Abundance Patterns (abundance + pattern)

Distribution by Scientific Domains
Distribution within Life Sciences

Selected Abstracts

Patterns of abundance of fire ants and native ants in a native ecosystem

Abstract 1.,This correlational study examines the relationship between the red imported fire ant (Solenopsis invicta) and native ants in a longleaf pine savanna. Fire ants are frequently associated with a decline in native ants throughout the invaded range, but fire ant invasion is often coupled with habitat disturbance. Invasion of fire ants into the longleaf pine savanna provides an opportunity to examine the structure of the ant community in the absence of habitat disturbance. 2.,Pitfall trapping was conducted within the longleaf pine savanna as well as across a naturally occurring soil moisture gradient, in plots that had been artificially watered. 3.,Species richness did not vary as a function of fire ant density. There was an inverse relationship between native ant density and fire ant density, but this abundance pattern does not necessarily imply a causal link between fire ant invasion and native ant decline. For individual species, fire ant densities were negatively correlated with the densities of only two native ant species, including Solenopsis carolinensis, a native species that potentially limits the invasion of fire ants. Additionally, fire ants and native ants respond differently to soil moisture, with native ants favouring drier conditions than fire ants. 4.,The possible exclusion of fire ants by some native ants, as well as differences in habitat preferences, provide alternative explanations for the frequently observed negative correlation between fire ants and native ants. [source]

Trace element studies of silicate-rich inclusions in the Guin (UNGR) and Kodaikanal (IIE) iron meteorites

Gero Kurat
It contains a rutile grain and is in contact with a large Cl apatite. The latter is very rich in rare earth elements (REEs) (,80 × CI), which display a flat abundance pattern, except for Eu and Yb, which are underabundant. The devitrified glass is very poor in REEs (<0.1 × CI), except for Eu and Yb, which have positive abundance anomalies. Devitrified glass and Cl apatite are out of chemical equilibrium and their complementary REE patterns indicate a genesis via condensation under reducing conditions. Inclusion 1 in the Kodaikanal (IIE) iron consists of glass only, whereas inclusion 2 consists of clinopyroxene, which is partly overgrown by low-Ca pyroxene, and apatite embedded in devitrified glass. All minerals are euhedral or have skeletal habits indicating crystallization from the liquid precursor of the glass. Pyroxenes and the apatite are rich in trace elements, indicating crystallization from a liquid that had 10,50 × CI abundances of REEs and refractory lithophile elements (RLEs). The co-existing glass is poor in REEs (,0.1,1 × CI) and, consequently, a liquid of such chemical composition cannot have crystallized the phenocrysts. Glasses have variable chemical compositions but are rich in SiO2, Al2O3, Na2O, and K2O as well as in HFSEs, Be, B, and Rb. The REE abundance patterns are mostly flat, except for the glass-only inclusion, which has heavy rare earth elements (HREEs) > light rare earth elements (LREEs) and deficits in Eu and Yb,an ultrarefractory pattern. The genetic models suggested so far cannot explain what is observed and, consequently, we offer a new model for silicate inclusion formation in IIE and related irons. Nebular processes and a relationship with E meteorites (Guin) or Ca-Al-rich inclusions (CAIs) (Kodaikanal) are indicated. A sequence of condensation (CaS, TiN or refractory pyroxene-rich liquids) and vapor-solid elemental exchange can be identified that took place beginning under reducing and ending at oxidizing conditions (phosphate, rutile formation, alkali and Fe2+ metasomatism, metasomatic loss of REEs from glass). [source]

Petrology and chemistry of the new shergottite Dar al Gani 476

The meteorite is classified as a basaltic shergottite and is only the 13th martian meteorite known to date. It has a porphyritic texture consisting of a fine-grained groundmass and larger olivines. The groundmass consists of pyroxene and feldspathic glass. Minor phases are oxides and sulfides as well as phosphates. The presence of olivine, orthopyroxene, and chromite is a feature that DaG 476 has in common with lithology A of Elephant Moraine (EET) A79001. However, in DaG 476, these phases appear to be early phenocrysts rather than xenocrysts. Shock features, such as twinning, mosaicism, and impact-melt pockets, are ubiquitous. Terrestrial weathering was severe and led to formation of carbonate veins following grain boundaries and cracks. With a molar MgO/(MgO + FeO) of 0.68, DaG 476 is the most magnesian member among the basaltic shergottites. Compositions of augite and pigeonite and some of the bulk element concentrations are intermediate between those of lherzolitic and basaltic shergottites. However, major elements, such as Fe and Ti, as well as LREE concentrations are considerably lower than in other shergottites. Noble gas concentrations are low and dominated by the mantle component previously found in Chassigny. A component, similar to that representing martian atmosphere, is virtually absent. The ejection age of 1.35 ± 0.10 Ma is older than that of EETA79001 and could possibly mark a distinct ejection. Dar al Gani 476 is classified as a basaltic shergottite based on its mineralogy. It has a fine-grained groundmass consisting of clinopyroxene, pigeonite and augite, feldspathic glass and chromite, Ti-chromite, ilmenite, sulfides, and whitlockite. Isolated olivine and single chromite grains occur in the groundmass. Orthopyroxene forms cores of some pigeonite grains. Shock-features, such as shock-twinning, mosaicism, cracks, and impact-melt pockets, are abundant. Severe weathering in the Sahara led to significant formation of carbonate veins crosscutting the entire meteorite. Dar al Gani 476 is distinct from other known shergottites. Chemically, it is the most magnesian member among known basaltic shergottites and intermediate in composition for most trace and major elements between Iherzolitic and basaltic shergottites. Unique are the very low bulk REE element abundances. The CI-normalized abundances of LREEs are even lower than those of Iherzolitic shergottites. The overall abundance pattern, however, is similar to that of QUE 94201. Textural evidence indicates that orthopyroxene, as well as olivine and chromite, crystallized as phenocrysts from a magma similar in composition to that of bulk DaG 476. Whether such a magma composition can be a shergottite parent melt or was formed by impact melting needs to be explored further. At this time, it cannot entirely be ruled out that these phases represent relics of disaggregated xenoliths that were incorporated and partially assimilated by a basaltic melt, although the texture does not support this possibility. Trapped noble gas concentrations are low and dominated by a Chassigny-like mantle component. Virtually no martian atmosphere was trapped in DaG 476 whole-rock splits. The exposure age of 1.26 ± 0.09 Ma is younger than that of most shergottites and closer to that of EETA79001. The ejection age of 1.35 ± 0.1 Ma could mark another distinct impact event. [source]

HD 209621: abundances of neutron-capture elements,

Aruna Goswami
ABSTRACT High-resolution spectra obtained from the Subaru Telescope High Dispersion Spectrograph have been used to update the stellar atmospheric parameters and metallicity of the star HD 209621. We have derived a metallicity of [Fe/H]=,1.93 for this star, and have found a large enhancement of carbon and of heavy elements, with respect to iron. Updates on the elemental abundances of four s-process elements (Y, Ce, Pr, Nd) along with the first estimates of abundances for a number of other heavy elements (Sr, Zr, Ba, La, Sm, Eu, Er, Pb) are reported. The stellar atmospheric parameters, the effective temperature, Teff, and the surface gravity, log g (4500 K, 2.0), are determined from local thermodynamic equilibrium analysis using model atmospheres. Estimated [Ba/Eu]=+0.35, places the star in the group of CEMP-(r+s) stars; however, the s-elements abundance pattern seen in HD 209621 is characteristic of CH stars; notably, the second-peak s-process elements are more enhanced than the first-peak s-process elements. HD 209621 is also found to show a large enhancement of the third-peak s-process element lead (Pb) with [Pb/Fe]=+1.88. The relative contributions of the two neutron-capture processes, r and s, to the observed abundances are examined using a parametric model-based analysis, which hints that the neutron-capture elements in HD 209621 primarily originate in s-process. [source]

Feeding and breeding across host plants within a locality by the widespread thrips Frankliniella schultzei, and the invasive potential of polyphagous herbivores

M. Milne
Abstract. Polyphagous insect herbivores could be expected to perform relatively well in new areas because of their ability to exploit alternative resources. We investigated relative abundance patterns of the polyphagous thrips species Frankliniella schultzei, which is characteristically found on plants from many different families, to establish the role of different host plant species in a single locality where the species is not indigenous (Brisbane, south-eastern Queensland, Australia). F. schultzei females and larvae were always present in flowers (where oviposition takes place) and never on leaves of the eight plant species that we surveyed regularly over one year. They were present in flowers of Malvaviscus arboreus in much higher densities than for any other host. F. schultzei females were more fecund and larvae developed faster on floral tissue diets of M. arboreus than on those of other hosts. M. arboreus is therefore regarded as the ,primary' host plant of F. schultzei in the locality that we investigated. The other species are regarded as ,minor' hosts. Available evidence indicates a common geographical origin of F. schultzei and M. arboreus. F. schultzei may therefore be primarily adapted to M. arboreus. The flowers of the minor species on which F. schultzei is also found may coincidentally share some features of the primary host. Adult thrips may therefore accumulate on minor hosts and breed there, but to a lesser extent than on the primary host. The general implications for investigating polyphagous host relationships and interpreting the ecology of these species as generalist invaders are spelt out. [source]

Edaphic niche differentiation among Polybotrya ferns in western Amazonia: implications for coexistence and speciation

ECOGRAPHY, Issue 3 2006
Hanna TuomistoArticle first published online: 22 FEB 200
To study the degree of edaphic specialization in Amazonian plants, the distribution patterns of seven species of Polybotrya ferns were studied in 109 sites in a climatically uniform area of northwestern Amazonia (Colombia, Ecuador and northern Peru). The two most abundant species of Polybotrya were found in about two-thirds of the sites with almost 7000 individuals each, the rarest species occurred in just one site with 40 individuals. Each of the seven species appeared to have a unique realised niche, when niche dimensions were defined by gradients in soil texture, soil cation content, and inundation. The species also differed in how broadly or narrowly they were distributed along each gradient. Some species were practically never found in the same sites, whereas others co-occurred with a high frequency, in spite of showing clearly different abundance patterns among sites. A single site only contains a small part of the edaphic variation present in the landscape, and a small proportion of any species' niche space, so broad-scale studies are needed to adequately describe and compare species' niches and to assess to what degree niche differences promote species coexistence. The distribution patterns in Polybotrya are consistent with, but do not prove, that ecological speciation may have been important in the radiation of the genus. If such a pattern is found to be common in other Amazonian plants, this would indicate that each evolutionary lineage has adapted to the available habitats largely independently of the others. [source]

Effects of plant diversity, plant productivity and habitat parameters on arthropod abundance in montane European grasslands

ECOGRAPHY, Issue 4 2005
Jörg Perner
Arthropod abundance has been hypothesized to be correlated with plant diversity but the results of previous studies have been equivocal. In contrast, plant productivity, vegetation structure, abiotic site conditions, and the physical disturbance of habitats, are factors that interact with plant diversity, and that have been shown to influence arthropod abundance. We studied the combined effect of plant species diversity, productivity and site characteristics on arthropod abundance in 71 managed grasslands in central Germany using multivariate statistics. For each site we determined plant species cover, plant community biomass (productivity), macro- and micronutrients in the soil, and characterized the location of sites with respect to orographic parameters as well as the current and historic management regimes. Arthropods were sampled using a suction sampler and classified a priori into functional groups (FGs). We found that arthropod abundance was not correlated with plant species richness, effective diversity or Camargo's evenness, even when influences of environmental variables were taken into account. In contrast, plant community composition was highly correlated with arthropod abundances. Plant community productivity influenced arthropod abundance but explained only a small proportion of the variance. The abundances of the different arthropod FGs were influenced differentially by agricultural management, soil characteristics, vegetation structure and by interactions between different FGs of arthropods. Herbivores, carnivores and detritivores reacted differently to variation in environmental variables in a manner consistent with their feeding mode. Our results show that in natural grassland systems arthropod abundance is not a simple function of plant species richness, and they emphasize the important role of plant community composition for the abundance patterns of the arthropod assemblages. [source]

A multi-scale test for dispersal filters in an island plant community

ECOGRAPHY, Issue 4 2005
Kevin C. Burns
Constraints on plant distributions resulting from seed limitation (i.e. dispersal filters) were evaluated on two scales of ecological organization on islands off the coast of British Columbia, Canada. First, island plant communities were separated into groups based on fruit morphology, and patterns in species diversity were compared between fruit-type groups. Second, abundance patterns in several common fleshy-fruited, woody angiosperm species were compared to species-specific patterns in seed dispersal by birds. Results from community-level analyses showed evidence for dispersal filters. Dry-fruited species were rare on islands, despite being common on the mainland. Island plant communities were instead dominated by fleshy-fruited species. Patterns in seed dispersal were consistent with differences in diversity, as birds dispersed thousands of fleshy-fruited seeds out to islands, while dry fruited species showed no evidence of mainland-island dispersal. Results from population-level analyses showed no evidence for dispersal filters. Population sizes of common fleshy-fruited species were unrelated to island isolation, as were rates of seed dispersal. Therefore, island isolation distances were not large enough to impose constraints on species' distributions resulting from seed limitation. Rates of seed dispersal were also unrelated to island area. However, several species increased in abundance with island area, indicating post-dispersal processes also help to shape species distributions. Overall results suggest that seed dispersal processes play an important role in determining the diversity and distribution of plants on islands. At the community-level, dry-fruited species were seed limited and island communities were instead dominated by fleshy-fruited species. At the population-level, common fleshy-fruited species were not seed limited and showed few differences in distribution among islands. Therefore, although evidence for dispersal filters was observed, their effects on plant distributions were scale-dependent. [source]

Diversity and abundance patterns of phytophagous insect communities on alien and native host plants in the Brassicaceae

ECOGRAPHY, Issue 6 2003
Mark Frenzel
The herbivore load (abundance and species richness of herbivores) on alien plants is supposed to be one of the keys to understand the invasiveness of species. We investigate the phytophagous insect communities on cabbage plants (Brassicaceae) in Europe. We compare the communities of endophagous and ectophagous insects as well as of Coleoptera and Lepidoptera on native and alien cabbage plant species. Contrary to many other reports, we found no differences in the herbivore load between native and alien hosts. The majority of insect species attacked alien as well as native hosts. Across insect species, there was no difference in the patterns of host range on native and on alien hosts. Likewise the similarity of insect communities across pairs of host species was not different between natives and aliens. We conclude that the general similarity in the community patterns between native and alien cabbage plant species are due to the chemical characteristics of this plant family. All cabbage plants share glucosinolates. This may facilitate host switches from natives to aliens. Hence the presence of native congeners may influence invasiveness of alien plants. [source]

The implicit assumption of symmetry and the species abundance distribution

David Alonso
Abstract Species abundance distributions (SADs) have played a historical role in the development of community ecology. They summarize information about the number and the relative abundance of the species encountered in a sample from a given community. For years ecologists have developed theory to characterize species abundance patterns, and the study of these patterns has received special attention in recent years. In particular, ecologists have developed statistical sampling theories to predict the SAD expected in a sample taken from a region. Here, we emphasize an important limitation of all current sampling theories: they ignore species identity. We present an alternative formulation of statistical sampling theory that incorporates species asymmetries in sampling and dynamics, and relate, in a general way, the community-level SAD to the distribution of population abundances of the species integrating the community. We illustrate the theory on a stochastic community model that can accommodate species asymmetry. Finally, we discuss the potentially important role of species asymmetries in shaping recently observed multi-humped SADs and in comparisons of the relative success of niche and neutral theories at predicting SADs. [source]

A niche for neutrality

Peter B. Adler
Abstract Ecologists now recognize that controversy over the relative importance of niches and neutrality cannot be resolved by analyzing species abundance patterns. Here, we use classical coexistence theory to reframe the debate in terms of stabilizing mechanisms (niches) and fitness equivalence (neutrality). The neutral model is a special case where stabilizing mechanisms are absent and species have equivalent fitness. Instead of asking whether niches or neutral processes structure communities, we advocate determining the degree to which observed diversity reflects strong stabilizing mechanisms overcoming large fitness differences or weak stabilization operating on species of similar fitness. To answer this question, we propose combining data on per capita growth rates with models to: (i) quantify the strength of stabilizing processes; (ii) quantify fitness inequality and compare it with stabilization; and (iii) manipulate frequency dependence in growth to test the consequences of stabilization and fitness equivalence for coexistence. [source]

Microbial community dynamics in a humic lake: differential persistence of common freshwater phylotypes

Ryan J. Newton
Summary In an effort to better understand the factors contributing to patterns in freshwater bacterioplankton community composition and diversity, we coupled automated ribosomal intergenic spacer analysis (ARISA) to analysis of 16S ribosomal RNA (rRNA) gene sequences to follow the persistence patterns of 46 individual phylotypes over 3 years in Crystal Bog Lake. Additionally, we sought to identify linkages between the observed phylotype variations and known chemical and biological drivers. Sequencing of 16S rRNA genes obtained from the water column indicated the presence of phylotypes associated with the Actinobacteria, Bacteroidetes, Firmicutes, Proteobacteria, TM7 and Verrucomicrobia phyla, as well as phylotypes with unknown affiliation. Employment of the 16S rRNA gene/ARISA method revealed that specific phylotypes varied independently of the entire bacterial community dynamics. Actinobacteria, which were present on greater than 95% of sampling dates, did not share the large temporal variability of the other identified phyla. Examination of phylotype relative abundance patterns (inferred using ARISA fragment relative fluorescence) revealed a strong correlation between the dominant phytoplankton succession and the relative abundance patterns of the majority of individual phylotypes. Further analysis revealed covariation among unique phylotypes, which formed several distinct bacterial assemblages correlated with particular phytoplankton communities. These data indicate the existence of unique persistence patterns for different common freshwater phylotypes, which may be linked to the presence of dominant phytoplankton species. [source]

Two hundred years of a diverse Daphnia community in Lake Naivasha (Kenya): effects of natural and human-induced environmental changes

Joachim Mergeay
Summary 1. We used fossil diapausing eggs extracted from 210Pb-dated sediment cores to reconstruct historical changes in the Daphnia community of Lake Naivasha, a climate-sensitive lake in Kenya which over the past 200 years has experienced a series of well-documented natural and anthropogenic environmental changes. 2. Contiguous sampling and analysis of four cores yielded ephippial capsules of eight Daphnia species. Only two of these had been recorded previously in live collections from Lake Naivasha, and one species is new to science. The four more common species (Daphnia barbata, D. laevis, D. magna, and D. pulex) show striking differences in abundance patterns and population dynamics through time. Four other species (D. lumholtzi, D. curvirostris, D. longispina s.l., and Daphnia sp. nov. type Limuru.) appear to have been present only occasionally. Nevertheless, between 1895 and 1915 seven species of Daphnia inhabited Lake Naivasha simultaneously. 3. Despite considerable natural environmental change associated with climate-driven lake-level fluctuations, the Daphnia community of Lake Naivasha has been severely affected by human activities over the past century, especially the introduction of exotic fishes and water-quality changes because of agricultural soil erosion. The recent reappearance of large-bodied Daphnia species (D. magna, D. barbata, D. lumholtzi, Daphnia sp. nov. type Limuru) after 20,110 years of absence can be explained by their release from fish predation, following a dramatic increase in turbidity caused by excess clastic sediment input from eroded catchment soils. The small-bodied species D. laevis has fared less well recently, presumably because the benefit of lowered predation pressure is counteracted by more pronounced negative effects of increased turbidity on this species and loss of submerged macrophyte beds which formerly served as predation refuge. 4. Our results suggest that, despite considerable environmental instability and the absence of specialised zooplanktivores, top-down control of fish on large zooplankton is important in Lake Naivasha. Predation pressure from fish has led to clear-cut shifts in local Daphnia species composition, but failed to drive the larger taxa to extinction. [source]

The Temporal Asynchrony of Planktonic Cladocerans Population at Different Environments of the Upper Paraná River Floodplain

Erica Mayumi Takahashi
Abstract The aim of this study was to investigate the existence of synchronic fluctuation patterns in cladoceran populations of the Upper Paraná River floodplain. The following hypothesis were tested: (i) the populations of a given species present the same fluctuation pattern in abundance for different environments and (ii) synchrony is higher when we consider subsets of neighboring environments or those belonging to the same category (e.g., lagoons, rivers). Samplings were performed every three months from February 2000 to November 2002 at 11 sites. To evaluate spatial synchrony, the intraclass correlation coefficient was used. The results showed no significant correlation for the most abundant species, meaning that fluctuation patterns of planktonic cladocerans were asynchronous. Asynchrony indicated that the influence of floods and regional climatic factors was not strong enough to synchronize the populations, suggesting that local factors were more important than regional effects in determining zooplankton abundance patterns. The implications of these results are that the observations from a single environment cannot be extrapolated to other environments in a manner that would allow its use as a sentinel site. This means that a monitoring program for floodplain systems, or at least for the Paraná River floodplain, has to comprise greater spatial extents. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Patterns of density, diversity, and the distribution of migratory strategies in the Russian boreal forest avifauna

Russell Greenberg
Abstract Aim, Comparisons of the biotas in the Palaearctic and Nearctic have focused on limited portions of the two regions. The purpose of this study was to assess the geographic pattern in the abundance, species richness, and importance of different migration patterns of the boreal forest avifauna of Eurasia from Europe to East Asia as well as their relationship to climate and forest productivity. We further examine data from two widely separated sites in the New World to see how these conform to the patterns found in the Eurasian system. Location, Boreal forest sites in Russia and Canada. Methods, Point counts were conducted in two to four boreal forest habitats at each of 14 sites in the Russian boreal forest from near to the Finnish border to the Far East, as well as at two sites in boreal Canada. We examined the abundance and species richness of all birds, and specific migratory classes, against four gradients (climate, primary productivity, latitude, and longitude). We tested for spatial autocorrelation in both dependent and independent variables using Moran's I to develop spatial correlograms. For each migratory class we used maximum likelihood to fit models, first assuming uncorrelated residuals and then assuming spatially autocorrelated residuals. For models assuming unstructured residuals we again generated correlograms on model residuals to determine whether model fitting removed spatial autocorrelation. Models were compared using Akaike's information criterion, adjusted for small sample size. Results, Overall abundance was highest at the eastern and western extremes of the survey region and lowest at the continent centre, whereas the abundance of tropical and short-distance migrants displayed an east,west gradient, with tropical migrants increasing in abundance in the east (and south), and short-distance migrants in the west. Although overall species richness showed no geographic pattern, richness within migratory classes showed patterns weaker than, but similar to, their abundance patterns described above. Overall abundance was correlated with climate variables that relate to continentality. The abundances of birds within different migration strategies were correlated with a second climatic gradient , increasing precipitation from west to east. Models using descriptors of location generally had greater explanatory value for the abundance and species-richness response variables than did those based on climate data and the normalized difference vegetation index (NDVI). Main conclusions, The distribution patterns for migrant types were related to both climatic and locational variables, and thus the patterns could be explained by either climatic regime or the accessibility of winter habitats, both historically and currently. Non-boreal wintering habitat is more accessible from both the western and eastern ends than from the centre of the boreal forest belt, but the tropics are most accessible from the eastern end of the Palaearctic boreal zone, in terms of distance and the absence of geographical barriers. Based on comparisons with Canadian sites, we recommend that future comparative studies between Palaearctic and Nearctic faunas be focused more on Siberia and the Russian Far East, as well as on central and western Canada. [source]

Local,regional boundary shifts in oribatid mite (Acari: Oribatida) communities: species,area relationships in arboreal habitat islands of a coastal temperate rain forest, Vancouver Island, Canada

Zoë Lindo
Abstract Aim, This study investigates the species,area relationship (SAR) for oribatid mite communities of isolated suspended soil habitats, and compares the shape and slope of the SAR with a nested data set collected over three spatial scales (core, patch and tree level). We investigate whether scale dependence is exhibited in the nested sampling design, use multivariate regression models to elucidate factors affecting richness and abundance patterns, and ask whether the community composition of oribatid mites changes in suspended soil patches of different sizes. Location, Walbran Valley, Vancouver Island, Canada. Methods, A total of 216 core samples were collected from 72 small, medium and large isolated suspended soil habitats in six western redcedar trees in June 2005. The relationship between oribatid species richness and habitat volume was modelled for suspended soil habitat isolates (type 3) and a nested sampling design (type 1) over multiple spatial scales. Nonlinear estimation parameterized linear, power and Weibull function regression models for both SAR designs, and these were assessed for best fit using R2 and Akaike's information criteria (,AIC) values. Factors affecting oribatid mite species richness and standardized abundance (number per g dry weight) were analysed by anova and linear regression models. Results, Sixty-seven species of oribatid mites were identified from 9064 adult specimens. Surface area and moisture content of suspended soils contributed to the variation in species richness, while overall oribatid mite abundance was explained by moisture and depth. A power-law function best described the isolate SAR (S = 3.97 × A0.12, R2 = 0.247, F1,70 = 22.450, P < 0.001), although linear and Weibull functions were also valid models. Oribatid mite species richness in nested samples closely fitted a power-law model (S = 1.96 × A0.39, R2 = 0.854, F1,18 = 2693.6, P < 0.001). The nested SAR constructed over spatial scales of core, patch and tree levels proved to be scale-independent. Main conclusions, Unique microhabitats provided by well developed suspended soil accumulations are a habitat template responsible for the diversity of canopy oribatid mites. Species,area relationships of isolate vs. nested species richness data differed in the rate of accumulation of species with increased area. We suggest that colonization history, stability of suspended soil environments, and structural habitat complexity at local and regional scales are major determinants of arboreal oribatid mite species richness. [source]

Nocturnal fish utilization of a subtropical mangrove-seagrass ecotone

MARINE ECOLOGY, Issue 2 2010
Neil Hammerschlag
Abstract Whereas diel fish migration between mangrove and seagrass habitats has been recognized for decades, quantitative studies have focused mainly on diurnal patterns of fish distribution and abundance. In general, previous studies have shown that fish abundances decline with increasing distance from mangroves; however, evidence for such a pattern at night, when many fishes are actively feeding, is scarce. The present study is the first to report nocturnal fish abundances along a continuous distance gradient from mangroves across adjacent seagrass habitat (0,120 m). Here, we used nocturnal seine sampling to test the null hypothesis (based on diurnal studies and limited nocturnal work) that fish abundance would decrease with increasing distance from shoreline. We focused on species and life-stage-specific abundance patterns of Lutjanus griseus, Sphyraena barracuda, Archosargus rhomboidalis, and Haemulon sciurus. Results indicated that assemblage composition and structure differed significantly by season, likely influenced by temperature. However, within each season, the fish habitat use pattern at both the assemblage and species-specific level generally failed to support our working null hypothesis. Species-specific analyses revealed that, for most species and life-stages examined, nocturnal abundance either did not change with distance or increased with distance from the mangrove-seagrass ecotone. Our results suggest that analyses where taxa are grouped to report overall patterns may have the potential to overlook significant species- and stage-specific variation. For fishes known to make nocturnal migrations, we recommend nocturnal sampling to determine habitat utilization patterns, especially when inferring nursery value of multiple habitats or when estimating fish production. [source]

Larval habitats and seasonal abundance of Culicoides biting midges found in association with sheep in northern Sardinia, Italy

Between January 2005 and December 2006, the larval habitats and seasonal abundances of 21 species of Culicoides (Diptera: Ceratopogonidae) found in association with livestock on a farm in northern Sardinia were studied. Culicoides were collected using two light traps (one placed in a sheep shed and the other near water ponds) and reared from mud collected in and along the margins of a small and a large water pond. The mammalophilic Culicoides imicola Kieffer and Culicoides newsteadi Austen were the most prevalent (>95%) of 20 species in the sheep shed, whereas the ornithophilic Culicoides univittatus Vimmer, Culicoides sahariensis Kieffer, Culicoides festivipennis Kieffer, Culicoides circumscriptus Kieffer and Culicoides cataneii Clastrier were most abundant in the traps set at the ponds (73%) and in 16 species of Culicoides reared from laboratory-maintained mud samples retrieved from three microhabitats (a non-vegetated pond shoreline, 20 cm above a pond shoreline, the shoreline of a secondary, permanently inundated, grass-covered pool). The species reared most abundantly from along the pond shoreline were C. festivipennis, C. circumscriptus and C. sahariensis, whereas those most prevalent at the grassed pool were C. cataneii and C. festivipennis. C. imicola was found to breed preferentially in mud 20 cm above the pond shoreline, whereas C. newsteadi was restricted almost entirely to the grassed pool, which had a high organic matter content. Using the light trap and adult emergence data, the seasonal abundance patterns of the eight species of Culicoides were determined. In general, there was good correspondence between light trap catches and emergence trends. Well-defined emergence peaks indicate four or five generations for C. festivipennis and C. circumscriptus and three generations for C. cataneii, C. newsteadi and Culicoides jumineri Callot & Kremer. The emergence trends for C. imicola and C. sahariensis were unimodal, but, because they stretched over several months, indicated that a number of overlapping generations had occurred. Adults of C. imicola were reared and captured only sporadically in the first half of the year, gradually building to a peak in autumn. Conversely, C. newsteadi was reared throughout the year and displayed three clearly defined peaks (in winter, spring and autumn); captures of C. newsteadi in the light traps peaked in May,June and again to a lesser extent in autumn. In Sardinia the late seasonal peak in the abundance of C. imicola occurs in synchrony with outbreaks of bluetongue (BT) in sheep, which is consistent with earlier findings elsewhere in the Mediterranean basin and in Africa that it is the principal vector of bluetongue virus (BTV). Although the status of C. newsteadi as a vector of BTV is not known, its low-level presence in winter and heightened abundances in spring may provide a pathway along which the virus can overwinter. [source]

Compositions and taxonomy of 15 unusual carbonaceous chondrites

Won Hie CHOE
1152 (anomalous CV3); Pecora Escarpment (PCA) 91008 (anomalous, metamorphosed CM); Queen Alexandra Range 99038 (type 2 ungrouped); Sahara 00182 (type 3 ungrouped, possibly related to HaH 073 and/or to C-L 001); and WIS 91600 (mildly metamorphosed, anomalous, CM-like chondrite, possibly a member of a new grouplet that includes Belgica-7904, Dhofar 225, and Y-86720). Many of these meteorites show fractionated abundance patterns, especially among the volatile elements. Impact volatilization and dehydration as well as elemental transport caused by terrestrial weathering are probably responsible for most of these compositional anomalies. The metamorphosed CM chondrites comprise two distinct clusters on the basis of their ,17O values: approximately ,4, for PCA 91008, GRO 95566, DaG 978, and LEW 85311, and approximately 0, for Belgica-7904 and WIS 91600. These six meteorites must have been derived from different asteroidal regions. [source]

Drill core LB-08A, Bosumtwi impact structure, Ghana: Geochemistry of fallback breccia and basement samples from the central uplift

Two boreholes were drilled to acquire hard-rock samples of the deep crater moat and from the flank of the central uplift (LB-07A and LB-08A, respectively) during a recent ICDP-sponsored drilling project. Here we present results of major and trace element analysis of 112 samples from drill core LB-08A. This core, which was recovered between 235.6 and 451.33 m depth below lake level, contains polymict lithic breccia intercalated with suevite, which overlies fractured/brecciated metasediment. The basement is dominated by meta-graywacke (from fine-grained to gritty), but also includes some phyllite and slate, as well as suevite dikelets and a few units of a distinct light greenish gray, medium-grained meta-graywacke. Most of the variations of the major and trace element abundances in the different lithologies result from the initial compositional variations of the various target rock types, as well as from aqueous alteration processes, which have undeniably affected the different rocks. Suevite from core LB-08A (fallback suevite) and fallout suevite samples (from outside the northern crater rim) display some differences in major (mainly in MgO, CaO, and Na2O contents) and minor (mainly Cr and Ni) element abundances that could be related to the higher degree of alteration of fallback suevites, but also result from differences in the clast populations of the two suevite populations. For example, granite clasts are present in fallout suevite but not in fallback breccia, and calcite clasts are present in fallback breccia and not in fallout suevite. Chondrite-normalized rare earth element abundance patterns for polymict impact breccia and basement samples are very similar to each other. Siderophile element contents in the impact breccias are not significantly different from those of the metasediments, or compared to target rocks from outside the crater rim. So far, no evidence for a meteoritic component has been detected in polymict impact breccias during this study, in agreement with previous work. [source]

Parent stars of extrasolar planets , VIII.

Chemical abundances for 18 elements in 31 stars
ABSTRACT We present the results of detailed spectroscopic abundance analyses for 18 elements in 31 nearby stars with planets (SWPs). The resulting abundances are combined with other similar studies of nearby SWPs and compared to a sample of nearby stars without detected planets. We find some evidence for abundance differences between these two samples for Al, Si and Ti. Some of our results are in conflict with a recent study of SWPs in the SPOCS data base. We encourage continued study of the abundance patterns of SWPs to resolve these discrepancies. [source]

Gradients of abundance of fish across no-take marine reserve boundaries: evidence from Philippine coral reefs

Rene A. Abesamis
Abstract 1.An abundance gradient from high inside to low outside a no-take marine reserve may indicate net emigration of adult fish from the reserve (,spillover'). 2.We examined spatial patterns of abundance of fish across two ,900 m long sections of coral reef slope at each of two small Philippine islands (Apo and Balicasag). One section sampled the entire length of a no-take reserve and extended 200,400 m outside the two lateral reserve boundaries. The other section, without a reserve, was a control. The reserves had had 20 (Apo) and 15 (Balicasag) years of protection when sampled in 2002. 3.Significant spatial gradients of decreasing abundance of target fish occurred across only one (Apo Reserve northern boundary = ARNB) of four real reserve boundaries, and across none of the control ,boundaries'. Abundance of non-target fish did not decline significantly across reserve boundaries. 4.Abundance of target fish declined sharply 50 m outside the ARNB, but enhanced abundance extended 100,350 m beyond this boundary, depending on fish mobility. 5.Density of sedentary target fish declined 2,6 times faster than density of highly vagile and vagile target fish across the ARNB. 6.Habitat factors could not account for these ARNB results for target fish, but did influence abundance patterns of non-target fish. 7.The lack of abundance gradients of target fish at Balicasag may reflect reduced fishing outside the reserve since it was established. 8.Apo Reserve had a gradient of abundance of target fish across at least one boundary, a result consistent with spillover. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Elemental abundance analyses with Coudé Echelle spectrograms from the TÜB,TAK National Observatory of Turkey: I. The HgMn stars 11 Per, HR 2801, and , Cnc,

S.J. Adelman
Abstract Using coadded spectrograms taken with the Coudé Echelle Spectrograph (CES) of the 1.50-m Russian-Turkish Telescope of the TÜB,TAK National Observatory (TUG) near Antalya in Turkey, elemental abundance analyses of three HgMn stars 11 Per, HR 2801, and , Cnc were performed. Comparisons are made with spectra obtained with the long camera of the Dominion Astrophysical Observatory (DAO) coudé spectrograph and its SITe4 CCD. The CES equivalent widths are about 12% larger than that for the DAO long camera. Our first results from TUG data/spectra show that all three stars exhibit the Hg II ,3984 line and somewhat diverse abundance patterns. 11 Per tends to have underabundant light elements with underabundant and overabundant Fe-peak elements. HR 2801 has mostly underabundant elements, with a few elements having solar abundances while N and Mn are overabundant. The coolest star , Cnc has light elements having mostly solar abundances, overabundant iron group abundances, and very overabundant SrYZr and Ba. Comparisons with the abundance patterns of other HgMn stars show that they have a wide diversity of abundance patterns (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

CNO Abundances in the Quintuplet Cluster M Supergiant 5-7

S. V. Ramírez
Abstract We present and analyze infrared spectra of the supergiant VR 5,7, in the Quintuplet cluster 30 pc from the Galactic center. Within the uncertainties, the [C/H], [N/H], and [O/H] abundances in this star are equal to those of , Ori, a star which exhibits mixing of CNO processed elements, but are distinct from the abundance patterns in IRS 7. [source]

Microhabitat relationships among five lizard species associated with granite outcrops in fragmented agricultural landscapes of south-eastern Australia

Abstract A fundamental part of developing effective biodiversity conservation is to understand what factors affect the distribution and abundance of particular species. However, there is a paucity of data on ecological requirements and habitat relationships for many species, especially for groups such as reptiles. Furthermore, it is not clear whether habitat relationships for particular species in a given environment are transferable to other environments within their geographical range. This has implications for the type of ,landscape model' used to guide management decisions in different environments worldwide. To test the hypothesis that species-specific habitat relationships are transferable to other environments, we present microhabitat models for five common lizard species from a poorly studied habitat , insular granite outcrops, and then compared these relationships with studies from other environments in south-eastern Australia. We recorded twelve species from five families, representing 699 individuals, from 44 outcrops in the south-west slopes of New South Wales. Five lizard species were abundant and accounted for 95% of all observations: Egernia striolata, Ctenotus robustus, Cryptoblepharus carnabyi, Morethia boulengeri and Carlia tetradactyla (Scincidae). Linear regression modelling revealed suites of different variables related to the abundance patterns of individual species, some of which were broadly congruent with those measured for each species in other environments. However, additional variables, particular to rocky environments, were found to relate to reptile abundance in this environment. This finding means that species' habitat relationships in one habitat may not be readily transferable to other environments, even those relatively close by. Based on these data, management decisions targeting reptile conservation in agricultural landscapes, which contain rocky outcrops, will be best guided by landscape models that not only recognize gradients in habitat suitability, but are also flexible enough to incorporate intraspecies habitat variability. [source]

Seasonal pattern of insect abundance in the Brazilian cerrado

F. Pinheiro
Abstract In Brazil, a severe dry season lasting for approximately 5 months and frequent fires make life difficult for cerrado insects. In certain aspects, the cerrado can be considered to be an understudied ecosystem; even basic information such as knowledge about the annual peak in abundance of different insect orders is unknown. Insect abundance patterns have only been investigated for a few groups in the cerrado region. Thus, our study concerns the temporal distribution of insect abundance in the savanna-like vegetation of the central Brazilian cerrado (sensu stricto) in Distrito Federal. The region has a well-defined, long dry season between May and September. The insects were sampled by window, malaise tent and pitfall traps within 1 year. We used a multiple linear regression to analyse the relationship between abundance of insects of each order and climate variables. A total of 50 127 individuals from 15 orders was collected. The orders were Coleoptera (26%), Hymenoptera (23%), Diptera (20.5%), Isoptera (20%), Homoptera (4%), Lepidoptera (4%), Orthoptera (1.5%) and Hemiptera (1%). The abundance of Diptera, Homoptera, Lepidoptera and Orthoptera was randomly distributed over time, Isoptera peaked in the first half of the wet season, Coleoptera and Hemiptera in the second half of the wet season and Hymenoptera in each season. A significant correlation was found only between Coleoptera and delayed climatic variables. There were no obvious trends that might help explain the abundance patterns observed. The study provides baseline information about phenological patterns of insect abundance and permits evaluation of this group as a resource for various food chains and different trophic levels. [source]