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Invasion Ecology (invasion + ecology)
Kinds of Invasion Ecology Selected AbstractsReducing redundancy in invasion ecology by integrating hypotheses into a single theoretical frameworkDIVERSITY AND DISTRIBUTIONS, Issue 1 2009Jane A. Catford ABSTRACT Aim, Invasion ecology includes many hypotheses. Empirical evidence suggests that most of these can explain the success of some invaders to some degree in some circumstances. If they all are correct, what does this tell us about invasion? We illustrate the major themes in invasion ecology, and provide an overarching framework that helps organize research and foster links among subfields of invasion ecology and ecology more generally. Location, Global. Methods, We review and synthesize 29 leading hypotheses in plant invasion ecology. Structured around propagule pressure (P), abiotic characteristics (A) and biotic characteristics (B), with the additional influence of humans (H) on P, A and B (hereon PAB), we show how these hypotheses fit into one paradigm. P is based on the size and frequency of introductions, A incorporates ecosystem invasibility based on physical conditions, and B includes the characteristics of invading species (invasiveness), the recipient community and their interactions. Having justified the PAB framework, we propose a way in which invasion research could progress. Results, By highlighting the common ground among hypotheses, we show that invasion ecology is encumbered by theoretical redundancy that can be removed through integration. Using both holistic and incremental approaches, we show how the PAB framework can guide research and quantify the relative importance of different invasion mechanisms. Main conclusions, If the prime aim is to identify the main cause of invasion success, we contend that a top-down approach that focuses on PAB maximizes research efficiency. This approach identifies the most influential factors first, and subsequently narrows the number of potential causal mechanisms. By viewing invasion as a multifaceted process that can be partitioned into major drivers and broken down into a series of sequential steps, invasion theory can be rigorously tested, understanding improved and effective weed management techniques identified. [source] Evaluating extreme risks in invasion ecology: learning from banking complianceDIVERSITY AND DISTRIBUTIONS, Issue 4 2008James Franklin ABSTRACT Increasing international trade has exacerbated the risks of ecological damage due to invasive pests and diseases. For extreme events such as invasions of damaging exotic species or natural catastrophes, there are no or very few directly relevant data, so expert opinion must be relied on heavily. Expert opinion must be as fully informed and calibrated as possible , by available data, by other experts, and by the reasoned opinions of stakeholders. We survey a number of quantitative and non-quantitative methods that have shown promise for improving extreme risk analysis, particularly for assessing the risks of invasive pests and pathogens associated with international trade. We describe the legally inspired regulatory regime for banks, where these methods have been brought to bear on extreme ,operational risks'. We argue that an ,advocacy model' similar to that used in the Basel II compliance regime for bank operational risks and to a lesser extent in biosecurity import risk analyses is ideal for permitting the diversity of relevant evidence about invasive species to be presented and soundly evaluated. We recommend that the process be enhanced in ways that enable invasion ecology to make more explicit use of the methods found successful in banking. [source] Plant invasion ecology , dispatches from the front lineDIVERSITY AND DISTRIBUTIONS, Issue 5-6 2004David M. Richardson ABSTRACT This issue of Diversity and Distributions carries papers on a wide range of topics dealing with invasions of introduced plant species. The collection of articles did not arise from a conference or workshop, but grew from a founder population of contributed manuscripts. Some additional papers were solicited to ensure coverage of other established or emerging fields of research in plant invasion ecology. The compilation represents a reasonable cross section of issues that currently occupy plant invasion ecologists. The editorial places the contributions in context and summarizes some key findings. It also suggests some profitable avenues for future research in plant invasion ecology. [source] Naturalization and invasion of alien plants: concepts and definitionsDIVERSITY AND DISTRIBUTIONS, Issue 2 2000David M. Richardson Abstract., Much confusion exists in the English-language literature on plant invasions concerning the terms ,naturalized' and ,invasive' and their associated concepts. Several authors have used these terms in proposing schemes for conceptualizing the sequence of events from introduction to invasion, but often imprecisely, erroneously or in contradictory ways. This greatly complicates the formulation of robust generalizations in invasion ecology. Based on an extensive and critical survey of the literature we defined a minimum set of key terms related to a graphic scheme which conceptualizes the naturalization/invasion process. Introduction means that the plant (or its propagule) has been transported by humans across a major geographical barrier. Naturalization starts when abiotic and biotic barriers to survival are surmounted and when various barriers to regular reproduction are overcome. Invasion further requires that introduced plants produce reproductive offspring in areas distant from sites of introduction (approximate scales: > 100 m over < 50 years for taxa spreading by seeds and other propagules; > 6 m/3 years for taxa spreading by roots, rhizomes, stolons or creeping stems). Taxa that can cope with the abiotic environment and biota in the general area may invade disturbed, seminatural communities. Invasion of successionally mature, undisturbed communities usually requires that the alien taxon overcomes a different category of barriers. We propose that the term ,invasive' should be used without any inference to environmental or economic impact. Terms like ,pests' and ,weeds' are suitable labels for the 50,80% of invaders that have harmful effects. About 10% of invasive plants that change the character, condition, form, or nature of ecosystems over substantial areas may be termed ,transformers'. [source] The role of research for integrated management of invasive species, invaded landscapes and communitiesJOURNAL OF APPLIED ECOLOGY, Issue 2 2008Yvonne M. Buckley Summary 1Invaded landscapes and ecosystems are composed of multiple interacting networks and feed-back loops, sometimes leading to unexpected effects of management actions. In order to plan management for invaded systems we need to explicitly consider management goals before putting actions in place. Actions taken must be justified in terms of their amelioration of impacts of invaders, contribution to the management goals and the costs incurred. 2This Special Profile brings together papers on the management of invasive plants, transgenes, animals and diseases, leading to conclusions with clear policy and management relevance and contributing to some of the hottest current topics in invasion ecology: unexpected impacts of invaders, restoration of invasion resistance, distribution mapping, spatial epidemiology, escape of transgenes, community interactions and complex effects of management. 3As papers in this Special Profile demonstrate, management for amelioration of the impacts of invasive species will include a wide range of manipulations, not just of the invader itself but of both abiotic and biotic components of the system. In fact, several papers in this Special Profile show that indirect management of the community may be more effective than removal of the invader alone. 4As little information is generally available at the beginning of a management programme, an adaptive approach should be taken and the management objectives/goals revised throughout the management process. New methods are emerging for adaptive management; an example is presented in this Special Profile where a Bayesian model used for assessing eradication goals can be updated throughout the management process leading to refinement of management. 5Synthesis and applications. Applied research should be directed at providing decision support for managers throughout the management process and can be used to provide predictive tools for risk assessment of new invaders. The science of invasion ecology has much to contribute to the new challenge of natural or enhanced movement of organisms in relation to climate change. Methods and information from invasion ecology can be used to assess management goals, management actions and the risks of potential translocations before they are put in place. [source] Plant invasions and the nicheJOURNAL OF ECOLOGY, Issue 4 2009Andrew S. MacDougall Summary 1For plant invaders, being different is often equated with being successful, yet the mechanistic connection remains unclear. 2Classic niche theory predicts that invaders with niches distinct from the native flora should coexist with little interaction with native species, yet such invaders often have substantial impacts. Meanwhile, invaders that overlap in niche space with native species should either be repelled or dominate, yet these invaders often naturalize with little effect. Such discrepancies between theory and observation raise questions about how species differences influence invader establishment and impact. 3Here, we review these issues in light of recent work on coexistence theory, which shows how niche and fitness differences between natives and invaders interact to determine invasion outcomes. We show how successful invader establishment depends on either a fitness advantage or niche difference from resident species, but that only the former allows invaders to become dominant. 4By identifying the role of niche and fitness differences in leading invasion hypotheses, we unify their predictions for invasion success while highlighting new approaches for evaluating the importance of species differences for invasion. 5Synthesis. Situating the invasion process within a recent coexistence framework broadens our understanding of invasion mechanisms and more tightly links problems in invasion ecology with our more general understanding of community dynamics. [source] Barley yellow dwarf viruses (BYDVs) preserved in herbarium specimens illuminate historical disease ecology of invasive and native grassesJOURNAL OF ECOLOGY, Issue 6 2007CAROLYN M. MALMSTROM Summary 1In plant invasion ecology, viruses and other pathogens are often considered in terms of the enemy release hypothesis, which predicts that plants become invasive in new ranges if they escape pathogens from their home range. However, pathogens may sometimes facilitate host spread rather than hinder it. 2Previously, we hypothesized that apparent competition mediated by barley and cereal yellow dwarf viruses (Luteoviridae: BYDVs, CYDVs) may have facilitated historical grassland invasion in California, USA, where Eurasian grasses displaced native grasses in the 18th and 19th centuries (the disease facilitation hypotheses). However, this could have happened only if the viruses were present during the invasion, which is unknown. 3To investigate the historical ecology of BYDVs in California grasses, we analysed preserved virus infections in herbarium specimens and used the historical virus sequences to determine rough time estimates of relevant phylogenetic events. 4The historical viral RNA sequences we identified in invasive and native grasses date from 1917 and are among the oldest recovered from plants thus far and the oldest from North America. 5Herbarium evidence and phylogenetic analysis suggest that BYDVs were likely to have been present in wild grasses during the California grassland invasion and to have shared some functional characteristics with present-day isolates, supporting the disease facilitation hypothesis. 6We found evidence of virus spread from California to Australia (or, less likely, from Australia to California) in the late 19th century, when much horticultural exchange occurred, as well as potential correspondence in the timing of virus diversification events and the beginning of extensive human exchange between the Old and New Worlds. 7Synthesis. Increasing evidence indicates that viruses are important in the ecology of grasslands and may, in some cases, mediate apparent competition among species. Historical data provide essential insight into plant virus ecology and suggest the need to examine human influence on plant virus diversification and spread within natural ecosystems. [source] The importance of biological inertia in plant community resistance to invasionJOURNAL OF VEGETATION SCIENCE, Issue 3 2003Betsy Von Holle Abstract. Insights into the ecology of historic invasions by introduced species can be gained by studying long-term patterns of invasions by native species. In this paper, we review literature in palaeo-ecology, forest-stand simulation modelling, and historical studies of plant species invasions to illustrate the relevance of biological inertia in plant communities to invasion ecology. Resistance to invasion occurs in part because of environmental, demographic, and biotic factors influencing the arrival and establishment of invading species. We propose that biological inertia within the resident community is a fourth component of resistance to invasion, because of the lag time inherent in eliminating resident species and perhaps their traces after environmental conditions become suitable for invasion by immigrating species. Whether or not an introduced species invades can be conditioned by the presence of the pre-existing community (and/or its legacy) in addition to the other biotic and abiotic factors. [source] Detecting the effects of introduced species: a case study of competition between Apis and BombusOIKOS, Issue 3 2006Diane M. Thomson Developing tools for rapid assessment of introduced species impacts is one of the most important challenges in invasion ecology. Most assessments of impact rely on correlational data or other indirect measures. Yet few studies have evaluated invasion effects using multiple, simultaneously applied monitoring and experimental approaches, in order to compare easily obtained metrics with more difficult but direct measures of reproductive success or population dynamics. In this study, I use data from an experimental test of introduced honey bee (Apis mellifera) impacts on native bumble bees (Bombus spp.) to address two major questions: 1) how well did observational data on niche overlap and spatial correlations between Apis and Bombus predict the results of experimental tests of competitive effects? and 2) how well did effects of the experimental Apis manipulations on Bombus foragers, which are easy to observe, predict changes in reproductive success of colonies, which are difficult to measure? Niche overlap between Apis and Bombus varied substantially, but increased to levels as high as 80,90% during periods of resource scarcity. Correlations between numbers of Apis foragers and numbers of Bombus foragers were also highly variable, but I detected a significant negative relationship in only one of the seven months observed. In contrast, the experimental results showed that mean numbers of Bombus foragers observed on a given transect increased significantly with greater distance from introduced Apis colonies. Of these three measures (niche overlap, correlations in abundances, and effects of experimental introductions), only the experimental data on forager abundances accurately estimated competitive effects on colony reproductive success previously reported for the same experiment, and the correlational data in particular completely failed to predict the effects observed in the experimental study. This work suggests that great caution is warranted in making assessments of invasion impact on the basis of spatial or temporal correlations between invasive and native species. Thus, investing in even small and limited experimental studies may be more valuable than extensive observational work in quantifying invasion impacts. [source] Molecular systematics and population genetics of biological invasions: towards a better understanding of invasive species managementANNALS OF APPLIED BIOLOGY, Issue 1 2009J. Le Roux Abstract The study of population genetics of invasive species offers opportunities to investigate rapid evolutionary processes at work, and while the ecology of biological invasions has enjoyed extensive attention in the past, the recentness of molecular techniques makes their application in invasion ecology a fairly new approach. Despite this, molecular biology has already proved powerful in inferring aspects not only relevant to the evolutionary biologist but also to those concerned with invasive species management. Here, we review the different molecular markers routinely used in such studies and their application(s) in addressing different questions in invasion ecology. We then review the current literature on molecular genetic studies aimed at improving management and the understanding of invasive species by resolving of taxonomic issues, elucidating geographical sources of invaders, detecting hybridisation and introgression, tracking dispersal and spread and assessing the importance of genetic diversity in invasion success. Finally, we make some suggestions for future research efforts in molecular ecology of biological invasions. [source] Ever since Clements: from succession to vegetation dynamics and understanding to interventionAPPLIED VEGETATION SCIENCE, Issue 1 2009S.T.A. Pickett Abstract Introduction: This paper surveys a framework for vegetation dynamics to provide conceptual background for a series of papers addressing the role of vegetation dynamics in restoration. Richness of the foundation: Classical succession theory provides key ingredients for contemporary process studies of vegetation dynamics. The contemporary framework incorporates processes identified by Gleason and other critics of Clements' theory. Multiple causality: The Clementsian causes, when expanded to include interaction and to clarify net effects, accommodate those now recognized in vegetation dynamics. A mature successional framework: A hierarchical framework has emerged to evaluate the causes of vegetation dynamics. The framework identifies the general causes as site availability, species availability, and species performance. Differentials as drivers: Differentials in any of the three general causes can drive change in plant communities. Each general cause consists of specific mechanisms. A model template: To predict vegetation dynamics trajectories, models are required. A model template is presented to operationalize the hierarchical framework. Outcomes are contingent on species pools and environmental contexts and may be progressive or retrogressive. Relationships of frameworks: Other contemporary frameworks in biology relate to vegetation dynamics. Application to restoration: The vegetation dynamics framework is relevant to restoration through linkages with landscape ecology, disturbance ecology, competition, invasion ecology, and community assembly. The differentials of site availability, species availability, and species performance suggest the processes and strategies available for restoration. Conclusions: A synthetic framework of vegetation brings together the mechanisms required for successful restoration. [source] | |||||||||||||