Defining the Impact of Non‐Native Species

Non‐native species cause changes in the ecosystems to which they are introduced. These changes, or some of them, are usually termed impacts; they can be manifold and potentially damaging to ecosystems and biodiversity. However, the impacts of most non‐native species are poorly understood, and a synthesis of available information is being hindered because authors often do not clearly define impact. We argue that explicitly defining the impact of non‐native species will promote progress toward a better understanding of the implications of changes to biodiversity and ecosystems caused by non‐native species; help disentangle which aspects of scientific debates about non‐native species are due to disparate definitions and which represent true scientific discord; and improve communication between scientists from different research disciplines and between scientists, managers, and policy makers. For these reasons and based on examples from the literature, we devised seven key questions that fall into 4 categories: directionality, classification and measurement, ecological or socio‐economic changes, and scale. These questions should help in formulating clear and practical definitions of impact to suit specific scientific, stakeholder, or legislative contexts. Definiendo el Impacto de las Especies No‐Nativas     

Establishing IUCN Red List Criteria for Threatened Ecosystems

Abstract: The potential for conservation of individual species has been greatly advanced by the International Union for Conservation of Nature's (IUCN) development of objective, repeatable, and transparent criteria for assessing extinction risk that explicitly separate risk assessment from priority setting. At the IV World Conservation Congress in 2008, the process began to develop and implement comparable global standards for ecosystems. A working group established by the IUCN has begun formulating a system of quantitative categories and criteria, analogous to those used for species, for assigning levels of threat to ecosystems at local, regional, and global levels. A final system will require definitions of ecosystems; quantification of ecosystem status; identification of the stages of degradation and loss of ecosystems; proxy measures of risk (criteria); classification thresholds for these criteria; and standardized methods for performing assessments. The system will need to reflect the degree and rate of change in an ecosystem's extent, composition, structure, and function, and have its conceptual roots in ecological theory and empirical research. On the basis of these requirements and the hypothesis that ecosystem risk is a function of the risk of its component species, we propose a set of four criteria: recent declines in distribution or ecological function, historical total loss in distribution or ecological function, small distribution combined with decline, or very small distribution. Most work has focused on terrestrial ecosystems, but comparable thresholds and criteria for freshwater and marine ecosystems are also needed. These are the first steps in an international consultation process that will lead to a unified proposal to be presented at the next World Conservation Congress in 2012.     

Use of Congeneric Assessment to Reveal the Linked Genetic Histories of Two Threatened Fishes in the Murray‐Darling Basin,Australia

Abstract: The intensely regulated Murray‐Darling Basin in southeastern Australia is the nation's most extensive and economically important river system, and it contains fragmented populations of numerous fish species. Among these is the Murray hardyhead (Craterocephalus fluviatilis), a species listed as endangered (International Union for Conservation of Nature Red List) in the mid‐1990s prior to its acute decline with the progression of a severe drought that began in 1997. We compared the genetic structure of Murray hardyhead with 4 congeneric species (Darling hardyhead[C. amniculus], Finke hardyhead[C. centralis], Lake Eyre hardyhead[C. eyresii], and unspecked hardyhead[C. stercusmuscarum]), selected on the basis of their taxonomic or biological similarity to Murray hardyhead, in order to affirm species boundaries and test for instances of introgressive hybridization, which may influence species ecology and conservation prospects. We used allozyme (52 loci) and mtDNA markers (1999 bp of ATPase and cytochrome b) to provide a comparative genetic assessment of 139 Murray hardyhead, which represented all extant and some recently extirpated populations, and 71 congeneric specimens from 12 populations. We confirmed that Murray hardyhead and Darling hardyhead are taxonomically distinct and identified a number of potential conservation units, defined with genetic criteria, in both species. We also found allozyme and mtDNA evidence of historic genetic exchange between these 2 allopatric species, apparently involving one population of each species at the geographic edge of the species’ ranges, not in the most proximate populations sampled. Our results provide information on species boundaries and offer insight into the likely causes of high genetic diversity in certain populations, results which are already being used to guide national recovery planning and local action. Given the prevalence of incorrect taxonomies and introgression in many organismal groups, we believe these data point to the need to commence genetic investigations of any threatened species from an initially broad taxonomic focus.     

The Role of Hybrid Vigor in the Replacement of Pecos Pupfish by Its Hybrids with Sheepshead Minnow

Abstract:  Many species are jeopardized by hybridization and genetic introgression with closely related species. Unfortunately, the mechanisms that promote or retard gene flow between divergent populations are little studied and poorly understood. Like many imperiled fish species, the Pecos pupfish ( Cyprinodon pecosensis ) is threatened with replacement by its hybrids with a close congener. We examined swimming performance and growth rate of hybrid pupfish to determine the role of hybrid vigor in the genetic homogenization of C. pecosensis by its hybrids with sheepshead minnow ( C. variegatus ). The F1 hybrids, backcross hybrids, and purebred C. variegatus displayed greater swimming endurance than purebred C. pecosensis . In addition, F1 hybrids and C. variegatus grew more rapidly than C. pecosensis . The ecological superiority of hybrids probably promoted their rapid spread through and beyond the historic range of C. pecosensis . These results indicate that eradication of hybrids and restoration of C. pecosensis to its native range is unlikely. Extinction of unique species via genetic homogenization can result from human activities that increase gene flow between historically fragmented populations; conservation managers must weigh the potential for such a catastrophe against the presumed benefits of increased interpopulation gene flow. This example illustrates how, after hybridization has occurred, conflict may arise between formerly complementary conservation goals.     

Scale Mismatches,Conservation Planning,and the Value of Social‐Network Analyses

Many of the challenges conservation professionals face can be framed as scale mismatches. The problem of scale mismatch occurs when the planning for and implementation of conservation actions is at a scale that does not reflect the scale of the conservation problem. The challenges in conservation planning related to scale mismatch include ecosystem or ecological process transcendence of governance boundaries; limited availability of fine‐resolution data; lack of operational capacity for implementation; lack of understanding of social‐ecological system components; threats to ecological diversity that operate at diverse spatial and temporal scales; mismatch between funding and the long‐term nature of ecological processes; rate of action implementation that does not reflect the rate of change of the ecological system; lack of appropriate indicators for monitoring activities; and occurrence of ecological change at scales smaller or larger than the scale of implementation or monitoring. Not recognizing and accounting for these challenges when planning for conservation can result in actions that do not address the multiscale nature of conservation problems and that do not achieve conservation objectives. Social networks link organizations and individuals across space and time and determine the scale of conservation actions; thus, an understanding of the social networks associated with conservation planning will help determine the potential for implementing conservation actions at the required scales. Social‐network analyses can be used to explore whether these networks constrain or enable key social processes and how multiple scales of action are linked. Results of network analyses can be used to mitigate scale mismatches in assessing, planning, implementing, and monitoring conservation projects. Discordancia de Escalas, Planificación de la Conservación y el Valor del Análisis de Redes Sociales     

Value Plurality among Conservation Professionals

Abstract: Debate on the values that underpin conservation science is rarely based on empirical analysis of the values conservation professionals actually hold. We used Q methodology to investigate the values held by international conservation professionals who attended the annual Student Conference in Conservation Science at the University of Cambridge (U.K.) in 2008 and 2009. The methodology offers a quantitative means of examining human subjectivity. It differs from standard opinion surveys in that individual respondents record the way they feel about statements relative to other statements, which forces them to focus their attention on the issues they believe are most important. The analysis extracts the diverse viewpoints of the respondents, and factor analysis is used to reduce the viewpoints to a smaller set of factors that reflect shared ways of thinking. The junior conservation professionals attending the conference did not share a unifying set of core values; rather, they held a complex series of ideas and a plurality of opinions about conservation and how it should be pursued. This diversity of values empirically challenges recent proposals for conservation professionals to unite behind a single philosophy. Attempts to forge an artificial consensus may be counterproductive to the overall goals conservation professionals are pursuing.     

Acknowledging Conservation Trade‐Offs and Embracing Complexity

Abstract: There is a growing recognition that conservation often entails trade‐offs. A focus on trade‐offs can open the way to more complete consideration of the variety of positive and negative effects associated with conservation initiatives. In analyzing and working through conservation trade‐offs, however, it is important to embrace the complexities inherent in the social context of conservation. In particular, it is important to recognize that the consequences of conservation activities are experienced, perceived, and understood differently from different perspectives, and that these perspectives are embedded in social systems and preexisting power relations. We illustrate the role of trade‐offs in conservation and the complexities involved in understanding them with recent debates surrounding REDD (Reducing Emissions from Deforestation and Degradation), a global conservation policy designed to create incentives to reduce tropical deforestation. Often portrayed in terms of the multiple benefits it may provide: poverty alleviation, biodiversity conservation, and climate‐change mitigation; REDD may involve substantial trade‐offs. The gains of REDD may be associated with a reduction in incentives for industrialized countries to decrease carbon emissions; relocation of deforestation to places unaffected by REDD; increased inequality in places where people who make their livelihood from forests have insecure land tenure; loss of biological and cultural diversity that does not directly align with REDD measurement schemes; and erosion of community‐based means of protecting forests. We believe it is important to acknowledge the potential trade‐offs involved in conservation initiatives such as REDD and to examine these trade‐offs in an open and integrative way that includes a variety of tools, methods, and points of view.