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Particular Species (particular + species)
Selected AbstractsTrade-Offs between Species Conservation and the Size of Marine Protected AreasCONSERVATION BIOLOGY, Issue 1 2010P. M. CHITTARO áreas marinas protegidas; conservación de la biodiversidad; relaciones especies,área Abstract:,Moving from single-species- to ecosystem-based management requires an understanding of how community-level attributes such as diversity change with area. We used survey data from bottom trawls to examine spatial patterns of species richness in U.S. Pacific coastal fishes. Specifically, we generated and compared species,area relationships (SARs) for species classified into several groups on the basis of maximum body size, trophic level, diet, maximum depth, geographic affinity, and taxonomic order. Because SARs among groups were not parallel and z values varied significantly for several groups, groups of species were under- or overrepresented (depending on the size of the area) relative to their proportions in the entire community (i.e., entire U.S. Pacific coast). In this way, differences in SARs help demonstrate trade-offs between species representation and coastal area and suggest strategies (such as targeting the protection of habitats and locations where a particular species or groups of species are maximized) that may minimize the size of marine protected areas (MPAs) but protect diversity at the level of the community and functional group. Resumen:,El traslado del manejo de una sola especie al manejo basado en ecosistemas requiere del entendimiento de los cambios en atributos de la comunidad como el cambio de diversidad con el área. Utilizamos datos de muestreo de redes de arrastre para examinar patrones espaciales de la riqueza de especies en peces costeros del Pacífico en E. U. A. Específicamente, generamos y comparamos relaciones especies,área (REAs) para especies clasificadas en varios grupos con base en la talla máxima, nivel trófico, profundidad máxima, afinidad geográfica y orden taxonómico. Debido a que las REAs entre grupos no fueron paralelas y que los valores de z variaron significativamente para varios grupos, los grupos de especies estuvieron sub- o sobre- representados (dependiendo del tamaño del área) en relación con sus proporciones en toda la comunidad (i.e., toda la costa del Pacífico en E. U. A.). De esta manera, las diferencias en REAs ayudan a demostrar el balance entre la representación de especies y el área costera y sugieren estrategias (como la protección de hábitats y localidades donde se maximiza una especie o grupo de especies) que pueden minimizar el tamaño de áreas marinas protegidas pero proteger la diversidad al nivel de la comunidad y grupo funcional. [source] Post-fire recovery of ant communities in Submediterranean Pinus nigra forestsECOGRAPHY, Issue 2 2006Anselm Rodrigo This study analyzes the variations in the structure and composition of ant communities in burned Pinus nigra forests in central Catalonia (NE Spain). Pinus nigra forests do not recover after fire, changing to shrublands and oak coppices. For this reason, we suggest that ant communities of burned P. nigra forests will change after fire, because the post-fire scenario, in particular with the increase of open areas, is different to the unburned one, and more favourable for some species than for others. In four locations previously occupied by P. nigra forests where different fires occurred 1, 5, 13 and 19 yr before the sampling, we sampled the structure and composition of ant communities with pitfall traps, tree traps and net sweeping in unburned plots and in plots affected by canopy and understory fire. The results obtained suggest that canopy and understory fire had little effect on the structure of ant communities. Thus, many variables concerning ant communities were not modified either by fire type (understory or canopy fire) or by time since fire. However, a number of particular species were affected, either positively or negatively, by canopy fire: three species characteristic of forest habitats decreased after fire, while eight species characteristic of open habitats increased in areas affected by canopy fire, especially in the first few years after fire. These differences in ant community composition between burned and unburned plots imply that the maximum richness is achieved when there is a mixture of unburned forests and areas burned with canopy fire. Moreover, as canopy cover in P. nigra forests burned with canopy fire is not completed in the period of time studied, the presence of the species that are characteristic of burned areas remains along the chronosequence studied, while the species that disappear after fire do not recover in the period of time considered. Overall, the results obtained indicate that there is a persistent replacement of ant species in burned P. nigra forests, as is also the case with vegetation. [source] Using age grading by wing injuries to estimate size-dependent adult survivorship in the field: a case study of the yellow dung fly Scathophaga stercorariaECOLOGICAL ENTOMOLOGY, Issue 5 2002Dieter U. Burkhard Abstract 1. Studies of natural selection depend on estimates of longevity and mortality in the wild. In small and mobile species such as insects, direct, mark,recapture (resight), studies are difficult to perform because individuals cannot be tracked easily. 2. It was investigated whether age grading based on wing injuries alone can be used to estimate size-specific survivorship in the field in the yellow dung fly Scathophaga stercoraria (L.) (Diptera: Scathophagidae). 3. The accumulation of different types of wing injury throughout the spring and autumn flight seasons for both sexes was recorded: tears, notches (both reflecting regular wear), and large missing areas (probably due to intra- and inter-specific interactions). 4. Female longevity increased with body size in both spring and autumn, whereas male longevity increased slightly with size in spring but decreased in autumn. 5. The two sexes and males of different size classes accumulated the various types of wing injury differentially, presumably due to differential patterns of intraspecific interactions. Additionally, body size exhibited a seasonal pattern, complicating interpretation of the relationship between body size and wing injuries. 6. It is therefore concluded that estimating adult viability selection on body size using wing injuries is problematic in dung flies, and potentially also in other species. It is suggested that before this method is applied in any particular species, pilot studies should be conducted to verify whether wing injuries accumulate equally in all classes of individuals of interest. In addition, it is necessary to investigate the causes of different types of wing injury. [source] Structural dynamics and robustness of food websECOLOGY LETTERS, Issue 7 2010Phillip P. A. Staniczenko Ecology Letters (2010) 13: 891,899 Abstract Food web structure plays an important role when determining robustness to cascading secondary extinctions. However, existing food web models do not take into account likely changes in trophic interactions (,rewiring') following species loss. We investigated structural dynamics in 12 empirically documented food webs by simulating primary species loss using three realistic removal criteria, and measured robustness in terms of subsequent secondary extinctions. In our model, novel trophic interactions can be established between predators and food items not previously consumed following the loss of competing predator species. By considering the increase in robustness conferred through rewiring, we identify a new category of species , overlap species , which promote robustness as shown by comparing simulations incorporating structural dynamics to those with static topologies. The fraction of overlap species in a food web is highly correlated with this increase in robustness; whereas species richness and connectance are uncorrelated with increased robustness. Our findings underline the importance of compensatory mechanisms that may buffer ecosystems against environmental change, and highlight the likely role of particular species that are expected to facilitate this buffering. [source] The silver spoon effect and habitat selection by natal dispersersECOLOGY LETTERS, Issue 11 2006Judy A. Stamps Abstract The silver spoon effect in the context of habitat selection occurs when dispersers in good condition are more likely to settle in high-quality habitats than dispersers in poor condition. Positive relationships between disperser condition and the quality of post-dispersal habitats are predicted by at least two non-exclusive ultimate hypotheses. The competition hypothesis assumes that a disperser's condition affects its chances of competing for space or joining an established group after arriving at a high-quality habitat, while the search hypothesis assumes that a disperser's condition affects its selectivity, and hence its chances of accepting a lower-quality habitat when it is searching for a new habitat. Thus far, silver spoon effects in the context of habitat selection have been reported in only a handful of species (several birds and marine invertebrates), but this study suggests that they may be relatively common in particular species and situations. [source] Probiotics: do they have a role in oral medicine and dentistry?EUROPEAN JOURNAL OF ORAL SCIENCES, Issue 3 2005Jukka H. Meurman This review describes current knowledge on probiotic bacteriotherapy from the oral health perspective. Recent experimental studies and results from randomized controlled trials have shown that certain gut bacteria, in particular species of Lactobacillus and Bifidobacterium, may exert beneficial effects in the oral cavity by inhibiting cariogenic streptococci and Candida sp. Probiotics have been successfully used to control gastro-intestinal diseases. They also appear to alleviate symptoms of allergy and diseases with immunological pathology. The mechanisms of probiotic action appear to link with colonization resistance and immune modulation. Lactic acid bacteria can produce different antimicrobial components such as organic acids, hydrogen peroxide, carbon peroxide, diacetyl, low molecular weight antimicrobial substances, bacteriocins, and adhesion inhibitors, which also affect oral microflora. However, data is still sparse on the probiotic action in the oral cavity. More information is needed on the colonization of probiotics in the mouth and their possible effect on and within oral biofilms. There is every reason to believe that the putative probiotic mechanisms of action are the same in the mouth as they are in other parts of the gastrointestinal tract. Because of the increasing global problem with antimicrobial drug resistance, the concept of probiotic therapy is interesting and pertinent, and merits further research in the fields of oral medicine and dentistry. [source] Fungal cannons: explosive spore discharge in the AscomycotaFEMS MICROBIOLOGY LETTERS, Issue 1 2007Frances Trail Abstract The ascomycetous fungi produce prodigious amounts of spores through both asexual and sexual reproduction. Their sexual spores (ascospores) develop within tubular sacs called asci that act as small water cannons and expel the spores into the air. Dispersal of spores by forcible discharge is important for dissemination of many fungal plant diseases and for the dispersal of many saprophytic fungi. The mechanism has long been thought to be driven by turgor pressure within the extending ascus; however, relatively little genetic and physiological work has been carried out on the mechanism. Recent studies have measured the pressures within the ascus and quantified the components of the ascus epiplasmic fluid that contribute to the osmotic potential. Few species have been examined in detail, but the results indicate diversity in ascus function that reflects ascus size, fruiting body type, and the niche of the particular species. [source] Molecular analysis of ammonia oxidation and denitrification in natural environmentsFEMS MICROBIOLOGY REVIEWS, Issue 5 2000Hermann Bothe Abstract This review summarizes aspects of the current knowledge about the ecology of ammonia-oxidizing and denitrifying bacteria. The development of molecular techniques has contributed enormously to the rapid recent progress in the field. Different techniques for doing so are discussed. The characterization of ammonia-oxidizing and -denitrifying bacteria by sequencing the genes encoding 16S rRNA and functional proteins opened the possibility of constructing specific probes. It is now possible to monitor the occurrence of a particular species of these bacteria in any habitat and to get an estimate of the relative abundance of different types, even if they are not culturable as yet. These data indicate that the composition of nitrifying and denitrifying communities is complex and apparently subject to large fluctuations, both in time and in space. More attempts are needed to enrich and isolate those bacteria which dominate the processes, and to characterize them by a combination of physiological, biochemical and molecular techniques. While PCR and probing with nucleotides or antibodies are primarily used to study the structure of nitrifying and denitrifying communities, studies of their function in natural habitats, which require quantification at the transcriptional level, are currently not possible. [source] Species concepts: the basis for controversy and reconciliationFISH AND FISHERIES, Issue 3 2002Michael T Ghiselin Abstract Some of the disputes about species concepts can be resolved through clarification of the conceptual issues. Others are intractable because incompatible preferences are being optimized. According to the current biological consensus species (taxa) are populations rendered cohesive by sex. The philosophical consensus has it that the species and other categories are (abstract) classes, whereas particular species and other taxa are (concrete) individuals (in the ontological sense). Natural kinds are classes that have the properties they do because of laws of nature. Individuals such as species and clades owe their properties to history, not laws of nature; they are not kinds at all and calling them natural kinds is, therefore, grossly misleading. Having the species of taxonomy be equivalent to the species of evolutionary theory facilitates the integration of history and laws of nature within biology. Efforts to define the species category on the basis of similarity create misleading impressions about the laws and mechanisms of speciation processes. A diversity of incompatible species concepts (pluralism) is undesirable because the various kinds of units that are called ,species' differ with respect to the underlying laws of nature that make them natural kinds. [source] Soil arthropods as indicators of water stress in Antarctic terrestrial habitats?GLOBAL CHANGE BIOLOGY, Issue 12 2003Peter Convey Abstract Abiotic features of Antarctic terrestrial habitats, particularly low temperatures and limited availability of liquid water, strongly influence the ecophysiology and life histories of resident biota. However, while temperature regimes of a range of land microhabitats are reasonably well characterized, much less is known of patterns of soil water stress, as current technology does not allow measurement at the required scale. An alternative approach is to use the water status of individual organisms as a proxy for habitat water status and to sample over several years from a population to identify seasonal or long-term patterns. This broad generalization for terrestrial invertebrates was tested on arthropods in the maritime Antarctic. We present analyses of a long-term data set of body water content generated by monthly sampling for 8,11 years of seven species of soil arthropods (four species of Acari, two Collembola and one Diptera) on maritime Antarctic Signy Island, South Orkney Islands. In all species, there was considerable within- and between-sample variability. Despite this, clear seasonal patterns were present in five species, particularly the two collembolans and a prostigmatid mite. Analyses of monthly water content trends across the entire study period identified several statistically significant trends of either increase or decrease in body water content, which we interpret in the context of regional climate change. The data further support the separation of the species into two groups as follows: firstly, the soft-bodied Collembola and Prostigmata, with limited cuticular sclerotization, which are sensitive to changes in soil moisture and are potentially rapid sensors of microhabitat water status, secondly, more heavily sclerotized forms such as Cryptostigmata (=Oribatida) and Mesostigmata mites, which are much less sensitive and responsive to short-term fluctuations in soil water availability. The significance of these findings is discussed and it is concluded that annual cycles of water content were driven by temperature, mediated via radiation and precipitation, and constituted reliable indicators of habitat moisture regimes. However, detailed ecophysiological studies are required on particular species before such information can be used to predict over long timescales. [source] Sexual dimorphism in limb bones of ibex (Capra ibex L.): mixture analysis applied to modern and fossil dataINTERNATIONAL JOURNAL OF OSTEOARCHAEOLOGY, Issue 5 2007H. Fernández Abstract Estimating sex ratios of fossil bone assemblages is an important step in the determination of demographic profiles, which are essential for understanding the palaeobiology and palaeoethology of any particular species, as well as its exploitation patterns by humans. This is especially true for ibex (Capra ibex), which was a main source of food for hominids during Pleistocene times. Classical methods for determining sexual dimorphism and sex ratio, such as analyses using uni- and bivariate plots, are based on an arbitrary fixing of limits between sexes. Here we use a more robust statistical method termed mixture analysis (MA) to determine the sex of postcranial remains (long bones, metapodials and tarsals) from ibex. For the first time, we apply MA to both a modern and a fossil sample of one species, by using metric data taken from (i) a collection of present-day ibex skeletons and (ii) a Palaeolithic sample of the same species. Our results clearly show that the forelimb (humerus and radius) is more dimorphic than the hindlimb (femur and tibia) and is therefore better suited for sexing ibex. It also appears that metapodials should be used carefully for estimating sex ratios. On the basis of these results, we propose a classification of bone measurements that are more or less reliable for sexing ibex. The results of MA applied to the ibex fossil bones from the Upper Palaeolithic site of the Observatoire (Monaco) lead us to the conclusion that this assemblage consists of a majority of males. The quantitative estimations calculated by the MA make it possible to compare the size of Pleistocene and modern ibex for the whole set of variables used in this study. Copyright © 2006 John Wiley & Sons, Ltd. [source] Ecosystem functioning in stream assemblages from different regions: contrasting responses to variation in detritivore richness, evenness and densityJOURNAL OF ANIMAL ECOLOGY, Issue 3 2008B. G. McKie Summary 1The diversity of species traits in a biological assemblage varies not only with species richness, but also with species evenness and organism density, which together influence the concentration of traits within functional guilds. Potential trait diversity at local scales is also constrained by the regional species pool. Implications of such variation for spatio-temporal variability in biodiversity,ecosystem functioning relationships are likely to be complex, but are poorly understood. 2In microcosm experiments conducted at laboratories in Sweden, Ireland and Romania, we investigated effects of species richness, evenness and density of stream-living detritivores on two related processes: detritivore leaf-processing efficiency (LPE) and growth. Assemblage composition varied among laboratories: one taxonomic order (Plecoptera) was studied in Sweden, whereas two orders, encompassing wider trait variation, were studied in Romania (Trichoptera and Plecoptera) and Ireland (Trichoptera and Isopoda). 3Relationships between density and both LPE and growth ranged from negative to positive across the study species, highlighting the potential for density-dependent variation in process rates to alter ecosystem functioning, but indicating that such effects depend on species identity. 4LPE varied with species diversity in the two more heterogeneous assemblages, but whereas LPE in the Romanian study was generally enhanced as richness increased, LPE in the Irish study increased only in less-even polycultures dominated by particular species. Transgressive overyielding was detected in the Irish experiment, indicating complementary resource use and/or facilitation (complementarity). These mechanisms could not be distinguished from the selection effect in the Romanian study. 5Growth was elevated in Romanian species mixtures, reflecting positive complementarity, but lower than expected growth in some Swedish mixtures was associated with negative complementarity, indicating interspecific interference competition. 6Our results emphasize the potential importance of detritivore diversity for stream ecosystem functioning, but both the effects of diversity on the studied processes, and the mechanisms underlying those effects, were specific to each assemblage and process. Such variability highlights challenges in generalizing impacts of diversity change for functional integrity in streams and other ecosystems in which the occurrence of important species traits fluctuates over relatively small spatio-temporal scales. [source] OLIGONUCLEOTIDE PRIMERS FOR THE DETECTION OF BIOLUMINESCENT DINOFLAGELLATES REVEAL NOVEL LUCIFERASE SEQUENCES AND INFORMATION ON THE MOLECULAR EVOLUTION OF THIS GENE,JOURNAL OF PHYCOLOGY, Issue 2 2008Andrea Baker Bioluminescence is reported in members of 18 dinoflagellate genera. Species of dinoflagellates are known to have different bioluminescent signatures, making it difficult to assess the presence of particular species in the water column using optical tools, particularly when bioluminescent populations are in nonbloom conditions. A "universal" oligonucleotide primer set, along with species and genus-specific primers specific to the luciferase gene were developed for the detection of bioluminescent dinoflagellates. These primers amplified luciferase sequences from bioluminescent dinoflagellate cultures and from environmental samples containing bioluminescent dinoflagellate populations. Novel luciferase sequences were obtained for strains of Alexandrium cf. catenella (Whedon et Kof.) Balech and Alexandrium fundyense Balech, and also from a strain of Gonyaulax spinifera (Clap. et Whitting) Diesing, which produces bioluminescence undetectable to the naked eye. The phylogeny of partial luciferase sequences revealed five significant clades of the dinoflagellate luciferase gene, suggesting divergence among some species and providing clues on their molecular evolution. We propose that the primers developed in this study will allow further detection of low-light-emitting bioluminescent dinoflagellate species and will have applications as robust indicators of dinoflagellate bioluminescence in natural water samples. [source] Modelling species diversity through species level hierarchical modellingJOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES C (APPLIED STATISTICS), Issue 1 2005Alan E. Gelfand Summary., Understanding spatial patterns of species diversity and the distributions of individ-ual species is a consuming problem in biogeography and conservation. The Cape floristic region of South Africa is a global hot spot of diversity and endemism, and the Protea atlas project, with about 60 000 site records across the region, provides an extraordinarily rich data set to model patterns of biodiversity. Model development is focused spatially at the scale of 1, grid cells (about 37 000 cells total for the region). We report on results for 23 species of a flowering plant family known as Proteaceae (of about 330 in the Cape floristic region) for a defined subregion. Using a Bayesian framework, we developed a two-stage, spatially explicit, hierarchical logistic regression. Stage 1 models the potential probability of presence or absence for each species at each cell, given species attributes, grid cell (site level) environmental data with species level coefficients, and a spatial random effect. The second level of the hierarchy models the probability of observing each species in each cell given that it is present. Because the atlas data are not evenly distributed across the landscape, grid cells contain variable numbers of sampling localities. Thus this model takes the sampling intensity at each site into account by assuming that the total number of times that a particular species was observed within a site follows a binomial distribution. After assigning prior distributions to all quantities in the model, samples from the posterior distribution were obtained via Markov chain Monte Carlo methods. Results are mapped as the model-estimated probability of presence for each species across the domain. This provides an alternative to customary empirical ,range-of-occupancy' displays. Summing yields the predicted richness of species over the region. Summaries of the posterior for each environmental coefficient show which variables are most important in explaining the presence of species. Our initial results describe biogeographical patterns over the modelled region remarkably well. In particular, species local population size and mode of dispersal contribute significantly to predicting patterns, along with annual precipitation, the coefficient of variation in rainfall and elevation. [source] Chemical ecology of triatomine bugs: vectors of Chagas diseaseMEDICAL AND VETERINARY ENTOMOLOGY, Issue 4 2001L. Cruz-López Abstract. Knowledge of chemical ecology of haematophagous triatomine bugs (Hemiptera: Heteroptera: Reduviidae) could be of practical value because this polyphyletic subfamily includes species of medical importance, such as vectors of Trypanosoma cruzi Chagas (Kinetoplastida: Trypanosomatidae), the aetiological agent of Chagas disease. For particular species of Dipetalogaster, Panstrongylus, Rhodnius and Triatoma, therefore, we review information on exocrine glands and products, interpreting their apparent roles as semiochemicals in the aggregation, alarm, defence, host-finding and sexual behaviour of these Triatominae. [source] Chloroquine resistance in the malarial parasite, Plasmodium falciparumMEDICINAL RESEARCH REVIEWS, Issue 5 2002Lyann M.B. Ursos Abstract Malarial parasites remain a health problem of staggering proportions. Worldwide, they infect about 500 million, incapacitate tens of millions, and kill approximately 2.5 million (mostly children) annually. Four species infect humans, but most deaths are caused by one particular species, Plasmodium falciparum. The rising number of malarial deaths is due in part to increased drug resistance in P. falciparum. There are many varieties of antimalarial drug resistance, and there may very well be several molecular level contributions to each variety. This is because there are a number of different drugs with different mechanisms of action in use, and more than one molecular event may sometimes be relevant for resistance to any one class of drugs. Thus, "multidrug" resistance in a clinical setting likely entails complex combinations of overlapping resistance pathways, each specific for one class of drug, that then add together to confer the particular multidrug resistance phenotype. Nonetheless, rapid progress has been made in recent years in elucidating mechanisms of resistance to specific classes of antimalarial drugs. As one example, resistance to the antimalarial drug chloroquine, which has been the mainstay therapy for decades, is becoming well understood. This article focuses on recent advances in determining the molecular mechanism of chloroquine resistance, with particular attention to the biochemistry and biophysics of the P. falciparum digestive vacuole, wherein changes in pH have recently been found to be associated with chloroquine resistance. © 2002 Wiley Periodicals, Inc. Med Res Rev, 22, No. 5, 465,491, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/med.10016 [source] Pathogenetical significance of porencephalic lesions associated with intracerebral inoculation of sheep with the bovine spongiform encephalopathy (BSE) agentNEUROPATHOLOGY & APPLIED NEUROBIOLOGY, Issue 3 2009S. Sisó Decreased rates of transmission of transmissible spongiform encephalopathies (TSEs) to sheep have been attributed to some polymorphisms of the prion protein (PrP) and to a ,species barrier' on interspecies experiments. In addition, the blood,brain barrier may be a further impediment to TSE neuroinvasion. The intracerebral (I/C) route is generally considered the most efficient for TSE transmission, as it may help to bypass those factors. Therefore, susceptibility of particular species to specific TSE agents is conducted by this route. Aims: This study characterizes the traumatic brain lesions associated with the I/C injection of the bovine spongiform encephalopathy agent in sheep, assesses the relevance of such lesions in the outcome of clinical disease and provides insight into the mechanisms of PrPd conversion and amplification following I/C challenge. Methods: A total of 27 hemibrains have been macroscopically and immunohistochemically examined to investigate the presence of lesions compatible with the needle track and the PrPd distribution, respectively. Results: No residual inoculum was found and the extension and severity of the traumatic brain lesions were unrelated to the clinical outcome. Sheep with PrPd accumulation in the brain also showed conspicuous focal aggregates in the porencephalic lesions and in the circumventricular organs. In contrast, sheep without PrPd deposits in the brain were also negative in the traumatic lesions. Conclusion: Overall, these findings suggest that the efficiency of the I/C route is due to effective absorption and blood recirculation of infection, rather than to primary amplification at the site of injection. [source] Factors related to the inter-annual variation in plants' pollination generalization levels within a communityOIKOS, Issue 5 2010Amparo Lázaro The number of pollinators of a plant species is considered a measure of its ecological generalization and may have important evolutionary and ecological implications. Many pollination studies report inter-annual fluctuations in the composition of pollinators to particular species. However, the factors causing such variation are still poorly understood. Here we investigate how flowering duration and plant and pollinator assemblages influenced the inter-annual changes in the functional generalization level of the 20 most common plant species of a semi-natural meadow in southern Norway. We also studied the extent to which changes in generalization levels were controlled by flower-shape and flowering time. Large inter-annual changes in generalization levels were common and there was no relationship between the generalization level one year and the following. Generalization level of particular plant species increased with flowering duration, sampling effort, and the abundance of managed honeybees in the community. Generalization level decreased with the flowering synchrony between the focal plant species and the rest of the plant community and with the focal species' own abundance, which we attribute to inter-specific competition for pollinator attraction and foraging decisions made by pollinators. Plants with different flower-shapes and flowering times did not differ in the extent of inter-annual variation in generalization levels. Most studies do not consider the effect of the plant community on the generalization level of particular plant species. We show here that both pollinator and plant assemblages can affect the inter-annual variation in generalization levels of plant species. Studies like ours will help to understand how pollination interactions are structured at the community level, and the ecological and evolutionary consequences that these inter-annual changes in generalization levels may have. [source] Negative native,exotic diversity relationship in oak savannas explained by human influence and climateOIKOS, Issue 9 2009Patrick L. Lilley Recent research has proposed a scale-dependence to relationships between native diversity and exotic invasions. At fine spatial scales, native,exotic richness relationships should be negative as higher native richness confers resistance to invasion. At broad scales, relationships should be positive if natives and exotics respond similarly to extrinsic factors. Yet few studies have examined both native and exotic richness patterns across gradients of human influence, where impacts could affect native and exotic species differently. We examined native,exotic richness relationships and extrinsic drivers of plant species richness and distributions across an urban development gradient in remnant oak savanna patches. In sharp contrast to most reported results, we found a negative relationship at the regional scale, and no relationship at the local scale. The negative regional-scale relationship was best explained by extrinsic factors, surrounding road density and climate, affecting natives and exotics in opposite ways, rather than a direct effect of native on exotic richness, or vice versa. Models of individual species distributions also support the result that road density and climate have largely opposite effects on native and exotic species, although simple life history traits (life form, dispersal mode) do not predict which habitat characteristics are important for particular species. Roads likely influence distributions and species richness by increasing both exotic propagule pressure and disturbance to native species. Climate may partially explain the negative relationship due to differing climatic preferences within the native and exotic species pools. As gradients of human influence are increasingly common, negative broad-scale native,exotic richness relationships may be frequent in such landscapes. [source] Seasonal and spatial patterns of population density in the marine macroalga Mazzaella splendens (Gigartinales, Rhodophyta)PHYCOLOGICAL RESEARCH, Issue 1 2006Leonard James Dyck SUMMARY Insight into demographic processes that operate at larger spatial scales can be achieved through studying local populations when a particular species of interest is examined over time, by many investigators, in a variety of locations. On the west coast of North America, Mazzaella splendens (Setchell et Gardner) Fredericq is such a species of interest. A synthesis of local demographic studies of M. splendens from the late 1960s to the present reveals a pattern that is potentially common to the larger natural populations. This is the pattern: population density is high in summer and low in winter for both alternate free-living life history phases of M. splendens. The magnitude of this seasonal change decreases in increasingly wave-exposed habitats. In wave-sheltered habitats there is a seasonal alternation from summer haploid to winter diploid dominance. This alternation gradually changes to constant diploid dominance as wave exposure in the habitat increases. Changes in population density are primarily a function of appearances and disappearances of perennating basal crusts (genets), as modules are produced or lost, rather than differential module production by genets of one phase over those of the other. To test the generality of this pattern, we examined seasonal changes in density, in local populations of M. splendens, in both a wave-sheltered and a wave-exposed habitat at Second Beach, Barkley Sound. Greater seasonal fluctuation in population density at wave-sheltered, compared to wave-exposed habitats is supported as a pattern potentially common to the natural populations of M. splendens. A change from summer haploid dominance in wave-sheltered areas to summer diploid dominance in wave-exposed areas is similarly supported. All changes in population density were the result of appearances and disappearances of genets rather than differential module production by haploid versus diploid basal crusts, also consistent with previous observations. A seasonal alternation in phase dominance, however, was absent from the wave-sheltered site at Second Beach, Barkley Sound for 3 consecutive years. Seasonal alternation in phase dominance of M. splendens appears dependent on local conditions and is not common to all natural populations. [source] Gaits of Japanese macaques (Macaca fuscata) on a horizontal ladder and arboreal stabilityAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 4 2009Yasuo Higurashi Abstract Most primates use diagonal sequence (DS), diagonal couplets (DC) gaits when they walk or run quadrupedally, and it has been suggested that DSDC gaits contribute to stability in their natural arboreal habitats compared to other symmetrical gaits. However, this postulate is based solely on studies of primate gaits using continuous terrestrial and arboreal substrates. A particular species may select suitable gaits according to the substrate properties. Here, we analyzed the gaits of Japanese macaques moving on a horizontal ladder with rung intervals ranging from 0.40 to 0.80 m to elucidate the relative advantages of each observed form of gait. The rung arrangement forced our macaques to choose either diagonal coupling or DS gaits. One macaque consistently used diagonal coupling (i.e., DSDC and LSDC gaits) across narrow and intermediate rung intervals, whereas the other macaque used DS gaits (i.e., DSDC and DSLC gaits). At wider rung intervals, both macaques shifted to a two-one sequence (TOS), which is characterized by two nearly simultaneous touchdowns of both forelimbs and one touchdown of each hind limb in a stride. The transition to the TOS sequence increased the duration of support on multiple limbs, but always included periods of a whole-body aerial phase. These results suggest that Japanese macaques prefer DSDC gaits, because the diagonal coupling and DS contribute separately to stability on complex supports compared to the lateral coupling and lateral sequence. We also postulate that stability triggers the transition from symmetrical gaits to the TOS sequence. Am J Phys Anthropol, 2009. © 2008 Wiley-Liss, Inc. [source] Using Dominance-Diversity Curves to Assess Completion Criteria After Bauxite Mining Rehabilitation in Western AustraliaRESTORATION ECOLOGY, Issue 1 2003C. D. Grant Abstract Dominance-diversity curves have been previously constructed for a range of ecosystems around the world to illustrate the dominance of particular species and show how their relative abundances compare between communities separated in time or space. We investigate the usefulness of dominance-diversity curves in rehabilitated areas to compare the floristic composition and abundance of "undisturbed" areas with disturbed areas, using bauxite mining rehabilitation in Western Australia as an example. Rehabilitated pits (11,13 years old) subjected to prescribed fire in autumn and spring were compared with unburned rehabilitated areas and the native jarrah (Eucalyptus marginata) forest. Dominance diversity curves were constructed by ranking the log of the species density values from highest to lowest. Species were categorized according to a variety of functional responses: life form (trees, shrubs, subshrubs, and annuals), fire response syndrome (seeder or resprouter), nitrogen fixing capability, and origin (native or adventive). Exponential functions showed extremely good fits for all sites (r2 = 0.939,0.995). Dominance diversity graphs showed that after burning of rehabilitated areas, sites exhibited a more similar dominance-diversity curve than before burning. This was emphasized in a classification (UPGMA) of the regression equations from the dominance-diversity curves that showed that sites burned in spring were more similar to the native forest than sites burned in autumn. There was no significant segregation of the nitrogen-fixing and species origin categories, although the life form and fire response groupings showed significant segregation along the dominance-diversity curve. Resprouters tended to be over-represented in the lower quartiles and under-represented in the upper quartiles of post-burn sites. It is suggested that using dominance-diversity curves in the monitoring of rehabilitated areas may be a useful approach because it provides an easily interpretable visual representation of both species richness and abundance relationships and may be further utilized to emphasize categories of plants that are over- or under-represented in rehabilitated areas. This will assist in the post-rehabilitation management of these sites. [source] General organization of the perinatal and adult accessory olfactory bulb in miceTHE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 9 2006Ignacio Salazar Abstract The vomeronasal system is currently a topical issue since the dual functional specificity, vomeronasal system-pheromones, has recently been questioned. Irrespective of the tools used to put such specificity in doubt, the diversity of the anatomy of the system itself in the animal kingdom is probably of more importance than has previously been considered. It has to be pointed out that a true vomeronasal system is integrated by the vomeronasal organ, the accessory olfactory bulb, and the so-called vomeronasal amygdala. Therefore, it seems reasonable to establish the corresponding differences between a well-developed vomeronasal system and other areas of the nasal cavity in which putative olfactory receptors, perhaps present in other kinds of mammals, may be able to detect pheromones and to process them. In consequence, a solid pattern for one such system in one particular species needs to be chosen. Here we report on an analysis of the general morphological characteristics of the accessory olfactory bulb in mice, a species commonly used in the study of the vomeronasal system, during growth and in adults. Our results indicate that the critical period for the formation of this structure comprises the stages between the first and the fifth day after birth, when the stratification of the bulb, the peculiarities of each type of cell, and the final building of glomeruli are completed. In addition, our data suggest that the conventional plexiform layers of the main olfactory bulb are not present in the accessory bulb. Anat Rec Part A, 288A:1009,1025, 2006. © 2006 Wiley-Liss, Inc. [source] Resource distribution and the trade-off between seed number and seed weight: a comparison across crop speciesANNALS OF APPLIED BIOLOGY, Issue 1 2010B.L. Gambín In grain crops, total sink capacity is usually analysed in terms of two components, seed number and individual seed weight. Seed number and potential individual seed weight are established at a similar timing, around the flowering period, and seed weight at maturity is highly correlated with the potential established earlier. It is known that, within a species, available resources during the seed set period are distributed between both yield components, resulting in a trade-off between seed number and seed weight. Here we tested if this concept could apply for interspecific comparisons, where combinations of numbers and size across species could be related to the total available resources being either allocated to more seed or larger potential individual seed weight during the seed set period. Based on this, species differences in seed weight should be related to resource availability per seed around the period when seed number is determined. Resource availability per seed was estimated as the rate of increase in aboveground biomass per seed around the period of seed set. Data from 15 crop species differing in plant growth, seed number, seed weight and seed composition were analysed from available literature. Because species differed in seed composition, seed weight was analysed following an energy requirement approach. There was an interspecific trade-off relationship between seed number per unit of land area and seed weight (r = 0.92; F(1, 13) = 32.9; n = 15; P < 0.001). Seed weight of different species was positively correlated (r = 0.90; F(1, 13) = 52.9; n = 15; P < 0.001) with resource availability per seed around the seed set period. This correlation included contrasting species like quinoa (Chenopodium quinoa; ,100000 seeds m,2, ,4 mg equivalent-glucose seed,1) or peanut (Arachis hypogaea; ,800 seeds m,2, ,1000 mg equivalent-glucose seed,1). Seed number and individual seed weight combinations across species were related and could be explained considering resource availability when plants are adjusting their seed number to the growth environment and seeds are establishing their storage capacity. Available resources around the seed set period are proportionally allocated to produce either many small seeds or few larger seeds depending on the particular species. [source] Microhabitat relationships among five lizard species associated with granite outcrops in fragmented agricultural landscapes of south-eastern AustraliaAUSTRAL ECOLOGY, Issue 2 2010DAMIAN R. MICHAEL 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] | ||||||||||||||||||||||||||||||||||