Community Structure

The kinetics of abiotic oxidation in the dark and the kinetics of biological mineralization in soil and in a compost environment of thermally oxidized LDPE were studied. It was demonstrated that different activation energies are obtained for the thermal oxidation, depending on the composition of the materials. Significantly higher levels of biodegradability have been obtained in a soil environment at 23 C compared with the compost environment at 58 C. After two years of mineralization, 91% conversion to carbon dioxide was obtained in the soil test, compared with 43% in the compost test. The differences between fungal, archaeal and bacterial community structures in soil and compost after 607 days of biodegradability assay were mapped out. It was found that the most dominant bacterial and fungal terminal restriction fragments (TRFs) in the compost containing the test material are significantly different from the TRFs in the other environments.

Understanding how landscape characteristics affect biodiversity patterns and ecological processes at local and landscape scales is critical for mitigating effects of global environmental change. In this review, we use knowledge gained from human-modified landscapes to suggest eight hypotheses, which we hope will encourage more systematic research on Teja Tscharntke and others the role of landscape composition and configuration in determining the structure of ecological communities, ecosystem functioning and services. We organize the eight hypotheses under four overarching themes. Section A: 'landscape moderation of biodiversity patterns' includes (1) the landscape species pool hypothesis-the size of the landscape-wide species pool moderates local (alpha) biodiversity, and (2) the dominance of beta diversity hypothesis-landscapemoderated dissimilarity of local communities determines landscape-wide biodiversity and overrides negative local effects of habitat fragmentation on biodiversity. Section B: 'landscape moderation of population dynamics' includes (3) the cross-habitat spillover hypothesis-landscape-moderated spillover of energy, resources and organisms across habitats, including between managed and natural ecosystems, influences landscape-wide community structure and associated processes and (4) the landscape-moderated concentration and dilution hypothesis-spatial and temporal changes in landscape composition can cause transient concentration or dilution of populations with functional consequences. Section C: 'landscape moderation of functional trait selection' includes (5) the landscape-moderated functional trait selection hypothesis-landscape moderation of species trait selection shapes the functional role and trajectory of community assembly, and (6) the landscape-moderated insurance hypothesis-landscape complexity provides spatial and temporal insurance, i.e. high resilience and stability of ecological processes in changing environments. Section D: 'landscape constraints on conservation management' includes (7) the intermediate landscape-complexity hypothesis-landscapemoderated effectiveness of local conservation management is highest in structurally simple, rather than in cleared (i.e. extremely simplified) or in complex landscapes, and (8) the landscape-moderated biodiversity versus ecosystem service management hypothesis-landscape-moderated biodiversity conservation to optimize functional diversity and related ecosystem services will not protect endangered species. Shifting our research focus from local to landscape-moderated effects on biodiversity will be critical to developing solutions for future biodiversity and ecosystem service management.

Omnivory is an important interaction that has been the centre of numerous theoretical and empirical studies in recent years. Most of these studies examine the conditions necessary for coexistence between an omnivore and an intermediate consumer. Trait variation in ecological interactions (competition and predator tolerance) among intermediate consumers has not been considered in previous empirical studies despite the evidence that variation in species-specific traits can have important community-level effects. 2. I conducted a multifactorial microcosm experiment using species from the Sarracenia purpurea phytotelmata community, organisms that inhabit the water collected within its modified leaves. The basal trophic level consisted of bacterial decomposers, the second trophic level (intermediate consumers) consisted of protozoa and rotifers, and the third trophic level (omnivore) were larvae of the pitcher plant mosquito Wyeomyia smithii . Trophic level number (1, 2 and 3), resources (low and high), omnivore density (low and high) and intermediate consumer (monoculture of five protozoa and rotifers) identity were manipulated. Abundance of the basal trophic level, intermediate consumers, and growth of the omnivore were measured, as well as time to extinction (intermediate consumers) and time to pupation (mosquito larvae).

The influence of wild fires on microbial community structure, soil organic matter, sulphur oxidising and nitrifying microbial populations in the floodplains of the Okavango Delta of Botswana was assessed. Microbial community structure was assessed by phospholipids ester-linked fatty acids (PLFA) quantification while microbial sulphur oxidisers were assessed by Most Probable Number (MPN). Community structure assessment showed that burning shifted the microbial community structure from single cellular bacteria being the dominant groups to filamentous fungi and actinomycetes being the most dominant groups. Generally burning increased the fungal component (18:2 ω6) matrix from 3.40 to 8.35 while the actinomycetes and sulphur reducing bacterial (10 Me 16:0) component also increased from 1.02 to 1.70 mostly in the floodplains. Generally, the organic matter content declined with burning. However, the influence of burning on soil pH was non conclusive. Soil microbial biomass carbon increased slightly after the fire. The number of heterotrophic and nitrite-oxidizing and sulphur reducing bacteria increased. Overall, these results indicate that burning significantly alters the microbial community structure as large above ground losses of nutrients during and after burning often results in low quantities of nutrients released into the soil. Figure 1. Map of the Okavango Delta showing mapped fire sites since 2000. Rectangular block indicates sampling site.

Changes in ecosystem functions following disturbances are of central concern in ecology and a challenge for ecologists is to understand the factors that affect the resilience of community structures and ecosystem functions. In many forest ecosystems, one such important natural disturbance is fire. The aim of this study was to understand the variation of resilience in six functional groups of invertebrates in response to different fire frequencies in southern Switzerland. We measured resilience by analysing arthropod species composition, abundance and diversity in plots where the elapsed time after single or repeated fires, as determined by dendrochronology, varied. We compared data from these plots with data from plots that had not burned recently and defined high resilience as the rapid recovery of the species composition to that prior to fire. Pooling all functional groups showed that they were more resilient to single fires than to repeated events, recovering 6–14 years after a single fire, but only 17–24 years after the last of several fires. Flying zoophagous and phytophagous arthropods were the most resilient groups. Pollinophagous and epigaeic zoophagous species showed intermediate resilience, while ground-litter saprophagous and saproxylophagous arthropods clearly displayed the lowest resilience to fire. Their species composition 17–24 years post-burn still differed markedly from that of the unburned control plots. Depending on the fire history of a forest plot, we found significant differences in the dominance hierarchy among invertebrate species. Any attempt to imitate natural disturbances, such as fire, through forest management must take into account the recovery times of biodiversity, including functional group composition, to ensure the conservation of multiple taxa and ecosystem functions in a sustainable manner.

This article explores the relationship between communities and short cycles in complex networks, based on the fact that nodes more densely connected amongst one another are more likely to be linked through short cycles. By identifying combinations of 3-, 4-and 5-edge-cycles, a subnetwork is obtained which contains only those nodes and links belonging to such cycles, which can then be used to highlight community structure. Examples are shown using a theoretical model (Sznajd networks) and a real-world network (NCAA football).

In ecotoxicological studies involving community-level investigations, rapid and multiparametric fluorescence-based methods may provide substantial advantages over traditional methods used for structural and functional community analysis. Therefore, multiwavelength-excitation pulse-amplitude modulated (PAM) fluorometry was applied in this study to assess long-term changes in periphyton community structure, shortterm effects on periphyton functioning (photosynthesis) and pollution induced community tolerance (PICT). For inter-calibration, periphyton structure was evaluated by chemotaxonomic analysis of accessory pigments and a four-wavelength-excitation PAM fluorometer. Short-term effects of herbicides were evaluated by fluorescence quenching analysis and 14 C-incorporation as a proxy of primary production. Subsequently, the method was applied to assess structural and functional changes in periphyton communities after isoproturon exposure for 14 and 26 days, respectively. Results showed good correlation of the PAM fluorescence-based measurements with traditional methods for biofilms in the initial colonisation phase for structural and functional parameters. However, for biofilms older than 9 weeks PAM fluorescence may underestimate biomass. Multiwavelength-excitation PAM fluorometry showed good correlation with marker pigment concentrations indicating that this method provides a reliable estimate of the community structure. PAM fluorometry was able to quantify changes of biomass and follow relative shifts in class composition of biofilms under exposure of isoproturon. Short-term tests based on the quantification of the inhibition of the effective quantum yield revealed a concentration-dependent increase of PICT. The observation of two succession phases of the biofilms after 14 and 26 days of growth, respectively, revealed that sensitivity of biofilms decreased with increasing age and biomass, respectively, but PICT remained a characteristic parameter of exposed communities in a concentration-dependent relationship. In conclusion, multiwavelength-excitation PAM fluorometry has considerable potentials in multispecies and multiparameter assessment of toxic effects on community level in terms of (1) a combined and rapid evaluation of structural and functional parameters in parallel, (2) screening of trends over time, (3) observing effects in replication and (4) being non-destructive. The approach therefore provides a perspective for a better understanding of community-level effects as species interactions in terms of PICT and therefore a higher ecological realism in risk assessment of toxicants.

Purely observational studies have documented differences in the abundance and diversity of several litterdwelling arthropods between sites adjacent to, and far from, CWD, which suggests that reduction of fallen coarse woody debris (CWD) in temperate forests by traditional forestry practices may affect the litter arthropod community. As few field experiments have directly tested the impact of CWD on arthropods inhabiting the litter at different distances from CWD, we removed CWD from replicated open plots on the floor of a second-growth deciduous forest in order to reveal the causal connection between CWD and litter-dwelling spiders, often the most diverse and abundant predators among the litter macrofauna of temperate forests. We also documented the impact of the CWD manipulation on spider prey and several other major macroarthropod groups. Before removing CWD (∅ = 14.3 ± 0.7 cm), we measured response variables as a function of distance (0.5-1.5 m) from CWD in both removal and control plots. In agreement with results of previous research that solely utilized this observational approach in temperate forests, volume and dry mass of litter, spider diversity, overall spider density, and densities of 8 of 16 major spider genera were higher adjacent to CWD before experimental manipulations. Removing CWD reduced the amount of litter and the density of spiders in litter close to where the CWD had been. Removing CWD also altered spider community structure, which had differed between litter sites adjacent to, and far from, CWD prior to the experimental removal of CWD. The patterns, though, were not completely congruent, as some of the taxa affected by the manipulation had not differed between sites prior to the removal of CWD, and vice-versa. Our findings suggest that complex interactions among structural, biotic and microclimatic factors underlie the observed responses to CWD removal by spiders and other arthropods in the litter layer. We also conclude that drawing inferences solely from observational studies is not a reliable approach for predicting the impact of changes in the amount of CWD on arthropods of forestfloor leaf litter. Further field experiments manipulating different volumes of CWD are needed in order to determine the minimum amount of CWD that should be kept on the forest floor of managed forests in order to maintain densities and diversities of major leaf-litter arthropods.

In this paper we study the community structure of endorsement networks, i.e., social networks in which a directed edge u → v is asserting an action of support from user u to user v. Examples include scenarios in which a user u is favoring a photo, liking a post, or following the microblog of user v.

We measured the size structure and taxonomic composition of phytoplankton in temperate rivers during base flows of summer to investigate the influence of river size, ambient nutrient concentration, and light availability on potamoplankton community structure. Algal biomass was measured in three size classes (2-20, 20-64, and Ͼ64 m) by microscope enumeration of water samples collected in 31 rivers and by chlorophyll a in water samples collected in 46 rivers in another year across Ontario and western Quebec. Nanoplankton dominated the potamoplankton biomass across the range of river nutrient concentrations (total phosphorus 5-280 g P L Ϫ1 ), water residence times (1-39 d), and light regimes (euphotic zone to mixing depth ratio 0.1-33). Both nanoplankton (2-20 m) and total potamoplankton biomass were significantly correlated with water column total phosphorus concentrations and were not related to water residence time or light availability. On average, diatoms contributed the largest percentage of the total biomass, followed by cryptophytes and an equal percentage of chlorophytes and chrysophytes. The contribution of any one division to total biomass was not significantly correlated with nutrients, water residence time, or light regime. In contrast to temperate lake systems, both the proportion of biomass in larger size classes and the contribution of cyanobacteria did not change significantly as a function of nutrient concentrations. However, community size structure varied in relation to river size: netplankton (Ͼ64 m) contributed slightly more to total biomass at sites with both shorter (Ͻ2 d) and longer (Ͼ10 d) water residence times. These results point to differences between the phytoplankton of lakes and rivers in response to eutrophication.

Habitat utilization of native young-ofthe-year (YOY) muskellunge, Esox masquinongy, was quantified by the type and density of vegetation present, water depth, and fish communities associated with their presence and abundance in nursery bays of the Upper St. Lawrence River. We completed 441 seine hauls and captured 400 YOY muskellunge in 11 bays that were sampled each July and August over a 3year period (2002)(2003)(2004). We hypothesized a change in habitat utilization related to increasing body size, as YOY muskellunge doubled in total length from July to August. Fine-leafed submerged and emergent macrophytes and prey availability (cyprinids, Notropis sp., banded killifish, Fundulus diaphanous and tessellated darter, Etheostoma olmstedi), were positively related to muskellunge use in July, while in August coverage of broad-leafed submerged macrophytes and increased overall vegetation density were the best habitat descriptor. In both months, muskellunge were associated with moderate (20-60%) vegetation coverage and density, however, captures were in areas of significantly greater vegetation coverage and density than was generally available. A negative relation of muskellunge occurrence with water depth, yellow perch, Perca flavescens, and stonewort, Chara vulgaris, was observed in both months. The negative relationship between muskellunge and depth, plus their strong linkages to nearshore submerged vegetation and forage fish that inhabit the nearshore areas, highlights the importance of protecting the ecological integrity of nearshore habitats. Our findings should assist managers in protecting native stocks, planning restoration and enhancement initiatives, and in regulating riparian and nearshore development.

Quantifying the relationship between mesozooplankton and water quality parameters identifies the factors that structure the mesozooplankton community and can be used to generate hypotheses regarding the mechanisms that control the mesozooplankton population and potentially the trophic network. To investigate this relationship, mesozooplankton and water quality data were collected in Florida Bay from 1994 to 2004. Three key characteristics were found in the mesozooplankton community structure: (1) there are significant differences between the four sub-regions of Florida Bay; (2) there is a break in May of 1997 with significant differences before and after this date; and (3) there is a positive correlation between mesozooplankton abundance and salinity. The latter two characteristics are closely correlated with predator abundance, indicating the importance of top-down control. Hypersaline periods appear to provide a refuge from predators, allowing mesozooplankton to increase in abundance despite the increased physiological stress.

In der gesamten Biosphäre üben schnelle und sich beschleunigende Veränderungen in der Landnutzung, des Klimas und der atmosphärischen Zusammensetzung, die vor allem durch anthropogene Kräfte angetrieben werden, gröXten Einfluss auf die Produktivität, die Biodiversität und die nachhaltige Bereitstellung von Ökosystemgutern und -leistungen aus. Bisher konzentrierten sich viele Untersuchungen, die ökologische Konsequenzen des globalen Wandels abschätzen, auf einzelne trophische Level. Das Verständnis dieser Veränderungen und die Vorhersage ihrer Konsequenzen kann jedoch davon profitieren, dass enträtselt wird, wie die Interaktionen zwischen den Primärproduzenten und den primären und sekundären Konsumenten (Pflanzen, Herbivore und Karnivore) beeinflusst werden. Naturschutz und -wiederherstellung kann verbessert werden, wenn die Arten und ihre Interaktionen auf angemessenen Skalen und unter Berücksichtigung, dass ober-und unterirdische Biota ökologisch miteinander verbunden sind, eingeschätzt werden. Der Selektionsdruck auf eine Art kann von anderen Arten abhängen, so dass der Verlust einer Art mehr für die Diversität bedeutet als nur den reinen Verlust eines Taxons. Er kann ebenso den Verlust anderer Arten des gleichen oder eines anderen trophischen Levels zur Folge haben sowie die Abschwächung oder sogar den Verlust von verschiedenen Selektionsdrücken. Wir geben einen Überblick über die Diskussionen zu trophischen Interaktionen in einer sich verändernden Welt in Bezug auf (i) die Skala der Ökosystemantwort auf Umweltveränderungen mit Betonung des Bodensubsystems, (ii) die Verbindung zwischen oberund unterirdischen Subsystemen und (iii) die natürliche Selektion und die Stabilität der Gemeinschaftsstruktur sowie der Ökosystemfunktion. Wir diskutieren die Notwendigkeit isolierte Subdisziplinen der Ökologie zusammen zu führen, um die Implikationen des globalen Wandels für Ökosystemprozesse zu verstehen.

Qualitative and quantitative aspects of the phytoplankton of the River Meuse were studied during 1992, at a point 537 km from the source. The phytoplankton was dominated by diatoms and green algae. The Stephanodiscus hantzschii-group was especially prominent. Other important taxa were Cyclotella meneghiniana, small Cyclotella and Thalassiosira, Aulacoseira ambigua and Nitzschia acicularis. Cell abundances varied from less than 1000 units mll to about 25 000 -30 000 units ml-during the blooms. The Stephanodiscus hantzchii-group constituted almost entirely the first spring bloom. During the summer period, small Thalassiosiraceae developed markedly and large Thalassiosira weissflogii appeared. During this period, green algae dominated diatoms as expressed in cell abundances. The main Chlorococcales were Scenedesmus quadricauda, Scenedesmus div. sp., Dictyosphaerium ehrenhergianum and Pediastrum duplex. Dinophyceae contributed a significant biomass during the summer period. Total biomass varied between 100 and 3 650 ttg Cl ' . As previously observed , the factors regulating the phytoplankton growth were clearly physical variables: discharge, temperature and irradiance. However, in the summer period, low abundances might indicate a regulation by biotic factors. The impact of grazing by zooplankton is discussed, on the basis of observations of zooplankton development in the River Meuse and on the basis of simulation by a mathematical model. A comparison is carried out with recent data of phytoplankton in large European rivers.

Abstract: The Galápagos Islands harbor some of the least impacted marine ecosystems in the tropics Efectos de la Pesca Artesanal en Comunidades Marinas en las Islas Galápagos Resumen: Las Islas Galápagos albergan algunos de los ecosistemas marinos menos afectados en los trópi-cos, pero hay indicios de que la pesca artesanal afecta a las comunidades marinas explotadas. Para cuantificar estos efectos, se muestrearon las comunidades de peces y erizos de mar en numerosos sitios con pesca intensiva y no intensiva en las islas centrales del archipiélago. Los sitios fueron seleccionados con base en la información colectada como parte de un estudio de monitoreo de pesquerías locales y estandarizada para diversos factores abióticos. La abundancia y la biomasa de las principales especies explotadas fue significativamente menor en los sitios con pesca intensiva versus no intensiva. La estructura de la comunidad también

Fish communities and habitat structures were evaluated by underwater visual censuses a rocky location impacted by thermal discharge (I) and at two control locations, one in a Sargassum bed (C1) and the other in a rocky shore with higher structural complexity (C2). Habitat indicators and fish communities exhibited significant differences between the impacted and control locations, with the impacted one

We compared the community structure of benthic algae inside and outside pomacentrid damselfish (Stegastes nigricans) territories in a moat at Sesoko Island, Okinawa, Japan. S. nigricans maintained ''algae farms'' that were dominated by the filamentous rhodophyte, Womersleyella setacea. Species richness and biomass were higher inside damselfish territories than outside, while species diversity and evenness were higher outside. Detrended correspondence analysis (DCA) based on species composition showed that the dominance of W. setacea was maintained throughout the year in all samples collected from inside damselfish territories. The observed strong dominance of filamentous rhodophytes was consistent with the findings of most studies on damselfish territories worldwide. However, the dominance of a single species of alga and low species diversity inside the territories was in contrast to the findings of previous studies, in which the reduction of grazing pressure caused intermediate disturbance and enhanced algal species diversity. This discrepancy in algal species diversity inside the damselfish territories seems to have been caused by unique characteristics of the alga and the fish. W. setacea traps sediment, which reduces the availability of firm substrata for attachment and inhibits the recruitment of some algae. Moreover, S. nigricans ''weeds'' indigestible calcareous and thicker algae. The algal assemblage outside damselfish territories varied among samples, and included mat-forming cyanophytes (Calothrix aeruginosa and Calothrix codicola), a prostrate laminar phaeophyte (Padina sp.), thin and small-scaled algae (Cladophora sp. and Feldmannia indica), finely branched filamentous rhodophytes (Taenioma perpusillum and Herposiphonia obscura), and a coarsely branched rhodophyte (Gelidiopsis variabilis).

While recent results have provided strong evidence for the presence of a stable gut microbiota among several termite species, little is known about variations at the colony or individual level. Using a cultivation-independent approach, we investigated the structure of the bacterial community in the gut of termites from four different colonies of Hodotermes mossambicus. 16S rRNA-based terminal restriction fragment length polymorphism (T-RFLP) analysis of the bacterial gut microbiota revealed (1) a high consistency of the gut microbiota among nestmates and (2) subtle but distinct differences in community structure between individuals from different colonies. Since products of bacterial metabolism may contribute to a colony odor that can be used as discriminatory signal, the presence of a colony-specific bacterial community adds support to the hypothesis that the gut microbiota of termites is involved in nestmate recognition.

We propose that cavity-nesting bird communities are structured in nest webs analogous to food webs, where interspeci®c and intraspeci®c interactions are centered around nest site availability. Our sites of mixed deciduous coniferous forest in northcentral BC, Canada, support a rich diversity of eight species of primary cavity nesters (PCNs) (woodpeckers), four species of weak cavity nesters (nuthatch, chickadees) and 20 secondary cavity-nesting species (ducks, passerines and birds of prey). Richness varied across forest-types with some plots being`hotspots' and others being depauperate. Across a range of foresttypes, we measured species richness and abundance of birds and squirrels using point count census techniques, playbacks of taped calls of woodpeckers and owls, and by searching for active nests. We also measured resource use (trees able to support cavities, or existing cavities) in relation to availability (tree species, abundance and habitat characteristics such as edge-type and degree of fragmentation). In both 1995 and 1996, we found signi®cant positive correlations between the abundance of primary and secondary cavity-nesting birds, and negative correlations between both of these groups and weak cavity excavators. None of the three cavity-nesting groups was positively correlated with open-nesting (non-cavity) forest birds, rejecting our null hypothesis of common habitat quality. In contrast, the abundance of secondary cavity-nesting species was signi®cantly negatively correlated with non-cavity species, possibly because these species compete for resources other than nest sites, such as invertebrate prey. Using these data, we construct a nest web for the cavity-nesting community in northcentral British Columbia. This approach demonstrated strong and weak links among species in the web and identi®ed key species whose presence may be critical to the integrity of the community. We plan to test how nest web structure shifts in response to different forest-cutting regimes, and whether changes in species richness and abundance can be ameliorated with selective harvesting. #

In this study, we discuss communication aspects concerning a segmented bus platform. Placed somewhere midway between the classical system bus and the network on chip approaches, the segmented bus architecture provides performance improvements in comparison with the first, while employing a much simpler communication structure and algorithm than those thought for the second. Our focus is on the arbitration policy exercised at the level of the central arbiter. We present a new solution for this policy, that avoids the starvation symptoms of the present version while preserving the overall performance of the original platform.

A hailstorm in October 1994 was found to have moderately or severely impacted on 5.3% of the mangrove forests in Port Curtis. All mangrove species showed evidence of hail damage, including the three most common species (Rhizophora stylosa, Ceriops tagal and Avicennia marina). Physical effects of hail damage included stripping of leaves from plants, holes punched through leaves, bruising to bark, divots removed from bark, branch and plant death. Species-specific differences in vulnerability to the effects of hail were observed with C. tagal experiencing relatively higher mortality rates than the other two common mangrove species. A delayed pattern of mortality was observed in two species-C. tagal and A. marina. Alterations to mangrove community structure included: (1) reductions in stem density, stem diameter and basal area, (2) reductions in canopy cover (based on a photographic index of foliage projective cover) and (3) changes in relative abundance of species in mangrove zones. Recovery was observed in some stands but others had not recovered to pre-hail levels of canopy cover two years after the hailstorm. Recovery had occurred by regeneration of fresh leaves but no recruitment of young plants had been observed during the study. The forests in the impact area were dominated by either Ceriops tagal or Rhizophora stylosa with Avicennia marina as a subdominant in places. C. tagal dominated forests within the impact area were relatively more severely affected (41.8% in the severe category) than R. stylosa dominated communities (only 17.4% in the severe category). This indicated that C. tagal dominated forests were more vulnerable to the effects of hail damage than R. stylosa dominated forests. In addition, hail-impacted C. tagal dominated forests represented a relatively high percentage of the area of C. tagal dominated forests in Port Curtis (44.3%). This percentage was much higher than hail-impacted R. stylosa dominated forests in Port Curtis (2.7%). These two factors-relatively severe impact on C. tagal communities and a relatively higher percentage affected within the Port Curtis areaillustrate that hailstorms, as a form of natural disturbance, are an important influence on the forest ecology of mangrove ecosystems in this region.

In addition to answering Hutchinson's question ''Why are there so many species?'', we need to understand why certain species are found only under certain environmental conditions and not others. Trait-based approaches are being increasingly used in ecology to do just that: explain and predict species distributions along environmental gradients. These approaches can be successful in understanding the diversity and community structure of phytoplankton. Among major traits shaping phytoplankton distributions are resource utilization traits, morphological traits (with size being probably the most influential), grazer resistance traits, and temperature responses. We review these trait-based approaches and give examples of how trait data can explain species distributions in both freshwater and marine systems. We also outline new directions in trait-based approaches applied to phytoplankton such as looking simultaneously at trait and phylogenetic structure of phytoplankton communities and using adaptive dynamics models to predict trait evolution.

A method is presented to identify absorption characteristics of three optically-distinct phytoplankton classes from a suite of measurements of total phytoplankton absorption coefficient and chlorophyll-a concentration by successive application of the two-population absorption model of Sathyendranath et al. (2001) and Devred et al. (2006a). The total phytoplankton absorption coefficient at multiple wavelengths is expressed as the weighted sum of the

Photosynthetic pico-and nanoplankton dominate phytoplankton biomass and primary production in the oligotrophic open ocean. Species composition, community structure, and dynamics of the eukaryotic components of these size classes are poorly known primarily because of the difficulties associated with their preservation and identification. Molecular techniques utilizing 18S rRNA sequences offer a number of new and rapid means of identifying the picoplankton. From the available 18S rRNA sequence data for the algae, we designed new group-specific oligonucleotide probes for the division Chlorophyta, the division Haptophyta, and the class Pelagophyceae (division Heterokonta). Dot blot hybridization with polymerase chain reaction amplified target rDNA and whole-cell hybridization assays with fluorescence microscopy and flow cytometry were used to demonstrate probe specificity. Hybridization results with representatives from seven algal classes supported the phylogenetic affinities of the cells. Such group-or taxon-specific probes will be useful in examining community structure, for identifying new algal isolates, and for in situ detection of these three groups, which are thought to be the dominant algal taxa in the oligotrophic regions of the ocean.

Tube-dwelling polychaetes provide habitat structures that potentially affect the composition of the benthic community. This study describes the long-term effects of tubes as a physical structure on the fauna of an intertidal sandflat, based on a field experiment with tubes that mimicked those of the terebellid polychaete Lanice conchilega.

Many complex networks display a mesoscopic structure with groups of nodes sharing many links with the other nodes in their group and comparatively few with nodes of different groups. This feature is known as community structure and encodes precious information about the organization and the function of the nodes. Many algorithms have been proposed but it is not yet clear how they should be tested. Recently we have proposed a general class of undirected and unweighted benchmark graphs, with heterogenous distributions of node degree and community size. An increasing attention has been recently devoted to develop algorithms able to consider the direction and the weight of the links, which require suitable benchmark graphs for testing. In this paper we extend the basic ideas behind our previous benchmark to generate directed and weighted networks with built-in community structure. We also consider the possibility that nodes belong to more communities, a feature occurring in real systems, like social networks. As a practical application, we show how modularity optimization performs on our new benchmark.

Ha Long Bay in North Vietnam is characterized by karst towers and bigger islands totalling more than 3000 isles. Karst processes carved hundreds of caves out of the limestone and contributed to the formation of many enclosed and semi-enclosed saltwater lakes. Here, we report the results of a general survey of several lakes and the first data on the Hang Du I lake, a small basin devoid of any apparent communication with the surrounding sea. Hang Du I is characterized by the presence of Rhizostomeae, genus Mastigias, suggesting strong similarities with the famous lakes described from the archipelago of Palau. Among the benthic organisms sponges are the most important group. Temperature and abundance of the monsoon rains are the main factors influencing remarkable seasonal variations in physical-chemical parameters and the community structure of the lake. A thermal crisis with water temperatures up to 36 • C was recorded in September 2003. In this period, usually abundant medusae and sea anemones totally disappeared. Sponge populations showed fast growth rates in winter and spring and a partial degeneration to face the harsh conditions of the summer season. When isolated from the surrounding marine environment, the saltwater lakes share the condition of oceanic islands, representing spots of habitats surrounded by a completely different environment. The Ha Long Bay marine lakes are not easy to access, being surrounded by tropical forest, but local people usually exploit them for both fishery and oyster harvesting. There is an urgent need to develop measures of protection for these endangered and unique environments, natural laboratories that facilitate the study of evolution of marine organisms, where biodiversity has been until now totally unexplored.

Abstract: Community detection is an important research topic in complex networks. We present the employment of a genetic algorithm to detect communities in complex networks which is based on optimizing network modularity. It does not need any prior knowledge about the number of communities. Its performance is tested on two real life networks with known community structures and a set of synthetic networks. As the performance measure an information theoretical metric variation of information is used. The results are promising ...

The influence of habitat structure on abundance and taxonomic richness of epibenthic harpacticoid copepods in seagrass beds of Port Phillip Bay, Australia was investigated using artificial seagrass plants. The density and length of artificial seagrass plants was manipulated at three sites over two sampling times. Results for artificial plants were also compared with controls without plants. The presence of habitat structure in the form of artificial seagrass resulted in a significant increase in harpacticoid abundance at all sites and taxonomic richness at one site. In terms of artificial seagrass treatments, higher blade density resulted in higher harpacticoid abundance, but blade length and surface area had no significant effect. Taxonomic richness did not vary amongst artificial seagrass treatments. At the site where taxonomic richness was increased in the presence of artificial seagrass, rarefaction showed that the result was consistent with a passive increase related to increased sample size. In contrast, although abundances in artificial seagrass were significantly higher than in controls at the other two sites, the taxonomic richness was similar to controls, suggesting that the full range of taxa available was represented in control samples. This study shows that structural aspects of complexity can have importance beyond the simple provision of complexity in the form of increased surface area of habitat, and may depend on the scale examined. Further, the study emphasises the importance of spatial and temporal replication of experiments to give generality to results.

We compared the community structure of benthic algae inside and outside pomacentrid damselfish (Stegastes nigricans) territories in a moat at Sesoko Island, Okinawa, Japan. S. nigricans maintained ''algae farms'' that were dominated by the filamentous rhodophyte, Womersleyella setacea. Species richness and biomass were higher inside damselfish territories than outside, while species diversity and evenness were higher outside. Detrended correspondence analysis (DCA) based on species composition showed that the dominance of W. setacea was maintained throughout the year in all samples collected from inside damselfish territories. The observed strong dominance of filamentous rhodophytes was consistent with the findings of most studies on damselfish territories worldwide. However, the dominance of a single species of alga and low species diversity inside the territories was in contrast to the findings of previous studies, in which the reduction of grazing pressure caused intermediate disturbance and enhanced algal species diversity. This discrepancy in algal species diversity inside the damselfish territories seems to have been caused by unique characteristics of the alga and the fish. W. setacea traps sediment, which reduces the availability of firm substrata for attachment and inhibits the recruitment of some algae. Moreover, S. nigricans ''weeds'' indigestible calcareous and thicker algae. The algal assemblage outside damselfish territories varied among samples, and included mat-forming cyanophytes (Calothrix aeruginosa and Calothrix codicola), a prostrate laminar phaeophyte (Padina sp.), thin and small-scaled algae (Cladophora sp. and Feldmannia indica), finely branched filamentous rhodophytes (Taenioma perpusillum and Herposiphonia obscura), and a coarsely branched rhodophyte (Gelidiopsis variabilis).

Through their grazing activities limpets have an important role in controlling macroalgal abundance and as a result the structure and dynamics of rocky shore assemblages. Using two congeneric limpet species, with different biogeographic distributions, and whose ranges are expected to alter with climatic warming, we separated the magnitude of their grazing activity over time and the subsequent consequence for macroalgal growth. The northern/boreal limpet, Patella vulgata (L.), consistently grazed more than the southern/lusitanian limpet, P. depressa (Pennant), particularly during spring and summer when P. depressa was reproductively active. Individuals of Fucus vesiculosus (L.) that settled during this time were able to grow to a size where they escaped the grazing activities of P. depressa, resulting in mature F. vesiculosus being present in all P. depressa treatments. In contrast, P. vulgata, which was not reproductively active during this period, exhibited no reduction in its grazing activity and prevented macroalgae from growing in experimental treatments. It therefore appears that P. vulgata has a stronger role, than P. depressa, in controlling macroalgal abundance on shores of southwest Britain. We present a conceptual model highlighting the direct and indirect interactions between these two limpet species and F. vesiculosis. If as predicted, under current warming scenarios, P. depressa becomes the dominant limpet on shores of southwest Britain there will be subsequent changes in rocky shore community structure and ecosystem functioning. Our research emphasises that even closely related species with similar ecological niches can exhibit different behaviours that fundamentally alter their biological interactions with other organisms leading to idiosyncratic responses to predicted changes in climate.

Aquatic macrophyte community distribution along the eastern shoreline of the Itaipu Reservoir (one of the South America's largest impoundments) is described in relation to limnological and sedimentological factors. The central body of the reservoir is mesotrophic, while the arms (flooded influent river valleys) along the eastern shore may be oligo-mesotrophic to eutrophic, depending on time of year and sub-catchment characteristics. Macrophyte community composition and species cover were surveyed at 30 sites in four arms, in relation to sediment total P and organic matter; underwater light regime; and water total P and Kjeldahl N concentration, alkalinity, conductivity, depth and pH. Seventeen euhydrophyte and six emergent macrophyte species were recorded. Large stands of Egeria najas dominated the euhydrophyte vegetation, together with free-floating weed species (Pistia stratiotes Linn., Salvinia auriculata Aublet and Eichhornia crassipes (Mart.) Solms.). Canonical Correspondence Analysis of the data showed that two sets of variables were important predictors of aquatic macrophyte community structure. Floating macrophyte assemblage was closely related to concentration of nutrients in both water and sediment, while light penetration was the strongest predictor of submerged species occurrence. Although a large number of potential nuisance species were present, dense growths were restricted to shallower areas of the Itaipu Reservoir, causing localised problems. The possibility of increasing interference by these plants with fisheries, recreational use, transport and hydroelectricity generation suggests a need for continued monitoring of weed distribution and abundance, and investigation of appropriate management measures.

This study was conducted to investigate the relationship between ground-dwelling spider communities and the degree of soil contamination of heavy metals, Cd and Pb. Six sites were selected according to expected differences in Cd and Pb contamination levels in soil and similarity in vegetation composition. Ground-dwelling spiders were collected monthly in 2003 and 2004 by pitfall trapping. Species diversity of ground-dwelling spiders between unpolluted and moderately polluted sites was not significantly different although the value was higher in the unpolluted site. Species diversity tended to decrease with increasing Pb levels in soil although no statistical significance was obtained. No trend was shown between species diversity and Cd levels in soil. The community structure of ground-dwelling spiders was similar for the two types of sites. Overall grounddwelling spider communities may be not sensitive enough to discriminate moderate heavy metal contamination levels in soil. However, among the dominant spider families, the composition and structure of Linyphiidae separated unpolluted and moderately polluted sites. Pardosa astrigera and P. laura (Lycosidae) have a potential as heavy metal accumulator indicator species and Oedothorax insulanus (Linyphiidae) has a potential as a heavy metal sentinel indicator species.

Environmental microbiology studies commonly use terminal restriction fragment length polymorphism (T-RFLP) of 16S rRNA genes, for example, to analyze changes in community structure in relation to changing physicochemical and biological conditions over space and time. Although T-RFLP is most useful for comparing samples from different environments, a large number of samples makes effective analysis difficult using the Web-based tools that are currently available. To resolve this dilemma, we used a new approach for calculating data from multiple T-RFLP samples by estimating terminal fragment combinations, then applying a correlation analysis using two different fluorescent dyes generated simultaneously from all samples. This calculation was based on the expectation that the proportions of two terminal fragments from one full-length polymerase chain reaction fragment would be nearly the same in each analysis. Using this program, the oral microflora in 73 human saliva samples were analyzed, and 24 bacterial groups, with peak areas of at least 0.5% and correlation coefficients of 0.55 or greater, were identified from the T-RFs within 40 s.

The effect of a topoclimatic gradient on soil nematode communities was investigated in the Israeli Judean Desert. Four locations along a 35 km gradient, from an elevation of 650 m above sea level with 620 mm rainfall to a –60 m relative to sea level with a rainfall below 110 m, were studied: Givat Yearim, Maale Adumim, Mishor Adumim and Kalia. Monthly soil samples were collected between January 1994 and December 1995. Thirteen nematode families and 17 genera were observed. Cephalobus, Heterocephalobus, Aphelenchoides, Tylenchus, Dorylaimus and Eudorylaimus were found to be the dominant genera. Ecological measurements of soil nematode community structure, diversity, and maturity indices were assessed, and comparisons between four locations and four seasons were made. Significant differences in the total numbers of nematodes were found between the locations (p < 0.01) and seasons (p < 0.05), where Givat Yearim > Maale Adumim > Mishor Adumim > Kalia, winter > spring > autumn > summer. Bacterivores were found to be the most abundant trophic group across locations and seasons, with a mean relative abundance of 55.0%. The densities of bacterivores, plant parasites and omnivores-predators during the winter season exhibited similar trends at all four locations, with Givat Yearim > Maale Adumim > Mishor Adumim > Kalia. None of the ecological indices were significantly different between locations. However, the maturity index (MI), trophic diversity (TD) and Simpson diversity (SI) exhibited significant differences between seasons.

Summarizing complex temporal dynamics in communities is difficult to achieve in a way that yields an intuitive picture of change. Rank clocks and rank abundance statistics provide a graphical and analytical framework for displaying and quantifying community dynamics. We used rank clocks, in which the rank order abundance for each species is plotted over time in temporal clockwise direction, to display temporal changes in species abundances and richness. We used mean rank shift and proportional species persistence to quantify changes in community structure in long-term data sets from fertilized and control plots in a late successional old field, frequently and infrequently burned tallgrass prairie, and Chihuahuan desert grassland and shrubland communities. Rank clocks showed that relatively constant species richness masks considerable temporal dynamics in relative species abundances. In the old field, fertilized plots initially experienced high mean rank shifts that stabilized rapidly below that of unfertilized plots. Rank shifts were higher in infrequently burned vs. annually burned tallgrass prairie and in desert grassland compared to shrubland vegetation. Proportional persistence showed that arid grasslands were more dynamic than mesic grasslands. We conclude that rank clocks and rank abundance statistics provide important insights into community dynamics that are often hidden by traditional univariate approaches.

Multiple disturbances to ecosystems can influence community structure by modifying resistance to and recovery from invasion by non-native species. Predicting how invasibility responds to multiple anthropogenic impacts is particularly challenging due to the variety of potential stressors and complex responses. Using manipulative field experiments, we examined the relative impact of perturbations that primarily change abiotic or biotic factors to promote invasion in coastal salt marsh plant communities. Specifically we test the hypotheses that nitrogen enrichment and human trampling facilitate invasion of upland weeds into salt marsh, and that the ability of salt marsh communities to resist and/or recover from invasion is modified by hydrological conditions. Nitrogen enrichment affected invasion of non-native upland plants at only one of six sites, and increased aboveground native marsh biomass at only two sites. Percent cover of native marsh plants declined with trampling at all sites, but recovered earlier at tidally flushed sites than at tidally restricted sites. Synergistic interactions between trampling and restricting tidal flow resulted in significantly higher cover of non-native upland plants in trampled plots at tidally restricted sites. Percent cover of non-native plants recovered to pre-trampling levels in fully tidal sites, but remained higher in tidally restricted sites after 22 months. Thus, perturbations that reduce biotic resistance interact with perturbations that alter abiotic conditions to promote invasion. This suggests that to effectively conserve or restore native biodiversity in altered systems, one must consider impacts of multiple human disturbances, and the interactions between them.

Lessonia trabeculata is a brown seaweed inhabiting the rocky subtidal zone along the coast of central and northern Chile, where it is the dominant kelp, and an important species in community structure. Morphological and reproductive aspects of this alga are dependent on environmental conditions and geographic distribution, and the present study gives data on its reproductive periodicity. The reproductive phenology for three populations from northern Chile (29-30°S) was evaluated by means of seasonal examination of morphological and reproductive characteristics of both macroscopic sporophytes and microscopic gametophytes. Comparative laboratory cultures of spores were made to determine seasonal differences in their capacity to produce viable plants. This species is perennial, and demonstrates year-round presence of reproductive tissues, although showing variation in reproductive phenology over time and among populations. The size of blades increases in spring and summer, whereas its reproductive potential (e.g., area and proportion of the reproductive tissue and the release of spores) increases in autumn. Culture experiments showed that spring and summer reproductive tissue released zoospores which had low germination rates compared to those of autumn and winter, and which produced female gametophytes of low fertility. The population differences depended on the character analysed and the season of the year. The development of both phases of the life cycle of L. trabeculata may be influenced by the local environmental conditions and their seasonal changes, and were expressed as morphological and/ or reproductive changes in the plants. A better understanding of the seasonal adaptations may be obtained if future comparisons are made between widely separated populations or between individuals from the extremes of geographic distribution of the species.