Urban Plants as Genetic Reservoirs or Threats to the Integrity of Bushland Plant Populations

Abstract:  Remnant plants in urban fringes and native plants in gardens have the potential to contribute to the conservation of threatened plants by increasing genetic diversity, effective size of populations, and levels of genetic connectedness. But they also pose a threat through the disruption of locally adapted gene pools. At Hyams Beach, New South Wales, Australia, four bushland stands of the rare shrub, Grevillea macleayana McGillivray, surround an urban area containing remnant and cultivated specimens of this species. Numbers of inflorescences per plant, fruits per plant, and visits by pollinators were similar for plants in urban gardens and bushland. Urban plants represented a substantial but complex genetic resource, displaying more genetic diversity than bushland plants judged by H_e , numbers of alleles per locus, and number of private alleles. Of 27 private alleles in urban plants, 17 occurred in a set of 19 exotic plants. Excluding the exotic plants, all five stands displayed a moderate differentiation ( F_ST = 0.14 ± 0.02), although the urban remnants clustered with two of the bushland stands. These patterns may be explained by high levels of selfing and inbreeding in this species and by long-distance dispersal (several seeds in the urban stand were fathered by plants in other stands). Genetic leakage (gene flow) from exotic plants to 321 seeds on surrounding remnant or bushland plants has not occurred. Our results demonstrate the conservation value of this group of urban plants, which are viable, productive, genetically diverse, and interconnected with bushland plants. Gene flow has apparently not yet led to genetic contamination of bushland populations, but high levels of inbreeding would make this a rare event and difficult to detect. Remnant plants in urban gardens could successfully contribute to recovery plans for endangered and vulnerable species.     

Predicting the Range of Chinese Mitten Crabs in Europe

Abstract:  Ecological niche modeling provides a means for predicting the potential future distribution of a nonindigenous species based on environmental characteristics of the species' native range. We applied this method to the Chinese mitten crab (Eriocheir sinensis) , a catadromous crustacean with a long history of invasion in Europe. We used genetic algorithm for rule-set prediction to predict the potential European distribution of mitten crab based on its distribution in 42 locations in its native Asia. The climatic variables, air temperature, number of days, amount of precipitation, and wetness index, contributed significantly to predictions of native distribution limits. Although the genetic algorithm for rule-set prediction model was developed for the native range, the species' extensive distribution in Europe ( n = 434) allowed independent validation of the predictions. Application of the model to Europe was successful, with 84% of occurrences in regions predicted to be suitable by >80% of the models and <4% of occurrences in areas predicted suitable by <50% of the models (mainly along the northern range). At the watershed scale, areas with established mitten crab populations had significantly higher habitat matching than sites that were not invaded. The independent validation of the Asian-based model by the European distribution revealed that predictions were highly accurate. The model also identified large areas of Europe, particularly along the Mediterranean coast, as vulnerable to future invasion. These predictions can be used to develop strategies to control the spread of mitten crab by preventing introductions into vulnerable areas.     

THE ECONOMICS OF RENEWABLE ENERGY SYSTEMS FOR DEVELOPING COUNTRIES

In many parts of the Third World, projects are being developed to test such renewable energy systems as biogas plants and solar cell arrays for powering pumps and grinders. Virtually nowhere, however, has adequate work been done to determine if these systems are worth their costs. This paper outlines the cost-benefit techniques which allow systems to be evaluated from the standpoint of individual buyers (financial analysis) and the society as a whole (economic analysis). Special attention is given to problems of particular importance in reviewing energy systems, including local measurement of costs and benefits, determination of investors' discount rates, shadow-pricing and allowance for social costs. Detailed cost-benefit analyses are provided for two representative systems: a family-scale Indian biogas plant and a 5.5 kW solar cell irrigation pump on the borders of Lake Chad. The family-scale biogas plant does not appear to be profitable in either financial or economic terms under any plausible sets of assumptions. The solar cell pump has positive net benefits by economic (if not financial) measures, but is unlikely soon to be competitive with diesel power for most applications. At best, some of these devices might ultimately become competitive with expensive commercial energy. Such devices will therefore be of interest first to people now using substantial amounts of such energy – that is, the relatively wealthy. Only much later might significant benefits begin to filter down to the poor. In the light of these findings renewed attention should be given to meeting basic energy needs through less sophisticated systems. By finding systems whose benefits are commensurate with their costs, and whose costs are within reach of the poor, it may be possible to provide more energy to those most in need of it. Dans de nombreuses parties du Tiers Monde, des projets sont en cours d'exécution en vue d'évaluer des systèmes en matière d'énergie de remplacement, tels que des usines de gaz de fermentation et des assemblages de cellules solaires pour activer pompes et broyeurs. Toutefois, il semblerait qu'il n'y ait eu nulle part aucune étude valable permettant de déterminer si ces systèmes justifient leur coût. Cet article relève les techniques de coût-utilité qui permettent d'évaluer ces systèmes du point de vue des acheteurs individuels (analyse financière) et de la société dans son ensemble (analyse économique). En analysant ces systèmes, l'article souligne des problèmes d'importance particulière, y compris l'évaluation locale des coûts et profits, la détermination des taux d'actualisation d'investissement, l'estimation des prix virtuels et l'établissement de marges de coûts sociaux. Des analyses détaillées de coût-utilité sont présentées pour deux systèmes concrets: une usine de gaz de fermentation indienne à l'échelle de la famille, et une pompe d'irrigation à cellules solaires de 5,5 kW sur les rives du lac Chad. L'usine de gaz de fermentation à l'échelle de la famille ne semble ni financièrement, ni économiquement rentable quelque soient les termes plausibles des hypothèses. La pompe à cellules solaires offre des profits positifs nets selon des critères économiques (sinon financiers) mais, dans la plupart des cas, elle ne semble pas pouvoir concurrencer le moteur diesel dans un proche avenir. Au mieux, quelques-unes de ces installations peuvent à la longue concurrencer l'énergie commerciale à prix élevé. Par conséquent, elles seront d'intérêt particulier tout premièrement aux usagers de grande quantité de cette énergie, c'est-à-dire ceux possédant des moyens relativement élevés. Ce n'est que bien plus tard que les classes défavorisées pourront commencer à bénéficier sensiblement des profits qui en résulteront. Sur la base de ces données, les organisations s'intéressant aux classes défavorisées peuvent se pencher à nouveau sur la manière de répondre aux besoins essentiels en matière d'énergie en utilisant des systèmes plus simples: bois appartenant aux villages, fours à bois améliorés, pompes et broyeurs à pédales ou à bras, pompes foulantes hydrauliques, etc. En conçevant des systèmes dont les profits sont proportionnels aux coûts et dont les coûts sont à la portée des classes défavorisées, il se peut que l'on puisse mettre plus d'énergie à la disposition de ceux qui en ont le plus besoin. En muchas partes del Tercer Mundo se han llevado a cabo proyectos para ensayar sistemas de energía renovables tales como plantas de biogas, y celdas solares para operar bombas y molinos. Sin embargo practicamente en ninguna parte se ha hecho el esfuerzo apropiado para determinar si estos sistemas valen lo que cuestan. Este artículo esboza las técnicas de beneficio-costo para evaluar dichos sistemas desde el punto de vista del usuario individual (análisis financiero) y del de la sociedad como un todo (análisis económico). Se da especial atención a los problemas de importancia particular en el análisis de sistemas de energía, incluyendo mediciónes locales de costos y beneficios, determinación de la tasa de descuento del inversionista, precios-sombra y costos sociales. Detallados análisis de beneficio-costo se proveen para dos sistemas representativos: una planta de biogas en escala familiar y una bomba de agua operada por celadas solares de 5.5 kW al borde del Lago Chad. La planta de biogas a escala familiar parece no ser rentable financieramente ni económicamente bajo ninguna serie de hipótesis realistas. La bomba de celdas solares tiene un benefico económico positivo (aunque no financiero), pero es poco provable que sea competitivo con el motor diesel para la mayoría de las aplicaciones. En el mejor de los casos, alguno de estos sistemas pueden ser competitivos con una energía comercial cara. Estos sistemas en consecuencia serán de gran interés primeramente para las personas que hacen uso intensivo de energía, esto es, las personas relativamente adineradas. Pueda qui solo mucho despues beneficios significativos lleguen a los pobres. A la luz de estos resultados debe ponerse renovada atención a satisfacer las necesidades básicas de energía a través de sistemas menos sofisticados. Pueda que sea posible proveer mas energía a los que más necesitan de ella si se buscan sistemas cuyo beneficios sea proporcionados a sus costos y que dichos costos esten al alcance de los pobres.     

Vectors and Timing of Freshwater Invasions in Great Britain

Abstract: Nonindigenous freshwater species cause large ecological and economic impacts in Great Britain. In response the government is in the process of implementing a broad, new nonindigenous species strategy. We assembled a list of all nonindigenous freshwater species that are or were established in Great Britain, their date of first record, and their vector of introduction. This list provides a baseline against which the success of new policies can be assessed. Because the biota of Great Britain has been well recorded, our results provide a highly resolved case study of the vectors and drivers of species transport and establishment. A total of 117 nonindigenous freshwater species are currently established in Great Britain; a further 17 species were once established but are now extirpated. Between 1800 and 2000 the number of established species increased at an accelerating rate, and this increase correlated with the growth in human population and gross domestic product. The construction of large reservoirs in Great Britain occurred over a short period and overlapped high rates of new species establishment, indicating that habitat modification may have been an important driver of establishment. Nonindigenous species now account for 24% of fish, 12% of plant, 54% of amphibian, and 88% of decapod crustacean freshwater species richness in Great Britain. The ornamental trades have been responsible for the greatest percentages of intentionally (73%) and unintentionally (34%) introduced species that have become established. Shipping and aquaculture have also been strong vectors. These vectors should be prioritized for management within the new nonindigenous species strategy.     

Assessing the Threat Status of Ecological Communities

Abstract: Conservationists are increasingly interested in determining the threat status of ecological communities as a key part of their planning efforts. Such assessments are difficult because of conceptual challenges and a lack of generally accepted criteria. We reviewed 12 protocols for assessing the threat status of communities and identified conceptual and operational issues associated with developing a rigorous, transparent, and universal set of criteria for assessing communities, analogous to the International Union for Conservation of Nature (IUCN) Red List standards for species. We examined how each protocol defines a community and its extinction and how each applies 3 overarching criteria: decline in geographic distribution, restricted geographic distribution, and changes to ecological function. The protocols vary widely in threshold values used to assess declines and distribution size and the time frames used to assess declines, leading to inconsistent assessments of threat status. Few of the protocols specify a scale for measuring distribution size, although assessment outcomes are highly sensitive to scale. Protocols that apply different thresholds for species versus communities tend to require greater declines and more restricted distributions for communities than species to be listed in equivalent threat categories. Eleven of the protocols include a reduction in ecological function as a criterion, but almost all assess it qualitatively rather than quantitatively. We argue that criteria should be explicit and repeatable in their concepts, parameters, and scale, applicable to a broad range of communities, and address synergies between types of threats. Such criteria should focus on distribution size, declines in distribution, and changes to key ecological functions, with the latter based on workable proxies for assessing the severity, scope, and immediacy of degradation. Threat categories should be delimited by thresholds that are assessed at standard scales and are logically consistent with the viability of component species and important ecological functions.     

Increased Infectious Disease Susceptibility Resulting from Outbreeding Depression

Abstract:  The mechanisms by which outbreeding depression leads to reduced fitness are poorly understood. We considered the hypothesis that outbreeding can depress fitness by increasing the susceptibility of hybrid individuals and populations to infectious disease. Competitive breeding trials in experimental ponds indicated that outbred largemouth bass (  Micropterus salmoides ) crossed from two geographically and genetically distinct populations suffered a reduction in fitness of approximately 14% relative to parental stocks. We measured the comparative susceptibility of these same outbred stocks to a novel viral pathogen, largemouth bass virus. Following experimental inoculation, F2 generation hybrids suffered mortality at a rate 3.6 times higher than either F1 generation hybrids or wild-type parental fish. Analysis of viral loads indicated that viral replication was more rapid in F2 fish than in F1 hybrids or wild-type parental fish. We attribute these results to the disruption of coadapted gene complexes in the immune systems of outbred fish in the F2 generation. Increased susceptibility to infectious disease may be an important but underappreciated mechanism by which outbreeding reduces the fitness of individuals and populations and by which novel infectious diseases emerge in populations of hybrid organisms.