, conservation, and evolution. According to the author, there are various studies which identified as well as investigated individual foraging specialization; however, the results of said investigations failed to come with a common definition of specialization. The author further argues that there is a need to clearly identify characteristics of niches that feature information about individual foraging specialization in order to remedy the complexity brought about by the diverse approaches.

We investigated the occurrence and distribution of multi-annual cycles in abundance of mountain hare populations across a wide area of their range in northern Europe. We analysed 125 time-series of mountain hare abundance indexed from hunting bag records and questionnaire responses from Scotland, Sweden, Finland and Switzerland. We also reanalysed 17 previously published time-series based on hunting bag records and snow track indices from mountain hare populations in Scotland, Norway, Sweden, Finland, Russia and Italy. Autocorrelation analysis showed that 45% of mountain hare populations showed evidence of cycles, characterised by significant negative autocorrelations at half or the whole cycle period. The amplitude and periodicity of cycles varied between and within countries. Time-series in Scotland were characterised by high-amplitude weak cycles with a mean periodicity of nine years but with a range of 4–15 years. Norwegian and Swedish time-series revealed low amplitude weak cycles with a 3–7 year period. Finnish time-series showed low amplitude cycles with a 4–11 year period. Alpine time-series were predominantly non-cyclic, while the limited number of series from Russia showed high amplitude weak cycles with an 8–11 year period. The results reveal that mountain hare populations show a wide range of population dynamics with distinct regional differences in periodicity, amplitude and density dependent structure of cycles. These findings suggest that different factors may limit or regulate mountain hare populations in different regions of Europe thus supporting the results of recent field studies. [ABSTRACT FROM AUTHOR]

1. Changing plant composition in a community can have profound consequences for herbivore and parasitoid population dynamics. To understand such effects, studies are needed that unravel the underlying behavioural decisions determining the responses of parasitoids to complex habitats. 2. The searching behaviour of the parasitoid Diadegma semiclausum was followed in environments with different plant species composition. In the middle of these environments, two Brassica oleracea plants infested by the host Plutella xylostella were placed. The control set-up contained B. oleracea plants only. In the more complex set-ups, B. oleracea plants were interspersed by either Sinapis alba or Hordeum vulgare. 3. Parasitoids did not find the first host-infested plant with the same speed in the different environments. Sinapis alba plants were preferentially searched by parasitoids, resulting in fewer initial host encounters, possibly creating a dynamic enemy-free space for the host on adjacent B. oleracea plants. In set-ups with H. vulgare, also, fewer initial host encounters were found, but in this case plant structure was more likely than infochemicals to interfere with the searching behaviour of parasitoids. 4. On discovering a host-infested plant, parasitoids located the second host-infested plant with equal speed, demonstrating the effect of experience on time allocation. Further encounters with host-infested plants that had already been visited decreased residence times and increased the tendency to leave the environment. 5. Due to the intensive search of S. alba plants, hosts were encountered at lower rates here than in the other set-ups. However, because parasitoids left the set-up with S. alba last, the same number of hosts were encountered as in the other treatments. 6. Plant composition of a community influences the distribution of parasitoid attacks via its effects on arrival and leaving tendencies. Foraging experiences can reduce or increase the importance of enemy-free space for hosts on less attractive plants. [ABSTRACT FROM AUTHOR]

1. Social species in the spider genus Anelosimus predominate in lowland tropical rainforests, while congeneric subsocial species occur at higher elevations or higher latitudes. 2. We conducted a comparative study to determine whether differences in total biomass, insect size or both have been responsible for this pattern. 3. We found that larger average insect size, rather than greater overall biomass per se, is a key characteristic of lowland tropical habitats correlating with greater sociality. 4. Social species occupied environments with insects several times larger than the spiders, while subsocial species nearing dispersal occupied environments with smaller insects in either high or low overall biomass. 5. Similarly, in subsocial spider colonies, individuals lived communally at a time when they were younger and therefore smaller than the average insect landing on their webs. 6. We thus suggest that the availability of large insects may be a critical factor restricting social species to their lowland tropical habitats. [ABSTRACT FROM AUTHOR]

The concept of a generalist flower appears to mean different things to different people, depending upon their background and training. We assess the different meanings of generalist flowers with respect to the ecological "set and setting" of pollination, and then we discuss notions of ecological, functional and phenotypic generalization. These ideas are explored in more detail using examples from our own published and unpublished studies on the pollination ecology of Daucus carota, Hedera helix, and Chamerion angustifolium, and from the published work of other researchers. Finally we relate these ideas and clarified definitions of "generalist" and "specialist" flowers to the pollination syndrome concept. [ABSTRACT FROM AUTHOR]

Aim The aim of this study is to answer the questions: (1) do small organisms disperse farther than large, or vice versa; and (2) does the observed pattern differ for passive and active dispersers? These questions are central to several themes in biogeography (including microbial biogeography), macroecology, metacommunity ecology and conservation biology. Location The meta-analysis was conducted using published data collected worldwide. Methods We collected and analysed 795 data values in the peer-reviewed literature for direct observations of both maximal dispersal distance and mass of the dispersing organisms (e.g. seeds, not trees). Analysed taxa ranged in size from bacteria to whales. We applied macroecology analyses based on null models (using Monte Carlo randomizations) to test patterns relative to specific hypotheses. Results Collected dispersal distance and mass data spanned 9 and 21 orders of magnitude, respectively. Active dispersers dispersed significantly farther ( P < 0.001) and were significantly greater in mass ( P < 0.001) than passive dispersers. Overall, size matters: larger active dispersers attained greater maximum observed dispersal distances than smaller active dispersers. In contrast, passive-disperser distances were random with respect to propagule mass, but not uniformly random, in part due to sparse data available for tiny propagules. Conclusions Size is important to maximal dispersal distance for active dispersers, but not for passive dispersers. Claims that microbes disperse widely cannot be tested by current data based on direct observations of dispersal: indirect approaches will need to be applied. Distance–mass relationships should contribute to a resolution of neutral and niche-based metacommunity theories by helping scale expectations for dispersal limitation. Also, distance–mass relationships should inform analyses of latitudinal species richness and conservation biology topics such as fragmentation, umbrella species and taxonomic homogenization. [ABSTRACT FROM AUTHOR]

Habitat loss and fragmentation threaten a large proportion of terrestrial biodiversity, and identifying the ecological traits associated with extinction proneness is of widespread interest. We used a multivariate statistical approach to identify combinations of ecological traits that best allowed us to identify extinction-prone amphibians and reptiles in a fragmented landscape in north-eastern Bolivia. Extinction-prone amphibians were rare and did not utilize the savannah matrix separating forest islands, whereas extinction-prone reptiles were trophically specialized. Rarity and matrix aversion are among the most widely reported correlates to extinction proneness, and we argue that an increased understanding of their role as drivers of extinction processes is necessary. We suggest that the absence of reptilian vertebrate predators may exacerbate trophic cascades in habitat patches. [ABSTRACT FROM AUTHOR]

Predictive species distribution modelling (SDM) has become an essential tool in biodiversity conservation and management. The choice of grain size (resolution) of environmental layers used in modelling is one important factor that may affect predictions. We applied 10 distinct modelling techniques to presence-only data for 50 species in five different regions, to test whether: (1) a 10-fold coarsening of resolution affects predictive performance of SDMs, and (2) any observed effects are dependent on the type of region, modelling technique, or species considered. Results show that a 10 times change in grain size does not severely affect predictions from species distribution models. The overall trend is towards degradation of model performance, but improvement can also be observed. Changing grain size does not equally affect models across regions, techniques, and species types. The strongest effect is on regions and species types, with tree species in the data sets (regions) with highest locational accuracy being most affected. Changing grain size had little influence on the ranking of techniques: boosted regression trees remain best at both resolutions. The number of occurrences used for model training had an important effect, with larger sample sizes resulting in better models, which tended to be more sensitive to grain. Effect of grain change was only noticeable for models reaching sufficient performance and/or with initial data that have an intrinsic error smaller than the coarser grain size. [ABSTRACT FROM AUTHOR]

Plant phenotypes often differ in their resistance to natural enemies, but the mechanism for this has seldom been identified. The aim of this study was to determine if the spatial patterns of phenotype use of a highly specialized insect herbivore (the galling sawfly Pontania triandrae) in a natural willow population can be related to phenotypic variation in plant secondary chemistry. Furthermore, we tested if traits that confer resistance to one type of natural enemy, i.e. the galling sawfly, also confer resistance to others, in our case a leaf beetle Gonioctena linnaeana and the rust fungus Melampsora amygdalinae. We identified 18 phenotypes with high and 18 phenotypes with low gall density in our field population and determined gall densities, the degree of leaf damage and rust infection on each phenotype and collected leaves for chemical analyses. The concentration of phenolics was higher in phenotypes with high density of galls suggesting that this galling sawfly may use phenolics as oviposition cues. Rust infection showed the opposite pattern, with lower levels on clones with high concentration of phenolics, while leaf damage by G. linnaeana did not differ between clone types. This indicates that these important natural enemies may assert divergent selection on willow phenotypes and that this might provide a mechanism for maintaining phenotypic variation within willow populations. [ABSTRACT FROM AUTHOR]

Individual traits are often assumed to be linked in a straightforward manner to plant performance and processes such as population growth, competition and community dynamics. However, because no trait functions in isolation in an organism, the effect of any one trait is likely to be at least somewhat contingent on other trait values. Thus, to the extent that the suite of trait values differs among species, the magnitude and even direction of correlation between values of any particular trait and performance is likely to differ among species. Working with a group of clonal plant species, we assessed the degree of this contingency and therefore the extent to which the assumption of simple and general linkages between traits and performance is valid. To do this, we parameterized a highly calibrated, spatially explicit, individual-based model of clonal plant population dynamics and then manipulated one trait at a time in the context of realistic values of other traits for each species. The model includes traits describing growth, resource allocation, response to competition, as well as architectural traits that determine spatial spread. The model was parameterized from a short-term (3 month) experiment and then validated with a separate, longer term (two year) experiment for six clonal wetland sedges, Carex lasiocarpa, Carex sterilis, Carex stricta, Cladium mariscoides, Scirpus acutus and Scirpus americanus. These plants all co-occur in fens in southeastern Michigan and represent a spectrum of clonal growth forms from strong clumpers to runners with long rhizomes. Varying growth, allocation and competition traits produced the largest and most uniform responses in population growth among species, while variation in architectural traits produced responses that were smaller and more variable among species. This is likely due to the fact that growth and competition traits directly affect mean ramet size and number of ramets, which are direct components of population biomass. In contrast, architectural and allocation traits determine spatial distribution of biomass; in the long run, this also affects population size, but its net effect is more likely to be mediated by other traits. Such differences in how traits affect plant performance are likely to have implications for interspecific interactions and community structure, as well as on the interpretation and usefulness of single trait optimality models. [ABSTRACT FROM AUTHOR]

To investigate the evolution of background matching (crypsis) when prey are viewed against uniform and heterogeneous (alternating) backgrounds, we conducted some web-based experiments. Visitors to our experimental web site were rewarded for finding artificial prey, thereby providing a measure of their detectability. We first compared the “survivorship” of a range of pixilated prey phenotypes presented against both light green and dark green pixilated backgrounds and found clear evidence for a concave tradeoff curve, indicating that specialism on one or the other background would maximise their overall survivorship. We then compared the survivorship of a range of spotted prey phenotypes presented against backgrounds with small spots and large spots and found evidence for a more linear tradeoff curve, indicating that both intermediates and specialists would have approximately equal survivorship. Replicated evolutionary experiments were then conducted in which the survivors in any given system automatically reproduced themselves (subject to occasional mutation) when their population size was depleted to a critical threshold. Here close background matching readily evolved when prey were presented against a single uniform pixilated environment and when prey were presented against a single uniform spotted environment. As expected, the background matching that evolved in alternating light and dark green environments involved specialism on one or other background, and no intermediate forms evolved. By contrast, a more polymorphic range of phenotypes evolved in the alternating small and large spotted environments. To our knowledge this is the first time that automatically regenerating populations of web based prey have been set up to address evolutionary questions. Our findings have clearly shown conditions under which jack-of-all-trades cryptic forms survive poorly, and, although more work is needed, it may also help explain why background matching frequently appears so specialized in natural systems. [ABSTRACT FROM AUTHOR]

The article presents a discussion on alternative stable states (ASS) in ecology. It argues the theories of R. K. Didham and colleagues regarding ASS of ecological communities. It also cites the three major criteria for ASS such as it must be shown to occur in the same environment, the perturbation which causes the change in species composition must be applied as a pulse and must not cause a prolonged change in the environment, and it must be self sustaining. ASS has been discussed mainly for semi-arid rangelands.

Hubbell's neutral theory of biodiversity has generated much debate over the need for niches to explain biodiversity patterns. Discussion of the theory has focused on its neutrality assumption, i.e. the functional equivalence of species in competition and dispersal. Almost no attention has been paid to another critical aspect of the theory, the assumptions on the nature of the speciation process. In the standard version of the neutral theory each individual has a fixed probability to speciate. Hence, the speciation rate of a species is directly proportional to its abundance in the metacommunity. We argue that this assumption is not realistic for most speciation modes because speciation is an emergent property of complex processes at larger spatial and temporal scales and, consequently, speciation rate can either increase or decrease with abundance. Accordingly, the assumption that speciation rate is independent of abundance (each species has a fixed probability to speciate) is a more natural starting point in a neutral theory of biodiversity. Here we present a neutral model based on this assumption and we confront this new model to 20 large data sets of tree communities, expecting the new model to fit the data better than Hubbell's original model. We find, however, that the data sets are much better fitted by Hubbell's original model. This implies that species abundance data can discriminate between different modes of speciation, or, stated otherwise, that the mode of speciation has a large impact on the species abundance distribution. Our model analysis points out new ways to study how biodiversity patterns are shaped by the interplay between evolutionary processes (speciation, extinction) and ecological processes (competition, dispersal). [ABSTRACT FROM AUTHOR]

Allee effects can play a critical role in slowing or preventing the establishment of low density founder populations of non-indigenous species. Similarly, the spread of established invaders into new habitats can be influenced by the degree to which small founder populations ahead of the invasion front are suppressed through Allee effects. We develop an approach to use empirical data on the gypsy moth, a non-indigenous invader in North America, to quantify the Allee threshold across geographical regions, and we report that the strength of the Allee effect is subject to spatial and temporal variability. Moreover, we present what is to our knowledge the first empirical evidence that geographical regions with higher Allee thresholds are associated with slower speeds of invasion. [ABSTRACT FROM AUTHOR]

Short-term, transient population dynamics can differ in important ways from long-term asymptotic dynamics. Just as perturbation analysis (sensitivity and elasticity) of the asymptotic growth rate reveals the effects of the vital rates on long-term growth, the perturbation analysis of transient dynamics can reveal the determinants of short-term patterns. In this article, I present a completely new approach to transient sensitivity and elasticity analysis, using methods from matrix calculus. Unlike previous methods, this approach applies not only to linear time-invariant models but also to time-varying, subsidized, stochastic, nonlinear and spatial models. It is computationally simple, and does not require calculation of eigenvalues or eigenvectors. The method is presented along with applications to plant and animal populations. [ABSTRACT FROM AUTHOR]

Despite the importance of community-structuring processes operating at both local and regional scales, there is relatively little work examining both forces within a single system. I used a combination of observational and experimental approaches to examine the processes structuring larval dragonfly distributions in lentic habitats that encompass a gradient of both permanence and top predator type. I compared the relative vulnerability of species to predators from different portions of this gradient to assess the role of predation as a local force structuring communities. I also assessed the role of regional processes on species’ distributions by examining species’ propensity to disperse to and colonize artificial ponds distributed across a landscape. In both studies I contrasted habitat specialist species, which had larvae restricted to permanent lakes, with habitat generalist species, which had larvae that occur broadly across the habitat permanence and top predator transition. Results from this work suggest that dispersal and colonization behavior were critical mechanisms restricting the distributions of habitat specialist species, but that predation may act to reinforce this pattern. The habitat specialists dispersed less frequently, colonized artificial ponds less often when they did reach them, and most moved shorter distances than the habitat generalist species. Habitat specialists were also more vulnerable than habitat generalists to an invertebrate top predator with which they do not co-exist. Results from these studies suggest that species distributions can be shaped by processes operating at both regional and local spatial scales. The role of dispersal and recruitment limitation may be generally underestimated as a force shaping species distributions and community structure across habitat gradients in which there is a transition in both the biotic interactions and the disturbance interval across that gradient. [ABSTRACT FROM AUTHOR]

1 This review brings into focus what is known about the response of the herbaceous layer of forest ecosystems to increasing nitrogen deposition. The emphasis on forests in general is important for two reasons. First, forests often occupy areas receiving high rates of atmospheric deposition of N. Second, compared with herb-dominated communities, about which much is known regarding response to excess N, forests generally display greater biological and structural complexity. The more specific focus on the herbaceous layer – here defined as all vascular (herbaceous and woody) plants ≤ 1 m in height – is warranted because most of the species diversity of forests occurs in the herb layer. 2 Most responses of forest ecosystems to N saturation, defined here as ecosystem supply of N exceeding ecosystem demand for N, can be characterized by two complementary hypotheses, each emphasizing different facets of ecosystem structure and function. One focuses on ecosystem processes, such as net primary productivity, whereas the other addresses seasonal patterns of concentrations of in stream water. Although neither hypothesis considers the effects of chronically elevated N deposition on forest herbs, both share a prediction – a dramatic increase in availability of – that is relevant to forest herb response. Such a shift towards dominance has important implications for changes in herbaceous layer dynamics. For example, increases in soil pools can increase invasibility by exotic species. Also, because preferential use of vs. can be highly species-specific among forest herbs, predominance of availability can bring about further changes in herb layer species composition. Also important to forest herbs is the tendency for enhanced mobility of to increase mobility and decrease availability of essential cations, such as Ca2+. 3 The response of plant species of the herbaceous layer of forest ecosystems to excess N availability can arise from N-mediated changes in several processes. Here I identify six – competition, herbivory, mycorrhizal infection, disease, species invasions and exotic earthworm activity – and discuss how they respond to excess N and how this response affects the herb layer of forests. With the exception of the activity of exotic earthworms (which is correlated with, but not necessarily caused by, high N deposition), there is compelling evidence that all processes respond sensitively to N deposition and that this response generally leads to drastic shifts in species composition and decreases in biodiversity of forest herb communities. 4 A hypothesis is suggested – the nitrogen homogeneity hypothesis – that predicts loss of biodiversity in forest ecosystems experiencing chronically elevated N deposition. This hypothesis is based on the decrease in spatial heterogeneity of N availability that is typically high in forest soils under N-limited conditions. [ABSTRACT FROM AUTHOR]

1 The effects of hybridization on the abundance of parental taxa depends on their relative frequency, the viability of hybrid offspring and the degree of ecological differentiation among parental and hybrid taxa. Habitat overlap can facilitate competition for suitable sites and threaten the persistence of parental taxa, especially those in small populations. 2 Here we examine ecological differentiation between the endangered North American red mulberry ( Morus rubra), introduced white mulberry ( M. alba) and red × white hybrids in a reciprocal transplant experiment. Fitness of red, white and hybrid mulberry was estimated as survival and above-ground biomass of seedling and juvenile life stages, transplanted into open (white habitat) and shaded (red habitat) forest environments. In addition, all taxa, including reciprocal hybrids (R × W, W × R), were compared in a common garden in full sun. 3 In the reciprocal transplant study, red mulberry was consistently less fit than white and hybrid mulberry regardless of transplant habitat; F1 hybrids were as fit as white mulberry. In the common garden, red mulberry and hybrids with red mothers had lower fitness than white mulberry and hybrids with white mothers. Reciprocal hybrid crosses differed significantly with respect to survival and cumulative fitness, but not biomass. 4 Red mulberry is not ecologically differentiated from white or hybrid mulberry in the three transplant environments examined; rather, it is consistently the least fit taxon. Therefore, all else being equal, hybridization with white mulberry and the subsequent presence of hybrids will place red mulberry at a strong disadvantage during establishment. 5 The results highlight the potential effect of hybridization by introduced species on the abundance of native species, particularly at the northern extremes of its geographical range, where populations are small and native environments may be degraded or at the limits of ecological tolerance. [ABSTRACT FROM AUTHOR]

1 Global change and emerging concepts in ecology and evolution are leading to a growing interest in phenotypic plasticity (PP), the environmentally contingent trait expression observed in a given genotype. The need to quantify PP in a simple manner in comparative ecological studies has resulted in the prevalence of various indices instead of the classic approaches, i.e. a comparison of slopes in the norms of reactions (trait vs. environment plots). 2 The objectives of this study were: (i) to review the most common methods for quantitative estimation of PP; (ii) to apply them to a specific case study of growth and shoot–root allocation responses to irradiance in seedlings of four woody species grown at 1%, 6%, 20% and 100% full sunlight; and (iii) to propose new methods of estimating PP. 3 The 17 different plasticity indices analysed rendered disparate results, with cross-overs in species PP rankings. Statistical comparisons of PP among species were not possible with most of the indices due to the lack of confidence intervals. The non-linear responses of the traits made the use of the slope of the reaction norm to quantify PP unrealistic, and raised awareness on values derived from studies that consider just two environments. 4 We propose an alternative approach to quantify PP based on phenotypic distances among individuals of a given species exposed to different environments, which is summarized in a relative distance plasticity index (RDPI) that allows for statistical comparisons of PP between species (or populations within species). RDPI was significantly correlated with 12 out of the 17 PP indices analysed. An index including the environmental range leading to the different phenotypes (environmentally standardized plasticity index, ESPI), and thus expressing plasticity per unit of environmental change, is also proposed. 5 The new indexes can statistically segregate and unambiguously rank species according to their PP, which can foster a better understanding of plant ecology and evolution, particularly when common protocols are used by different investigators. [ABSTRACT FROM AUTHOR]

The article discusses the effects of precipitation change on ecosystems. Almost all terrestrial biomes is influenced by the availability of water influences ecosystem structure and function in almost all terrestrial biomes. Precipitation is the main input of this limiting resource, which drives both biotic and abiotic processes. The inherent variability in precipitation is one of the grand challenges associated with studies of precipitation change. An increasing number of experiments are focusing on the interaction of precipitation change with other potential abiotic or biotic driving variables becuase many global changes are occuring simultaneously.

Range edges are of particular interest to ecology because they hold key insights into the limits of the realized niche and associated population dynamics. A recent feature of Oikos summarized the state of the art on range edge ecology. While the typical question is what causes range edges, another important question is how range edges influence the distribution of abundances across a species geographic range when dispersal is present. We used a single species population dynamics model on a coupled-lattice to determine the effects of dispersal on peripheral populations as compared to populations at the core of the range. In the absence of resource gradients, the reduced neighborhood and thus lower connectivity or higher isolation among populations at the range edge alone led to significantly lower population sizes in the periphery of the range than in the core. Lower population sizes mean higher extinction risks and lower adaptability at the range edge, which could inhibit or slow range expansions, and thus effectively stabilize range edges. The strength of this effect depended on the potential population growth rate and the maximum dispersal distance. Lower potential population growth rates led to a stronger effect of dispersal resulting in a higher difference in population sizes between the two areas. The differential effect of dispersal on population sizes at the core and periphery of the range in the absence of resource gradients implies that traditional, habitat-based distribution models could result in misleading conclusions about the habitat quality in the periphery. Lower population sizes at the periphery are also relevant to conservation, because habitat removal not only eliminates populations but also creates new edges. Populations bordering these new edges may experience declines, due to their increased isolation. [ABSTRACT FROM AUTHOR]