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Many invasive and some native tree species in North America exhibit strong allelopathic effects that may contribute to their local dominance. Pyrogenic carbon (PyC; including soot, charcoal, and black carbon) is produced by the incomplete combustion of organic matter and is widespread in forest soils. Many forms of PyC have sorptive properties that can reduce the bioavailability of allelochemicals. We investigated the potential for PyC produced by controlled pyrolysis of biomass ("biochar" [BC]) to reduce the allelopathic effects of black walnut (Juglans nigra) and Norway maple (Acer platanoides), a common native tree species and a widespread invasive species in North America, respectively. Seedling growth of two native tree species (Acer saccharinum [silver maple] and Betula papyrifera [paper birch]) in response to leaf‐litter‐incubated soils was examined; litter incubation treatments included leaves of black walnut, Norway maple, and a nonallelopathic species (Tilia americana [American basswood]) in a factorial design with varying dosages; responses to the known primary allelochemical of black walnut (juglone) were also examined. Juglone and leaf litter of both allelopathic species strongly suppressed seedling growth. BC treatments substantially mitigated these effects, consistent with the sorption of allelochemicals; in contrast no positive effects of BC were observed in leaf litter treatments involving controls or additions of nonallelopathic leaf litter. Treatments of leaf litter and juglone with BC increased the total biomass of silver maple by ~35% and in some cases more than doubled the biomass of paper birch. We conclude that BCs have the capacity to largely counteract allelopathic effects in temperate forest systems, suggesting the effects of natural PyC in determining forest community structure, and also the applied use of BC as a soil amendment to mitigate allelopathic effects of invasive tree species. [ABSTRACT FROM AUTHOR]

Aim: Much of what is known about invasion biology is based on research conducted in North America and Europe, leading to limitations and potential biases in our knowledge. We address these limitations by conducting a systematic review to assess the literature on ecological studies of two major tropical and subtropical invasive plant species, Ageratina adenophora and Chromolaena odorata. Our goals were to: (1) collect the literature on the invasion biology of these species by broadly searching five databases (one international and four regional); (2) determine limitations to the international literature available in the ISI Web of Science (WOS); (3) quantitatively summarize the scope of the invasion literature on the two species; and (4) propose future studies based on what we found. Location: Global. Methods: Using specific search terms, we searched the literature for A. adenophora and C. odorata in the ISI WOS, Chinese National Knowledge Infrastructure (CNKI), Indian Journals, Nepal Journals Online and African Journals Online (AJOL). We extracted information on journal titles, publication years, study area locations, habitats investigated and study focus. Results: We found 101 papers for A. adenophora and 61 papers for C. odorata, published from 1987 to 2015. A high percentage of the studies were conducted in China, western and southern Africa, and India. Studies from WOS most frequently focused on the mechanism of invasion, while studies from CNKI and AJOL focused on the impacts of the invader. Main conclusions: Web of Science is not sufficient for generalizing about the invasion biology literature, particularly if the goal is a comprehensive assessment that includes areas other than North America, Hawaii, Europe, Australia, South Africa and New Zealand. In future systematic reviews, other databases should be used if possible, including those in languages other than English. For future research, several research areas should be studied more thoroughly for A. adenophora and C. odorata invasions, including possible multiple factors responsible for invasion, and impacts of co-occurring invasive species. [ABSTRACT FROM AUTHOR]

Nonnative species are a key agent of global change. However, nonnative invertebrates remain understudied at the community scales where they are most likely to drive local extirpations. We use the North American NEON pitfall trapping network to document the number of nonnative species from 51 invertebrate communities, testing four classes of drivers. We sequenced samples using the eDNA from the sample's storage ethanol. We used AICc informed regression to evaluate how native species richness, productivity, habitat, temperature, and human population density and vehicular traffic account for continent‐wide variation in the number of nonnative species in a local community. The percentage of nonnatives varied 3‐fold among habitat types and over 10‐fold (0%–14%) overall. We found evidence for two types of constraints on nonnative diversity. Consistent with Capacity rules (i.e., how the number of niches and individuals reflect the number of species an ecosystem can support) nonnatives increased with existing native species richness and ecosystem productivity. Consistent with Establishment Rules (i.e., how the dispersal rate of nonnative propagules and the number of open sites limits nonnative species richness) nonnatives increased with automobile traffic—a measure of human‐generated propagule pressure—and were twice as common in pastures than native grasslands. After accounting for drivers associated with a community's ability to support native species (native species richness and productivity), nonnatives are more common in communities that are regularly seasonally disturbed (pastures and, potentially deciduous forests) and those experiencing more vehicular traffic. These baseline values across the US North America will allow NEON's monitoring mission to document how anthropogenic change—from disturbance to propagule transport, from temperature to trends in local extinction—further shape biotic homogenization. [ABSTRACT FROM AUTHOR]

The carnivorous pitcher plant Sarracenia purpurea is native to North America, but has been introduced into Europe, where it is now widespread. Understanding of how this species functions in its non‐native range is limited. We measured pitcher morphology and prey capture by S. purpurea in its non‐native range in Britain and Ireland. Pitchers were removed from different plants at each of six bogs covering the species range in Britain and Ireland (n = 10 pitchers per site). For each pitcher we counted and identified every prey item and took measurements of morphology. We also compiled prey capture data for existing studies in Europe and North America. Prey capture characteristics varied between sites in Britain and Ireland. The amount of prey captured varied 20‐fold between sites and was partially explained by differences in pitcher size; larger pitchers caught more prey. The primary prey was Formicidae, Diptera and Coleoptera. At the rank of order, prey composition varied between bogs, some contained mainly Formicidae, some mainly Diptera and some a mix. Prey capture was less evenly distributed at some bogs compared to others, suggesting more specialization. There was no overall difference in prey capture (composition or evenness) at the rank of order between plants in Europe compared to those in North America. At the rank of species, prey capture varied between populations even within the same order. This study demonstrates a large amount of variability between sites in prey capture characteristics. This may reflect different site characteristics and/or plant strategies, which will likely impact plant function, and may impact the inquiline community. In terms of prey capture at the rank of order, S. purpurea functions identically in its non‐native range. This supports its use as a model system in a natural experiment for understanding food webs. [ABSTRACT FROM AUTHOR]

Rapid warming in the Gulf of Maine may influence the success or invasiveness of the Asian shore crab, Hemigrapsus sanguineus. To better predict the effects of climate change on this invasive species, it is necessary to measure its energy dynamics under a range of conditions. However, previous research has only focused on the metabolism of this intertidal species in water. We sampled adult crabs from three different sites and measured their metabolic rates in the air. We show that metabolic rate increases with body mass and the number of missing limbs, but decreases with the number of regenerating limbs, possibly reflecting the timing of energy allocation to limb regeneration. Importantly, metabolic rates measured here in the air are ~4× higher than metabolic rates previously measured for this species in water. Our results provide baseline measurements of aerial metabolic rates across body sizes, which may be affected by climate change. With a better understanding of respiration in H. sanguineus, we can make more informed predictions about the combined effects of climate change and invasive species on the northeast coasts of North America. [ABSTRACT FROM AUTHOR]

Premise: Digitized collections can help illuminate the mechanisms behind the establishment and spread of invasive plants. These databases provide a record of traits in space and time that allows for investigation of abiotic and biotic factors that influence invasive species. Methods: Over 1100 digitized herbarium records were examined to investigate the invasion history and trait variation of Microstegium vimineum. Presence–absence of awns was investigated to quantify geographic patterns of this polymorphic trait, which serves several functions in grasses, including diaspore burial and dispersal to germination sites. Floret traits were further quantified, and genomic analyses of contemporary samples were conducted to investigate the history of M. vimineum's introduction and spread into North America. Results: Herbarium records revealed similar patterns of awn polymorphism in native and invaded ranges of M. vimineum, with awned forms predominating at higher latitudes and awnless forms at lower latitudes. Herbarium records and genomic data suggested initial introduction and spread of the awnless form in the southeastern United States, followed by a putative secondary invasion and spread of the awned form from eastern Pennsylvania. Awned forms have longer florets, and floret size varies significantly with latitude. There is evidence of a transition zone with short‐awned specimens at mid‐latitudes. Genomic analyses revealed two distinct clusters corresponding to awnless and awned forms, with evidence of admixture. Conclusions: Our results demonstrate the power of herbarium data to elucidate the invasion history of a problematic weed in North America and, together with genomic data, reveal a possible key trait in introduction success: presence or absence of an awn. [ABSTRACT FROM AUTHOR]

Aim: Studies focusing on relatively small spatial scales have shown that alien plants are more likely to invade phylogenetically clustered communities, and that the introduction of alien plants further increases phylogenetic clustering in the recipient communities. However, whether these patterns hold at a continental scale remains untested. Here, we investigate the phylogenetic structure of native and alien regional assemblages of angiosperms across North America. Location: North America north of Mexico. Time period: Current. Major taxon studied: Angiosperms (flowering plants). Methods: We divided North America into 65 regions across two longitudinal zones, and collated native and naturalized alien species lists of angiosperms for each region. Two phylogenetic metrics, which represent different evolutionary depths, were used to quantify phylogenetic structure of angiosperms as a whole and each major clade in each region, and were related to temperature and precipitation using correlation analyses. Results: We found that alien angiosperm richness is highest in regions with diverse and phylogenetically dispersed native floras. The introduction of alien species nearly uniformly increases phylogenetic clustering. Main conclusions: Alien species are generally from the same major clades as native species, consistent with Darwin's preadaptation hypothesis. The results of this study are consistent across a wide range of phylogenetic extents, but not always with analyses conducted at smaller spatial extents. [ABSTRACT FROM AUTHOR]

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Aim: A better understanding of native and non‐native species responses to environmental conditions, historical processes, and human pressures is crucial in the face of global environmental changes affecting biodiversity. Here, we evaluate the relative roles of environmental, historical and anthropogenic factors in influencing species richness of native and non‐native freshwater fishes in watersheds across North America. Location: North America (exclusive of Mexico). Time period: Recent. Major taxa studied: Freshwater fishes. Methods: We compiled an extensive dataset of native and non‐native fish richness in 2,993 watersheds across North America, together with corresponding data for environmental (climatic, geographic), historical and anthropogenic factors. We used variance partitioning and hierarchical partitioning to quantify the relative importance of environmental, historical and anthropogenic factors in explaining richness variation in native and non‐native [overall, and by geographic origin (foreign/translocated) and pathway (authorized/unauthorized)] fishes, while accounting for correlations among explanatory variables and spatial autocorrelation. Results: Overall importance of environmental and anthropogenic factors was greater than historical factors in explaining both native and non‐native richness. Precipitation‐related factors were more important in explaining native richness, whereas non‐native richness was largely associated with temperature‐related factors. However, richness related to authorized introductions was less constrained by temperature than unauthorized introductions. Dam density, road density and urbanization gradient were major anthropogenic factors related to non‐native richness, yet their relative importance varied among origin‐ and pathway‐based categories. Conclusions: Our findings indicate different environmental drivers influence native and non‐native fish richness patterns in North America. The accumulation of non‐native species in watersheds depends on the interaction between environmental conditions and anthropogenic‐based processes related to introduction history including geographic origin, introduction pathway, and propagule pressure, where the latter likely plays a major role. Warmer regions with high human population densities and more impoundments are more prone to fish invasions, mostly via unauthorized introductions. [ABSTRACT FROM AUTHOR]

PREMISE: Invasive species are expected to undergo a reduction in genetic diversity due to founder effects, which should limit their ability to adapt to new habitats. Still, many invasive species achieve widespread distributions and dense populations. This paradox of invasions could potentially be overcome through multiple introductions or hybridization, both of which increase genetic diversity. We conducted a population genomics study of Japanese knotweed (Reynoutria japonica), which is a polyploid, clonally reproducing invasive species that has been notoriously successful worldwide despite supposedly low genetic diversity. METHODS: We used genotyping by sequencing to collect 12,912 SNP markers from 88 samples collected at 38 locations across North America for the species complex. We used alignment‐free k‐mer hashing analysis in addition to traditional population genetic analyses to account for the challenges of genotyping polyploids. RESULTS: Genotypes conformed to three genetic clusters, likely representing Japanese knotweed, giant knotweed, and hybrid bohemian knotweed. We found that, contrary to previous findings, the Japanese knotweed cluster had substantial genetic diversity, though it had no apparent genetic structure across the landscape. In contrast, giant knotweed and hybrids showed distinct population groups. We did not find evidence of isolation by distance in the species complex, likely reflecting the stochastic introduction history of this species complex. CONCLUSIONS: The results indicate that clonal invasive species can show substantial genetic diversity and can be successful at colonizing a variety of habitats without showing evidence of local adaptation or genetic structure. [ABSTRACT FROM AUTHOR]

Aim: Species distribution models (SDMs) are widely used to forecast potential range expansion of invasive species. However, invasive species occurrence datasets often have spatial biases that may violate key SDM assumptions. In this study, we examined alternative methods of spatial bias correction and multiple methods for model evaluation for seven invasive plant species. Location: North America. Taxon: Common Tansy (Tanacetum vulgare), Wild Parsnip (Pastinaca sativa), Leafy Spurge (Euphorbia virgata), Common Teasel (Dipsacus fullonum), Brown Knapweed (Centaurea jacea), Black Swallowwort (Vincetoxicum nigrum) and Dalmatian Toadflax (Linaria dalmatica). Methods: We employed bias‐correction measures for both occurrence sampling and background sampling inputs in a factorial design for Maxent resulting in six potential models for each species. We evaluated our models for complexity, model fit and using commonly employed evaluation metrics: AUC, partial AUC, the continuous Boyce index and sensitivity. We then developed a structured process for model selection. Results: Models developed without occurrence or background bias correction often were overly complex and did not transfer well to expanding range fronts. Conversely, models that employed occurrence and/or background bias‐correction measures were less complex, had better AICc scores and had greater projection into incipient areas. These simpler models were also more likely to be selected when evaluated using a process that integrated multiple evaluation metrics. We found that invasion history (e.g. established versus incipient) was associated with the effectiveness of spatial bias correction techniques. Main Conclusions: While challenges exist in building climate‐based correlative species distribution models for invasive species, we found that methods relying on maximizing AUC performed poorly for invasive species. We advocate for the use of multiple and diverse metrics for model evaluation. Users of species distribution models need to incorporate explicit consideration of model discrimination, model fit and model complexity into their decision‐making processes if they are to build biologically realistic models. [ABSTRACT FROM AUTHOR]

Native and nonnative plant species can exhibit differences in the timing of their reproductive phenology and their phenological sensitivity to climate. These contrasts may influence species' interactions and the invasion potential of nonnative species; however, a limited number of phenology studies expressly consider phenological mismatches among native and nonnative species over broad spatial or temporal scales. To fill this knowledge gap, we used two complementary approaches: First, we quantified the flowering phenology of native and nonnative plants at five old‐field sites across a spatially extensive range of eastern North America. Second, we used herbarium records to compare the sensitivity of flowering and fruiting phenology to climate across a 114‐yr time period in a subset of common old‐field species in southwestern Pennsylvania. Across the study region, nonnatives reproduced substantially earlier in the growing season than natives, suggesting that nonnatives occupy a unique phenological niche (0.55 months earlier flowering across the North American study sites; 50.1 d earlier flowering and 17.5 d earlier fruiting in southwestern Pennsylvania). Both natives and nonnatives advanced their reproductive phenology between 1900 and 2014 but exhibited contrasting phenological sensitivity to climate factors. During the flowering stage of phenology, nonnatives were more sensitive to changes in precipitation than natives and generally delayed flowering in wetter years. Nonnative plants had greater sensitivity and advanced fruiting when the month preceding fruiting was warmer, while native plants had greater sensitivity and advanced fruiting when the three‐month period preceding fruiting was warmer. Our findings suggest that nonnative old‐field species occupy an earlier phenological niche relative to native species, which may facilitate their invasion into old‐field communities. However, given the different sensitivities of native and nonnative plants to climate factors, present‐day patterns of phenology are likely to shift with future climate changes, potentially leading to novel species interactions that may influence the outcomes of invasion. [ABSTRACT FROM AUTHOR]

Admixture in natural populations is a long‐standing management challenge, with population genomic approaches offering means for adjudication. We now more clearly understand the permeability of species boundaries and the potential of admixture for promoting adaptive evolution. These issues particularly resonate in western North America, where tectonism and aridity have fragmented and reshuffled rivers over millennia, in turn promoting reticulation among endemic fishes, a situation compounded by anthropogenic habitat modifications and non‐native introductions. The melding of historic and contemporary admixture has both confused and stymied management. We underscore this situation with a case study that quantifies basin‐wide admixture among a group of native and introduced fishes by employing double‐digest restriction site‐associated DNA (ddRAD) sequencing. Our approach: (a) quantifies the admixed history of 343 suckers (10 species of Catostomidae) across the Colorado River Basin; (b) gauges admixture within the context of phylogenetic distance and "ecological specialization"; and (c) extrapolates potential drivers of introgression across hybrid crosses that involve endemic as well as invasive species. Our study extends across an entire freshwater basin and expands previous studies more limited in scope both geographically and taxonomically. Our results detected admixture involving all 10 species, with habitat alterations not only accelerating the breakdown of reproductive isolation, but also promoting introgression. Hybridization occurred across the genus despite phylogenetic distance, whereas introgression was only detected within subgenera, implicating phylogenetic distance and/or ecological specialization as drivers of reproductive isolation. Understanding the extent of admixture and reproductive isolation across multiple species serves to disentangle their reticulate evolutionary histories and provides a broadscale perspective for basin‐wide conservation and management. [ABSTRACT FROM AUTHOR]

Relationships between invasive plants and other species in their introduced ranges may facilitate or hinder the process of invasion. Fallopia japonica (Japanese knotweed), Fallopia sachalinensis (giant knotweed), and their hybrid Fallopia × bohemica (Bohemian knotweed) are widespread invasive plants in North America and Europe. These species possess extrafloral nectaries (EFNs) that attract mutualist insect protectors in their native ranges. Popillia japonica Newman, 1841 (Japanese beetle) is a primary herbivore of invasive Fallopia spp. in these species' native range in Japan. These natural enemies are reunited in North America, where Fallopia spp. have been repeatedly introduced as ornamental plantings of residential and commercial properties since the 1800s, and the Japanese beetle has become a widespread insect pest. Spread of Fallopia spp. and their hybrids along linear features of urban landscapes such as roads, railways, and waterways make their performance in urban environments important to these invasive species' impact. To test the role of insect interactions in the success of Fallopia japonica and F. × bohemica in urban conditions in their invasive range, we examined ant visitation, Japanese beetle abundance and herbivory, ant-Japanese beetle interactions, pollinator visits, and seed production. All active herbivory observed was by Japanese beetles. Leaf area loss to herbivory was much lower than levels reported in Japan, suggesting partial enemy release. New Fallopia leaves were more frequently visited by ants than mature leaves, while Japanese beetle herbivory was observed on mature but not on new leaves. All ant species observed visiting invasive Fallopia EFN were native to North America. Active physical defense by these ants against Japanese beetles was observed but was rare. Native and non-native insects visited Fallopia flowers, followed by seed production. Our results indicate that both native and non-native species may facilitate invasion of Fallopia through pollination and protection mutualisms. [ABSTRACT FROM AUTHOR]

Although Brook Trout are distributed across most of eastern North America, population numbers have declined in many regions due to habitat loss, climate change, and competition with non‐native species. In New York State, Brook Trout habitat has been substantially reduced, with many areas showing complete extirpation of Brook Trout populations, predominantly in the western portion of the state. Small, fragmented populations are at risk of genetic diversity loss, inbreeding depression, and reduced fitness, leading to a greater potential for local extirpation. Genetic monitoring is a practical tool that can facilitate further conservation‐decision making regarding small populations. In this study, we used 12 microsatellite loci to examine 3,436 sampled Brook Trout, representing 75 sites from the Allegheny, Erie/Niagara, Genesee, Oswego, Lake Ontario, and Susquehanna drainage basins throughout western New York State. Three Brook Trout hatchery strains were also genetically characterized to evaluate the degree of hatchery introgression between wild populations and hatchery strains stocked in the region. Overall, estimates of genetic diversity varied widely: Allelic richness ranged from 2.23 to 7.485, and expected heterozygosity ranged from 0.402 to 0.766. As observed for Brook Trout in other regions, we found a high degree of genetic differentiation among populations, with all comparisons except one showing significant FST values. Hatchery introgression was found to be minimal, with estimates ranging from 1.96% to 3.10% of wild individuals exhibiting membership proportions to a hatchery strain cluster exceeding 10% (q ≥ 0.10). Results from this investigation can be used to prioritize management efforts for Brook Trout in western New York State and act as a baseline to monitor future population trends. [ABSTRACT FROM AUTHOR]

With increasing availability of plant distribution data, the information about global plant diversity is improving rapidly. Recently, Ulloa Ulloa et al. (2017) presented the first comprehensive overview of the native vascular flora of the Americas, yielding a total count of 124,993 native species. Of these, 51,241 occur in North America and 82,052 in South America. By combining these data with the information in the Global Naturalized Alien Flora (GloNAF) database of naturalized alien floras, we point out that for a complete picture of the regional and continental plant richness, the naturalized alien species need to be considered. Ignoring this novel component of regional floras can lead to an inaccurate picture of overall change in biodiversity in the Anthropocene. We show that North and South America might face contrasting challenges in terms of potential threats to biodiversity posed by alien plant species, because of the different past and present dynamics of invasions and predictions of future development. In total, there are 7,042 naturalized alien plants occurring in the Americas, with 6,122 recorded in North America and 2,677 in South America; if only introductions from other continents are considered additions to the native continental flora make up 6.9 and 1.4 %, respectively. Nevertheless, predictions of naturalized plant trajectories based on global trade dynamics and climate change suggest that considerable increases in naturalized plant numbers are expected in the next 20 years for emerging South American economies, which could reverse the present state. [ABSTRACT FROM AUTHOR]

The Great Lakes fisheries present a history of tension between the hydrological and biological unity of the lakes and the jurisdictional divisions that have defined their management. In the 1950s these divisions were apparently overcome by the need to respond to a crisis: the entry of the parasitic sea lamprey into the upper lakes, where they decimated lake trout populations. In response, the Great Lakes Fishery Commission was formed to coordinate cooperation in controlling the sea lamprey. However, the subsequent history of Great Lakes fisheries management demonstrates how this tension persisted. In particular, the linked histories of the Pacific salmon, introduced as the basis for a new sport fishery, and of the alewife, which found its own way into the upper lakes and, while initially perceived as a 'nuisance,' eventually became a valued species, illustrate how species from elsewhere have contributed to both the forming and the fracturing of systemic approaches to the Great Lakes. Les pêcheries, les espèces envahissantes, et la formation et la fracturation du système des Grands Lacs L'histoire des pêcheries dans les Grands Lacs est marquée de tensions entre l'unité hydrologique et biologique des lacs d'une part, et des frontières juridiques qui forment la base de leur mode de gestion, d'autre part. Dans les années 1950, l'arrivée de la lamproie marine dans les lacs en amont, un parasite qui a décimé les populations de truites lacustres, a provoqué une situation de crise à laquelle on devait répondre rapidement et qui semblait avoir permis de dépasser ces divisions. C'est dans ce contexte qu'on a mis sur pied la Commission des pêcheries des Grands Lacs afin de coordonner la coopération en matière de lutte contre la lamproie marine. Cependant, comme l'histoire de la gestion des pêcheries des Grands Lacs en témoigne, on n'a jamais pu maîtriser les tensions. Rappelons les histoires parallèles du saumon du Pacifique qui est introduit avec l'objectif de soutenir une nouvelle pêche sportive, et du gaspareau qui, ayant réussi à remonter le courant pour se retrouver dans les lacs en amont, avait d'abord été perçu comme une « nuisance », mais compte finalement parmi les espèces prisées. Cela montre à quel point les espèces venues d'ailleurs ont contribué tant à la formation qu'à la fracturation des approches de gestion systémique des Grands Lacs. [ABSTRACT FROM AUTHOR]

Water flow gradients have been linked to phenotypic differences and swimming performance across a variety of fish assemblages. However, the extent to which water motion shapes patterns of phenotypic divergence within species remains unknown. We tested the generality of the functional relationship between swimming morphology and water flow by exploring the extent of fin and body shape polymorphism in 12 widespread species from three families (Acanthuridae, Labridae, Pomacentridae) of pectoral-fin swimming (labriform) fishes living across localized wave exposure gradients. The pectoral fin shape of Labridae and Acanthuridae species was strongly related to wave exposure: individuals with more tapered, higher aspect ratio (AR) fins were found on windward reef crests, whereas individuals with rounder, lower AR fins were found on leeward, sheltered reefs. Three of seven Pomacentridae species showed similar trends, and pectoral fin shape was also strongly related to wave exposure in pomacentrids when fin aspect ratios of three species were compared across flow habitats at very small spatial scales (,100 m) along a reef profile (reef slope, crest, and back lagoon). Unlike fin shape, there were no intraspecific differences in fish body fineness ratio across habitats or depths. Contrary to our predictions, there was no pattern relating species' abundances to polymorphism across habitats (i.e., abundance was not higher at sites where morphology is better adapted to the environment). This suggests that there are behavioral and/or physiological mechanisms enabling some species to persist across flow habitats in the absence of morphological differences. We suggest that functional relationships between swimming morphology and water flow not only structure species assemblages, but are yet another important variable contributing to phenotypic differences within species. The close links between fin shape polymorphism and local water flow conditions appear to be important for understanding species' distributions as well as patterns of diversification across environmental gradients. [ABSTRACT FROM AUTHOR]

Aim Environmental and biological characteristics interact in complex ways to determine ecosystem susceptibility to invasive species, and a greater understanding of their relative roles in invader spread and impact is needed. We evaluated relationships between environmental characteristics, biodiversity of indigenous species, and the abundance and ecological impact of an invasive fish, round goby ( Neogobius melanostomus). Location Tributaries to Lake Michigan, WI, USA. Methods We assessed the distribution and abundance of round gobies and native fishes in tributaries via electrofishing. We compared fish community composition and diversity in streams with ( n = 30) and without ( n = 52) round gobies and examined how trends in round goby abundance from 2007 to 2010 correlated with changes in abundance of five native benthic fishes. We used redundancy analysis to determine how indigenous stream communities related to environmental characteristics and round goby abundance. Results Round goby abundance was best explained by environmental characteristics, with watershed area and temperature explaining 22.4% of the variation. Species richness and Shannon diversity only explained 6.9% of the variation in round goby abundance and only an additional 2.3% after considering environmental characteristics. Round goby abundance was not a significant predictor of fish community composition, which was best explained by seven environmental variables (30.3% of the variation). Invaded communities had significantly higher indigenous species richness than uninvaded communities (8.38 vs. 6.54). Round goby abundance was low compared with estimates from other studies, but showed an increasing trend in many tributaries (average 10.8-fold increase from 2007 to 2010). Surprisingly, there were no temporal trends in native benthic fish abundance despite increases in round goby abundance. Main conclusions Environmental characteristics favouring high fish diversity (e.g. resource availability and warm water temperature) were positively associated with round goby abundance. However, round goby density and impact are relatively low in most tributaries at present, emphasizing the importance of considering heterogeneity in an invader's abundance when assessing invasion success. [ABSTRACT FROM AUTHOR]

I.II.III.IV.V.References Summary: We propose a conceptual framework for restoration of threatened plant species that encourages integration of technological, ecological, and social spheres. A sphere encompasses ideas relevant to restoration and the people working within similar areas of influence or expertise. Increased capacity within a sphere and a higher degree of coalescing among spheres predict a greater probability of successful restoration. We illustrate this with Castanea dentata, a foundation forest tree in North America that was annihilated by an introduced pathogen; the species is a model that effectively merges biotechnology, reintroduction biology, and restoration ecology. Because of C. dentata's ecological and social importance, scientists have aggressively pursued blight resistance through various approaches. We summarize recent advancements in tree breeding and biotechnology that have emerged from C. dentata research, and describe their potential to bring new tools to bear on socio‐ecological restoration problems. Successful reintroduction of C. dentata will also depend upon an enhanced understanding of its ecology within contemporary forests. We identify a critical need for a deeper understanding of societal influences that may affect setting and achieving realistic restoration goals. Castanea dentata may serve as an important model to inform reintroduction of threatened plant species in general and foundation forest trees in particular. [ABSTRACT FROM AUTHOR]

1. Invasive species are a major threat to global biodiversity and their introduction can have significant economic consequences. The invasive tunicate Didemnum vexillum is a notorious invader with significant negative impacts on cultured shellfish and natural benthic communities, including commercially important ones. 2. We conducted an expert survey, identifying the five most important transport vectors for D. vexillum along the west coast of North America. We determined the spatially explicit vector density for all vectors in order to identify introduction hotspots. Additionally, we developed an environmental niche model based on 46 occurrence points and nine environmental variables to identify areas suitable for D. vexillum. 3. Spatial distribution of the most important transport vectors (slow-moving vessels, aquaculture, fishing vessels, small vessels, and large commercial vessels) identified several hotspots with high vector densities. These proved to be a very good predictor of current D. vexillum occurrence in British Columbia (BC). Ecological niche modelling (Genetic Algorithm for Rule-set Prediction) predicted suitable environments in southern BC, parts of central BC and along the east coast of the Queen Charlotte Islands. Independent validation of the model based on the current distribution in BC indicated good predictive accuracy. Additional analytical steps confirmed that no environmental variable dominated the predictions and we identified ranges of environmental conditions predicted suitable by the model. 4. We identified areas of high establishment probability for D. vexillum by combining the vector model and environmental niche model. Parts of central BC, the west coast of Vancouver Island and the Strait of Georgia are areas where D. vexillum is most likely to establish. 5. Synthesis and applications. Spatially explicit predictions of the potential distribution of biological invaders are crucial for informing risk assessments, development of management strategies, and resource allocation. While most studies only focus on one step in the invasion process, we successfully combined the likelihood of introduction and establishment. Results from this study are informing the canadian risk assessment of invasive tunicates, guiding current monitoring efforts, and providing a basis for potential intervention/mediation measures. [ABSTRACT FROM AUTHOR]

The critical load concept facilitates communication between scientists and policy makers and land managers by translating the complex effects of air pollution on ecosystems into unambiguous numbers that can be used to inform air quality targets. Anthropogenic atmospheric nitrogen (N) deposition adversely affects a variety of ecosystems, but the information used to derive critical loads for North American ecosystems is sparse and often based on experiments investigating N loads substantially higher than current or expected atmospheric deposition. In a 4‐yr field experiment in the northern Great Plains (NGP) of North America, where current N deposition levels range from ~3 to 9 kg N·ha−1·yr−1, we added 12 levels of N, from 2.5 to 100 kg N·ha−1·yr−1, to three sites spanning a range of soil fertility and productivity. Our results suggest a conservative critical load of 4–6 kg N·ha−1·yr−1 for the most sensitive vegetation type we investigated, badlands sparse vegetation, a community that supports plant species adapted to low fertility conditions, where N addition at this rate increased productivity and litter load. In contrast, for the two more productive vegetation types characteristic of most NGP grasslands, a critical load of 6–10 kg N·ha−1·yr−1 was identified. Here, N addition at this level altered plant tissue chemistry and increased nonnative species. These critical loads are below the currently suggested range of 10–25 kg N·ha−1·yr−1 for NGP vegetation and within the range of current or near‐future deposition, suggesting that N deposition may already be inducing fundamental changes in NGP ecosystems. [ABSTRACT FROM AUTHOR]

Several dozen fish species have been introduced into Neotropical waters, causing significant biotic changes that include deterministic predation interactions with ecosystem effects. In general, reservoirs are preferred over lakes as places for stocking policies, due to their artificial aspect, consequently promoting fish introductions. In a meta‐analytic approach, we compared the biomass of plankton‐feeding (and top predators) with bottom‐feeding fish species between reservoirs and lakes, considering the influence of invaders and trophic levels. Among the 26 ecosystems (12 reservoirs and 14 lakes), there is a dominance of non‐native bottom‐feeding species in artificial environments. We revealed a mechanism behind this dominance in a study case, a tendency for trophic downgrading and biotic homogenization based on interactions between an expatriate invasive centrarchid (sunfish family) predator from North America (the largemouth bass Micropterus salmoides) and two omnivorous cichlids from Africa in novel environmental contexts in Brazil (the benthification process). Both juvenile and adult largemouth bass are keystone predators in aquatic food webs in both their native and introduced ranges. The omnivore–detritivore tilapiines Oreochromis spp. and the phytophagous–omnivorous Coptodon spp. are species that exhibits strong generalist tendencies. Such species feed on the omnivore and detritivore compartments, enhancing detritus cycling among a large variety of δ13C sources. Since their consumption is disproportionate, facilitation of other species occurs with multiplicative effects in the environment. Interactions between invasive species, that is, when an invasive predator (bird, fish, or invertebrate) eats an invasive prey (mainly fish and invertebrates), can serve to highlight biotic homogenization on fresh waters. [ABSTRACT FROM AUTHOR]

Dreissenid mussels (including the zebra mussel Dreissena polymorpha and the quagga mussel D. rostriformis) are among the world's most notorious invasive species, with large and widespread ecological and economic effects. However, their long‐term population dynamics are poorly known, even though these dynamics are critical to determining impacts and effective management. We gathered and analyzed 67 long‐term (>10 yr) data sets on dreissenid populations from lakes and rivers across Europe and North America. We addressed five questions: (1) How do Dreissena populations change through time? (2) Specifically, do Dreissena populations decline substantially after an initial outbreak phase? (3) Do different measures of population performance (biomass or density of settled animals, veliger density, recruitment of young) follow the same patterns through time? (4) How do the numbers or biomass of zebra mussels or of both species combined change after the quagga mussel arrives? (5) How does body size change over time? We also considered whether current data on long‐term dynamics of Dreissena populations are adequate for science and management. Individual Dreissena populations showed a wide range of temporal dynamics, but we could detect only two general patterns that applied across many populations: (1) Populations of both species increased rapidly in the first 1–2 yr after appearance, and (2) quagga mussels appeared later than zebra mussels and usually quickly caused large declines in zebra mussel populations. We found little evidence that combined Dreissena populations declined over the long term. Different measures of population performance were not congruent; the temporal dynamics of one life stage or population attribute cannot generally be accurately inferred from the dynamics of another. We found no consistent patterns in the long‐term dynamics of body size. The long‐term dynamics of Dreissena populations probably are driven by the ecological characteristics (e.g., predation, nutrient inputs, water temperature) and their temporal changes at individual sites rather than following a generalized time course that applies across many sites. Existing long‐term data sets on dreissenid populations, although clearly valuable, are inadequate to meet research and management needs. Data sets could be improved by standardizing sampling designs and methods, routinely collecting more variables, and increasing support. [ABSTRACT FROM AUTHOR]