Search

We asked whether wolf re-colonization would facilitate increased growth and reproduction of three browse-sensitive plant species. We hypothesized plant size and the proportion of reproductive individuals would be lowest in areas with no wolves, intermediate where wolves had been present for 4-6 years, and highest where wolves had been present for 12-13 years. Two plant species exhibited significantly greater reproduction where wolves were present for 12-13 years. Mean leaf size of indicator plants was significantly greater in areas where wolves were present for 12-13 years, as compared with that in areas where wolves were not present or were present for 4-6 years, but the effect size appears small. While the return of wolves to this region is likely to benefit browse-sensitive plant species, our findings suggest that wolf recovery will not generate atrophic cascade of sufficient magnitude to halt or reverse the loss of plant diversity in the Great Lakes region in the near term. [ABSTRACT FROM AUTHOR]

Purpose: Neuroinflammation is involved in neurological disorders through the activation of microglial cells. Imaging of neuroinflammation with radioligands for the translocator protein (18 kDa) (TSPO) could prove to be an attractive biomarker for disease diagnosis and therapeutic evaluation. The indoleacetamide-derived 7-chloro- N, N,5-trimethyl-4-oxo-3-phenyl-3,5-dihydro-4 H-pyridazino[4,5- b]indole-1-acetamide, SSR180575, is a selective high-affinity TSPO ligand in human and rodents with neuroprotective effects. Methods: Here we report the radiolabelling of SSR180575 with C and in vitro and in vivo imaging in an acute model of neuroinflammation in rats. Results: The image contrast and the binding of [C]SSR180575 are higher than that obtained with the isoquinoline-based TSPO radioligand, [C]PK11195. Competition studies demonstrate that [C]SSR180575 has high specific binding for the TSPO. Conclusion: [C]SSR180575 is the first PET radioligand for the TSPO based on an indoleacetamide scaffold designed for imaging neuroinflammation in animal models and in the clinic. [ABSTRACT FROM AUTHOR]

Abstract: When species presence–absence data are analyzed across a range of sites, many communities show a “checkerboard distribution” in which two or more species do not co-occur despite sharing geographic ranges and habitat requirements. It is not clear how the loss of native species might shift the underlying checkerboard structure. I tracked changes in the incidence of 175 vascular plant species across 59 sites in northern Wisconsin that have declined in species density between 1950 and 2000. Based on C-scores and the number of perfect checkerboard distributions, there was significant co-occurrence structure in both time periods. The nature of that structure depended on the particular null model was constructed. When only row values are fixed, plant species showed greater degrees of co-occurrence than the null model predicted, while fixing both rows and columns yielded less co-occurrence than found in the null model. Changes in species density did not strongly influence co-occurrence patterns, reflecting relative stability of co-occurrence patterns over a 50-year interval. This suggests that minor losses of species will not necessarily lead to fundamental changes in co-occurrence structure. [Copyright &y& Elsevier]

We resurveyed the under- and overstory species composition of 94 upland forest stands in southern Wisconsin in 2002-2004 to assess shifts in canopy and understory richness, composition, and heterogeneity relative to the original surveys in 1949-1950. The canopy has shifted from mostly oaks (Quercus spp.) toward more mesic and shade-tolerant trees (primarily Acer spp.). Oak-dominated early-successional stands and those on coarse, nutrient-poor soils changed the most in canopy composition. Understories at most sites (80%) lost native species, with mean species density declining 25% at the 1-m² scale and 23.1% at the 20-m² scale. Woody species have increased 15% relative to herbaceous species in the understory despite declining in absolute abundance. Initial canopy composition, particularly the abundance of red oaks (Quercus rubra and Q. velutina), predicted understory changes better than the changes observed in the overstory. Overall rates of native species loss were greater in later-successional stands, a pattern driven by differential immigration rather than differential extirpation. However, understory species initially found in early-successional habitats declined the most, particularly remnant savanna taxa With narrow or thick leaves. These losses have yet to be offset by compensating increases in native shade-adapted species. Exotic species have proliferated in prevalence (from 13 to 76 stands) and relative abundance (from 1.2% to 8.4%), but these increases appear unrelated to the declines in native species richness and heterogeneity observed. Although canopy succession has clearly influenced shifts in understory composition and diversity, the magnitude of native species declines and failure to recruit more shade-adapted species suggest that other factors now act to limit the richness, heterogeneity, and composition of these communities. [ABSTRACT FROM AUTHOR]

Ongoing species invasions and extinctions are changing biological diversity in different ways at different spatial scales. Biotic homogenization (or BH) refers to the process by which the genetic, taxonomic or functional similarities of regional biotas increase over time. It is a multifaceted process that encompasses species invasions, extinctions and environmental alterations, focusing on how the identities of species (or their genetic or functional attributes) change over space and time. Despite the increasing use of the term BH in conservation biology, it is often used erroneously as a synonym for patterns of species invasions, loss of native species or changes in species richness through time. This reflects the absence of an agreed-upon, cogent definition of BH. Here, we offer an operational definition for BH and review the various methodologies used to study this process. We identify the strengths and weaknesses of these approaches, and make explicit recommendations for future studies. We conclude by citing the need for researchers to: (1) consider carefully the definition of BH by recognizing the genetic, taxonomic and functional realms of this process; (2) recognize that documenting taxonomic homogenization requires tracking the identity of species (not species richness) comprising biotas through space and time; and (3) employ more rigorous methods for quantifying BH. [ABSTRACT FROM AUTHOR]

Deer have expanded their range and increased dramatically in abundance worldwide in recent decades. They inflict major economic losses in forestry, agriculture, and transportation and contribute to the transmission of several animal and human diseases. Their impact on natural ecosystems is also dramatic but less quantified. By foraging selectively, deer affect the growth and survival of many herb, shrub, and tree species, modifying patterns of relative abundance and vegetation dynamics. Cascading effects on other species extend to insects, birds, and other mammals. In forests, sustained overbrowsing reduces plant cover and diversity, alters nutrient and carbon cycling, and redirects succession to shift future overstory composition. Many of these simplified alternative states appear to be stable and difficult to reverse. Given the influence of deer on other organisms and natural processes, ecologists should actively participate in efforts to understand, monitor, and reduce the impact of deer on ecosystems. [ABSTRACT FROM AUTHOR]

Ecological change is often hard to document because of a lack of reliable baseline data. Several recent then-versus-now surveys of temperate forest and grassland communities demonstrate losses of local plant species, but most are based on data from a single site. We resurveyed understory communities in 62 upland forest stands in northern Wisconsin (U.S.A.) for which quantitative baseline data exist from 50 years ago. These stands are within a largely unfragmented region but vary in species composition and successional stage. We collected data on changes in (1) total and native species richness, (2) the ratio of exotic to native species, (3) the relative abundance of habitat generalists, and (4) community similarity among sites. We also compared how these rates of change varied over time. Over the past 50 years, native species density declined an average of 18.5% at the 20-m2 scale, whereas the ratio of exotic species to native species increased at 80% of all sites. Habitat generalists increased, and habitat specialists declined, accounting in part for an 8.7% rise in average similarity in species composition among sites. Most of these changes cannot be related to succession, habitat loss, or invasion by exotic species. Areas without deer hunting showed the greatest declines in native species density, with parks and research natural areas faring no better than unprotected stands. Animal-pollinated and animal-dispersed species also declined, particularly at unhunted sites. These results demonstrate the power of quantitative multistand data for assessing ecological change and identify overabundant deer as a key driver of community change. Because maintaining forest habitats alone fails to preserve plant diversity at local scales, local biotic simplification seems likely to continue in the region unless active efforts are taken to protect diversity. [ABSTRACT FROM AUTHOR]

When white-tailed deer populations reach high densities, they have negative and often dramatic effects on forest herb populations. However, it is not clear how deer affect the demographic processes of plant populations. We examined how the structure and dynamics of Trillium grandiflorum (Michx.) Salisb. populations are affected by deer browsing in the Upper Great Lakes region by sampling populations from nine study sites in a forested landscape in 1998 and 1999. We constructed a stage-based matrix population model for the regional population. Our model indicated that the long-term growth rate of the population to be -3.56% per year (λ = 0.965). Mortality rates were highest for seeds (97.5%) followed by seedlings (29.1%), and lower for all remaining stage classes (4.9 to 8.5%). The observed stage distribution significantly differed from the stable stage distribution, and the damping ratio (ρ = 1.103) indicated the population would not reach its stable stage distribution anytime soon. In the absence of deer browsing, the long-term growth rate would improve to between -3.46% and -1.61% per year. A moderate drought during the study could account for the negative population growth rate, but deer browsing accelerates the rate of decline. Population growth is most sensitive to the proportion of plants remaining in the nonflowering stage, and deer browsing reduces this proportion. Browsing damage was relatively low in this study (5.4% of stems in 1998, 11.5% in 1999) compared to another study of browsing impacts on T. grandiflorum, indicating deer could have far more severe demographic consequences in populations subject to higher levels of browsing. [ABSTRACT FROM AUTHOR]

Examines the Floristic Quality Index (FQI) used to estimate the significance of a natural area based on the identity of species present and the degree to which those species reflect nondegraded conditions. Advantages of the modified FQI approach; Two independent components of the approach, namely, the C values of the individual species in the survey and the number of species present in the survey.

The article discusses various aspects related to regional variations associated with recruitment of hemlock seedlings and saplings, in the U.S. It states that data from various geographically restricted studies, which analysed the cause low seedling or sapling density, was analysed and a positive correlation was observed between availability of sunlight and plant growth.