Large scale spatial and temporal variation in recruitment to fish populations on coral reefs

Summary Visual census was used to sample young of the year of fish species recruited to each of two habitats on seven lagoonal platform reefs of the Capricorn-Bunker Group, Great Barrier Reef. The reefs sampled span an area 70 km in extent. In 1983, 62 species from 13 families were detected as recruits on reef slope sites. The total number of cruits, and the number of each of 6 of 16 species tested, differed significantly among reefs, despite the fact that differences among sites within reefs did not exist, and that sampled slopes were chosen to be hydrographically, and physiographically as similar as possible. Lagoonal patch reefs were sampled in two years. In 1982, 76 species of 11 families occurred as recruits. In 1983, 86 species of 12 families were recorded. All of 22 species common enough to test showed some significant variation in abundance among reefs, years, or both. For 9 species, significant year x reef interactions occurred, demonstrating that relative recruitment success among reefs varied between years. Reasons for the substantial levels of variability are discussed, and implications for the organisation of reef fish communities are considered.     

西沙群岛主要岛礁鱼类物种多样性及其群落格局

为了解珊瑚礁海域鱼类物种多样性及其群落特征,作者2003年5月在西沙群岛7座主要岛礁(北礁、华光礁、金银岛、东岛、浪花礁、玉琢礁和永兴岛)采用底层刺网进行了调查,运用聚类分析和非度量多维标度(NMDS)等多元统计分析方法,对7个岛礁鱼类的种类组成、优势种、多样性和群落格局进行了分析.调查海域共记录鱼类146种,隶属10...     

The influence of habitat on the spatial variation in fish assemblage composition in an unimpacted tropical River of Ganga basin, India

Effects of local habitat variables on the structure of fish assemblage were evaluated from 50 sampling sites in a tropical River of Central India of the Ganges basin with limited anthropogenic disturbance covering premonsoon, monsoon and postmonsoon periods. Data were analyzed for 5,186 fish individuals of 24 freshwater fish species of conservation and fishery management interest. Out of the total fish species, seven belong to the ??endangered?? and 8 belong to the vulnerable category. A Cyprinid, Puntius sarana, was the most widely distributed species (frequency of occurrence 76%) out of the total species in this study. We used canonical correspondence analyses to determine the influence of environmental conditions on species occurrences and assemblage characteristics. Regarding the microhabitat, hydromorphological parameters (depth and current velocity) followed by temperature, turbidity and total dissolve solid were of significant for the structure of the fish community. Conductivity was another important factor that explained the major proportion of the variability affecting fish in their habitat choice. The other local habitat variables like overhanging vegetation and land use were of secondary but significantly important for the assemblage of the fishes. Our results suggests the importance of local environment influences on the fishes of conservation importance and their assemblage characteristics in an unimpacted river and provide a framework and reference conditions to support restoration efforts of relatively altered fish habitats in tropical rivers of India.     

Explaining variation in tropical plant community composition: influence of environmental and spatial data quality

The degree to which variation in plant community composition (beta-diversity) is predictable from environmental variation, relative to other spatial processes, is of considerable current interest. We addressed this question in Costa Rican rain forest pteridophytes (1,045 plots, 127 species). We also tested the effect of data quality on the results, which has largely been overlooked in earlier studies. To do so, we compared two alternative spatial models [polynomial vs. principal coordinates of neighbour matrices (PCNM)] and ten alternative environmental models (all available environmental variables vs. four subsets, and including their polynomials vs. not). Of the environmental data types, soil chemistry contributed most to explaining pteridophyte community variation, followed in decreasing order of contribution by topography, soil type and forest structure. Environmentally explained variation increased moderately when polynomials of the environmental variables were included. Spatially explained variation increased substantially when the multi-scale PCNM spatial model was used instead of the traditional, broad-scale polynomial spatial model. The best model combination (PCNM spatial model and full environmental model including polynomials) explained 32% of pteridophyte community variation, after correcting for the number of sampling sites and explanatory variables. Overall evidence for environmental control of beta-diversity was strong, and the main floristic gradients detected were correlated with environmental variation at all scales encompassed by the study (c. 100–2,000 m). Depending on model choice, however, total explained variation differed more than fourfold, and the apparent relative importance of space and environment could be reversed. Therefore, we advocate a broader recognition of the impacts that data quality has on analysis results. A general understanding of the relative contributions of spatial and environmental processes to species distributions and beta-diversity requires that methodological artefacts are separated from real ecological differences.     

Arctic fisheries catches in Russia, USA, and Canada: baselines for neglected ecosystems

The Amerasian Arctic, covering northern Siberia (Russia), Arctic Alaska (USA), and the Canadian Arctic, extends over seven coastal Large Marine Ecosystems and makes up the seasonally ice-free part of FAO Statistical Area 18 (Arctic Sea). Historically, the harsh climate has limited marine fisheries (here excluding marine mammal hunting) to small-scale operations conducted mainly in estuaries and river deltas. Most of the catches have traditionally not been reported to FAO, with the result that total catch estimated here from 1950 to 2006 is 75 times higher than the sum of the catches reported for FAO 18 (Arctic). Catches were reconstructed from data on fishing communities in Canada and Alaska, and from various government and non-government sources for Siberia. Based on national data supplied to FAO since 1950, catches have been reported as 12,700 t in toto (reported on behalf of the former Soviet Union). This compares with our reconstructed catches of over 950,000 t, i.e., 770,000, 89,000, and 94,000 t by Russia, USA, and Canada, respectively for the same time period. The reconstructed catch (mainly whitefishes in Siberia, various salmonids in Alaska, and Arctic char in Canada) was 24,100 t year⁻¹ in 1950, but declined to 10,200 t year⁻¹ by the mid-2000s. Reasons for these trends are discussed by country, along with sources of uncertainty (particularly large for Siberia). Catches were allocated to Large Marine Ecosystems to present ecosystem-relevant baselines for the impact of fisheries on the Arctic, which can be expected to increase, as industrial fisheries move into a warming Arctic following the invasion of boreal species, unless countries apply precautionary ecosystem-based management approaches.     

Rapid changes in bird community composition at multiple temporal and spatial scales in response to recent climate change

Although climate change is acknowledged to affect population dynamics and species distribution, details of how community composition is affected are still lacking. We investigate whether ongoing changes in bird community composition can be explained by contemporary changes in summer temperatures, using four independent long‐term bird census schemes from Sweden (up to 57 yr); two at the national scale and two at local scales. The change in bird community composition was represented by a community temperature index (CTI) that reflects the balance in abundance between low‐ and high‐temperature dwelling species. In all schemes, CTI tracked patterns of temperature increase, stability or decrease remarkably well, with a lag period of 1–3 yr. This response was similar at both the national and local scale. However, the communities did not respond fast enough to cope with temperature increase, suggesting that community composition lags behind changes in temperature. The change in CTI was caused mainly by changes in species’ relative abundances, and less so by changes in species composition. We conclude that ongoing changes in bird community structure are driven to a large extent by contemporary changes in climate and that CTI can be used as a simple indicator for how bird communities respond.     

Catastrophic and background disturbance of tropical ecosystems at the Luquillo Experimental Forest

The forests of the Luquillo Experimental Forest Long-Term Ecological Research site are subject to low-intensity, widespread disturbance that establishes levels of background mortality that contrast with periodic catastrophic mortality resulting from hurricanes and landslides. Although catastrophic mortality is more dramatic, background mortality is still more important in determining population turnover. However, catastrophic mortality may still be an important agent in determining ecosystem structure. Catastrophic disturbances affect forest function in many ways besides mortality, some of which are only apparent in the context of long-term studies. Since most ecosystems are subject to some form of catastrophic disturbance, general principles can be derived from comparative studies of disturbance in different systems.     

Primate communities: Their structure and role in tropical ecosystems

The structure of primate communities living in a number of undisturbed areas is described and compared. Species richness is highest in tropical rain forests of Africa and South America, where up to 14 different species can share the same habitat. The number of sympatric primates in woodlands and savannas is always much lower. Some striking differences in community structure may be observed between communities living in apparently similar habitats. Three major factors may be held responsible for such discrepancies: history and paleoecology, present spatial heterogeneity of the vegetation, and competition with other taxonomic groups. The role of primates in the functioning of forest ecosystems is discussed. Though their trophic impact may be important, the role they play in seed dispersal appears to be more significant; they contribute greatly to homeostasis, as well as to regeneration, of the rain forests. A number of ecological traits are particularly developed among primates and may have contributed to the rapid evolutionary success of the order. Their predominantly vegetarian diet allows them to build up higher population densities than sympatric carnivorous mammals;their arborealism permits them to make use of all edible plant material available in a tridimensional environment; the opportunistic tendencies of some cebids, cercopithecids, and pongids enable them to take advantage of a variety of habitats and situations; and finally, an extended socialization period and a long life-span, allowing them to develop social traditions, give to many of them a further possibility to adapt quickly to novel situations. This paper is a revised version of the third Osman Hill Memorial Lecture delivered at the joint meeting of the Primate Society of Great Britain and the Association for the Study of Animal Behaviour, held in London on 2/3 December 1982.     

GLay: community structure analysis of biological networks

SUMMARY: GLay provides Cytoscape users an assorted collection of versatile community structure algorithms and graph layout functions for network clustering and structured visualization. High performance is achieved by dynamically linking highly optimized C functions to the Cytoscape JAVA program, which makes GLay especially suitable for decomposition, display and exploratory analysis of large biological networks. AVAILABILITY: http://brainarray.mbni.med.umich.edu/glay/.     

Short-term spatial and temporal variation of sediment oxygen dynamics in a tropical tidal salt flat

Short-term spatial and temporal heterogeneity of oxygen dynamics and net primary production were studied in a tree day diurnal variation at a tidal tropical salt flat in the estuarine system of Sepetiba/Guaratiba coastal plain, Rio de Janeiro, Brazil. Oxygen concentrations were measured in situ with high temporal and spatial resolution oxygen microsensors. The results showed a remarkable heterogeneity of both oxygen penetration depth (from 0.18 to 0.85 cm) and net primary production (from −0.085 to 0.115 μmol O₂ cm⁻² s⁻¹) at different stations and sampling periods. Fast variations in abiotic factors like salinity and light due to the variable rainy weather were possibly the drivers of the high heterogeneity. In conclusion, short-term temporal changes could have a remarkable influence in sediment microalgae primary production. Not considering these changes can lead to wrong conclusions concerning the role and importance of sediment microalgae on tidal salt flats.     

Spatial and temporal community structure of desmids on a small spatial scale

Besides spatial heterogeneity, another important component of the diversity of protist communities is the variation in species assemblages through time. Despite its importance, temporal turnover of benthic communities has been studied to a lesser extent than spatial heterogeneity has. In this study, we examine the desmid assemblages on small spatial scale in relation to the spatial, temporal, and environmental parameters. The samples were collected within two different types of peatland localities in the Czech Republic over 3 years. The differences in species composition between samples were mainly correlated with the geographic distance, while the effects of the environmental and temporal variables were much weaker. Since the spatial heterogeneity of the assemblages was not induced by the variation of the environmental factors or by the restricted dispersal ability at such a small spatial scale, we assume that both the temporal stability and strong spatial autocorrelation might have been the result of a priority effect, with subsequent monopolization of resources. Stochasticity in colonization can introduce noise into the match between community composition and environmental conditions, which may result in stronger effect of the spatial parameters on the community structure.     

High-resolution spatial and temporal analysis of phytoalexin production in oats

The production of oat (Avena sativa L.) phytoalexins, avenanthramides, occurs in response to elicitor treatment with oligo-N-acetylchitooligosaccharides. In this study, avenanthramides production was investigated by techniques that provide high spatial and temporal resolution in order to clarify the process of phytoalexin production at the cellular level. The amount of avenanthramides accumulation in a single mesophyll cell was quantified by a combination of laser micro-sampling and low-diffuse nanoflow liquid chromatography–electrospray ionization tandem mass spectrometry (LC–ESI-MS/MS) techniques. Avenanthramides, NAD(P)H and chlorophyll were also visualized in elicitor-treated mesophyll cells using line-scanning fluorescence microscopy. We found that elicitor-treated mesophyll cells could be categorized into three characteristic cell phases, which occurred serially over time. Phase 0 indicated the normal cell state before metabolic or morphological change in response to elicitor, in which the cells contained abundant NAD(P)H. In phase 1, rapid NAD(P)H oxidation and marked movement of chloroplasts occurred, and this phase was the early stage of avenanthramides biosynthesis. In phase 2, avenanthramides accumulation was maximized, and chloroplasts were degraded. Avenanthramides appear to be synthesized in the chloroplast, because a fluorescence signal originating from avenanthramides was localized to the chloroplasts. Moreover, our results indicated that avenanthramides biosynthesis and the hypersensitive response (HR) occurred in identical cells. Thus, the avenanthramides production may be one of sequential events programmed in HR leading to cell death. Furthermore, the phase of the defense response was different among mesophyll cells simultaneously treated with elicitor. These results suggest that individual cells may have different susceptibility to the elicitor. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Baselines and degradation of coral reefs in the Northern Line Islands

Effective conservation requires rigorous baselines of pristine conditions to assess the impacts of human activities and to evaluate the efficacy of management. Most coral reefs are moderately to severely degraded by local human activities such as fishing and pollution as well as global change, hence it is difficult to separate local from global effects. To this end, we surveyed coral reefs on uninhabited atolls in the northern Line Islands to provide a baseline of reef community structure, and on increasingly populated atolls to document changes associated with human activities. We found that top predators and reef-building organisms dominated unpopulated Kingman and Palmyra, while small planktivorous fishes and fleshy algae dominated the populated atolls of Tabuaeran and Kiritimati. Sharks and other top predators overwhelmed the fish assemblages on Kingman and Palmyra so that the biomass pyramid was inverted (top-heavy). In contrast, the biomass pyramid at Tabuaeran and Kiritimati exhibited the typical bottom-heavy pattern. Reefs without people exhibited less coral disease and greater coral recruitment relative to more inhabited reefs. Thus, protection from overfishing and pollution appears to increase the resilience of reef ecosystems to the effects of global warming.     

Interactive influences of climate and parent material on soil microbial community structure in Bornean tropical forest ecosystems

Climate and parent material strongly control vegetation structure and function, yet their control over the belowground microbial community is poorly understood. We assessed variation in microbial lipid profiles in undisturbed forest soils (organic and surface mineral horizons) along an altitudinal gradient (700, 1,700, and 2,700 m a.s.l. mean annual temperature of 12–24°C) on two contrasting parent materials (acidic metasedimentary vs. ultrabasic igneous rock) in Mt. Kinabalu, Borneo. Soil organic carbon and nitrogen concentrations were generally higher at higher altitudes and, within a site, at upper soil horizons. Soil pH ranged from 3.9 to 5.3, with higher values for the ultrabasic soils especially at higher altitudes. The major shifts in microbial community structure observed were the decline in the ratio of fungal to bacterial lipid markers both with increasing soil depth and decreasing altitude. The positive correlation between this ratio with soil C and N concentrations suggested a strong substrate control in accord with the literature from mid to high-latitude ecosystems. Principal component analysis using seven groups of signature lipids suggested a significant altitude by parent material interaction—the significant difference in microbial community structure between the two rock types found at 2,700-m sites developed on weakly weathered soils diminished with decreasing altitude towards 700-m sites where soils were strongly weathered. These results are consistent with the hypothesis that parent material effect on soil microbial community (either directly via soil geochemistry or indirectly via floristic composition) is stronger at an earlier stage of ecosystem development.     

Monitoring rocky-shore communities: a critical look at spatial and temporal variation

Increasingly programmes are being set up to monitor rocky-shore communities in order to provide baseline data which will indicate changes resulting from subsequent pollution. However, these efforts are complicated by several factors. Firstly, there are overall changes in the composition of communities both within and between years. Secondly, there is variation within certain communities due to a mosaic distribution of components, the mosaic format changing continuously with a cycle of several years. This paper reports on studies of a medium-exposed rocky shore in the Isle of Man (U. K.). It describes patterns of spatial and temporal variation, and looks at certain implications for monitoring programmes: (a) the frequency of sampling, and the duration of the sampling programme, in the light of seasonal and long-term variation; (b) the efficiency, in terms of the minimisation of variability, of sampling the same area by different strategies — belt transects, small random quadrats, single large quadrat; (c) the effect of the distribution patterns of some commoner species on the variation between samples.