Identifying indicators and quantifying large-scale effects of dams on fishes

Although localized effects of individual dams on stream fish assemblages have been relatively well-studied, less is known about the effects of multiple dams within a stream network on fishes and the patterns that emerge when the combined effects of individual and multiple dams are viewed across entire river basins, ecoregions, and states. This study evaluated multiple stream network fragmentation metrics representing localized (e.g., distance-to-dams) and cumulative (e.g., total upstream reservoir storage) dam influences on streams in Michigan, Wisconsin, and Minnesota, developing an approach for identifying suitable fish indicators of dam effects. We used change point and correlation analyses to determine associations of stream fish catch per unit effort and various stream network fragmentation metrics with data from more than 2000 fish survey sites stratified by stream size, thermal regime, and ecoregion. Of the identified indicator species, predominantly warmwater, large river, and/or lentic species were positively associated with stream network fragmentation, whereas cold and coolwater lotic species were negatively associated with fragmentation. These results suggest a combination of downstream thermal effects and upstream influences from impoundments generated by dams. Variance partitioning analyses based on identified indicator species revealed greater upstream-dominated dam influences in headwaters than mid-sized streams, and a greater relative influence of dams vs. other non-dam anthropogenic influences in cold streams than warm streams. Overall, a combination of localized and cumulative fragmentation metrics, as well as upstream and downstream-oriented measures, were influential in indicator species responses, emphasizing the importance of selecting a diversity of fragmentation metrics when assessing effects of dams on stream fishes. Understanding multiple dam influences on stream fishes, including localized effects from individual dams and cumulative effects from all dams within a river basin, would provide useful information for a variety of management activities, including dam operation and dam removal prioritization. Dams significantly affect conservation and management options for stream fishes, with identification of multi-scale dam influences on fishes being critical to restoration and maintenance of aquatic biodiversity throughout the world.     

Determinants of Land Degradation and Fragmentation in Semiarid Vegetation at Landscape Scale

The objective of this paper was to investigate the sensitivity to degradation of semiarid plant communities in terms of plant cover and fragmentation, quantifying relationships between landscape characteristic (physical, socio-economical and historical) and vegetation degradation. The degradation of vegetation was measured as the degree of coverage of the two dominant vegetation types (i.e. tall arid brush and tall grass steppe), while fragmentation was measured as patch size and isolation. Data were obtained using GIS tools, and analyzed by logistic regression and linear multivariate regression. Results showed denser coverage at more elevated, gradual slopes that were not sea-oriented. Historical elements of the landscape had a significant effect on current natural vegetation. According to the fragmentation patterns, the vegetation is in fairly good condition (medium coverage had the largest patches but dense coverage was less isolated) but attention must be given to preserve vegetation, due to the relationships between fragmentation and human activities. Moreover, the protection plan under way in the area appeared to favour denser vegetation cover, while human activities had a measurable effect on vegetation degradation.     

Species richness and composition of amphibians and reptiles in a fragmented forest landscape in northeastern Bolivia

We quantified patterns of species richness and species composition of frogs and reptiles (lizards and snakes) among three habitats (continuous forest, forest islands, and a seasonally flooded savannah) and between forest island size and isolation classes in a floristic transition zone in northeastern Santa Cruz Department, Bolivia. Species richness was similar across macrohabitats, as was faunal composition of forested habitats, although savannah harbored a distinct herpetofauna. On forest islands, richness and composition of forest frogs was largely related to isolation, whereas reptiles were affected by both isolation and habitat. The observation that isolation rather than area was the primary driver of distribution patterns on forest islands stands in contrast to many studies, and may be a function of (1) the greater range in forest island isolation values compared to area or (2) the long history of isolation in this landscape.     

Combining population monitoring with habitat vulnerability to assess conservation status in populations of rare and endangered plants

In this paper, we propose an integrative framework to assess the conservation status of rare plant populations that combines population trends with four criteria to assess habitat vulnerability. We illustrate how population trends can be studied using a presence/absence method for a species that is inappropriate for a demographic study. The four other criteria concern habitat fragmentation, the human footprint in the surrounding landscape, observed impacts on a population and elements of habitat structure and quality that may impinge on population status. Each criterion is assessed with various indicators that can be adapted to the biology and ecology of the studied species. To test the feasibility of the proposed framework, we perform a case study of a Mediterranean geophyte Allium chamaemoly L., a species listed for protection in France. The results show a wide range of conservation status among a regional set of populations in the study species. Variation among the indicators used to assess different criteria illustrates the importance of assessing a range of different factors and ways to combine them if population conservation status is to be objectively identified. The study of diverse criteria may allow for a more precise assessment of the causes of differences in conservation status among populations of a single species. The framework of five criteria could be adapted by modification or substitution of indicators or adaptation of thresholds among classes, and thus be applied to other species of conservation importance.     

Area-dependent migration by ringlet butterflies generates a mixture of patchy population and metapopulation attributes

Interpretation of spatially structured population systems is critically dependent on levels of migration between habitat patches. If there is considerable movement, with each individual visiting several patches, there is one ”patchy population”; if there is intermediate movement, with most individuals staying within their natal patch, there is a metapopulation; and if (virtually) no movement occurs, then the populations are separate (Harrison 1991, 1994). These population types actually represent points along a continuum of much to no mobility in relation to patch structure. Therefore, interpretation of the effects of spatial structure on the dynamics of a population system must be accompanied by information on mobility. We use empirical data on movements by ringlet butterflies, Aphantopus hyperantus, to investigate two key issues that need to be resolved in spatially-structured population systems. First, do local habitat patches contain largely independent local populations (the unit of a metapopulation), or merely aggregations of adult butterflies (as in patchy populations)? Second, what are the effects of patch area on migration in and out of the patches, since patch area varies considerably within most real population systems, and because human landscape modification usually results in changes in habitat patch sizes? Mark-release-recapture (MRR) data from two spatially structured study systems showed that 63% and 79% of recaptures remained in the same patch, and thus it seems reasonable to call both systems metapopulations, with some capacity for separate local dynamics to take place in different local patches. Per capita immigration and emigration rates declined with increasing patch area, while the resident fraction increased. Actual numbers of emigrants either stayed the same or increased with area. The effect of patch area on movement of individuals in the system are exactly what we would have expected if A. hyperantus were responding to habitat geometry. Large patches acted as local populations (metapopulation units) and small patches simply as locations with aggregations (units of patchy populations), all within 0.5 km². Perhaps not unusually, our study system appears to contain a mixture of metapopulation and patchy-population attributes.     

2‐(2‐Nitrovinyl)furan Promotes Oxidation of Cellular Proteins,Lipids, and DNA of Male Rat Liver and Kidney

The effect of 2‐(2‐nitrovinyl)furan on the redox status of male rat liver and kidney was evaluated. Twenty male rats were randomized into four groups; group A received olive oil and groups B, C, and D rats received 12.5, 25, and 50 mg/kg bodyweight of 2‐(2‐nitrovinyl)furan intraperitoneally, daily at 24 h interval, respectively, for 14 days. 2‐(2‐Nitrovinyl)furan significantly reduced (P < 0.05) alkaline phosphatase, alanine, and aspartate aminotransferase activities in male rat liver and kidney with a corresponding increase in serum. The activities of superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, and levels of reduced glutathione/glutathione disulfide (GSSG) ratio in the liver and kidney of 2‐(2‐nitrovinyl)furan‐treated rats decreased significantly (P < 0.05). In contrast, GSSG, protein carbonyl, conjugated dienes, lipid hydroperoxides, malondialdehyde, and fragmented DNA (%) in 2‐(2‐nitrovinyl)furan‐treated rats increased significantly (P < 0.05). Overall, data from this study revealed that 2‐(2‐nitrovinyl)furan exhibited its toxic effect by suppressing or depleting the antioxidant systems.     

Asexual reproduction, habitat colonization and habitat maintenance in bryophytes

Asexual reproduction s. l. is widespread in plants and also a basic reproductive mechanism in bryophytes. Today, three types of asexual reproduction are recognized: (1) the asexual reproduction s. str. by regeneration from ± specialized caducous organs (leaves, leaf apices, shoots, branches, bulbils) and by production of specialized propagules (gemmae, protonemal brood cells, tubers), (2) fragmentation of plants, resp. part of plants into ± unspecialized fragments, and (3) clonal reproduction (cloning). The latter occurs in bryophytes by protonema decay, by disintegration of modules, resp. formation of ramets (dividuals, “daughter plants”) that leads to self-cloning or forced-cloning of parts of the gametophyte (shoots, stoloniferous and rhizomatous axes, rhizoid wicks, basiscopic innovation plants). Clonal reproduction (cloning), in former time scarcely noted, gained great interest within the last decade mainly in vascular plants showing clonal growth. This reproduction mechanism is thought to be a keystone factor for asexual reproduction, habitat colonization and habitat maintenance. Species which reproduce clonally are able to colonize and maintain habitats in an effective way by the so-called “consequent vegetative multiplication”. The review presents an overview of the current state of knowledge of asexual reproduction types in bryophytes, with a focus on fragmentation and clonal reproduction (cloning), the mechanisms of habitat colonization and habitat maintenance, which all are of important significance in the dynamic processes of development of bryophyte populations.     

Extent and spatial patterns of grass bald land cover change (1948–2000), Oregon Coast Range,USA

Globally, temperate grasslands and meadows have sharply declined in spatial extent. Loss and fragmentation of grasslands and meadows may impact biodiversity, carbon storage, energy balance, and climate change. In the Pacific Northwest region of North America, grasslands and meadows have declined in extent over the past century. Largely undocumented in this regional decline are the grass balds of the Oregon Coast Range, isolated grasslands in a landscape dominated by coniferous forests. This study was conducted to quantify the spatial extent and patterns of grass bald change. Five balds in the Oregon Coast Range were evaluated using historical aerial photographs and recent digital orthophoto quadrangles (DOQ). Over the time period of study (1948/1953 to 1994/2000), bald area declined by 66%, primarily from forest encroachment. The number and average size of bald vegetation patches declined, while edge density increased. Tree encroachment into balds was inversely related to distance from nearest potential parent trees. Spatial patterns of bald loss may result from a forest to bald gradient of unfavorable environmental conditions for tree establishment and/or seed dispersal limitation. Species dependent on balds may be at risk from loss of bald area and increased fragmentation, although metrics of habitat fragmentation may not reflect species-specific habitat requirements. Tree encroachment patterns and increased bald edge densities suggest increasing rates of bald loss in the future. The remote sensing nature of this study cannot determine the fundamental causes of bald decline, although prior research suggests climate change, cessation of native burning, successional changes in response to prior wildfires, and cessation of livestock grazing all may have potential influence.