Spatial patterns in fish distributions and structure of the ichthyocenosis in the Água Nanci stream,upper Paraná River basin,Brazil

Samples of fishes were collected quarterly at three reaches in the Água Nanci stream, upper Paraná River basin, Brazil: near the spring, in the middle course, and near the mouth. Richness and evenness of the fish fauna increased between reaches towards the river mouth showing a correlation with stream width, pH and the presence of riparian vegetation. These variations in species richness and evenness, verified through Principal Component Analysis and Pearson correlation, suggest relations to habitat complexity, especially characterized by both the degree of preservation of dense riparian vegetation and high width at the lower reaches of the stream, providing a wide variety of hiding places for fish. Abundant species showed correlations with some environmental factors, suggesting habitat preferences.     

Do temperate tree species diversity and identity influence soil microbial community function and composition?

Studies of biodiversity–ecosystem function in treed ecosystems have generally focused on aboveground functions. This study investigates intertrophic links between tree diversity and soil microbial community function and composition. We examined how microbial communities in surface mineral soil responded to experimental gradients of tree species richness (SR ), functional diversity (FD ), community‐weighted mean trait value (CWM ), and tree identity. The site was a 4‐year‐old common garden experiment near Montreal, Canada, consisting of deciduous and evergreen tree species mixtures. Microbial community composition, community‐level physiological profiles, and respiration were evaluated using phospholipid fatty acid (PLFA ) analysis and the MicroResp^? system, respectively. The relationship between tree species richness and glucose‐induced respiration (GIR ), basal respiration (BR ), metabolic quotient (qCO ₂) followed a positive but saturating shape. Microbial communities associated with species mixtures were more active (basal respiration [BR ]), with higher biomass (glucose‐induced respiration [GIR ]), and used a greater number of carbon sources than monocultures. Communities associated with deciduous tree species used a greater number of carbon sources than those associated with evergreen species, suggesting a greater soil carbon storage capacity. There were no differences in microbial composition (PLFA ) between monocultures and SR mixtures. The FD and the CWM of several functional traits affected both BR and GIR . In general, the CWM of traits had stronger effects than did FD , suggesting that certain traits of dominant species have more effect on ecosystem processes than does FD . Both the functions of GIR and BR were positively related to aboveground tree community productivity. Both tree diversity (SR ) and identity (species and functional identity—leaf habit) affected soil microbial community respiration, biomass, and composition. For the first time, we identified functional traits related to life‐history strategy, as well as root traits that influence another trophic level, soil microbial community function, via effects on BR and GIR .     

Impacts of methamidophos, copper, and their combinations on bacterial community structure and function in black soil

The potential ecotoxicologial risks of methamidophos, copper, and their combinations on microbial community of black soil ecosystem in the Northeast China were assessed in species richness and structures by using 16S rDNA-PCR-DGGE analysis approach, and functional characteristics at community levels by using BIOLOGGN system analysis method as well as two conventional methods(DHA and SIR). All results of DGGE banding fingerprint pat-terns(amplified by bacterial specific 16S rDNA V3 high variable region universal primer) indicated that the species richness of bacterial community in tested soil was significantly decreased to different extents by using different concentrations of single methamidophos, copper, especially some of their combinations had worse effects than their corresponding single factors. In addition, the structures of soil bacterial community had been disturbed under all stresses applied in this study because of the enrichment of some species and the disappearance of other species from the b     

Acetylation of αA-crystallin in the human lens: Effects on structure and chaperone function

α-Crystallin is a major protein in the human lens that is perceived to help to maintain the transparency of the lens through its chaperone function. In this study, we demonstrate that many lens proteins including αA-crystallin are acetylated in vivo. We found that K70 and K99 in αA-crystallin and, K92 and K166 in αB-crystallin are acetylated in the human lens. To determine the effect of acetylation on the chaperone function and structural changes, αA-crystallin was acetylated using acetic anhydride. The resulting protein showed strong immunoreactivity against a N^ε-acetyllysine antibody, which was directly related to the degree of acetylation. When compared to the unmodified protein, the chaperone function of the in vitro acetylated αA-crystallin was higher against three of the four different client proteins tested. Because a lysine (residue 70; K70) in αA-crystallin is acetylated in vivo, we generated a protein with an acetylation mimic, replacing Lys70 with glutamine (K70Q). The K70Q mutant protein showed increased chaperone function against three client proteins compared to the Wt protein but decreased chaperone function against γ-crystallin. The acetylated protein displayed higher surface hydrophobicity and tryptophan fluorescence, had altered secondary and tertiary structures and displayed decreased thermodynamic stability. Together, our data suggest that acetylation of αA-crystallin occurs in the human lens and that it affects the chaperone function of the protein.     

Acetylation of αA-crystallin in the human lens: effects on structure and chaperone function

α-Crystallin is a major protein in the human lens that is perceived to help to maintain the transparency of the lens through its chaperone function. In this study, we demonstrate that many lens proteins including αA-crystallin are acetylated in vivo. We found that K70 and K99 in αA-crystallin and, K92 and K166 in αB-crystallin are acetylated in the human lens. To determine the effect of acetylation on the chaperone function and structural changes, αA-crystallin was acetylated using acetic anhydride. The resulting protein showed strong immunoreactivity against a N(ε)-acetyllysine antibody, which was directly related to the degree of acetylation. When compared to the unmodified protein, the chaperone function of the in vitro acetylated αA-crystallin was higher against three of the four different client proteins tested. Because a lysine (residue 70; K70) in αA-crystallin is acetylated in vivo, we generated a protein with an acetylation mimic, replacing Lys70 with glutamine (K70Q). The K70Q mutant protein showed increased chaperone function against three client proteins compared to the Wt protein but decreased chaperone function against γ-crystallin. The acetylated protein displayed higher surface hydrophobicity and tryptophan fluorescence, had altered secondary and tertiary structures and displayed decreased thermodynamic stability. Together, our data suggest that acetylation of αA-crystallin occurs in the human lens and that it affects the chaperone function of the protein.     

How do plants regulate the function, community structure, and diversity of mycorrhizal fungi?

In many semi-natural and natural ecosystems, mycorrhizal fungi are the most abundant and functionally important group of soil micro-organisms. They are almost wholly dependent on their host plants to supply them with photosynthate in return for which they enable the plant to access greater quantities of nutrients. Thus, there is considerable potential for plant communities to regulate the structure and function of mycorrhizal communities. This paper reviews some of the key recent developments that have enabled the influence of plant species richness, composition, and age on mycorrhizal communities in boreal forests and temperate grassland to be determined. It discusses the emerging evidence that, in some situations, plant species richness is related to mycorrhizal species richness, in contrast to previous thinking. The paper also includes some preliminary data on the effect of host stand age on root-associated basidiomycete communities. It concludes by highlighting some of the new methodological advances that promise to unravel the linkages between mycorrhizal diversity and their function in situ.     

Do molecules matter more than morphology? Promises and pitfalls in parasites

Systematics involves resolving both the taxonomy and phylogenetic placement of organisms. We review the advantages and disadvantages of the two kinds of information commonly used for such inferences--morphological and molecular data--as applied to the systematics of metazoan parasites generally, with special attention to the malaria parasites. The problems that potentially confound the use of morphology in parasites include challenges to consistent specimen preservation, plasticity of features depending on hosts or other environmental factors, and morphological convergence. Molecular characters such as DNA sequences present an alternative data source and are particularly useful when not all the parasite's life stages are present or when parasitaemia is low. Nonetheless, molecular data can bring challenges that include troublesome DNA isolation, paralogous gene copies, difficulty in developing molecular markers, and preferential amplification in mixed species infections. Given the differential benefits and shortcomings of both molecular and morphological characters, both should be implemented in parasite taxonomy and phylogenetics.     

Do bridge construction activities influence birds using the River Mersey,in northwest England?

Capsule: Bridge construction works over a major river did not adversely impact the overall wintering and breeding bird assemblage, although contrasting species-specific trends in breeding number were noted.

Aims: To determine whether the wintering water-bird and breeding bird assemblage using the River Mersey, in northwest England, was influenced by bridge construction works.

Methods: Common bird census and wintering bird surveys were carried out before and during construction of the Mersey Gateway bridge. The species abundance and richness of wintering water-birds, assigned to a group (‘Waterfowl’, ‘Wader’, ‘Wetland species’ and ‘Gull’) and breeding birds, assigned to a group (‘Salt marsh species’, ‘Waterfowl species’, ‘Wader species’, ‘Warbler species’ and ‘Other passerine species’), were separately compared before and during the works.

Results: We found little evidence that the bridge construction displaced wintering water-birds and instead found that for most bird groups, their assemblages were higher during the construction works, compared to before. Similarly, we found no evidence that the bridge construction reduced breeding density of any bird group. Contrasting species-specific trends were, however, noted, with some species only recorded breeding during the construction works, and other species recorded in higher breeding densities before the works.

Conclusion: The inadvertent increase in the mud-flats around the bridge structure since the works resulted in more mud-flat being exposed for a greater amount of time, and thus increased the foraging opportunities for many birds. This may at least partly explain why overall wintering bird abundance and richness increased since the works began. Although most breeding birds either increased or remained stable, in number since the works, a small number reduced. This may have been a consequence of the removal of suitable nesting habitat. This study provides a preliminary assessment of the influence of bridge construction on birds.     

Control of freshwater fish and crayfish community structure in Taranaki,New Zealand: dams,diadromy or habitat structure?

1. Freshwater fish and crayfish communities were surveyed along elevational gradients in streams radiating from Mount Taranaki, New Zealand. Six of the 38 streams surveyed had dams or weirs and 32 of the 85 sites were above these barriers. 2. Of the 15 fish and one crayfish species captured, 14 were native. The number of species declined with increasing elevation and distance from the sea. Species richness was also lower above dams even when effects of elevation and distance from the sea were accounted for. 3. Linear regression models using sites without dams were constructed to predict the effect of elevation on fish and crayfish community structure and to allow the effect of dams to be evaluated. The number of species predicted by these models was consistently higher than the number of species found at the above-dam sites. 4. Four fish community groups were classified using two-way indicator species analysis (TWINSPAN). One high elevation group of sites consisted of short steep streams on the west side of the mountain and a second contained longer, lower gradient streams on the east side. The other two groups (3 and 4) consisted of mid-elevation sites and low-elevation sites, respectively. 5. Discriminant analysis was used to predict biotic group membership using the environmental data. Overall, 80% of sites were classified correctly. Correlation of environmental variables with axis scores in the canonical variate analysis revealed that distance from the sea, site elevation and presence of dams were most strongly associated with fish distribution patterns.     

Redundant or complementary? Impact of a colonizing species on community structure and function

Recent studies suggest that species with similar functional traits will have similar effects on ecosystems, but evidence for redundancy of species impacts is limited. Here we use a long‐term experiment to gain insight into functional relationships within a desert rodent community. Experimental removal of kangaroo rats, Dipodomys spp., coupled with the recent, serendipitous colonization of a single species of large pocket mouse Chaetodipus baileyi yielded treatments that differed in the diversity of large granivorous rodents present. We evaluated functional overlap of C. baileyi and the other resident large granivores (i.e. the kangaroo rats) by comparing total energy use of granivorous rodents and total abundance and species richness of small granivores across treatments before and after the arrival of C. baileyi. We found that C. baileyi almost completely compensated for the changes in these key ecosystem‐level properties caused by kangaroo rat removal, but it differentially impacted the population dynamics of individual small granivorous rodent species. Thus, its effects were largely complementary, rather than redundant, to those of the missing kangaroo rats. Although short‐term or single‐measure analyses may suggest redundancy, our results support the longstanding dictum that niches of coexisting species are often similar but rarely, if ever, identical.     

Do more sociable dogs gaze longer to the human face than less sociable ones?

Domestic dogs (Canis familiaris) are especially skillful in communicating with humans, and they rely on special abilities to do that. One of these skills involves gazing at human faces in cases of uncertainty or when seeking for something out of reach. In this study, we evaluated the relationship between dogs' sociability level and the ability to learn to gaze in a situation with food in sight but out of their reach. Thirty-nine adult dogs were tested in two procedures: (1) a sociability test that involved interacting with an unknown person, and (2) a learning task that consisted of training trials in which gazing at the experimenter's face was food reinforced, followed by extinction trials in which gazing was not followed by food. A significant positive correlation was found between the duration of physical contact with the unknown person in the sociability test and gaze duration during extinction. Moreover, high sociability dogs gazed significantly longer at humans during extinction trials. We discuss the possibility that, more sociable animals, such as those who pay more attention to the person in our sociability test, may be more persistent in their communicative attempts because the presence of the human is intrinsically reinforcing to them. Finally, we comment on the importance of these findings for training purposes.     

Do trees in urban or ornamental plantings receive more damage by insects than trees in natural forests?

Abstract.

• 1 To determine if trees in urban or ornamental plantings are more susceptible to attack and receive more damage to foliage by herbivores than trees in natural forests, we compared the amount of leaf damage caused by several guilds of insects feeding on seven species of native, broadleaf trees in two geographic locations.
• 2 Total leaf damage did not differ significantly between urban or ornamental and natural forests, although trees in natural forests tended to have slightly higher levels of leaf damage.
• 3 Damage caused by chewing insects was consistently higher on trees in natural forests than in urban or ornamental plantings. All other feeding guilds showed no consistent pattern in levels of damage between the two habitats.
• 4 Total damage levels were highest on canopy trees and lowest on understorey trees.
• 5 These results are inconsistent with the view that trees in urban or ornamental settings are more susceptible to insect attack than trees in natural forests.
• 6 The lower level of foliar damage caused by chewing insects on trees in urban or ornamental plantings may arise because of low rates of dispersal by insects into urban environments, higher levels of plant resistance to insect attack in urban or ornamental plantings, or lower survival rates of herbivorous insects in urban environments.

     

Do rivers influence fine-scale population genetic structure of tigers in the Sundarbans?

Global tiger Panthera tigris populations mostly survive within the geographically fragmented forest patches, thereby limited genetic exchange between isolated populations. Assessing the genetic status of these populations can reveal the effects of dispersal barriers and provide critical insights to guide future conservation actions. Using non-invasively collected biological samples, we investigated fine-scale genetic structure of tigers in the Sundarbans mangrove forests intersected by the complex river systems, and which holds one of the largest global tiger populations. We genotyped 52 tiger samples at 10 polymorphic microsatellite loci, and sequenced 33 of them for a total of 1263 base-pairs at four mitochondrial gene fragments. Microsatellite analyses exhibit a signature of fine-scale genetic structure, which might have been the consequence of limited tiger dispersal due to wide rivers across the Sundarbans. Similarly, mitochondrial data show a historic pattern of population isolation that might be due to wider rivers across the entire Sundarbans shared by Bangladesh and India. Given the intrinsic nature of the mangrove habitat embedded with numerous rivers, increased commercial traffic and human activities may further impede tiger dispersal across wide rivers, escalating further genetic isolation of the Sundarbans tigers.     

Habitat structure, trophic structure and ecosystem function: interactive effects in a bromeliad–insect community

Although previous studies have shown that ecosystem functions are affected by either trophic structure or habitat structure, there has been little consideration of their combined effects. Such interactions may be particularly important in systems where habitat and trophic structure covary. I use the aquatic insects in bromeliads to examine the combined effects of trophic structure and habitat structure on a key ecosystem function: detrital processing. In Costa Rican bromeliads, trophic structure naturally covaries with both habitat complexity and habitat size, precluding any observational analysis of interactions between factors. I therefore designed mesocosms that allowed each factor to be manipulated separately. Increases in mesocosm complexity reduced predator (damselfly larva) efficiency, resulting in high detritivore abundances, indirectly increasing detrital processing rates. However, increased complexity also directly reduced the per capita foraging efficiency of the detritivores. Over short time periods, these trends effectively cancelled each other out in terms of detrital processing. Over longer time periods, more complex patterns emerged. Increases in mesocosm size also reduced both predator efficiency and detritivore efficiency, leading to no net effect on detrital processing. In many systems, ecosystem functions may be impacted by strong interactions between trophic structure and habitat structure, cautioning against examining either effect in isolation.     

Variation in fish community structure, richness, and diversity in 56 Danish lakes with contrasting depth, size, and trophic state: does the method matter?

Organisms inhabiting shallow near-shore waters are at risk of desiccation during water level fluctuations. Using laboratory experiments, we investigated the survival and behavioural defences of four freshwater amphipod species during substratum drying: three Ponto-Caspian invaders (Pontogammarus robustoides, Dikerogammarus haemobaphes and Dikerogammarus villosus) and the native Gammarus fossarum. We hypothesized that they would be able to survive air exposure events as well as to adjust their behaviour by following the decreasing water level and/or burying in the sediments. To test these hypotheses, we examined survival of each species on gradually drying sandy substratum as well as their horizontal and vertical migration behaviours. P. robustoides was most resistant to substratum drying and was the only species burying into the substratum. On the other hand, G. fossarum exhibited distinct horizontal migrations following the retreating waterline. These two species seem to be particularly well adapted to the drying environment. Defence mechanisms of D. haemobaphes and D. villosus were less efficient, though the former species also followed the retreating waterline to some extent. Our study demonstrates that exotic and native gammarids have several adaptations that enable them to invade and persist in habitats experiencing common water level fluctuations.     

Does bait type and bait container configuration influence the performance of remote underwater video systems in temperate freshwater lakes for assessing fish community structure?

Hydrobiologia - Methods for the use of baited remote underwater video stations (BRUVS) have been tested and refined such that they are now widely used in marine research for assessing fish...     

Fish diversity and community structure in two small tributaries of the Paraná River,Paraná State,Brazil

In eleven sites on two small tributaries of the Paraná River (North-West Paraná State), 6.8 and 4.0 km in length, 1263 fish specimens of 28 taxons and 14 families were collected using electrofishing. Up to twelve years ago the catchments of the two rivers were covered by tropical jungle; this has now been replaced by pasture and arable fields. Mean diversity indices of Simpson and Shannon indices were close to 0.6, which would indicate that human impact affected fish populations although the river beds have retained their original shape, except cleared of riparian trees. Despite their close location (about 18 km), the two streams differed from each other in their fish faunal composition. The distinctive nature of the fish communities in the two streams was a result of: conductivity, pH, also hiding places, riparian vegetation, submerged macrophytes and depth and width of the rivers.