Investigating environmental variation and landscape characteristics of an urban–rural gradient using woodland carabid assemblages

Aim To investigate environmental variation and associated assemblage changes of carabid beetles along an urban–rural gradient. Location ‘Quercus–Acer’ (oak–sycamore) woodlands in the city of Birmingham, UK. Methods We collected carabid data using pitfall traps on 12 sites in the city. The traps were run from April–September in 2000, and we collected environmental data on 24 individual variables associated with the individual sites and their landscape context. Changes in carabid assemblages were analysed using repeat measures anova and the environment–species relationships with a Redundancy Analyses (RDA) and Generalized Linear Modelling (GLM). Results We found that: (1) species richness and diversity were lower in the urban and suburban zone and higher in the rural zone; (2) Berger Parker dominance index was higher in the urban and suburban zones; (3) the number of woodland and woodland associated species was significantly higher at the rural end of the gradient; (4) the number of short‐winged (brachypterous) species was highest in the rural zone and decreased towards the urban woodlands, whereas the long‐winged species were more abundant in suburban woodlands; (5) the median weight length (WML) of the assemblage declined along the gradient from the rural to the urban zone, as did the number of large species; and (6) five of the 24 environmental variables showed a significant relationship with variation in the carabid assemblage. At site level the carabid assemblages were related to the level of site disturbance and soil penetrability, whereas site size and amount of woodland and urban land within 5 km of the site were important at a larger landscape scale. Main conclusions The results suggest that urbanization has a deleterious impact on carabid assemblages, causing a reduction in species richness from the rural fringe to the centre of the city. Changes in assemblage structure were related to woodland fragmentation, which led to variations in woodland size, woodland location and site disturbance due to trampling. Large, flightless and specialist woodland species are more susceptible to changes associated with urbanization, presumably due to their longer life spans, lower reproductive rates, more specialized niches and more limited dispersal potential.     

Edge effects reduce the nesting success of Acadian Flycatchers in a moderately fragmented forest

ABSTRACT.   Forest fragmentation can create negative edge effects that reduce the reproductive success of birds nesting near the forest/nonforest interface, and threaten bird populations deeper in remnant forest habitats. Negative edge effects may be more pronounced in landscapes that are moderately fragmented, particularly where agriculture is the primary land-use fragmenting forests. Information about the extent and strength of edge effects at a site can help guide conservation actions, and determine their effectiveness. We examined edge effects for birds breeding in a nearly contiguous forest fragmented by relatively narrow agricultural corridors in Illinois (USA). We measured rates of nest predation and brood parasitism for Acadian Flycatchers ( Empidonax virescens ) over a continuum of distances from the edge of an agricultural inholding. Nest predation and brood parasitism were highest near the edge and decreased with increasing distance from the edge. Given the cumulative effects of nest predation and brood parasitism on reproductive success, we determined that forest within 600 m of the inholding was sink habitat. We found, however, that deeper forest interior areas currently serve as source habitat, and that conversion of the entire 205 ha agricultural corridor to forest would add 1350 ha of source habitat for Acadian Flycatchers. Such results provide support for a local conservation strategy of forest consolidation and establish baseline measures necessary to determine the relative effectiveness of any subsequent reforestation efforts.     

Measuring and modeling dispersal of adult zooplankton

Habitat fragmentation poses an inherent problem for metacommunity dynamics, as dispersal among communities is hindered by increasing isolation and the loss of patches. Wetlands are one such system that have undergone excessive destruction and fragmentation in recent years. Zooplankton within these communities have historically been considered frequent and widespread dispersers, but direct, quantitative measures of zooplankton dispersal are rare. In this study, I performed two experiments to quantify zooplankton dispersal and to identify the primary dispersal vectors. I first set up an array of traps at 10, 30, 60, 120 and 180 m around an isolated pond to collect dispersing individuals. Nearly 1,500 adult zooplankton were captured in traps up to 180 m from the pond, with approximately 60% of dispersers being captured in traps at 10 m from the pond. A second experiment using open and animal-excluded traps suggested that large animals were the primary dispersal vector for these zooplankton. Using a subset of these data, I fit four models to describe the shape and magnitude of adult cladoceran dispersal at this site. All models showed the majority of cladocerans were deposited very close to the source pond, with three models suggesting that the trapping area encompassed 67% or more of the dispersal distances. These results suggest that adult zooplankton movement among ponds may be significant in areas where aquatic habitats are plentiful. Yet, in recent years climate change and anthropogenic disturbances have reduced the number and size of aquatic habitats in many regions of the world, likely curtailing effective transport of individuals in many cases. As a result, fragmented zooplankton metacommunities may experience increased dispersal limitation, stronger priority effects, higher levels of inbreeding and selection against traits engendering high dispersability. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Molecular basis of guanine nucleotide dissociation inhibitor activity of human neuroglobin by chemical cross-linking and mass spectrometry

Oxidized human neuroglobin (Ngb), a heme protein expressed in the brain, has been proposed to act as a guanine nucleotide dissociation inhibitor (GDI) for the GDP-bound form of the heterotrimeric G protein alpha-subunit (Galpha(i)). Here, to elucidate the molecular mechanism underlying the GDI activity of Ngb, we used an glutathione-S-transferase pull-down assay to confirm that Ngb competes with G-protein betagamma-subunits (Gbetagamma) for binding to Galpha(i), and identified the Galpha(i)-binding site in Ngb by chemical cross-linking with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and sulfo-N-hydroxysuccinimide, coupled with mass spectrometry (MS). Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) MS analysis for tryptic peptides derived from the cross-linked Ngb-Galpha(i) complex revealed several binding regions in Ngb. Furthermore, MALDI-TOF/TOF MS analysis of the cross-linked Ngb and Galpha(i) peptides, together with the MS/MS scoring method, predicted cross-linking between Glu60 (Ngb) and Ser206 (Galpha(i)), and between Glu53 (Ngb) and Ser44 (Galpha(i)). Because Ser206 of Galpha(i) is located in the region that contacts Gbetagamma, binding of Ngb could facilitate the release of Gbetagamma from Galpha(i). Binding of Ngb to Galpha(i) would also inhibit the exchange of GDP for GTP, because Ser44 (Galpha(i)) is adjacent to the GDP-binding site and Glu53 (Ngb), which is cross-linked to Ser44 (Galpha(i)), could be located close to GDP. Thus, we have identified, for the first time, the sites of interaction between Ngb and Galpha(i), enabling us to discuss the functional significance of this binding on the GDI activity of Ngb.     

近50年陕西凤县林麝分布区的变迁

于2005年夏季和2006年春季,采用问卷调查结合野外实地验证,对陕西风县林麝(Moschus berezovskii)的现时及历史分布进行了分析,并将所得分布信息叠加至数字化地图,绘制成林麝近50年的分布区变迁图.结果表明:历史上,凤县是秦巴山区林麝的主要分布区之一,从20世纪80年代初开始,该县林麝数量大幅下降,至今分布区已严重萎缩并破碎化,总分布面积减少至50年前的1/3;目前林麝分布区主要在相对偏远、人为干扰较少的乡与乡的交界和县的边缘地区,分布区被人类聚居地及主要公路所隔离.造成这种现状的主要原因是过度捕杀、森林减少及道路建设.     

High levels of variation despite genetic fragmentation in populations of the endangered mountain pygmy-possum, Burramys parvus, in alpine Australia

In endangered mammals, levels of genetic variation are often low and this is accompanied by genetic divergence among populations. The mountain pygmy-possum (Burramys parvus) is an endangered marsupial restricted to the alpine region of Victoria and New South Wales, Australia. By scoring variation at eight microsatellite loci, we found that B. parvus populations exhibit high levels of genetic divergence and fall into three distinct groups from the northern, central and southern areas of the distribution of this species, consistent with previous assessments of mitochondrial DNA variation. F(ST) values between populations from these regions ranged from 0.19 to 0.54. Within the central area, there was further genetic fragmentation, and a linear association between genetic and geographical distance. This pattern is likely to reflect limited dispersal across barriers despite the fact that individual B. parvus can move several kilometres. Levels of genetic variation within populations were high with the exception of a southern population where there was evidence of inbreeding. From a conservation perspective, all three areas where B. parvus are found should be considered as separate gene pools; management of populations within these areas needs to take into account the low gene flow between populations, as well as threats posed by roads, resorts and other developments in the alpine region. The low genetic variability and inbreeding in the southern population is of particular concern given the high levels of variability in other B. parvus populations.     

Population genetics of the wood-decay fungus Phlebia centrifuga P. Karst. in fragmented and continuous habitats

The basidiomycete Phlebia centrifuga is a wood-decay fungus characteristic for unmanaged old-growth forests of spruce, a habitat that has become increasingly fragmented due to forest management. The aim of this study was to investigate the genetic population structures of P. centrifuga in both continuous and fragmented habitats, and estimate the potential impact of fragmentation on the genetic diversity of the fungus. Three hundred fifteen single spore isolates (representing 47 spore families and 33 single isolates) from eight populations across northern Europe (Russia, Finland, and Sweden) were screened with seven microsatellite markers and arbitrary primed polymerase chain reaction with the M13 minisatellite. The two molecular methods generally gave the same pattern for the genetic population structure. There were no significant differences between the observed and the expected heterozygosities, and the inbreeding coefficient (FIS) did not indicate any inbreeding. The fixation index (FST) revealed a general pattern with little to moderate genetic differentiation for the majority of populations, while the southernmost Swedish population Norra Kvill was the only one showing high differentiation from about half of the other populations. Swedish population Fiby with the shortest distance to the continuous habitat was moderately differentiated from most of the others and to the largest extent differed from geographically closest population of Norra Kvill. The results indicate that the fragmentation of old-growth forest in Russia and Finland is more recent than the fragmentation in Sweden, and the genetic population structures of P. centrifuga in northern Europe might be related to differences in forest landscape dynamics between the two areas.     

Composition of the pollinator community,pollination and the mating system for a shrub in fragments of species rich kwongan in south-west Western Australia

In this study we investigate the composition of the potential honeyeater pollinator community, patterns of honeyeater visitation, pollination and the mating system in a range of population fragments for the bird-pollinated mixed mating system shrub Calothamnus quadrifidus R.Br. Specifically, we aimed to answer the following questions. For smaller and more isolated population fragments are honeyeater species lost from the pollinator community, patterns of visitation different, levels of pollination lower and rates of selfing, biparental inbreeding and correlated paternity higher. The composition of the honeyeater community was similar across population fragments and there was no relationship between the abundance of birds and population fragment size. Honeyeaters were most commonly observed visiting numerous inflorescences within single plants in all populations, but as population fragments became larger movements between plants were more commonly observed. Our observations of honeyeater visitation were generally consistent with our measurements of pollination and patterns in the mating system across population fragments. We found no significant relationship between population fragment size and levels of pollination. Mating system studies showed outcrossing rates (t _m) comparable to those found in other bird-pollinated Myrtaceae, and ranged from 0.54 to 0.90 across populations. Outcrossing rates were not significantly correlated with log population size, but correlations of outcrossed paternity indicate a clear trend from low correlated paternity in larger populations to significantly higher correlated paternities in smaller populations. As a consequence mating in small populations will occur between much smaller groups of plants, and this may affect population fitness in subsequent generations.