Parasites of the flounder Platichthys flesus (L.) from the German Bight, North Sea, and their potential use in ecosystem monitoring

As part of integrated biological-effect monitoring, the parasite fauna of the flounder Platichthys flesus (L.) was investigated at five locations in the German Bight, with a view to using parasite species as bio-indicators. Over a period of 6 years, parasites from 30 different taxa were identified, but only 7 taxa of the parasite community occurred regularly at all locations and in sufficient abundance that they could be considered as potential indicator species. These species were the ciliophoran Trichodina spp., the copepods Acanthochondria cornuta, Lepeophtheirus pectoralis and Lernaeocera branchialis, the helminths Zoogonoides viviparus and Cucullanus heterochrous and metacercaria of an unidentified digenean species. Infection characteristics of these parasites are presented, with a comparison of the results from individual sampling periods and those of the long-term data set. Natural influences on the infection levels, such as temporal variations, habitat conditions and host-related factors, were evaluated. All of these parasite species showed significant differences in their infection levels between the Elbe estuary, as the most polluted site, and the less polluted coastal and marine locations: Helgoland, Outer Eider estuary and Spiekeroog, especially in the long-term data set. Gradual differences between the Elbe, the Outer Eider and Helgoland, which were not detected in individual sampling periods, also became evident in the pooled-data set. These were found in the prevalence of Trichodina spp., A. cornuta, Z. viviparus and C. heterochrous. Although salinity is considered as the most important natural factor, influencing the distribution pattern of the majority of the potential indicator species, infection levels of most of these species differed between locations with similar salinity conditions. Infection levels corresponded to a contamination gradient (Elbe > Inner Eider, Outer Eider > Helgoland) established across the locations. Seasonal variation in the infection parameters affected the spatial distribution of the copepod species Lepeophtheirus pectoralis and Lernaeocera branchialis. Annual variations are considered to occur in the range of natural variability, so no trend of increasing or decreasing infection levels of the parasites was found during the course of the study. This study underlined the idea that an analysis of fish-parasite fauna is very useful in ecosystem monitoring. Communicated by H. von Westerhagen, A. Diamant     

Parasites of flounder (Platichthys flesus L.) from the German Bight, North Sea, and their potential use in biological effects monitoring

In the frame of an integrated biological effect monitoring programme, the parasite community of flounder (Platichthys flesus) was investigated at different locations in the German Bight from 1995 to 2000. In order to assess the impact of environmental contamination caused by anthropogenic activities on the parasite community, selected parasitological parameters that displayed significant differences between the sampling sites were subjected to correlation analyses with site-specific contamination and individual pollution loads of their fish hosts. In addition, correlation analyses were conducted with the responses of selected genetic, biochemical, histopathological, physiological and immunological parameters of fish, used as potential biomarkers. In total, 802 flounder were analysed for these parameters. Information on the chemical background at the sampling sites was derived from sediment samples and from 120 samples of blue mussel (Mytilus edulis) tissue, collected at each of the sampling sites. Based on chemical data available from the sediment and blue mussel samples, a pollution gradient could be established between the sampling sites for individual contaminants. The relative abundance of Acanthochondria cornuta, Cucullanus heterochrous and Zoogonoides viviparus, and the community measures species richness and number of heteroxenous species decreased with increasing concentrations of individual heavy metals or hydrocarbons in sediment and blue mussel samples. Most of the parasitological parameters significantly reflected the established site-specific contamination gradient, when data were pooled over all sampling campaigns. Significant correlations were also found with the contamination level of individual flounder. The parasitological parameters included the parasite species Lepeophtheirus pectoralis and Lernaeocera branchialis, which were not correlated to site-specific contamination. Several biomarkers were significantly correlated to the abundance of parasitic copepods A. cornuta, Lernaeocera branchialis and Lepeophtheirus pectoralis and to parasite community parameters. The results showed that the abundance of several metazoan parasite species, species richness and parasite diversity were reduced in contaminated habitats, and that differences between sites were not only related to natural factors, such as salinity, but also to pollution-induced stress. Thus, it can be concluded that the parasite community of fish responds to the level of pollution at a specific site as well as to residues of xenobiotics in individual fish. These findings give indications that the parasite community of fish is a valuable parameter for the assessment of ecological consequences of chemical contamination in aquatic habitats.     

Environmental factors as forces structuring the fish community of the Elbe Estuary

Smelt, flounder, eel, three-spined stickleback, twaite shad, ruffe and herring were the major species among 62 forming the fish community of the Elbe estuary. Species richness, species diversity, evenness and total fish biomass decreased in the upstream direction. Total abundance was greatest during summer. Salinity was the most significant physico-chemical factor affecting species richness and total fish biomass, whereas water temperature was the best predictor of total abundance. Marine fish species decreased with decreasing salinity, while the freshwater species roach and ide were absent at salinities > 15‰. Bream, blue bream, white bream, perch and pikeperch occurred more frequently in shallow marginal regions with lower current velocities, while herring and other marine species occurred closer to the deep central regions with high current velocities. Annual and seasonal variations of the community structure mainly reflected in population dynamics of smelt, flounder, twaite shad, three-spined stickleback and eel, especially those of 0-age smelt. Populations of smelt and ruffe and their importance in the fish community increased between 1989 and 1992, while those of twaite shad and eel decreased. At oxygen concentrations <3 mg I¹, smelt and flounder were rare, but eels were at their maximum at 3.5 mg I⁻¹. Changes of species composition and fish abundance were closely related to daytime and tidal cycle.     

Intestinal helminth parasites in flounder Platichthys flesus from the River Thames: an infracommunity analysis

An analysis was undertaken of intestinal helminth communities in flounder Platichthys flesus from two sites on the River Thames. A comparison was made between helminth community richness and diversity from these sites at the component and infracommunity levels. At the component community level, a richer and more diverse parasite community was found in flounder from the Tilbury location (marine influence) than that from the Lots Road location (freshwater influence). At the infracommunity level, more parasite species and parasite individuals per host were found at Lots Road and the percentage of similarity values were low at both locations. Helminth species with high prevalence values in the parasite communities of the flounder are the dominant species in any individual fish, harbouring multi-specific infections. The presence of more invertebrate species, which are intermediate hosts in the helminth life cycle in the Thames, fish vagility and the high prevalence and abundance values of Pomphorhynchus laevis in the flounder, may explain the differences between the two locations.     

Accumulation of organochlorines and mercury in flounder — an approach to pollution assessments

Levels of PCBs, HCB and Hg were determined in the muscle tissue of flounder (Platichthys flesus L.), sampled at two sites of the highly industrialized Elbe estuary which is characterized by a decreasing gradient of contaminant levels in water and sediments towards the mouth of the river. The contaminant levels were compared to those found in muscle tissue of flounders caught in an unpolluted reference area, the Eider estuary. Juvenile flounders (1–2 cm total length) caught during their migration from the southern North Sea coast into the Elbe estuary in early summer showed a significantly higher level of contamination at both Elbe stations than those from the reference area. In the following spring, the flounders, having grown to a length of 12–14 cm, reflected the gradient of contaminants measured in water and sediment. However, during summer and late autumn a drastic increase in average contaminant concentration was observed in the muscle tissue of flounders taken from the less polluted estuarine site. It became evident that severe oxygen depletion in the heavily polluted area near Hamburg had provoked the migration of highly contaminated fish downstream to the less polluted sampling area; thus intermingling with the less contaminated flounder population of this region had occurred. The results obtained indicate that careful analysis of environmentally controlled behavioural patterns in the species used for monitoring purposes as well as an appropriate statistical treatment of the data gained from chemical analysis are essential for assessing the contaminant concentrations in organisms in relation to the pollution load of their habitats.     

The partitioning of macroinvertebrate diversity across multiple spatial scales in the upper Modder River System,South Africa

A method for assessing the alpha and beta diversity components of a macroinvertebrate community across numerous spatial scales is presented. Findings were not empirically linked to ecological questions as the purpose of this study was primarily the demonstration of a diversity partitioning method. Sampling was carried out at three sites on the upper Modder River in the Free State Province, South Africa between April 2008 and January 2009. Communities were analysed by investigating the relative frequency of species in specific biotopes, a Similarity Profile (SIMPROF) and cluster analyses of the Bray‐Curtis similarities between samples, and the partitioning of species richness and Shannon diversity across multiple spatial scales. Findings revealed that sites showed significant clustering (SIMPROF P < 0.05; <20% Bray‐Curtis similarity), and the species frequencies indicated preference to selected microhabitats. Species richness and Shannon diversity of macroinvertebrates differed significantly (5% confidence levels) from randomly simulated values for sampling sites, biotopes and seasons indicating that diversity is clustered and not homogeneously distributed. The diversity partitioning could have potential in diversity assessment for conservation biology, land management and environmental impact assessments.     

Microbial Community Diversity of Moonmilk Deposits at Ballynamintra Cave, Co. Waterford, Ireland

Caves are extreme and specialised habitats for terrestrial life that sometimes contain moonmilk, a fine-grained paste-like secondary mineral deposit that is found in subterranean systems worldwide. While previous studies have investigated the possible role of microorganisms in moonmilk precipitation, the microbial community ecology of moonmilk deposits is poorly understood. Bacterial and fungal community structure associated with four spatially isolated microcrystalline, acicular calcite moonmilk deposits at Ballynamintra Cave (S. Ireland) was investigated during this study. Statistical analyses revealed significant differences in microbial activity, number of bacterial species, bacterial richness and diversity, and fungal diversity (Shannon's diversity) among the moonmilk sites over an area of approximately 2.5 m². However, the number of fungal species and fungal community richness were unaffected by sampling location. SIMPER analysis revealed significant differences in bacterial and fungal community composition among the sampling sites. These data suggest that a rich assemblage of microorganisms exists associated with moonmilk, with some spatial diversity, which may reflect small-scale spatial differences in cave biogeochemistry.     

Species richness and diversity across rocky intertidal elevation gradients in Helgoland: testing predictions from an environmental stress model

Environmental stress affects species richness and diversity in communities, but the precise form of the relationship is unclear. We tested an environmental stress model (ESM) that predicts a unimodal pattern for total richness and diversity in local communities across the full stress gradient where a regional biota can occur. In 2008, we measured richness and diversity (considering all macrobenthic species) across the entire intertidal range on three rocky shores on Helgoland Island, Germany. Intertidal elevation is known to be positively related to abiotic stress. Since Helgoland is between the northern and southern biogeographic boundaries for the cold-temperate NE Atlantic intertidal biota, it exhibits low stress levels for this biota at low elevations and high stress at high elevations because of long (>6 h) emersion times. Thus, we predicted a unimodal trend for richness and diversity across elevation. On all three shores, richness increased from high to middle elevations, but remained similar between middle and low elevations. Diversity followed the same trend on one shore and different trends (although also non-unimodal) on the other two. Evenness explained the trend differences between richness and diversity. Overall, our study yielded little support for the ESM. Reasons for richness and diversity not decreasing at low elevations may be related to influences of mostly subtidal species, Helgoland’s intertidal range, or sampling resolution. Our study also suggests that the ESM must be developed further to differentiate between richness and diversity. We offer recommendations to improve future ESM research using intertidal systems.     

Facilitation by a dwarf shrub enhances plant diversity of human-valued species at high elevations in the Himalayas of Nepal

Facilitation is a global phenomenon that occurs when one species promotes the growth, survival, or reproduction of another species, mostly in stressful environments. However, the importance of facilitation by shrubs in maintaining plant community diversity is not well evaluated in the Himalayas, especially for the richness and conservation of medicinal and human-valued species. Therefore, we aimed to explore the facilitative role of a dwarf shrub species, Berberis angulosa, in maintaining plant composition and richness of human-valued species in the Langtang valley of Nepal's Himalayas. We censused plant species in open patches and beneath Berberis during monsoon and post-monsoon (dry) seasons at three elevations.Total species richness and richness of human-valued species were significantly higher inside the Berberis canopy than in gaps; the former being 39% and the latter 46% greater under shrubs than in open sites. Facilitation by Berberis shrubs promoted plant community diversity irrespective of season and elevation; however, higher differences in mean species richness for both total plant species and human-valued species during the dry season and at high elevation indicated increased facilitation intensity under more stressful conditions. The facilitative effect of Berberis shrubs increased, combining both seasons, overall plant diversity by 19% (total=105), and human-valued species by 16% (total=56). Our results show the importance of facilitation by nurse shrubs in structuring plant communities and protecting medicinal and socio-ecologically important plants, thus enriching ecosystem services in the Himalayas. These results suggest nurse plant species should be incorporated into conservation policies and management strategies for effective biodiversity conservation and sustainability, especially in the face of climate change.     

Diversity of medium and large mammals in the Loka Abaya National Park,southern Ethiopia

We evaluated the richness, diversity, and composition of the medium and large mammal community in the Loka Abaya National Park (LANP), southern Ethiopia, and how these parameters differ among four habitat types: wooded grassland, riverine forest, hilly scrubland and wetland, and between seasons. We recorded a total of 2,573 individual animals of 28 medium and large mammal species in the park. This included three globally threatened species: the endangered African wild dog (Lycaon pictus), the vulnerable Leopard (Panthera pardus), and Hippopotamus (Hippopothamus amphibius). Season had little effect on species richness, diversity, and composition both across and within habitat types. However, species richness across seasons was significantly different among the four habitat types, in the declining order of the following: wooded grassland > riverine forest > hilly scrubland > wetland. The strongest similarity in species composition, both across and within seasons, was found between wooded grassland and riverine forest. In terms of relative abundance, mammal assemblage of the wooded grassland and wetland habitats had more evenly distributed number of species with different relative abundance categories. Overall, Anubis Baboon (Papio anubis), Grivet Monkey (Chlorocebus aethiops), and Greater Kudu (Tragelephus strepsiceros) were the three most abundant species across habitat types. In conclusion, findings of our study reveal that LANP plays an important role in Ethiopia's mammal conservation. Our findings will serve as baseline information for managers of the park to make effective conservation decisions and as a baseline for researchers wishing to conduct related ecological studies.     

Preliminary analysis of the fish species of the Pacific Central American Mangrove of Zancudo, Golfo Dulce, Costa Rica

The aim of the present paper is to provide first information on the mangrove fish community of the tropical fjord-like Golfo Dulce (GD), to study its importance for fish diversity and fisheries in the area and to give preliminary results on its spatial–temporal variation. Eighty-two species belonging to 30 families were identified. More than half of them belonged to the estuarine transient fish group and only 14 species were estuarine resident, highlighting the importance of the Zancudo mangrove as a transition area. The most diverse families were Sciaenidae, Carangidae and Haemulidae for both rainy and dry seasons. As much as 71% of the species captured were of first or second grade economic value and only 11% had no commercial value. Comparing our data with fisheries and scientific surveys inside and outside the gulf suggests the importance of the Zancudo mangrove for regional fisheries and fish diversity. Multidimensional scaling (MDS) indicated gradual changes in the fish community composition from the river mouth to the more internal sampling sites for rainy and dry seasons. Moreover, shifts in abundance and species composition between seasons were observed, mainly an increase in the differences between the boundaries and the central zones of the mangrove. These changes were attributed to the higher salinity differences between sites during the dry season forcing the occasional visitor fish downstream and freshwater fish taxa upstream. While the results contribute to initiatives for participative fisheries management in the region, further studies are needed to analyse the variations in detail.     

Temporal shifts and niche overlapping in <Emphasis Type="Italic">Copestylum</Emphasis> (Diptera,Syrphidae) communities reared in cactus species in a central Mexican scrubland

Semiarid scrubland communities are highly dynamic in terms of their species composition, abundance, and functioning, given the drastic changes in climate among seasons. Spatiotemporal patterns of saprophagous Copestylum (Diptera: Syrphidae) communities in different cactus species richness have not yet been studied, although seasonal changes and plant species richness have been shown to strongly impact the diversity and distribution of many insect communities in scrublands. We analyzed the impact of seasonality and of habitat type (disturbed and undisturbed) on Copestylum communities reared from cactus species at the Barranca de Metztitlán Biosphere Reserve, in central Mexico, by comparing their community structure between seasons and habitats, and assessing the contribution of diversity components for the total diversity of this genus. We also measured patterns of temporal niche overlap among hoverfly species considering their breeding medium. Seasonal variation influenced Copestylum community composition most significantly. Species richness and abundance of Copestylum were higher in the rainy season. Additive partitioning of diversity showed that the main component for species richness is beta diversity between seasons. We detected high niche overlap during the dry season and low overlap during the rainy season. This study provides evidence of temporal shifts in xeric hoverfly communities and suggests that the Copestylum species partition resources over time.     

人为干扰对武汉市城市绿地鸟类群落结构的影响

城市绿地生态系统是城市景观的重要组成部分,具有重要的生态与文化价值。鸟类是城市绿地生态系统的指示类群,研究人类活动对鸟类资源的影响能够为城市生态景观的建设与维护提供重要理论依据。本研究于2021年10月至2022年5月,采用样线法对武汉市不同干扰强度的城市绿地内林鸟群落进行调查。共记录到鸟类11目34科100种,其中国家二级重点保护鸟类9种,在物种组成上以雀形目为主(76种,占调查到总鸟种数的76%),在居留型上以留鸟为主(42种,42%),在区系上主要属于东洋界(45种,45%)。繁殖季鸟类物种数高于非繁殖季,主要是由于夏候鸟和旅鸟的增加导致。在不同干扰强度中,重度干扰斑块的平均鸟类个体数最多,轻度干扰斑块的鸟类物种丰富度、多样性指数和均匀度指数最高,而中度干扰斑块的鸟类个体数、物种丰富度、多样性指数和均匀度指数均为最低,且繁殖季和非繁殖季鸟类群落结构在不同人为干扰强度中的格局未发生变化。综上所述,武汉市城市绿地的鸟类多样性较为丰富,随着干扰强度增加,鸟类多样性出现非线性差异,揭示了人为干扰与自然干扰对生态影响的差异;在面积狭小、破碎化严重的斑块中,人为干扰可能有利于城市绿地鸟类多样性的维持。     

遂渝铁路边坡草本植物多样性季节动态和空间分布特征

以遂渝铁路边坡植物群落为研究对象,自然边坡为对照,分别于2008年9月、12月、2009年3月和6月对其进行植物调查。采用Margalef指数、Simpson指数、Shannon-Wiener指数和Pielou指数等指标评价不同季节、坡位和植被类型条件下草本植物多样性的变化。结果表明：在时间尺度上,铁路边坡坡中物种丰富度呈现明显的季节性差异(P<0.05),以秋季最大为2376;铁路边坡各坡位草本植物多样性和均匀度指数也呈现显著季节性变化(P<0.05),且变化规律一致：春季>夏季>冬季>秋季;与铁路边坡不同,自然边坡草本植物丰富度、多样性和均匀度指数变化趋势不明显(P>0.05)。在空间分布上,坡位对铁路边坡物种丰富度影响显著(P<0.05),其中,夏季坡上植物丰富度最大为2.164,春季、秋季和冬季丰富度最大值均在坡中最大,分别为2.261、2.376和1.983;坡位仅对自然边坡秋季物种丰富度和均匀度影响显著(P<0.05),其中,物种丰富度表现为坡上>坡下>坡中,而均匀度为坡中>坡上>坡下。不同植被类型的物种丰富度、多样性和均匀度也有较大差异,自然边坡物种多样性明显大于铁路边坡,总体上自然边坡植被恢复优于铁路边坡。因此,加强对植被恢复的管理是铁路边坡生态恢复的重要环节。     

Determinants of lepidopteran community composition and species diversity in eastern deciduous forests: roles of season, eco-region and patch size

Ecologists have long recognized that factors operating at both local and regional scales influence whether a given species occurs in an ecological community. The relative roles of variables manifested at local and regional scales on community structure, however, remain an unexplored issue for many faunas. To address this question, we compared the community composition and species diversity of forest Lepidoptera between (i) large forest tracts in historically glaciated and unglaciated regions of the eastern deciduous forest in North America, and (ii) large and small forest patches within a highly fragmented forest landscape. Specifically, we used seasonally stratified sampling to test whether regional and local differences in moth communities were related to variation in stand structure and floristic composition. At the local scale, we tested three alternative hypotheses describing the effects of patch size on moth species richness: species impoverishment, species replacement, or species supplementation. Cluster analysis revealed significant compositional differences in moth communities sampled between (i) early and late seasons, (ii) glaciated and unglaciated forest eco‐regions, and (iii) large and small forest patches. Canonical correspondence analysis suggested that floristic variation at regional scales had a greater role in determining moth community composition than local vegetation or patch‐size effects. Species richness was higher in the glaciated North Central Tillplain, and was attributable to a more diverse herbaceous feeding moth assemblage. Finally, we found evidence that both species impoverishment and species replacement processes structure the moth fauna of small woodlots; the richness of moths with larvae that feed on woody plants decreased with patch area, but herbaceous feeding species increased in diversity in smaller patches. Thus, our results suggest that local and regional differences in moth community structure are mediated by differences in host‐plant resources attributable to regional biogeographic history and local differences in patch size. Because community composition appeared to be more sensitive to environmental variation than species richness, we suggest that monitoring lepidopteran species diversity in forests will not detect significant changes in species composition due to environmental change.     

Scales of spatiotemporal variability in macroinvertebrate abundance and diversity in monsoonal streams: detecting environmental change

1. We quantified spatial and temporal variability in benthic macroinvertebrate species richness, diversity and abundance in six unpolluted streams in monsoonal Hong Kong at different scales using a nested sampling design. The spatial scales were regions, stream sites and stream sections within sites; temporal scales were years (1997–99), seasons (dry versus wet seasons) and days within seasons. 2. Spatiotemporal variability in total abundance and species richness was greater during the wet season, especially at small scales, and tended to obscure site‐ and region‐scale differences, which were more conspicuous during the dry season. Total abundance and richness were greater in the dry season, reflecting the effects of spate‐induced disturbance during the wet season. Species diversity showed little variation at the seasonal scale, but variability at the site scale was apparent during both seasons. 3. Despite marked variations in monsoonal rainfall, inter‐year differences in macroinvertebrate richness and abundance at the site scale during the wet season were minor. Inter‐year differences were only evident during the dry season when streams were at base flow and biotic interactions may structure assemblages. 4. Small‐scale patchiness within riffles was the dominant spatial scale of variation in macroinvertebrate richness, total abundance and densities of common species, although site or region was important for some species. The proportion of total variance contributed by small‐scale spatial variability increased during the dry season, whereas temporal variability associated with days was greater during the wet season. 5. The observed patterns of spatiotemporal variation have implications for detection of environmental change or biomonitoring using macroinvertebrate indicators in streams in monsoonal regions. Sampling should be confined to the dry season or, in cases where more resources are available, make use of data from both dry and wet seasons. Sampling in more than one dry season is required to avoid the potentially confounding effects of inter‐year variation, although variability at that scale was relatively small.     

Abundance of arbuscular mycorrhizal fungi spores in different environments in a tropical rain forest, Veracruz, Mexico

 The aim of this study was to compare mycorrhizal abundance and diversity in sites with different regimes of disturbance in a tropical rain forest at Los Tuxtlas, Veracruz, Mexico. Arbuscular mycorrhizal spores were quantified at two sites: closed canopy and gaps in the forest. Data were recorded during dry, rainy, and windy ("nortes") seasons. Spores of eight Glomus species, sporocarps of three Sclerocystis species, three species of Acaulospora and two of Gigaspora were found. Significant differences in the number of species and spores were found among seasons. The highest numbers of species and spores were observed during the dry season, with a marked decrease during the rainy season. Our results show that disturbance does not but seasonality does affect abundance and richness of mycorrhizal spores in this tropical wet forest. Accepted: 11 October 1998     

Bird diversity patterns in Neotropical temperate farmlands: The role of environmental factors and trophic groups in the spring and autumn

Productivity, habitat heterogeneity and environmental similarity are of the most widely accepted hypotheses to explain spatial patterns of species richness and species composition similarity. Environmental factors may exhibit seasonal changes affecting species distributions. We explored possible changes in spatial patterns of bird species richness and species composition similarity. Feeding habits are likely to have a major influence in bird–environment associations and, given that food availability shows seasonal changes in temperate climates, we expect those associations to differ by trophic group (insectivores or granivores). We surveyed birds and estimated environmental variables along line‐transects covering an E‐W gradient of annual precipitation in the Pampas of Argentina during the autumn and the spring. We examined responses of bird species richness to spatial changes in habitat productivity and heterogeneity using regression analyses, and explored potential differences between seasons of those responses. Furthermore, we used Mantel tests to examine the relationship between species composition similarity and both the environmental similarity between sites and the geographic distance between sites, also assessing differences between seasons in those relationships. Richness of insectivorous birds was directly related to primary productivity in both seasons, whereas richness of seed‐eaters showed a positive association with habitat heterogeneity during the spring. Species composition similarity between assemblages was correlated with both productivity similarity and geographic proximity during the autumn and the spring, except for insectivore assemblages. Diversity within main trophic groups seemed to reflect differences in their spatial patterns as a response to changes between seasons in the spatial patterns of food resources. Our findings suggest that considering different seasons and functional groups in the analyses of diversity spatial pattern could contribute to better understand the determinants of biological diversity in temperate climates.     

More species,but all do the same: contrasting effects of flood disturbance on ground beetle functional and species diversity

The role of habitat disturbance on biodiversity is central as it promotes changes in ecological systems. That said, still little is known about the functional consequences of such changes. Functional diversity can be used to revealing more mechanistically the disturbance effects on communities by considering the richness and the distribution of traits among the species. Here we analyzed the response of functional and species diversity of ground beetles to flood disturbance to better understand the functioning of alluvial invertebrate communities. Ground beetles were sampled in periodically flooded grasslands along the Elbe River in Germany. We used generalized linear mixed effects models to unveil the relationships between flood disturbance, species and functional diversity, respectively. We measured different components of functional diversity (functional richness, evenness, dispersion, and divergence) and analyzed species diversity by means of rarefied species richness, abundances, evenness and Simpson's diversity. We found contrasting relationships in that most species diversity measures peaked at highest disturbance levels, while most functional diversity measures decreased with increasing disturbance intensities. Inversed relationships between species and functional diversity are rarely observed, as most studies report on positive correlations. We explain increasing species diversity with a higher amount of resources available in highly disturbed sites. Decreasing functional diversity is best explained through the convergence of species traits by flood disturbance and uneven resource exploitation in highly disturbed plots (low functional evenness), suggesting strong impacts from functionally different generalist species in floodchannels. We show that the amount of resources available, and how these resources are exploited, play major roles in the functioning of floodplain ground beetle communities.     

Seasonal variation of black fly (Diptera: Simuliidae) species diversity and community structure in tropical streams of Thailand

Seasonal variation of the physicochemical conditions of streams plays an important role in aquatic insect diversity and community structure. Asian tropical streams profoundly change between seasons due to the effects of monsoons. However, little is known about how these changes affect aquatic insect diversity and community structure. The objectives of this study are to examine seasonal variations of the physicochemical conditions in tropical streams in Thailand and to assess the effects of these changes on black fly community structure and diversity. Black flies were sampled and physicochemical conditions recorded at eight sites between December 2007 and December 2008. A total of 10 black fly species were found. Comparisons of the streams between seasons revealed that physical conditions related to rainfall rate were significantly different. Canonical correspondence analysis differentiated sampling sites from each season. Streams in the rainy season were faster and deeper, with higher discharge and conductivity than those of the cold and dry seasons. Species richness was significantly higher in the rainy season than in the cold and dry seasons ( F  = 6.23, P  = 0.004). Community structure profoundly changed between the low-flow season (cold and dry) and high-flow season. Black fly species found predominantly in the low-flow season ( Simulium siamense "cytoform A", S. aureohirtum ) decreased dramatically during the high-flow season. In contrast, species found at high frequency during the high-flow season ( S. nakhonense , S. angulistylum ) disappeared in the low-flow season. The study demonstrates the importance of seasonal variation of stream conditions on black fly community structure and diversity.