Scale Distribution Patterns Research Articles

European bee diversity: Taxonomic and phylogenetic patterns

AbstractAimWild bees still face striking shortfalls in knowledge of biodiversity in key regions of the world. This includes Europe, where despite a long tradition of data gathering, the continental scale distribution patterns of wild bees have not been systematically analysed to date. This study aims to characterise large‐scale biodiversity patterns to: (i) understand spatial–temporal heterogeneity in large‐scale databases, (ii) locate genuine diversity hotspots and their relationship with biogeographical patterns or habitats of interests and (iii) identify understudied species and areas to further design conservation actions for most at risk species in key regions.LocationEurope.TaxonBees.MethodsWe present a continental and standardised study of bee taxonomic and phylogenetic diversity patterns in Europe, using a large compilation of occurrence records of nearly three million validated occurrence records for 1515 wild bee species.ResultsSouthern and eastern Europe suffer from the largest gaps in data availability while northern and western regions benefit from better historical coverage. Our models show that higher wild bee diversity in Europe is hosted in xeric, warm areas, as highlighted by a clear latitudinal gradient. However, phylogenetic diversity is predicted to be more homogenous across Europe than taxonomic diversity, suggesting that policies and strategies targeted to protect species richness may differ from those targeting greater phylogenetic diversity.Main conclusionsThis study represents a significant advance in the characterisation of wild bee distribution patterns across Europe and is an important stepping stone towards the design of more targeted survey efforts and conservation actions of this key group of pollinators. This, in turn, will provide the data necessary to improve the spatiotemporal coverage in a context of ongoing and future Europe‐wide monitoring schemes, to ultimately develop cost‐effective, coordinated and evidence‐based conservation actions and tailored habitat management actions that can be implemented on a smaller scale.

Particulate organic carbon exports from the terrestrial biosphere controlled by erosion

The transport of particulate organic carbon (POC) through rivers from land to sea affects the redistribution of global organic carbon. However, because of the limitation of the quantity and quality of monitoring data, the POC magnitude, scale and global distribution pattern of land-sea migration are still not well understood. Therefore, based on an updated GEMS-GLORI database and other reanalysis data, we use the soil erosion model (Ferosion), total suspended solids model (Ftss), and runoff model (Frunoff) to re-analyze and generate the POC flux of major rivers in the world dataset. The major results are as follows: the POC flux from global terrestrial biosphere rivers exports approximately 0.12–0.20 Pg C to oceans every year, including 0.20 Pg Ferosion, 0.17 Pg Ftss, and 0.12 Pg Frunoff. In contrast to earlier studies that the Pacific and Arctic Oceans are the main recipients of POC flux, we find that the Pacific and Atlantic received more POC flux and received 30.76%–62.51% and 26.77%–53.95%, respectively. This difference may be related to the combined effects of soil erosion, total suspended solids, and runoff. Asia exports more POC than other continents (60.50%–61.69%). The Amazon basin is the major contributor to the Atlantic POC, contributing 53.30%–58.68%. Furthermore, because of the intense human activities and the widespread distribution of many large watersheds in the highly eroded area, it was found that the POC flux has two key zones (25.75–41.5°N and 4.50°N–13.50°S) in the latitude zone. In summary, the above findings increase our understanding of the spatial redistribution of global organic carbon from land to sea.

Using correlative and mechanistic niche models to assess the sensitivity of the Antarctic echinoid Sterechinus neumayeri to climate change

The Southern Ocean is undergoing rapid environmental changes that are likely to have a profound impact on marine life, as organisms are adapted to sub-zero temperatures and display specific adaptations to polar conditions. However, species ecological and physiological responses to environmental changes remain poorly understood at large spatial scale owing to sparse observation data. In this context, correlative ecological niche modeling (ENMc) can prove useful. This approach is based on the correlation between species occurrences and environmental parameters to predict the potential species occupied space. However, this approach suffers from a series of limitations amongst which extrapolation and poor transferability performances in space and time. Mechanistic ecological niche modeling (ENMm) is a process-based approach that describes species functional traits in a dynamic environmental context and can therefore represent a complementary tool to understand processes that shape species distribution in a changing environment. In this study, we used both ENMc and ENMm projections to model the distribution of the Antarctic echinoid Sterechinus neumayeri. Both models were projected according to present (2005–2012) and future IPCC scenarios RCP 4.5 and 8.5 for (2050–2099). ENMc and ENMm projections are congruent and predict suitable current conditions for the species on the Antarctic shelf, in the Ross Sea and Prydz Bay areas. Unsuitable conditions are predicted in the northern Kerguelen Plateau and South Campbell Plateau due to observed lower food availability and higher sea water temperatures compared to other areas. In contrast, the two models diverge under future RCP 4.5 and 8.5 scenarios. According to ENMm projections, the species would not be able to grow nor reach sexual maturity over the entire ocean, whereas the Antarctic shelf is still projected as suitable by the ENMc. This study highlights the complementarity and relevance of EMN approaches to model large scale distribution patterns and assess species sensitivity and potential response to future environmental conditions.

Agonistic behavioural asymmetry in two species of montane lizard that exhibit elevational replacement

In montane systems, closely related species tend to segregate spatially along elevational gradients. The role of biotic interactions, relative to species physiological requirements, in maintaining these distribution patterns is an important question in spatial ecology. Theory suggests that the role of interspecific competition can be significant in the maintenance of elevation replacement distributions. Despite this, there has been limited work investigating factors beyond thermophysiology in determining ranges in temperate montane species. We investigated agonistic (i.e. aggressive) behaviour in response to a simulated intruder (conspecific versus heterospecific 3D printed models) in two sister species of temperate montane lizard, Liopholis guthega and L. montana, from south-eastern Australia. The two species have similar thermal tolerances at an area of distributional overlap between 1600 and 1700 m above sea level, above which L. montana is replaced by the high elevation specialist L. guthega. We found that response to intruder stimuli differed between the two species, with the high elevation L. guthega actively biting both conspecific and heterospecific models, whereas the lower elevation L. montana, never attacked either model type. Our findings provide evidence of asymmetric agonistic response in the two montane reptile species. These findings have important implications for understanding how biological interactions and behaviour, in addition to thermo-physiological data, might mediate landscape scale distribution patterns both now and as environments change in the future. More broadly, our results are not consistent with the widespread idea that low elevation species will inevitably ‘push’ higher elevation species out, as global warming erodes species’ thermal envelopes.

Modelling the factors influencing Sambar Deer (Rusa unicolor) occurrence in the wet eucalypt forests of south-eastern Australia

ABSTRACT Many invasive species have had negative effects on the Australian environment, including the introduced Sambar Deer (Rusa unicolor). However, there is a paucity of information on the factors influencing the fine scale distribution and abundance patterns of Sambar Deer in south-eastern Australia. We present the results of a field survey of Sambar Deer in the Critically Endangered Mountain Ash (Eucalyptus regnans) forests of the Central Highlands, Victoria. Our key question was: What factors influence detections of Sambar deer (based on scat counts) within the Mountain Ash forests of the Victorian Central Highlands? We surveyed 86 long-term field sites and detected a total of 245 groups of Sambar Deer pellets on 42% of these sites. Negative binomial regression modelling identified three factors associated with the occurrence of deer pellets. We recorded more pellets: (1) in 30 and 80 year old forest that remained unburned in fires that occurred in 2009, (2) on sites within closed National Parks relative to sites in State Forest, and (3) close to streams.

Correlations between plant climate optima across different spatial scales

Identifying the factors determining the abundance and distribution of species is a fundamental question in ecology. One key issue is how similar the factors determining species’ distributions across spatial scales are (here we focus especially on spatial extents). If the factors are similar across extents, then the large scale distribution pattern of a species may provide information about its local habitat requirements, and vice versa. We assessed the relationships between landscape and national optima as well as landscape and continental optima for growing degree days, maximum temperature and minimum temperature for 96 bryophytes and 50 vascular plants. For this set of species, we derived landscape optima from abundance weighted temperature data using species inventories in central Sweden and a fine-grained temperature model (50 m), national optima from niche centroid modelling based on GBIF data from Sweden and the same fine-grained climate model, and continental optima using the same method as for the national optima but from GBIF data from Europe and Worldclim temperatures (c. 1000 m). The landscape optima of all species were positively correlated with national as well as continental optima for maximum temperature (r = 0.45 and 0.46, respectively), weakly so for growing degree days (r = 0.30 and r = 0.28), but sometimes absent for minimum temperature (r = 0.26 and r = 0.04). The regression slopes of national or continental optima on local optima did not differ between vascular plants and bryophytes for GDD and Tmax. However, the relationship between the optima of Tmin differed between groups, being positive in vascular plants but absent in bryophytes. Our results suggest that positive correlations between optima at different spatial scales are present for some climatic variables but not for others. Moreover, our results for vascular plants and bryophytes suggest that correlations might differ between organism groups and depend on the ecology of the focal organisms. This implies that it is not possible to routinely up- or downscale distribution patterns based on environmental correlations, since drivers of distribution patterns might differ across spatial extents.

Invasion Dynamics of A Termite, Reticulitermes flavipes, at Different Spatial Scales in France.

Termites are social insects that can also be major pests. A well-known problem species is the subterranean termite, Reticulitermes flavipes. It is invasive in France and is thought to have arrived from Louisiana during the 18th century. While the putative source of French populations has been identified, little is known about how the termite spread following its establishment. Here, we examined expansion patterns at different spatial scales in urban areas to clarify how R. flavipes spread in France. Based on our analyses of phylogeography and population genetics, results suggest a scenario of successive introductions into the Charente-Maritime region, on the Atlantic Coast. Two major expansion fronts formed: one that spread toward the northeast and the other toward the southeast. At the regional scale, different spatial and genetic distribution patterns were observed: there was heterogeneity in Île-de-France and aggregation in Centre-Val de Loire. At the local scale, we found that our three focal urban sites each formed a single large colony that contained several secondary reproductives. Our findings represent a second step in efforts to reconstruct termite’s invasion dynamics. They also highlight the role that may have been played by the French railway network in transporting termites over long distances.

Spatiotemporal distribution of an invasive insect in an urban landscape: introduction, establishment and impact

Biological invasions are characterized by dynamic spatiotemporal distribution patterns. Yet landscape scale distribution patterns of invasive species are rarely leveraged to understand invasion in a comprehensive manner. Characterize three key stages of invasion from the landscape scale distribution patterns for an invasive insect—Asian citrus psyllid (Diaphorina citri), and investigate the potential spatial variability in establishment and impact risk. The study focuses on the recent invasion of D. citri in Southern California’s urban landscape. We used a combination of spatiotemporal pattern analyses and species distribution models (SDMs) to characterize the introduction, establishment and impact of D. citri invasion. Diaphorina citri detections in relation to major roadways revealed that initial detections are significantly closer to major roads than later detections, suggesting that transportation corridors serve as introduction pathways. SDMs of D. citri establishment and impact potential using presence-(pseudo)absence and abundance revealed percent impervious surface as the best landscape predictor. Inclusion of prior D. citri detections as a lagged spatiotemporal effect improved both model fit and performance suggesting that small-scale dispersal events do matter. Interestingly, interpolated risk maps based on the predicted occurrence and abundance highlighted substantial spatial variability in D. citri establishment and impact risk. Our study demonstrates how examining spatiotemporal patterns of an invasive species is useful in inferring key stages of the invasion, and how occurrence and abundance information can be leveraged to quantify variability in establishment and impact risk. The study thus provides a useful baseline in formulating effective landscape-level management actions.

Changes and drivers of plant community in the natural broadleaved forests across geographic gradient

Geographic variation can lead to the changes of local plant species, which play crucial roles in primary production and ecosystem structure. Therefore, understanding multiple scale distribution patterns of plant species is important for us to effectively monitor ecosystem changes due to climate changes and other modifications. Here, we mainly investigated the distribution pattern of wood vascular plants and key environmental controlling forces in natural broadleaved forest along the latitudinal gradient across 24 geographic regions of China continental territory. The results showed that the richness and diversity of plant community significantly decreased with the increasing latitude. The similarity of plant community also decreased with increasing latitudinal distance. The mean annual precipitation and mean annual temperature played the most important roles in the distribution of plant community across latitudinal gradient, followed by soil pH and soil moisture.

Biogeographical Patterns of Legume-Nodulating Burkholderia spp.: from African Fynbos to Continental Scales.

Rhizobia of the genus Burkholderia have large-scale distribution ranges and are usually associated with South African papilionoid and South American mimosoid legumes, yet little is known about their genetic structuring at either local or global geographic scales. To understand variation at different spatial scales, from individual legumes in the fynbos (South Africa) to a global context, we analyzed chromosomal (16S rRNA, recA) and symbiosis (nifH, nodA, nodC) gene sequences. We showed that the global diversity of nodulation genes is generally grouped according to the South African papilionoid or South American mimosoid subfamilies, whereas chromosomal sequence data were unrelated to biogeography. While nodulation genes are structured on a continental scale, a geographic or host-specific distribution pattern was not detected in the fynbos region. In host range experiments, symbiotic promiscuity of Burkholderia tuberum STM678(T) and B phymatum STM815(T) was discovered in selected fynbos species. Finally, a greenhouse experiment was undertaken to assess the ability of mimosoid (Mimosa pudica) and papilionoid (Dipogon lignosus, Indigofera filifolia, Macroptilium atropurpureum, and Podalyria calyptrata) species to nodulate in South African (fynbos) and Malawian (savanna) soils. While the Burkholderia-philous fynbos legumes (D lignosus, I filifolia, and P calyptrata) nodulated only in their native soils, the invasive neotropical species M pudica did not develop nodules in the African soils. The fynbos soil, notably rich in Burkholderia, seems to retain nodulation genes compatible with the local papilionoid legume flora but is incapable of nodulating mimosoid legumes that have their center of diversity in South America. This study is the most comprehensive phylogenetic assessment of root-nodulating Burkholderia and investigated biogeographic and host-related patterns of the legume-rhizobial symbiosis in the South African fynbos biome, as well as at global scales, including native species from the South American Caatinga and Cerrado biomes. While a global investigation of the rhizobial diversity revealed distinct nodulation and nitrogen fixation genes among South African and South American legumes, regionally distributed species in the Cape region were unrelated to geographic and host factors.

Exposure to solar radiation drives organismal vulnerability to climate: Evidence from an intertidal limpet

Understanding the physiological abilities of organisms to cope with heat stress is critical for predictions of species’ distributions in response to climate change. We investigated physiological responses (respiration and heart beat rate) of the ectotherm limpet Patella vulgata to heat stress events during emersion and the role of seasonal and microclimatic acclimatization for individual thermal tolerance limits. Individuals were collected from 5 microhabitats characterized by different exposure to solar radiation in the high intertidal zone of a semi-exposed rocky shore in winter and summer of 2014. Upper thermal tolerance limits (heat coma temperatures – HCTs, and heart rate Arrhenius break temperatures - ABTs) were determined for individuals from each microhabitat in both seasons under laboratory conditions. While we found a clear seasonal acclimatization, i.e., higher HCTs and ABTs in summer than in winter, we did not find evidence for microhabitat-specific responses that would suggest microclimatic acclimatization. However, operative limpet temperatures derived from in-situ temperature measurements suggest that individuals from sun exposed microhabitats have a much narrower thermal safety margins than those from less exposed surfaces or within crevices. Microhabitat specific thermal safety margins caused by high thermal heterogeneity at small spatial scales and the lack of short term acclimatization will likely shape small scale distribution patterns of intertidal species in response to the predicted increase in the frequency and intensity of heat waves.

Stand scale variability of topsoil organic matter composition in a high-elevation Norway spruce forest ecosystem

Our knowledge about the effect of single-tree influence areas on the physicochemical properties of the underlying mineral soil in forest ecosystems is still limited. This restricts our ability to adequately estimate future changes in soil functioning due to forest management practices. We studied the stand scale spatial variation of different soil organic matter species investigated by 13C NMR spectroscopy, lignin phenol and neutral sugar analysis under an unmanaged mountainous high-elevation Norway spruce (Picea abies L.) forest in central Europe. Multivariate geostatistical approaches were applied to relate the spatial patterns of the different soil organic matter species to topographic parameters, bulk density, oxalate- and dithionite-extractable iron, pH, and the impact of tree distribution. Soil samples were taken from the mineral top soil. Generally, the stand scale distribution patterns of different soil organic matter compounds could be divided into two groups: Those compounds, which were significantly spatially correlated with topography/altitude and those with small scale spatial pattern (range≤10m) that was closely related to tree distribution. The concentration of plant-derived soil organic matter components, such as lignin, at a given sampling point was significantly spatially related to the distance of the nearest tree (p≤0.05). In contrast, the spatial distribution of mainly microbial-derived compounds (e.g. galactose and mannose) could be attributed to the dominating impact of small-scale topography and the contribution of poorly crystalline iron oxides that were significantly larger in the central depression of the study site compared to crest and slope positions.Our results demonstrate that topographic parameters dominate the distribution of overall topsoil organic carbon (OC) stocks at temperate high-elevation forest ecosystems, particularly in sloped terrain. However, trees superimpose topography-controlled OC biogeochemistry beneath their crown by releasing litter and changing soil conditions in comparison to open areas. This may lead to distinct zones with different mechanisms of soil organic matter degradation and also stabilization in forest stands.

Modest utility of quantitative measures in 18F-fluorodeoxyglucose positron emission tomography scanning for the diagnosis of aortic prosthetic graft infection

The clinical dilemma in suspected aortic graft infection (AGI) is how to noninvasively obtain a reliable proof of infection. In addition to confirming the presence of infection, obtaining information regarding the extent of infection to select a proper strategy for reoperation is also necessary. Therefore, developing a more reliable noninvasive physiologic approach to detect infected prostheses is required. (18)F-fluorodeoxyglucose positron emission tomography scanning ((18)F-FDG PET) has been suggested to have a pivotal role in the detection of AGI. In this study, we assessed the contribution of two (semi) quantitative parameters-maximal standardized uptake value (SUVmax) and tissue-to-background ratio (TBR)-and of two visual parameters-fluorodeoxyglucose (FDG) distribution patterns and visual grading scale-in the final confirmation of the diagnosis of AGI. Patients with a central aortic prosthetic graft and symptoms clinically suggestive of AGI were gathered from a prospectively maintained database. Included were those who underwent (18)F-FDG PET scanning combined with computed tomography angiography and in whom periprosthetic samples were taken at some stage in the diagnostic process. AGI was considered proven in case of a positive culture and compared with a group with negative cultures. Positive predictive values (PPVs) and negative predictive values (NPVs) were calculated. Receiver operating characteristics curves were used to assess the ability of SUVmax and TBR to identify the presence and absence of AGI (ie, accuracy). In 37 of 77 patients with suspected AGI, (18)FDG-PET and perigraft material for culturing was obtained. The tissue culture was positive in 21 of these 37 patients (56.7%). Mean ± standard deviation SUVmax for proven infection was 8.1 ± 3.7 (range, 3.6-18.5) and TBR was 5.9 ± 2.7 (range, 1.7-13.0). The area under the curve for SUVmax was 0.78 (95% confidence interval, 0.63-0.93). A cutoff value of 8 yielded a PPV of 80% and a NPV of 54%. The area under the curve for TBR was 0.70 (95% confidence interval, 0.52-0.87). A cutoff value of 6 yielded a PPV of 73% and NPV of 52%. The PPVs for the visual grading scale and (18)F-FDG distribution patterns were 75% and 61%, respectively; the NPVs were 77% and 67%, respectively. Our study, performed in a small sample of patients suspected of AGI, showed that the diagnostic abilities of quantitative and visual (18)F-FDG PET parameters are modest.

A review of glass eel migratory behaviour, sampling techniques and abundance estimates in estuaries: implications for assessing recruitment, local production and exploitation

Recruitment of the three northern hemi- sphere eel species (European eel Anguilla anguilla, American eel Anguilla rostrata and Japanese eel Anguilla japonica) has reduced significantly over the past thirty-five years. The stock of the European eel is described as being outside safe biological limits, with urgent action required by European Union Member States to assist recovery of the panmictic stock. Stock recruitment models and estimates of silver eel output from a river catchment are strongly influenced by the degree of certainty in estimating key population parameters of each life history stage. Therefore, management decisions aimed at enhancing eel popu- lations rely on sound scientific evidence, based upon a fundamental understanding of the complex anguillid eel life cycle. This review paper focuses on the estuarine entry phase of the eel life cycle and synthesises the current scientific knowledge with regard to glass eel migratory behaviour, sampling methods and abundance estimates within estuaries. Although the behavioural and environmental pro- cesses modulating glass eel migration patterns are reasonably well understood, site specific factors play a significant role in determining fine scale distribution patterns at an individual estuary level. Given the large resource commitment required to adequately sample this key life history stage, behavioural studies of migration patterns on a local scale are crucially important to aid the design of robust sampling programmes aimed at quantifying seasonal abundance and annual recruitment.

Large scale distribution patterns of taxonomic diversity of fish in coral reef waters, South China Sea

The historical data of fish survey in Dongsha Islands,Xisha Zhongsha Islands and Nansha Islands since 1970s were systematically collected and examined to study the large scale distribution patterns of fish diversity in coral reef waters of South China Sea as biodiversity of coral reef takes a significant role in ecological research.Based on the species statistics,514 species were recorded in Dongsha Islands,620 in Xisha Zhongsha Islands,and 548 in Nansha Islands,respectively,which were less than expected and also below the average number in other reef waters elsewhere which have similar habitats with South China Sea.Additionally,we calculated the fish taxonomic diversity indices: the average taxonomic distinctness indices △+ in Dongsha,Xisha Zhongsha and Nansha Islands were 55.1,60.2 and 56.6,respectively;variation in taxonomic distinctness index ∧+ were 121,164 and 150 in those islands,respectively.All △+ values were lower than that of the continental shelf waters of East China Sea,while all ∧+ values were higher than it.Regarding the species' and family's taxon level,we calculated the similarity coefficients between reef waters of South China Sea and Calamine Islands,Milne Bay,southwest continental shelf waters of Nansha Islands and northern conti-nental shelf waters of South China Sea.The results indicated that there is greater difference in similarity coefficients on species level between Xisha Zhongsha Islands and the other reef waters,but less difference occurred on family level,and all similarity values on species and family level are higher in reef waters than those in continental shelf waters.Moreover,with Kruskal-Wallis detection,we studied the relative species richness of associated reef fish families in South China Sea reef areas,Calamine Islands and Milne Bay,but no significance difference were found.Hihgter species diver-sity and lower taxonomic diversity are the main characteristics of large scale distribution patterns of diversity of fish in coral reef waters,South China Sea.

Living where others dare not: Microhabitat distribution in Chorizanthe rigida, a serotinous desert annual

We studied the small scale distribution pattern of Chorizanthe rigida, a serotinous desert annual, in a shrub-mound-to-desert-pavement gradient. Two sites were established in the Mojave Desert and two sites where established in the Sonoran Desert. We placed transects along a soil surface gradient from shrub mounds to desert pavements, and measured land surface properties, soil characteristics, and C. rigida's small scale distribution. A Principal Components Analysis was done on the resulting site × soil variables matrix. C. rigida established preferentially in desert pavements outside shrub canopies. Pavements showed finer soil textures and higher electrical conductivities, while shrub mounds had sandy textures, low surface rockiness, higher nitrogen, and higher cover of annuals. We discuss a probable relationship between seed retention and the establishment on desert pavements: timing seed release allows this species to avoid wind- or animal-induced seed dispersal into shrub mounds and establish outside the nurse mounds, where most annual plants concentrate. The seeds encased in the serotinous involucres, released after rains, are dispersed by run-off into the desert pavements and transition zones where, once developed, the dead seed-retaining structures of adult C. rigida plants persist for years releasing seeds to subsequent rain events.

Patterns of spatial variation of assemblages associated with intertidal rocky shores: a global perspective.

Assemblages associated with intertidal rocky shores were examined for large scale distribution patterns with specific emphasis on identifying latitudinal trends of species richness and taxonomic distinctiveness. Seventy-two sites distributed around the globe were evaluated following the standardized sampling protocol of the Census of Marine Life NaGISA project (www.nagisa.coml.org). There were no clear patterns of standardized estimators of species richness along latitudinal gradients or among Large Marine Ecosystems (LMEs); however, a strong latitudinal gradient in taxonomic composition (i.e., proportion of different taxonomic groups in a given sample) was observed. Environmental variables related to natural influences were strongly related to the distribution patterns of the assemblages on the LME scale, particularly photoperiod, sea surface temperature (SST) and rainfall. In contrast, no environmental variables directly associated with human influences (with the exception of the inorganic pollution index) were related to assemblage patterns among LMEs. Correlations of the natural assemblages with either latitudinal gradients or environmental variables were equally strong suggesting that neither neutral models nor models based solely on environmental variables sufficiently explain spatial variation of these assemblages at a global scale. Despite the data shortcomings in this study (e.g., unbalanced sample distribution), we show the importance of generating biological global databases for the use in large-scale diversity comparisons of rocky intertidal assemblages to stimulate continued sampling and analyses.

Fine scale spatial distributions of two entomopathogenic nematodes in a grassland soil

Entomopathogenic nematodes (EPNs) are widespread lethal parasites of many insect species and are known to play an important part in the regulation of soil food webs. We studied the fine scale (5 × 5 cm) distribution and spatial pattern of EPNs in three replicate 0.25 m 2 plots of grassland. All soil was removed from plots (100 samples per plot at 0–5 cm and 100 samples at 5–10 cm depth) and the entire nematode community was extracted using a sieving/centrifugal flotation technique. Entomopathogenic nematode larvae were examined microscopically and identified to species. We found Steinernema feltiae in all three sampled plots and S. affine in two plots. Distribution and spatial pattern were analysed using Lloyd's index of patchiness and spatial analysis by distance indices (SADIE). Both methods showed that the two nematode species had aggregated distributions, and in the two plots where both species coexisted, SADIE showed a strong spatial association between the two species. In addition, we assigned all EPN larvae to one of four groups (I–IV) of increasing physiological age, based on the retention of the sheath and visible lipid content. Lloyds index identified group I as being the most aggregated, whereas SADIE identified group II as the most aggregated, probably because group I nematodes were aggregated at a scale finer than our sampling regime. Groups III and IV nematodes were found to have random distributions by SADIE, and Lloyd's index of patchiness had low values for these groups. Our findings are consistent with the hypothesis that when EPNs emerge from host insects they exist in large numbers of highly aggregated individuals, but as time after emergence increases, a combination of dispersal and death results in lower numbers of more randomly distributed individuals.

Oceanographic habitat, growth and mortality of larval anchovy (Engraulis encrasicolus) in the northern Aegean Sea (eastern Mediterranean)

Data from two ichthyoplankton surveys carried out during June 1995 and June 1996 were used to study the broad scale distribution patterns of anchovy eggs and larvae over the northern Aegean Sea continental shelf and the regional/inter-annual variability in growth and mortality rates of larvae. Two major spawning grounds were identified. One in the east, located in the area influenced by the Samothraki gyre (SG), in which a large amount of enriched, modified Black Sea water (BSW) is entrapped and one in the west, associated with zooplankton-rich waters in the semi-enclosed Thermaikos gulf close to several river mouths. In the NE Aegean, anticyclonic gyres generated over the continental shelf and fed by the circulating stream of BSW (like the SG) may act as retention areas for larval anchovy. In the west, the high enclosure of the Thermaikos Gulf contributes to reducing offshore dispersal. Major changes were observed in egg and larval abundance as well as larval mortality between June 1995 and June 1996 in both the western and eastern part of the continental shelf. Mean abundance of eggs and early larvae was >5 times higher in 1996 than in 1995, when waters were significantly cooler, fresher and richer in mesozooplankton. Larval survival decreased from 79 to 69% day−1 in the east and from 89 to 74% day−1 in the west between 1995 and 1996. Hence increased egg production was coupled with higher larval mortality during June 1996. Furthermore, a highly significant positive relationship between larval mortality (Z) and mean egg abundance (A) emerged (Z = −0154 + 0.205 log[A], r2 = 0.96, n = 7) when data from this study and a similar study in the NW Mediterranean were regressed. Mean growth rate of anchovy larvae in the study area (∼0.5 mm day−1) did not differ significantly between areas/years. A marked ontogenetic change was observed in the otolith size/recent otolith growth-on-fish size relationships, which exhibited significant inflection points at ∼6 mm formalin preserved length. This change seems to coincide with performance (e.g., catchability) and behavioral changes (e.g., onset of vertical migrations) in European anchovy associated with the development of the caudal fin (the flexion stage).

Basin‐scale distribution patterns of picocyanobacterial lineages in the Atlantic Ocean

Marine picocyanobacteria of the genera Prochlorococcus and Synechococcus are major contributors to oceanic primary production. The genera are genetically diverse, comprising several known ecotypes or lineages. However, little is known of the distribution of these lineages over large geographic areas. Here, we analysed the relative abundance of Prochlorococcus ecotypes and Synechococcus lineages at the ocean basin scale along an Atlantic Meridional Transect (AMT) using dot blot hybridization and fluorescence in situ hybridization (FISH) techniques. The transect covered several contrasting oceanic provinces (gyres, upwelling, temperate regions) as well as environmentally 'equivalent' regions in the northern and southern hemisphere (northern and southern gyres and temperate regions). Flow cytometric data revealed a discrete separation in abundance of major picocyanobacterial genera. Prochlorococcus reached highest abundance in oligotrophic regions, while more mesotrophic waters were dominated by Synechococcus. Individual genetic lineages of both Prochlorococcus and Synechococcus showed highly similar distributions in corresponding regions in the northern and southern hemisphere. In addition, Prochlorococcus showed a distinctive depth distribution, with HLI and HLII ecotypes near the surface and co-occurring LL ecotypes further down in the water column. Conversely, Synechococcus generally revealed no obvious depth preference, but did show highly specific distribution at the horizontal scale, with clades I and IV particularly dominating temperate, mesotrophic waters in both the northern and southern hemispheres. The data clearly reveal that specific picocyanobacterial lineages proliferate in similar oceanic provinces separated by large spatial scales. Furthermore, comparison with an earlier AMT dataset suggests that basin scale distribution patterns for Prochlorococcus ecotypes are remarkably reproducible from year to year.