Native Species

Since the Age of Exploration began, there has been a drastic breaching of biogeographic barriers that previously had isolated the continental biotas for millions of years. We explore the nature of these recent biotic exchanges and their consequences on evolutionary processes. The direct evidence of evolutionary consequences of the biotic rearrangements is of variable quality, but the results of trajectories are becoming clear as the number of studies increases. There are examples of invasive species altering the evolutionary pathway of native species by competitive exclusion, niche displacement, hybridization, introgression, predation, and ultimately extinction. Invaders themselves evolve in response to their interactions with natives, as well as in response to the new abiotic environment. Flexibility in behavior, and mutualistic interactions, can aid in the success of invaders in their new environment.

The effect of urbanization can be immense, yet our understanding is rudimentary. Here, we compile the most recent information on urban impacts on avian populations and communities. Compared to other vertebrates, birds are easily monitored by skilled observers and provide a mechanism to explore urban effects and responses to different urban designs. Taxonomically, bird communities in distinctly different habitats are most different in the least disturbed sites and the most similar in the most urbanized sites. Urbanization tends to select for omnivorous, granivorous, and cavity nesting species. Increased urbanization typically leads to an increase in avian biomass but a reduction in richness. Unlike most passerines, raptors may have home ranges that extend beyond the urban boundary and therefore do not need to meet all their ecological requirements within urban areas. Urban habitats are often of superior quality to raptors because there they are often free from persecution and have an adequate food supply. The processes that underlie the patterns of population and community level responses need more attention, but several areas of have been identified as being important. Birds respond to vegetation composition and structure, and urban areas that retain native vegetative characteristics retain more native species than those that do not. Avian fecundity in urban areas is a reflection of species-specific adaptability to urban resources, and to levels of nest predation and nest parasitism. Additionally, non-consumptive human activities that increase with urbanization are recognized as having negative impacts on avian populations and communities. Avian survivorship in urban areas is influenced by risk of collision with man-made objects, changes in the predator assemblage, food supply, and disease. Missing are thorough investigations in the regions of highest human population growth, e.g. Southeast Asia. Additionally, there is a paucity of information from regions of high avian diversity, e.g. tropical forests. Clearly, local knowledge and study is required before implementation of management policies to reduce urban impacts on bird communities. Hopefully, such policies will include long-term monitoring. Demographic parameters of fecundity and survivorship need to be examined in conjunction with measures of community diversity and density across the urban gradient to better understand the quality of different urban habitats, and the variation of quality among spatial patterns of urbanization within the native habitat matrix.

Few invaded ecosystems are free from habitat loss and disturbance, leading to uncertainty whether dominant invasive species are driving community change or are passengers along for the environmental ride. The ''driver'' model predicts that invaded communities are highly interactive, with subordinate native species being limited or excluded by competition from the exotic dominants. The ''passenger'' model predicts that invaded communities are primarily structured by noninteractive factors (environmental change, dispersal limitation) that are less constraining on the exotics, which thus dominate. We tested these alternative hypotheses in an invaded, fragmented, and fire-suppressed oak savanna. We examined the impact of two invasive dominant perennial grasses on community structure using a reduction (mowing of aboveground biomass) and removal (weeding of above-and belowground biomass) experiment conducted at different seasons and soil depths. We examined the relative importance of competition vs. dispersal limitation with experimental seed additions. Competition by the dominants limits the abundance and reproduction of many native and exotic species based on their increased performance with removals and mowing. The treatments resulted in increased light availability and bare soil; soil moisture and N were unaffected. Although competition was limiting for some, 36 of 79 species did not respond to the treatments or declined in the absence of grass cover. Seed additions revealed that some subordinates are dispersal limited; competition alone was insufficient to explain their rarity even though it does exacerbate dispersal inefficiencies by lowering reproduction. While the net effects of the dominants were negative, their presence restricted woody plants, facilitated seedling survival with moderate disturbance (i.e., treatments applied in the fall), or was not the primary limiting factor for the occurrence of some species. Finally, the species most functionally distinct from the dominants (forbs, woody plants) responded most significantly to the treatments. This suggests that relative abundance is determined more by trade-offs relating to environmental conditions (longterm fire suppression) than to traits relating to resource capture (which should most impact functionally similar species). This points toward the passenger model as the underlying cause of exotic dominance, although their combined effects (suppressive and facilitative) on community structure are substantial.

Community ecological theory may play an important role in the development of a science of restoration ecology. Not only will the practice of restoration benefit from an increased focus on theory, but basic research in community ecology will also benefit. We pose several major thematic questions that are relevant to restoration from the perspective of community ecological theory and, for each, identify specific areas that are in critical need of further research to advance the science of restoration ecology. We ask, what are appropriate restoration endpoints from a community ecology perspective? The problem of measuring restoration at the community level, particularly given the high amount of variability inherent in most natural communities, is not easy, and may require a focus on restoration of community function (e.g., trophic structure) rather than a focus on the restoration of particular species. We ask, what are the benefits and limitations of using species composition or biodiversity measures as endpoints in restoration ecology? Since reestablishing all native species may rarely be possible, research is needed on the relationship between species richness and community stability of restored sites and on functional redundancy among species in regional colonist "pools." Efforts targeted at restoring system function must take into account the role of individual species, particularly if some species play a disproportionate role in processing material or are strong interactors. We ask, is restoration of habitat a sufficient approach to reestablish species and function? Many untested assumptions concerning the relationship between physical habitat structure and restoration ecology are being made in practical restoration efforts. We need rigorous testing of these assumptions, particularly to determine how generally they apply to different taxa and habitats. We ask, to what extent can empirical and theoretical work on community succession and dispersal contribute to restoration ecology? We distinguish systems in which succession theory may be broadly applicable from those in which it is probably not. If community development is highly predictable, it may be feasible to manipulate natural succession processes to accelerate restoration. We close by stressing that the science of restoration ecology is so intertwined with basic ecological theory that practical restoration efforts should rely heavily on what is known from theoretical and empirical research on how communities develop and are structured over time.

The complexity of the "biodiversity" concept makes it difficult to give a concise definition of the term. Nevertheless, "biodiversity" is omnipresent in today's mass media, and vast is the ocean of (popular) scientific publications carrying this effective catchword in their titles. The reason is that we are facing a rapid, (mainly) anthropogenic decline in biodiversity which is widely accepted as a matter of great concern among scientists and considered one of the major aspects of the worldwide transformation process denoted as Global Change. The general public, however, seems strangely apathetic towards the loss of biodiversity and neither to care nor to lobby for its conservation. Plausible explanations for this broad-based indifference include the conservationists' failure to convey the relevance of biodiversity to the public, the prevalent uncertainty about the term biodiversity and the concept behind it, and the growing urbanisation which leads to an increasing lack of personal experience with biological diversity and to a general estrangement from nature. This trend and its long-term effects can only be overcome by taking suitable measures to reconnect people with their "natural environment".

Large catchment basins may be viewed as ecosystems in which natural and cultural attributes interact. Contemporary river ecology emphasizes the four-dimensional nature of the river continuum and the propensity for riverine biodiversity and bioproduction to be largely controlled by habitat maintenance processes, such as cut and fill alluviation mediated by catchment water yield. Stream regulation reduces annual flow amplitude, increases baseflow variation and changes temperature, mass transport and other important biophysical patterns and attributes. As a result, ecological connectivity between upstream and downstream reaches and between channels, ground waters and floodplains may be severed. Native biodiversity and bioproduction usually are reduced or changed and non-native biota proliferate.

Soil is the habitat of plant roots and of a diverse array of organisms—bacteria, fungi, protozoa and invertebrate animals —which contribute to the maintenance and productivity of agroecosystems. As intensification occurs, the regulation of functions through soil biodiversity is progressively replaced by regulation through chemical and mechanical inputs. However, the causal relationships between (l) composition, diversity and abundance of soil organisms and (2) sustained soil fertility are unclear. Furthermore, in tropical agricultural systems undergoing intensification, large numbers of farmers have limited access to inputs, and therefore the maintenance and enhancement of soil biodiversity may be particularly relevant to such farmers. In this paper we propose a number of hypotheses which could be tested to explore the relationships between agricultural intensification, biodiversity in tropical soils and ecosystem functions. We also provide a conceptual framework within which such hypotheses can be tested.

Phragmites expansion into tidal wetlands of North America is most extensive along the northern and middle Atlantic coasts, but over 80% of the US coastal wetland area occurs along the Gulf of Mexico and southern Atlantic coasts and may be susceptible to ongoing expansion. Rapid spread of Phragmites has been documented in freshwater (<0.5 ppt), oligohaline (0.5-5 ppt) and mesohaline (5-18 ppt) tidal wetlands. The advance of Phragmites into tidal wetlands of North America may have been facilitated by widespread coastal changes since European settlement, including disturbance of hydrologic cycles and nutrient regimes; the presence of Phragmites has become a signature of tidal wetland alteration. Although ploidy levels from 2n = 36 to 72 have been documented for Phragmites throughout the continent, no genetics research to date has tested whether recent introduction of aggressive clones could account for Phragmites expansion. A fundamental concern regarding Phragmites expansion, particularly into tidal freshwater wetlands, is the observed reduction in biodiversity as many native species of plants are replaced by a more cosmopolitan species. Commensurate with a shift in habitat type is a reduction in insect, avian and other animal assemblages. Ecosystem services, including support of higher trophic levels, enhancement of water quality and sediment stabilization, however, are not diminished when a tidal wetland becomes dominated by Phragmites, provided that tidal flooding is retained. (R.M. Chambers) 0304-3770/99/$ -see front matter ©1999 Elsevier Science B.V. All rights reserved. PII: S 0 3 0 4 -3 7 7 0 ( 9 9 ) 0 0 0 5 5 -8

Acclimation of photosynthesis to elevated CO 2 has previously been shown to be more pronounced when N supply is poor. Is this a direct effect of N or an indirect effect of N by limiting the development of sinks for photoassimilate? This question was tested by growing a perennial ryegrass (Lolium perenne) in the field under elevated (60 Pa) and current (36 Pa) partial pressures of CO 2 (pCO2) at low and high levels of N fertilization. Cutting of this herbage crop at 4-to 8-week intervals removed about 80% of the canopy, therefore decreasing the ratio of photosynthetic area to sinks for photoassimilate. Leaf photosynthesis, in vivo carboxylation capacity, carbohydrate, N, ribulose-1,5-bisphosphate carboxylase/ oxygenase, sedoheptulose-1,7-bisphosphatase, and chloroplastic fructose-1,6-bisphosphatase levels were determined for mature lamina during two consecutive summers. Just before the cut, when the canopy was relatively large, growth at elevated pCO 2 and low N resulted in significant decreases in carboxylation capacity and the amount of ribulose-1,5-bisphosphate carboxylase/oxygenase protein. In high N there were no significant decreases in carboxylation capacity or proteins, but chloroplastic fructose-1,6-bisphosphatase protein levels increased significantly. Elevated pCO 2 resulted in a marked and significant increase in leaf carbohydrate content at low N, but had no effect at high N. This acclimation at low N was absent after the harvest, when the canopy size was small. These results suggest that acclimation under low N is caused by limitation of sink development rather than being a direct effect of N supply on photosynthesis.

Surface freshwaters-lakes, reservoirs, and rivers-are among the most extensively altered ecosystems on Earth. Transformations include changes in the morphology of rivers and lakes, hydrology, biogeochemistry of nutrients and toxic substances, ecosystem metabolism and the storage of carbon (C), loss of native species, expansion of invasive species, and disease emergence. Drivers are climate change, hydrologic flow modification, land-use change, chemical inputs, aquatic invasive species, and harvest. Drivers and responses interact, and their relationships must be disentangled to understand the causes and consequences of change as well as the correctives for adverse change in any given watershed. Beyond its importance in terms of drinking water, freshwater supports human well-being in many ways related to food and fiber production, hydration of other ecosystems used by humans, dilution and degradation of pollutants, and cultural values. A natural capital framework can be used to assess freshwater ecosystem services, competing uses for freshwaters, and the processes that underpin the long-term maintenance of freshwaters. Upper limits for human consumption of freshwaters have been proposed, and consumptive use may approach these limits by the mid-century.

Ongoing species invasions and extinctions are changing biological diversity in different ways at different spatial scales. Biotic homogenization (or BH) refers to the process by which the genetic, taxonomic or functional similarities of regional biotas increase over time. It is a multifaceted process that encompasses species invasions, extinctions and environmental alterations, focusing on how the identities of species (or their genetic or functional attributes) change over space and time. Despite the increasing use of the term BH in conservation biology, it is often used erroneously as a synonym for patterns of species invasions, loss of native species or changes in species richness through time. This reflects the absence of an agreed-upon, cogent definition of BH. Here, we offer an operational definition for BH and review the various methodologies used to study this process. We identify the strengths and weaknesses of these approaches, and make explicit recommendations for future studies. We conclude by citing the need for researchers to: (1) consider carefully the definition of BH by recognizing the genetic, taxonomic and functional realms of this process;

Predation by exotic species has caused the extinction of many native animal species on islands, whereas competition from exotic plants has caused few native plant extinctions. Exotic plant addition to islands is highly nonrandom, with an almost perfect 1 to 1 match between the number of naturalized and native plant species on oceanic islands. Here, we evaluate several alternative implications of these findings. Does the consistency of increase in plant richness across islands imply that a saturation point in species richness has been reached? If not, should we expect total plant richness to continue to increase as new species are added? Finally, is the rarity of native plant extinctions to date a misleading measure of the impact of past invasions, one that hides an extinction debt that will be paid in the future? By analyzing historical records, we show that the number of naturalized plant species has increased linearly over time on many individual islands. Further, the mean ratio of naturalized to native plant species across islands has changed steadily for nearly two centuries. These patterns suggest that many more species will become naturalized on islands in the future. We also discuss how dynamics of invasion bear upon alternative saturation scenarios and the implications these scenarios have for the future retention or extinction of native plant species. Finally, we identify invasion-motivated research gaps (propagule pressure, time-lags to extinction, abundance shifts, and loss of area) that can aid in forecasting extinction and in developing a more comprehensive theory of species extinctions.

We present a review of more than 30 years of ecological restoration in the Brazilian part of the Atlantic Forest. Based on what has been done in this biome, we try to summarize the main findings and challenges for restoration in this highly threatened forest biome. We found that many past experiences did not result in self-perpetuating forests, for different reasons. Currently, most projects aim to construct self-sustaining communities and no longer see restoration as a deterministic process. We also found that the reconstruction of permanent forest with high diversity is feasible but it depends on the strategies applied and on the surrounding landscape. Although many new techniques have been created (e.g. seed rain management or promotion of natural regeneration), the most used one in the Atlantic Forest is still the planting of many native species from different functional groups. Native species are largely used and perform well even in highly disturbed environments. Today, many projects are trying to produce thousands of hectares of permanent forests and many technical advances are about to be incorporated. But restoration also faces some main challenges to become an effective and widespread means of conserving the Atlantic Forest which are, namely, reducing costs, planning restoration actions at landscape-level, and conforming to socio-political issues. The socio-political tools to overcome such barriers in practice have yet to be developed.

The generality of relationships between soil net nitrogen (N) mineralization, aboveground N cycling, and aboveground net primary production (ANPP) for temperate forest ecosystems is unclear. It is also not known whether these variables and their relationships differ between evergreen and deciduous forests, or across soil types. To address these questions we compiled data on annual rates of in situ net N mineralization and ANPP for 16 conifer and 34 hardwood forests, including plantations and natural stands on a range of soils at six locations in Wisconsin and Minnesota, USA. For 31 natural stands, 48 stands with native species (including plantations), and all data, ANPP increased linearly with annual net N mineralization rates. Native evergreen conifer and two deciduous hardwood types (oaks and mesic hardwoods) followed similar patterns in this regression, indicating common functional relationships at the ecosystem level. The relationship of N mineralization and ANPP differed between finer textured Alfisol soils and sandier Entisols, with higher ANPP at any given N mineralization level in Alfisols. A multiple regression of N mineralization on soil texture (percentage silt plus clay), litterfall N, and mean annual temperature explained 81% of the variance in annual N mineralization for natural stands, and a multiple regression of ANPP on soil texture and annual N mineralization rate explained 83% of the variance in ANPP.

The primary hypothesis for the astonishing success of many exotics as community invaders relative to their importance in their native communities is that they have escaped the natural enemies that control their population growth -the 'natural enemies hypothesis'. However, the frequent failure of introduced biocontrols, weak consumer effects on the growth and reproduction of some invaders, and the lack of consistent strong top-down regulation in many natural ecological systems indicate that other mechanisms must be involved in the success of some exotic plants. One mechanism may be the release by the invader of chemical compounds that have harmful effects on the members of the recipient plant community (i.e., allelopathy). Here, we provide an abbreviated compilation of evidence for allelopathy in general, present a detailed case study for Centaurea diffusa, an invasive Eurasian forb in western North America, and review general evidence for allelopathic effects of invasive plants in native communities. The primary rationale for considering allelopathy as a mechanism for the success of invaders is based on two premises. First, invaders often establish virtual monocultures where diverse communities once flourished, a phenomenon unusual in natural communities. Second, allelopathy may be more important in recipient than in origin communities because the former are more likely to be naïve to the chemicals possessed by newly arrived species. Indeed, results from experiments on C. diffusa suggest that this invader produces chemicals that long-term and familiar Eurasian neighbors have adapted to, but that C. diffusa's new North American neighbors have not. A large number of early studies demonstrated strong potential allelopathic effects of exotic invasive plants; however, most of this work rests on controversial methodology. Nevertheless, during the last 15 years, methodological approaches have improved. Allelopathic effects have been tested on native species, allelochemicals have been tested in varying resource conditions, models have been used to estimate comparisons of resource and allelopathic effects, and experimental techniques have been used to ameliorate chemical effects. We do not recommend allelopathy as a 'unifying theory' for plant interactions, nor do we espouse the view that allelopathy is the dominant way that plants interact, but we argue that non-resource mechanisms should be returned to the discussion table as a potential mechanism for explaining the remarkable success of some invasive species. Ecologists should consider the possibility that resource and non-resource mechanisms may work simultaneously, but vary in their relative importance depending on the ecological context in which they are studied. One such context might be exotic plant invasion.

Species richness is decreasing at a global scale. At subglobal scales, that is, within any defined area less extensive than the globe, species richness will increase when the number of nonnative species becoming naturalized is greater than the number of native species becoming extinct. Determining whether this has occurred is usually difficult because detailed records of species extinctions and naturalizations are rare; these records often exist, however, for oceanic islands. Here we show that species richness on oceanic islands has remained relatively unchanged for land birds, with the number of naturalizations being roughly equal to the number of extinctions, and has increased dramatically for vascular plants, with the number of naturalizations greatly exceeding the number of extinctions. In fact, for plants, the net number of species on islands has approximately doubled. We show further that these patterns are robust to differences in the history of human occupation of these isla...

Management of nonindigenous species is a crucial aspect of maintaining native biodiversity and normal ecosystem functions. We attempt to guide researchers in developing projects that will be of use to conservation practitioners, tangibly improving applied conservation measures. We advocate a directed approach for conservation research to aid in prioritizing nonindigenous species for intervention by resource managers. This approach includes outlining what needs to be known to make such relative judgments about the impacts of nonindigenous species and the most promising methods by which to obtain such information. We also address active measures that should be taken once priorities have been set, highlighting the roles of risk assessment and research in improving control efforts. Ultimately, a better match between research and practical conservation needs should result in more effective reduction of the effects of nonindigenous species on native species.

We examine the evolving concept of what constitutes a nonnative (or alien) freshwater fish. In an attempt to distinguish between biogeographical and socio-political perspectives, we review the patterns in the introduction and dispersal of nonnative fishes in Europe and North America, and especially the recent expansion of Ponto-Caspian gobies in Europe. We assess patterns in the development of national policy and legislation in response to the perceived threat of non-native fish introductions to native species and ecosystems. We review, and provide a glossary of, the terms and definitions associated with non-native species. Finally, we discuss perspectives as regards the future treatment of naturalized species.

The mortality of salmon smolts during their migration out of freshwater and into the ocean has been difficult to measure. In the Columbia River, which has an extensive network of hydroelectric dams, the decline in abundance of adult salmon returning from the ocean since the late 1970s has been ascribed in large measure to the presence of the dams, although the completion of the hydropower system occurred at the same time as large-scale shifts in ocean climate, as measured by climate indices such as the Pacific Decadal Oscillation. We measured the survival of salmon smolts during their migration to sea using elements of the large-scale acoustic telemetry system, the Pacific Ocean Shelf Tracking (POST) array. Survival measurements using acoustic tags were comparable to those obtained independently using the Passive Integrated Transponder (PIT) tag system, which is operational at Columbia and Snake River dams. Because the technology underlying the POST array works in both freshwater and the ocean, it is therefore possible to extend the measurement of survival to large rivers lacking dams, such as the Fraser, and to also extend the measurement of survival to the lower Columbia River and estuary, where there are no dams. Of particular note, survival during the downstream migration of at least some endangered Columbia and Snake River Chinook and steelhead stocks appears to be as high or higher than that of the same species migrating out of the Fraser River in Canada, which lacks dams. Equally surprising, smolt survival during migration through the hydrosystem, when scaled by either the time or distance migrated, is higher than in the lower Columbia River and estuary where dams are absent. Our results raise important questions regarding the factors that are preventing the recovery of salmon stocks in the Columbia and the future health of stocks in the Fraser River.

Leaf-off individual trees in a deciduous forest in the eastern USA are detected and analysed in small footprint, high sampling density lidar data. The data were acquired February 1, 2001, using a SAAB TopEye laser profiling system, with a sampling density of approximately 12 returns per square meter. The sparse and complex configuration of the branches of the leaf-off forest provides sufficient returns to allow the detection of the trees as individual objects and to analyse their vertical structures. Initially, for the detection of the individual trees only, the lidar data are first inserted in a 2D digital image, with the height as the pixel value or brightness level. The empty pixels are interpolated, and height outliers are removed. Gaussian smoothing at different scales is performed to create a three-dimensional scale-space structure. Blob signatures based on second-order image derivatives are calculated, and then normalised so they can be compared at different scale-levels. The grey-level blobs with the strongest normalised signatures are selected within the scale-space structure. The support regions of the blobs are marked one-at-a-time in the segmentation result image with higher priority for stronger blobs. The segmentation results of six individual hectare plots are assessed by a computerised, objective method that makes use of a ground reference data set of the individual tree crowns. For analysis of individual trees, a subset of the original laser returns is selected within each tree crown region of the canopy reference map. Indices based on moments of the first four orders, maximum value and number of canopy and ground returns, are estimated. The indices are derived separately for height and laser reflectance of branches for the two echoes. Significant differences ( p < 0.05) are detected for numerous indices for three major native species groups: oaks (Quercus spp.), red maple (Acer rubrum) and yellow poplar (Liriodendron tuliperifera). Tree species classification results of different indices suggest a moderate to high degree of accuracy using single or multiple variables. Furthermore, the maximum tree height is compared to ground reference tree height for 48 sample trees and a 1.1-m standard error (R 2 = 68% (adj.)) within the test-site is observed. D

Anthropogenic influences on the biosphere since the advent of the industrial age are increasingly causing global changes. Climatic change and the rising concentration of greenhouse gases in the atmosphere are ranking high in scientific and public agendas, and other components of global change are also frequently addressed, among which are the introductions of non indigenous species (NIS) in biogeographic regions well separated from the donor region, often followed by spectacular invasions. In the marine environment, both climatic change and spread of alien species have been studied extensively; this review is aimed at examining the main responses of ecosystems to climatic change, taking into account the increasing importance of biological invasions.

Changes in environmental conditions often reverse outcomes of competitive interactions among species. Such context dependency implies that the speed, persistence, and ubiquity of anthropogenic habitat alterations may suddenly put even previously well-adapted native species at a competitive disadvantage with non-native species. That is, anthropogenic disturbance may so drastically alter environments that a native species finds itself in an environment that in key ways is just as novel as it is to a non-indigenous species. Extreme disturbances may thereby erase a native species' prior advantage of local environmental adaptation accrued during its long-term incumbency over evolutionary time. I document examples from two areas of dramatic human alteration of selection regimes -eutrophication and the selective removal of top predators -that support this mechanism. Additionally, I highlight ways in which this mechanism is experimentally testable. Alteration of selection regimes may prove to be a powerful explanation for the enhanced success and impact of biological invasions in our globally disturbed biosphere.

While small-scale studies show that more diverse native communities are less invasible by exotics, studies at large spatial scales often find positive correlations between native and exotic diversity. This large-scale pattern is thought to arise because landscapes with favorable conditions for native species also have favorable conditions for exotic species. From theory, we proposed an alternative hypothesis: the positive relationship at large scales is driven by spatial heterogeneity in species composition, which is driven by spatial heterogeneity in the environment. Landscapes with more spatial heterogeneity in the environment can sustain more native and more exotic species, leading to a positive correlation of native and exotic diversity at large scales. In a nested data set for grassland plants, we detected negative relationships between native and exotic diversity at small spatial scales and positive relationships at large spatial scales. Supporting our hypothesis, the positive relationships between native and exotic diversity at large scales were driven by positive relationships between native and exotic beta diversity. Further, both native and exotic diversity were positively correlated with spatial heterogeneity in abiotic conditions (variance of soil depth, soil nitrogen, and aspect) but were uncorrelated with average abiotic conditions, supporting the spatial-heterogeneity hypothesis but not the favorable-conditions hypothesis.

Plant-animal mutualisms are characterized by weak or asymmetric mutual dependences between interacting species, a feature that could increase community stability. If invasive species integrate into mutualistic webs, they may alter web structure, with consequences for species persistence. However, the effect of alien mutualists on the architecture of plant-pollinator webs remains largely unexplored. We analyzed the extent of mutual dependency between interacting species, as a measure of mutualism strength, and the connectivity of 10 paired plant-pollinator webs, eight from forests of the southern Andes and two from oceanic islands, with different incidences of alien species. Highly invaded webs exhibited weaker mutualism than less-invaded webs. This potential increase in network stability was the result of a disproportionate increase in the importance and participation of alien species in the most asymmetric interactions. The integration of alien mutualists did not alter overall network connectivity, but links were transferred from generalist native species to super-generalist alien species during invasion. Therefore, connectivity among native species declined in highly invaded webs. These modifications in the structure of pollination webs, due to dominance of alien mutualists, can leave many native species subject to novel ecological and evolutionary dynamics.

Aim Conifers comprise an ancient and diverse group of plants showing a wide distribution range. To better understand the general patterns of species successfully established on islands, this review compiles information about the distribution, diversity, dispersal potential and conservation status of insular conifers, with special emphasis on those inhabiting remote oceanic islands.

Aquatic macrophytes are aquatic photosynthetic organisms, large enough to see with the naked eye, that actively grow permanently or periodically submerged below, floating on, or growing up through the water surface. Aquatic macrophytes are represented in seven plant divisions: Cyanobacteria, Chlorophyta, Rhodophyta, Xanthophyta, Bryophyta, Pteridophyta and Spermatophyta. Species composition and distribution of aquatic macrophytes in the more primitive divisions are less well known than for the vascular macrophytes (Pteridophyta and Spermatophyta), which are represented by 33 orders and 88 families with about 2,614 species in c. 412 genera. These c. 2,614 aquatic species of Pteridophyta and Spermatophyta evolved from land plants and represent only a small fraction (*1%) of the total number of vascular plants. Our analysis of the numbers and distribution of vascular macrophytes showed that whilst many species have broad ranges, species diversity is highest in the Neotropics, intermediate in the Oriental, Nearctic and Afrotropics, lower in the Palearctic and Australasia, lower again in the Pacific Oceanic Islands, and lowest in the Antarctic region. About 39% of the c. 412 genera containing aquatic vascular macrophytes are endemic to a single biogeographic region, with 61-64% of all aquatic vascular plant species found in the Afrotropics and Neotropics being endemic to those regions. Aquatic macrophytes play an important role in the structure and function of aquatic ecosystems and certain macrophyte species (e.g., rice) are cultivated for human consumption, yet several of the worst invasive weeds in the world are aquatic plants. Many of the threats to fresh waters (e.g., climate change, eutrophication) will result in reduced macrophyte diversity and will, in turn, threaten the faunal diversity of aquatic ecosystems and favour the establishment of exotic species, at the expense of native species.

The future of mammalian diversity in the tropics depends largely on the conservation value of human-dominated lands. We investigated the distribution of non-flying mammals in five habitats of southern Costa Rica: relatively extensive forest (227 ha), coffee plantation, pasture, coffee with adjacent forest remnant (<35 ha), and pasture with adjacent forest remnant (<35 ha). Of the 26 native species recorded in our study plots, 9 (35%) were restricted to forest habitat, 14 (54%) occurred in both forest and agricultural habitats, and 3 (11%) were found only in agricultural habitats. Species richness and composition varied significantly with habitat type but not with distance from the extensive forest. Interestingly, small forest remnants (<35 ha) contiguous with coffee plantations did not differ from more extensive forest in species richness and were richer than other agricultural habitat types. Small remnants contiguous with pasture were species-poor. When clearing started, the study region likely supported about 60 species. Since then, at least 6 species (10%), one family (4%), and one order (11%) have gone extinct locally. The species that disappeared were the largest in their families and included carnivorous (e.g., jaguar [Panthera onca]), herbivorous (e.g., Baird's tapir, [Tapirus bairdii]), and arboreal (e.g., mantled howler monkey [Alouatta palliata]) species. Although there is no substitute for native forest habitat, the majority of native, nonflying mammal species use countryside habitats. The populations of many persist even >5 km from relatively extensive forest, at least over the 40 years since forest clearance. Moreover, if hunting ceased, we expect that at least one of the locally extinct species could be reestablished in the existing landscape. Thus, there is an important opportunity to maintain and restore the diversity, abundance, and ecosystem roles of mammals in at least some human-dominated regions of the Neotropics. Biogeografía del Campo de Mamíferos Neotropicales: Oportunidades de Conservación en Paisajes Agrícolas de Costa Rica Resumen: El futuro de la diversidad de mamíferos en los trópicos depende principalmente del valor de la conservación de tierras dominadas por actividades humanos. Investigamos la distribución de mamíferos no voladores en cinco hábitats del sur de Costa Rica: selva relativamente extensa (227 ha), plantaciones de café, pastizal, café con remanente de selva adyacente (<35 ha) y pastizal con remanente de bosque adyacente (<35 ha). De las 26 especies nativas registradas en nuestras parcelas de estudio, 9 (35%) estaban restringidas al hábitat de bosque, 14 (54%) ocurrieron tanto en hábitats de bosque como agrícolas, y 3 (11%) solo se encontraron en hábitats agrícolas. La riqueza y composición de especies varió significativamente con el tipo de hábitat pero no con la distancia al bosque extenso. Lo interesante es que las, los remanentes pequeños de §Current address: Daily et al. Countryside Biogeography of Mammals 1815 bosque (<35 ha) contiguos a plantaciones de café no difirieron del bosque extenso en riqueza de especies y fueron más ricos que otros tipos de hábitat agrícolas. Los remanentes pequeños contiguos a pastizales fueron pobres en especies. Cuando comenzó la deforestación, la zona de estudio probablemente mantenía unas 60 especies. Desde entonces, por lo menos 6 especies (10%), una familia (4%) y un orden (11%) se han extinguido localmente. Las especies que desaparecieron fueron las mayores en sus familias e incluyeron especies carnívoras (por ejemplo, jaguar [Panthera onca]), herbívoras (por ejemplo, tapir, [Tapirus bairdii]) yárboricolas (por ejemplo, mono aullador [Alouatta palliata]). Aunque no hay sustituto para el hábitat de bosque nativo, la mayoría de las especies de mamíferos no voladores nativos utilizan hábitats rurales. Las poblaciones de muchas especies persisten aun a >5 km de bosque relativamente extenso, por lo menos en los 40 años desde la deforestación. Más aun, si cesara la cacería, esperamos que por lo menos una de las especies localmente extintas se reestablezca en el paisaje existente. Por lo tanto, hay una importante oportunidad para mantener y restaurar la diversidad, abundancia y papeles ecológicos de mamíferos en por lo menos algunas regiones dominadas por humanos en los neotrópicos.

The eects of biological invasions are most evident in isolated oceanic islands such as the Hawaiian Archipelago, where invasive plant species are rapidly changing the composition and function of plant communities. In this study, we compared the speci®c leaf area (SLA), leaf tissue construction cost (CC), leaf nutrient concentration, and net CO 2 assimilation (A) of 83 populations of 34 native and 30 invasive species spanning elevation and substrate age gradients on Mauna Loa volcano in the island of Hawaii. In this complex environmental matrix, where annual precipitation is higher than 1500 mm, we predicted that invasive species, as a group, will have leaf traits, such as higher SLA and A and lower leaf CC, which may result in more ecient capture of limiting resources (use more resources at a lower carbon cost) than native species. Overall, invasive species had higher SLA and A, and lower CC than native species, consistent with our prediction. SLA and foliar N and P were 22.5%, 30.5%, and 37.5% higher, respectively, in invasive species compared to native ones. Light-saturated photosynthesis was higher for invasive species (9.59 lmol m A2 s A1 ) than for native species (7.31 lmol m A2 s A1 ), and the dierence was larger when A was expressed on a mass basis. Leaf construction costs, on the other hand, were lower for the invasive species (1.33 equivalents of glucose g A1 ) than for native species (1.37). This dierence was larger when CC was expressed on an area basis. The trends in the above traits were maintained when groups of ecologically equivalent native and invasive species (i.e., sharing similar life history traits and growing in the same habitat) were compared. Foliar N and P were signi®cantly higher in invasive species across all growth forms. Higher N may partially explain the higher A of invasive species. Despite relatively high N, the photosynthetic nitrogen use eciency of invasive species was 15% higher than that of native species. These results suggest that invasive species may not only use resources more eciently than native species, but may potentially demonstrate higher growth rates, consistent with their rapid spread in isolated oceanic islands.

Growth, biomass allocation, and photosynthetic characteristics of seedlings of ®ve invasive nonindigenous and four native species grown under dierent light regimes were studied to help explain the success of invasive species in Hawaiian rainforests. Plants were grown under three greenhouse light levels representative of those found in the center and edge of gaps and in the understory of Hawaiian rainforests, and under an additional treatment with unaltered shade. Relative growth rates (RGRs) of invasive species grown in sun and partial shade were signi®cantly higher than those for native species, averaging 0.25 and 0.17 g g A1 week A1 , respectively, while native species averaged only 0.09 and 0.06 g g A1 week A1 , respectively. The RGR of invasive species under the shade treatment was 40% higher than that of native species. Leaf area ratios (LARs) of sun and partial-shade-grown invasive and native species were similar but the LAR of invasive species in the shade was, on average, 20% higher than that of native species. There were no dierences between invasive and native species in biomass allocation to shoots and roots, or in leaf mass per area across light environments. Light-saturated photosynthetic rates (Pmax) were higher for invasive species than for native species in all light treatments. Pmax of invasive species grown in the sun treatment, for example, ranged from 5.5 to 11.9 lmol m A2 s A1 as compared with 3.0A4.5 lmol m A2 s A1 for native species grown under similar light conditions. The slope of the linear relationship between Pmax and dark respiration was steeper for invasive than for native species, indicating that invasive species assimilate more CO 2 at a lower respiratory cost than native species. These results suggest that the invasive species may have higher growth rates than the native species as a consequence of higher photosynthetic capacities under sun and partial shade, lower dark respiration under all light treatments, and higher LARs when growing under shade conditions. Overall, invasive species appear to be better suited than native species to capturing and utilizing light resources, particularly in high-light environments such as those characterized by relatively high levels of disturbance.

The declining health of marine ecosystems around the world is evidence that current piecemeal governance is inadequate to successfully support healthy coastal and ocean ecosystems and sustain human uses of the ocean. One proposed solution to this problem is ecosystem-based marine spatial planning (MSP), which is a process that informs the spatial distribution of activities in the ocean so that existing and emerging uses can be maintained, use conflicts reduced, and ecosystem health and services protected and sustained for future generations. Because a key goal of ecosystem-based MSP is to maintain the delivery of ecosystem services that humans want and need, it must be based on ecological principles that articulate the scientifically recognized attributes of healthy, functioning ecosystems. These principles should be incorporated into a decision-making framework with clearly defined targets for these ecological attributes. This paper identifies ecological principles for MSP based on a synthesis of previously suggested and/or operationalized principles, along with recommendations generated by a group of twenty ecologists and marine scientists with diverse backgrounds and perspectives on MSP. The proposed four main ecological principles to guide MSP-maintaining or restoring: native species diversity, habitat diversity and heterogeneity, key species, and connectivity-and two additional guidelines, the need to account for context and uncertainty, must be explicitly taken into account in the planning process. When applied in concert with social, economic, and governance principles, these ecological principles can inform the designation and siting of ocean uses and the management of activities in the ocean to maintain or restore healthy ecosystems, allow delivery of marine ecosystem services, and ensure sustainable economic and social benefits.

Accurate predictions of the potential distribution of range-shifting species are required for effective management of invasive species, and for assessments of the impact of climate change on native species. Range-shifting species pose a challenge for traditional correlative approaches to range prediction, often requiring the extrapolation of complex statistical associations into novel environmental space. Here we take an alternative approach that does not use species occurrence data, but instead captures the fundamental niche of a species by mechanistically linking key organismal traits with spatial data using biophysical models. We demonstrate this approach with a major invasive species, the cane toad Bufo marinus in Australia, assessing the direct climatic constraints on its ability to move, survive, and reproduce. We show that the current range can be explained by thermal constraints on the locomotor potential of the adult stage together with limitations on the availability of water for the larval stage. Our analysis provides a framework for biologically grounded predictions of the potential for cane toads to expand their range under current and future climate scenarios. More generally, by quantifying spatial variation in physiological constraints on an organism, trait-based approaches can be used to investigate the range-limits of any species. Assessments of spatial variation in the physiological constraints on an organism may also provide a mechanistic basis for forecasting the rate of range expansion and for understanding a species' potential to evolve at range-edges. Mechanistic approaches thus have broad application to process-based ecological and evolutionary models of range-shift.

Total vegetation cover, cover of woody species, and participation of dominants in later (pre-forest) successional stages of 16 successional seres starting on bare ground in various human-disturbed habitats (Czech Republic, Central Europe) were compared and evaluated from the viewpoint of restoration ecology. Continuous vegetation was formed before the 15th year of succession in all the seres studied. The establishment and expansion of woody species tended to be easier under moderate environmental conditions and was retarded in rather extreme habitats (dry, wet, nutrient poor, acid). The later-successional dominants were all native species and some rare and endangered species were recorded in these stages. The main conclusion is that spontaneous succession can be relied upon in restoration projects except in the case of extreme, especially toxic substrata. To leave a site to allow spontaneous processes to revegetate it is especially advantageous if the disturbed site is small, surrounded by natural vegetation, and if site conditions were not principally altered by the disturbance. Spontaneous succession is cheap and spontaneously revegetated sites usually exhibit higher natural value.

We propose that the relationship between diversity and community invasibility depends on the degree to which community composition is driven by immigration processes. When immigration is enhanced by high propagule pressure or low-intensity disturbance, the relationship between diversity and exotic species invasion should be positive. Only when such immigration processes are limited should competitive interactions lead to a negative correlation between diversity and invasibility. Moreover, competition should be more apparent at smaller scales where individual plants compete directly for space; thus, diversity and invasibility are more likely to be negatively correlated at small spatial scales. We tested these predictions by comparing exotic and native species diversity of vascular plants across five spatial scales in riparian and upland plant communities in the southern Appalachians. We found a positive relationship between species diversity and exotic invasion in riparian areas at large scales (100 m 2 ), which graded into a negative relationship at small scales (0.01 m 2 ). In uplands, there was a slight positive relationship between native and exotic species diversity at both scales of observation. Overall, riparian areas had more exotic and native species than upland areas, and both native and exotic species diversity increased with flood frequency within the riparian zone.

Extensive cattle production currently occupies more than 27% of the rural landscapes in Latin America, and continues to expand. This activity, deeply rooted in the culture and rural economy of the region, requires an urgent transformation if it is to become both more efficient and environmentally friendly. Silvopastoral systems that incorporate native trees and shrubs are instrumental for the productive rehabilitation of cattle production and for biodiversity conservation in agricultural landscapes. We discuss research progress and adoption of intensive silvopastoral systems in Colombia and Mexico. Intensive silvopastoral systems (ISS) are a sustainable form of agroforestry for livestock production that combines fodder shrubs planted at high densities (more than 10,000 plants ha −1 ), trees and palms, and improved pastures. High stocking and the natural production of milk and meat in these systems are achieved through rotational grazing with electric fencing and a permanent supply of water for the cattle. While milk and meat production and cattle reproduction are enhanced, production costs decline as external inputs are replaced by natural processes related to fertility and biological control. We also discuss the importance of the ISS with native trees for climate change adaptation and mitigation, the barriers for their adoption, and how these have been successfully addressed using payment for environmental services, special credits and technical assistance. Finally, we highlight the need for enhancing landscape connectivity by integrating SPS to conservation corridors with native species to promote biodiversity conservation and other environmental services demanded by society.

A highly sensitive real-time PCR (qPCR) procedure, targeting the phosphatidylcholine-specific phospholipase C gene (pc-plc), was developed for specific detection and quantification of strains belonging to Bacillus cereus group. The target region was selected based on the enterotoxigenic profiles of 75 Bacillus strains. The inclusivity and exclusivity of the RTi-PCR assay were assessed with 59 isolates of the B. cereus group, 16 other Bacillus spp., and 4 non-Bacillus strains. The assay was also used to construct calibration curves for different food matrices, and it had a wide quantification range of 6 log units using both serial dilutions of purified DNA and calibrated cell suspensions of B. cereus CECT 148T. The detection limit for B. cereus in artificially contaminated liquid egg and reconstituted infant formula was about 3 CFU per reaction or 60 CFU/ml of food, with a relative accuracy of 86.27% to 116.12% in artificially contaminated liquid egg. Naturally contaminated food samples were tested for the presence of B. cereus with the standard method, a conventional PCR and the new developed RTi-PCR assay. Results showed that the new developed RTi-PCR assay is very suitable for detection and quantification of strains of B. cereus group in food samples without an enrichment step.