Diatom (Bacillariophyceae) assemblages in salt marshes of south‐central Chile: Relations with tidal inundation time and salinity

To reconstruct sea‐level history from changes in tidal environments using diatom assemblages, we need to better understand the relations among brackish diatom assemblages and changing environments along elevational gradients from diverse coastal sites. Our statistical analysis reveals relations between environmental variables and brackish benthic diatom assemblages in the little studied region of south‐central Chile. Along four transects across salt marshes at two sites, we identified 224 diatom taxa in 112 samples. Detrended canonical correspondence analysis showed that tidal exposure time index and salinity were appropriately regressed against the abundance of diatom species using unimodal‐based methods. Our tests of classical and inverse regressions of weighted average and weighted averaging partial least squares (WA‐PLS) showed that WA‐PLS resulted in the highest coefficient of determination and the lowest root‐mean square of the error of prediction. Our regression will be useful in reconstructing environmental variables from fossil diatom assemblages in Chile.     

New Zealand Demersal Fish Assemblages

Demersal fish assemblages in the New Zealand Exclusive Economic Zone were identified using presence–absence data from 19215 bottom trawl tows made over a 37-year period. The dataset spanned latitudes 34–54°S and depths of 4–1500m. A total of 123 taxa occurred in more than 1% of the tows (121 fish and 2 squid). Multivariate ordination and classification (correspondence analysis and Ward's cluster analysis) identified four primary species assemblages that were associated with the inner continental shelf, mid–outer continental shelf and shelf edge, upper continental slope and mid continental slope. The most frequently occurring species (> 40% of tows) in each assemblage were (in descending order): inshore – Chelidonichthys kumu, Pagrus auratus and Zeus faber; shelf – Nototodarus spp., Squalus acanthias and Thyrsites atun; upper slope – Macruronus novaezelandiae, Lepidorhynchus denticulatus, Genypterus blacodes and Hydrolagus sp.; mid slope – Hoplostethus atlanticus, Etmopterus baxteri, Halargyreus johnsonii, Coryphaenoides subserrulatus, Deania calcea, Coryphaenoides serrulatus, Pseudocyttus maculatus, Mora moro, Diastobranchus capensis and Centroscymnus crepidater. Further species associations were also identified within each primary assemblage. Canonical correspondence analysis revealed that most of the explainable variation in species composition was associated with depth and latitude; longitude and season explained little extra variance. The usefulness of our results is limited by the use of presence–absence rather than abundance data, and by the uneven spatial distribution of trawl tows. However, the present study provides a large-scale framework within which to interpret the results of studies using abundance data over smaller spatial and temporal scales.     

Eutrophication strengthens the response of zooplankton to temperature changes in a high‐altitude lake

To assess whether and how zooplankton communities respond to variations in temperature and how these assemblages change with eutrophication, we performed a large‐scale, monthly survey from August 2011 to July 2012 to determine the seasonal and spatial variations in these communities in a high‐altitude lake. A detrended correspondence analysis and a path analysis demonstrated that temperature and chlorophyll a were important factors influencing zooplankton. The path diagram showed that Daphnia was negatively affected directly by chlorophyll a and indirectly by temperature, whereas Bosmina was directly and positively affected by temperature. Daphnia spp. decreased in both absolute and relative biomass during warm seasons, whereas Bosmina spp. showed the opposite trend. Moreover, the lowest Daphnia spp. biomass was observed in the southern region, which was the most eutrophic. Our results indicate that increasing temperatures will continue to shift the dominant genus from Daphnia to Bosmina, and this change will be exacerbated by eutrophication. In addition, the zooplankton of Lake Erhai have shifted to smaller species over time as temperature and eutrophication have increased, which implies that zooplankton succession to small cladocerans may be markedly accelerated under further climate change and the increased eutrophication that has been observed in recent decades.     

Experimental management control of Opuntia dillenii Haw. and Agave americana L. in Teno Rural Park,Canary Islands

Invasion biology is an important element of global environmental change and represents one of the main threats to biodiversity. American species were introduced to Tenerife after the Spanish conquest during the eighteenth century, as is the case for Agave americana and Opuntia dillenii. The long period of naturalization and adaptation of these species has led them to become two of the most dispersed introduced species of the archipelago. We analyzed several eradication management processes in an area intensively invaded by both O. dillenii and A. americana. Three treatments were randomly applied: mechanical removal, use of herbicide (glyphosate at 10% volume), and mechanical and herbicide applied together. Both the effectiveness of the treatments to remove the target exotic species biovolume and the impact of the eradication methods on species richness and species composition of the area were analyzed. We found that the treatments had an impact on species composition but not on species richness. Species composition was mainly affected by mechanical treatment. The effect caused by the mechanical removal of the exotic target species in species composition is minor after 4 years, and is related to a higher dominance of shrub species typical of coastal shrubland and of annual or pioneer species. The control of O. dillenii and A. americana is evident from insignificant recovery 4 years after treatment application. A mechanical and herbicide treatment together, allowed not only the immediate removal of large individuals but also the herbicidal control of smaller ones.     

Trypanosoma evansi is alike to Trypanosoma brucei brucei in the subcellular localisation of glycolytic enzymes

Trypanosoma evansi, which causes surra, is descended from Trypanosoma brucei brucei, which causes nagana. Although both parasites are presumed to be metabolically similar, insufficient knowledge of T. evansi precludes a full comparison. Herein, we provide the first report on the subcellular localisation of the glycolytic enzymes in T. evansi, which is a alike to that of the bloodstream form (BSF) of T. b. brucei: (i) fructose-bisphosphate aldolase, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), hexokinase, phosphofructokinase, glucose-6-phosphate isomerase, phosphoglycerate kinase, triosephosphate isomerase (glycolytic enzymes) and glycerol-3-phosphate dehydrogenase (a glycolysis-auxiliary enzyme) in glycosomes, (ii) enolase, phosphoglycerate mutase, pyruvate kinase (glycolytic enzymes) and a GAPDH isoenzyme in the cytosol, (iii) malate dehydrogenase in cytosol and (iv) glucose-6-phosphate dehydrogenase in both glycosomes and the cytosol. Specific enzymatic activities also suggest that T. evansi is alike to the BSF of T. b. brucei in glycolytic flux, which is much faster than the pentose phosphate pathway flux, and in the involvement of cytosolic GAPDH in the NAD⁺/NADH balance. These similarities were expected based on the close phylogenetic relationship of both parasites.     

Conservation and possible reintroduction of an endangered plant based on an analysis of community ecology: a case study of Primulina tabacum Hance in China

The distribution of the rare and endangered perennial herb Primulina tabacum Hance is restricted to eight karst caves in southern China. To conserve P. tabacum and to evaluate possible reintroduction, we studied its historical distribution and conducted field surveys of both its biotic and physical environment. We used detrended correspondence analysis and canonical correspondence analysis to investigate the plant community structure and to identify the major environmental factors associated with its presence at eight sites and absence from three other sites where it formerly grew. The results revealed differences in community structure among sites and close correlations between species composition and environmental conditions. The data indicate that P. tabacum has special ecological requirements, including alkaline soil, low soil content of N, P, K and organic matter, low light, a high soil water content and high relative humidity, and a high atmospheric CO₂ concentration. Soil K content, relative humidity and atmospheric CO₂ concentration were the three variables most strongly associated with the vegetation composition and structure of the 11 sites. It appears that as a result of reductions in humidity, some of the historical localities of P. tabacum may no longer be suitable for reintroduction. Pilea notata , Pteris cretica var. nervosa and two moss species, Heteroscyphus coalitus and Gymnostomiella longinervis , were strongly associated with P. tabacum . The first two plants could be useful as indicators of suitable environments for P. tabacum , and the moss species could be useful as nurse plants for the reintroduction of P. tabacum into wild habitats.     

荒漠啮齿动物群落与植物群落的对应分析

动物与其生存环境变量之间的关系一直是生态学家们广泛关注的问题.啮齿动物作为荒漠生态系统中重要的功能群,其数量大小和生态功能对生态系统的平衡和稳定具有重要意义.生境中的植被为啮齿动物提供赖以生存的食物资源和栖息地,了解啮齿动物群落与植被特征之间的关系对于理解动物群落变动规律具有重要意义.不同植被条件下啮齿动物群落的结构不同,Hernández等(2005)研究发现北美Chihuahuan荒漠的灌木生境中啮齿动物密度高于草地生境.     

Nucleotide Correspondence between Protein-Coding Sequences of <Emphasis Type="Italic">Helicobacter pylori</Emphasis> Strains 26695 and J99

Comparison of ORFs between H. pylori strains 26695 and J99 showed that transitions (more than 3%) prevail over transversions (less than 1%). The predominance of transitions was explained by the high rates of cytosine replacement by thymine in the coding (3.5–5.3%) and noncoding (2.9–3.9%) DNA strands. The proportion of transversion-type correspondences (A → C, A → T, C → A, C → G, G → C, G → T, T → A, and T → G) did not exceed 0.84%. The highest proportion (28.3%) was observed for correspondences between C and T in ACGT-ATGT, the target site of active methyltransferase of H. pylori J99 (M.Hpy99XI). It was assumed that C → T mutations due to cytosine methylation-deamination are prevalent in H. pylori.     

Microhabitat Variation Explains Local‐scale Distribution of Terrestrial Amazonian Lizards in Rondônia,Western Brazil

We investigate the role of ecology and phylogeny in the association between lizard abundance and microhabitat variables in an Amazon rain forest site. Using pitfall trap arrays, we collected data from 349 individuals belonging to 23 lizard species. After accounting for spatial autocorrelation and using a canonical correspondence analysis (CCA), we found that lizard captures were significantly associated with microhabitat variables, which accounted for 48 percent of the observed variation. Furthermore, a canonical phylogenetic ordination (CPO) indicated that microhabitat variables are more important in determining the distribution of lizard species than phylogenetic relationships among species. Termite nests, canopy openness, and tree circumference were strongly associated with the number of captures of certain lizard species. Our results confirm autecology studies of individual lizard species for which data are available. We suggest that maintaining heterogeneous forested microhabitats should be a central goal for sustaining a high lizard biodiversity in Amazon rain forests.     

黑河上游蝗虫与植被关系的CCA分析

蝗虫与植物间存在复杂的耦合关系,能够反映蝗虫对生境的选择和适应能力以及种群内部的协同关系。2009年6-8月在野外实地采样的基础上,采用DCA除趋势对应分析（Detrended correspondence analysis）和CCA典范对应分析（Canonical correspondence analysis）方法,研究了草地蝗虫种类组成、蝗虫群落分类、优势植物与蝗虫的对应关系。结果表明：研究区的13种蝗虫分为6个类群,不同群组间蝗虫的种类数、食性和栖境选择存在较大差异,同组内的蝗虫在发生时间、生活型和营养生态位上不重叠;蝗虫的多度与优势植物盖度之间表现出极显著相关、显著相关和不相关的复杂关系,植物对蝗虫的影响更多的表现在为蝗虫提供适宜的栖息地而不完全是食物资源,禾本科和菊科植物对蝗虫空间分布的影响最大。蝗虫分布格局受自身的生物学特性和植物群落组成差异的影响,蝗虫与植物群落和优势植物之间的关系,能够为蝗虫灾害发生与防治提供可借鉴依据。     

Pluralism and diversity: trends in the use and application of ordination methods 1990‐2007

Question: What are the trends and patterns in the application of ordination techniques in vegetation science since 1990? Location: Worldwide literature analysis. Methods: Evaluation of five major journals of vegetation science; search of all ISI‐listed ecological journals. Data were analysed with ANCOVAs, Spearman rank correlations, GLMs, biodiversity indices and simple graphs. Results: The ISI search retrieved fewer papers that used ordinations than the manual evaluation of five selected journals. Both retrieval methods revealed a clear trend in increasing frequency of ordination applications from 1990 to the present. Canonical Correspondence Analysis was far more frequently detected by the ISI search than any other method. Applications such as Correspondence Analysis/Reciprocal Averaging and Detrended Correspondence Analysis have increasingly been used in studies published in “applied” journals, while Canonical Correspondence Analysis, Redundancy Analysis and Non‐Metric Multidimensional Scaling were more frequently used in journals focusing on more “basic” research. Overall, Detrended Correspondence Analysis was the most commonly applied method within the five major journals, although the number of publications slightly decreased over time. Use of Non‐Metric Multidimensional Scaling has increased over the last 10 years. Conclusion: The availability of suitable software packages has facilitated the application of certain techniques such as Non‐Metric Multidimensional Scaling. However, choices of ordination techniques are currently less driven by the constraints imposed by the software; there is also limited evidence that the choice of methods follows social considerations such as the need to use fashionable methods. Methodological diversity has been maintained or has even increased over time and reflects the researcher's need for diverse analytical tools suitable to address a wide range of questions.     

Distribution of prostaglandin ω-hydroxylases in different tissues

The conversion of prostaglandins E₂ and F_2α to their 19- and 20-hydroxy metabolites by various tissues has been measured by gas chromatography-mass spectrometry (GC-MS) using selected ion monitoring. A number of different tissues of the pregnant rabbit possess prostaglandin 20-hydroxylase activity (lung > liver > fetal placenta > maternal placenta ≈ uterus > renal cortex > renal medulla ≈ placental membranes). With the exception of the liver, prostaglandins E₂ and F_2α are metabolized at equal rates by the 20-hydroxylases of different tissues. Only lung and liver microsomes possess high levels of prostaglandin 20-hydroxylase in non-pregnant rabbits and only liver microsomes have appreciable 19-hydroxylase activity. Pulmonary prostaglandin 20-hydroxylase is induced in male rabbits by treatment with progesterone. On the basis of substrate specificity studies and the effects of a cytochrome P-450 inhibitor, SKF-525A, the prostaglandin 20-hydroxylases of lung and liver microsomes from pregnant rabbits appear to be different enzymes. In pregnant rats and hamsters, liver and kidney are the only tissues in which we detected prostaglandin ω-hydroxylase activity.     

Vegetation–environment relationships and classification of the seasonal savannas in Venezuela

The seasonal savannas dominated by the C₄ grasses of the genus Trachypogon, are widespread in northern South America. In Venezuela, they extend from the central lowland Llanos to intermediate elevations in the Coastal and Andean Mountains and to the Guiana Plateau (Gran Sabana) in the south. This study aims to classify these savannas and to understand the environmental factors that determine their composition and structure. Thirty-seven sites were sampled, plant cover and density were measured in 376 one square meter quadrats and the importance value index (IVI) was calculated. Climate data were obtained from climatological stations and soil properties were analyzed. The results were classified by clustering and TWINSPAN. Floristic and environmental data were ordered with the canonical correspondence analysis (CCA).Trachypogon savannas are heterogeneous, both floristically and environmentally. An altitudinal gradient of 2000 m separates the intermediate elevation Coastal Mountains (Type I) and the Guiana savannas (Type II) from the lowland Llanos. In the lowlands, sparsely covered and treeless communities on extremely oligotrophic and sandy soils (Type IV) differ structurally and floristically from woody savannas (Type III). The floristics and structure of the savannas respond directly or indirectly to elevation and water and nutrient availability. These responses were evidenced by: (a) floristic composition, as Neotropical lowland savanna species merged with those of the Andean sub-páramo in Type I savannas or with those from the Guianan flora in Type II savannas. (b) Species richness, which ranged from an average of 13.8 per site in sandy Type IV savannas to 38.9 per site in Type I intermediate elevation savannas. (c) Community physiognomy, which changes from an homogeneous herbaceous matrix with dispersed trees in Type III savannas to a shrubby Type I savannas to “treeless” Types II and IV savannas. (d) Plant cover which varied from 93.8% in the fertile Type I savannas to around 80% in the sandy oligotrophic savannas of Types II and IV. Each savanna type is related to one of the major geomorphological regions of Venezuela.     

Presence‐only versus presence–absence data in species composition determinant analyses

Aim Studying relationships between species and their physical environment requires species distribution data, ideally based on presence–absence (P–A) data derived from surveys. Such data are limited in their spatial extent. Presence‐only (P‐O) data are considered inappropriate for such analyses. Our aim was to evaluate whether such data may be used when considering a multitude of species over a large spatial extent, in order to analyse the relationships between environmental factors and species composition. Location The study was conducted in virtual space. However, geographic origin of the data used is the contiguous USA. Methods We created distribution maps for 50 virtual species based on actual environmental conditions in the study. Sampling locations were based on true observations from the Global Biodiversity Information Facility. We produced P–A data by selecting ∼1000 random locations and recorded the presence/absence of all species. We produced two P‐O data sets. Full P‐O set was produced by sampling the species in locations of true occurrences of species. Partial P‐O was a subset of full P‐O data set matching the size of the P–A data set. For each data set, we recorded the environmental variables at the same locations. We used CCA to evaluate the amount of variance in species composition explained by each variable. We evaluated the bias in the data set by calculating the deviation of average values of the environmental variables in sampled locations compared to the entire area. Results P–A and P‐O data sets were similar in terms of the amount of variance explained by the different environmental variables. We found sizable environmental and spatial bias in the P‐O data set, compared to the entire study area. Main conclusions Our results suggest that although P‐O data from collections contain bias, the multitude of species, and thus the relatively large amount of information in the data, allow the use of P‐O data for analysing environmental determinants of species composition.     

Ecological characterization of bat species distributions in Michoacán, México, using a geographic information system

Aim To investigate the relationship between chiropteran species distributions and four fundamental environmental factors — temperature, precipitation, soil and vegetation — and to construct a species richness prediction map based on the environmental factors. Location The state of Michoacán, México. Methods Bat specimens collected during a 2‐year project were combined with museum specimens to form a dataset of over 3200 entries pertaining to 71 species of bats. Coordinates of the collection localities were recorded with GPS receivers or determined from maps. ArcView GIS was used to characterize the distribution of the species relative to the four environmental factors by projecting coordinates of the collection sites onto digitized maps of those factors. Correspondence analysis (CA) was used to evaluate the relationship between species distributions and the environmental factors. Results The CA results indicated that the order of importance of these factors is (from highest to lowest): temperature, vegetation, precipitation and soil. A predicted distribution map was constructed for each species of bat, based on the result of the CA analysis, using correspondences of each species to climate, vegetation and precipitation. Soil types were excluded from the prediction model because soil type does not appear to carry high predictive value for bat species in Michoacán. Distribution maps of the 71 bat species were then overlaid to generate a map of bat species richness for the state of Michoacán. Main conclusions Neither family membership nor feeding guild affiliation appear to play important roles in chiropteran species distributions in Michoacán. The bat species richness prediction map will be a useful tool for conservation works in the region.     

Fish community structure of Oklahoma gulf coastal plains

We collected the common fish species in all available aquatic habitats (streams, oxbow lakes, swamps) in bottomlands of McCurtain County, Oklahoma. Abundance and distribution of fishes, and environmental data were analyzed by a multivariate approach and examined for fit to a hierarchical model. The variables maximum depth, substrate, and presence of flow were the most important variables predicting fish community structure. Our multivariate analyses demonstrate that environmental factors can explain much variation in presence and abundance of the common fish species. Kolasa's hierarchical model relates species to each other by comparing ranges. This habitat-based model explained the relationships of our species ranges.     

Analysis of oviposition behaviour in the parasitoidEpidinocarsis lopezi (Hym.: Encyrtidae): Comparison of flow charts on factorial maps

Females ofEpidinocarsis lopezi (De Santis) are presented with groups of unparasitized hosts or groups containing different ratios of parasitized hosts (Phenacoccus manihoti). Oviposition behaviour sequences obtained in various situations are filmed and split into units of behaviour or patterns. The succession of patterns is analyzed and translated into flow charts on factorial maps characteristic of each type of sequence. Comparison of flow charts reveals host discrimination by female parasitoids since the relative importance of behaviour patterns is modified according to the level of parasitized hosts encountered; it also gives clues to the strategy adopted by the female parasitoid during the search of a patch. In addition, the analysis divides the oviposition sequence into three separate patterns, specific to host search, oviposition act and post-oviposition behaviour. This series of patterns is closely related to factorial axes which indicates the fundamental trends of oviposition behaviour.