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Colonization Rates (colonization + rate)
Selected AbstractsCoexistence in a metacommunity: the competition,colonization trade-off is not deadECOLOGY LETTERS, Issue 8 2006V. Calcagno Abstract The competition,colonization trade-off model is often used to explain the coexistence of species. Yet its applicability has been severely criticized, mainly because the original model assumed a strict competitive hierarchy of species and did not allow for any preemptive effect. We considered the impact of relaxing both of these limitations on coexistence. Relaxing trade-off intensity makes coexistence less likely and introduces a minimum colonization rate below which any coexistence is impossible. Allowing for preemption introduces a limit to dissimilarity between species. Surprisingly, preemption does not impede coexistence as one could presume from previous studies, but can actually increase the likelihood of coexistence. Its effect on coexistence depends on whether or not species in the regional pool are strongly limited in their colonization ability. Preemption is predicted to favour coexistence when: (i) species are not strongly limited in their colonization ability; and (ii) the competitive trade-off is not infinitely intense. [source] Climate change affects colonization dynamics in a metacommunity of three Daphnia speciesGLOBAL CHANGE BIOLOGY, Issue 6 2008FLORIAN ALTERMATT Abstract Climate change is expected to alter the range and abundance of many species by influencing habitat qualities. For species living in fragmented populations, not only the quality of the present patches but also access to new habitat patches may be affected. Here, we show that colonization in a metacommunity can be directly influenced by weather changes, and that these observed weather changes are consistent with global climate change models. Using a long-term dataset from a rock pool metacommunity of the three species Daphnia magna, Daphnia longispina and Daphnia pulex with 507 monitored habitat patches, we correlated a four-fold increase in colonization rate with warmer, drier weather for the period from 1982 to 2006. The higher colonization rate after warm and dry summers led to an increase in metacommunity dynamics over time. A mechanistic explanation for the increased colonization rate is that the resting stages have a higher exposure to animal and wind dispersal in desiccated rock pools. Although colonization rates reacted in the same direction in all three species, there were significant species-specific effects that resulted in an overall change in the metacommunity composition. Increased local instability and colonization dynamics may even lead to higher global stability of the metacommunity. Thus, whereas climate change has been reported to cause a unidirectional change in species range for many other species, it changes the dynamics and composition of an entire community in this metacommunity, with winners and losers difficult to predict. [source] Pathogenesis of Streptoverticillium albireticuli on Caenorhabditis elegans and its antagonism to soil-borne fungal pathogensLETTERS IN APPLIED MICROBIOLOGY, Issue 5 2002J.-O. Park Aims: To examine the biological activity of Streptoverticillium albireticuli. Methods: Isolation of S. albireticuli was carried out using the dry-heat technique. Nematicidal and pathogenic activity on Caenorhabditis elegans was measured by mortality in metabolites and colonization rate on fishmeal extract agar. Antifungal and enzymatic activities of S. albireticuli were measured by the agar plate method and the semidefined solid media method, respectively. Results:S. albireticuli showed strong nematicidal activity against C. elegans . Pathogenic activity was also evident with the colonized nematode by the isolate on fishmeal extract agar. It also showed antifungal activity against certain fungal pathogens such as Rhizoctonia solani , Phytophthora cinnamomi and Fusarium oxysporum . Significance and Impact of the Study: The discovery of an actinomycete showing pathogenic activity against the nematode may indicate the potential for it to be used as a biocontrol agent of parasitic nematodes, in addition to its ability to suppress fungal pathogens. [source] ORIGINAL ARTICLE: In vitro and in vivo effects of the Mongolian drug Amu-ru 7 on Helicobacter pylori growth and viabilityMICROBIOLOGY AND IMMUNOLOGY, Issue 9 2010Cui Lan Bai ABSTRACT Amu-ru 7, a Mongolian folk medicine, is used to treat digestive diseases such as gastritis and gastric and duodenal ulcers. We examined the effect of Amu-ru 7 on the growth and viability of Helicobacter pylori in vivo and in vitro. By the agar dilution method, the MIC of Amu-ru 7 for H. pylori strains was shown to be 100,200 ,g/mL with a MIC90 of 200 ,g/mL. Two hundred micrograms per milliliter of Amu-ru 7 exhibited potent bactericidal activity against H. pylori in the stationary phase of growth 6 hr after treatment. Amu-ru 7 inhibited the growth of both AMPC-resistant and CAM-resistant strains, and also had a combined effect with AMPC on AMPC-resistant strain 403. The Amu-ru 7 inhibited biofilm formation by H. pylori and induced morphological changes, such as bleb-like formation and shortening of the cell. Although colonization of the stomach of the Mongolian gerbil by H. pylori was not cured by treatment with Amu-ru 7, both the mean number of H. pylori colonized and the colonization rate were decreased in Amu-ru 7 treated gerbils. These results suggest the effectiveness Amu-ru 7 as an adjunct therapy for eradication therapies consisting of a PPI combined with antibiotics. [source] The colonization incidence of group B streptococcus in pregnant women and their newborns in IstanbulPEDIATRICS INTERNATIONAL, Issue 1 2005Ilikkan Barbaros Abstracts,Background:,This study was designed to determine the incidence of group B Streptococcus (GBS) colonization in pregnant women and newborns, and to evaluate the antimicrobial resistance during delivery. Methods:,A total of 300 pregnant women and their newborns were enrolled in this prospective study performed in the maternity ward of Cerrahpasa Medical Faculty and Bakirkoy SSK Hospital, Istanbul, Turkey. Samples were collected from pregnant women and their newborns in the delivery room. Results:,GBS was isolated from 24 women and the colonization rate was found to be 8%. Two newborns were colonized with GBS. None of the isolates were resistant to penicillin, whereas 20% showed resistance to erythromycin and clindamycin. Conclusion:,Screening and antimicrobial susceptibility testing of GBS during pregnancy show similiar results with other studies performed in different regions of our country. [source] Importance of secondary inoculum of Plasmopara viticola to epidemics of grapevine downy mildewPLANT PATHOLOGY, Issue 4 2005D. Gobbin To quantify the magnitude and the spatial spread of grapevine downy mildew secondary sporangia, 4685 Plasmopara viticola single lesion samples were collected from 18 plots spread across central Europe. Disease symptoms were collected on two to 22 sampling dates per plot between 2000 and 2002. Four multiallelic microsatellite markers were used for genotypic identification of pathogen samples. Genetic analysis showed more than 2300 site-specific P. viticola genotypes, indicating that populations are genetically rich demographic units. Approximately 70% of the genotypes were sampled once and 14% were sampled twice throughout the various epidemics. In the 18 populations only seven genotypes (0.3%) were identified more than 50 times. Three genotypes particularly successful in causing disease through secondary cycles showed mainly a clustered distribution. The distance of sporangial migration per secondary cycle was less than 20 m and their plot colonization rate was calculated at around 1,2 m2 day,1. Downy mildew epidemics of grapevine are therefore the result of the interaction of a multitude of genotypes, each causing limited (or a few) lesions, and of a dominant genotype able to spread stepwise at plot-scale. These findings contrast with current theories about grapevine downy mildew epidemiology, which postulate that there is massive vineyard colonization by one genotype and long-distance migration of sporangia. [source] The myth of plant species saturationECOLOGY LETTERS, Issue 4 2008Thomas J. Stohlgren Abstract Plant species assemblages, communities or regional floras might be termed ,saturated' when additional immigrant species are unsuccessful at establishing due to competitive exclusion or other inter-specific interactions, or when the immigration of species is off-set by extirpation of species. This is clearly not the case for state, regional or national floras in the USA where colonization (i.e. invasion by exotic species) exceeds extirpation by roughly a 24 to 1 margin. We report an alarming temporal trend in plant invasions in the Pacific Northwest over the past 100 years whereby counties highest in native species richness appear increasingly invaded over time. Despite the possibility of some increased awareness and reporting of native and exotic plant species in recent decades, historical records show a significant, consistent long-term increase in exotic species (number and frequency) at county, state and regional scales in the Pacific Northwest. Here, as in other regions of the country, colonization rates by exotic species are high and extirpation rates are negligible. The rates of species accumulation in space in multi-scale vegetation plots may provide some clues to the mechanisms of the invasion process from local to national scales. [source] Invasion impacts local species turnover in a successional systemECOLOGY LETTERS, Issue 9 2004Kathryn A. Yurkonis Abstract Exotic plant invasions are often associated with declines in diversity within invaded communities. However, few studies have examined the local community dynamics underlying these impacts. Changes in species richness associated with plant invasions must occur through local changes in extinction and/or colonization rates within the community. We used long-term, permanent plot data to evaluate the impacts of the exotic vine Lonicera japonica. Over time, species richness declined with increasing L. japonica cover. L. japonica reduced local colonization rates but had no effect on extinction rates. Furthermore, we detected significant reductions in the immigration of individual species as invasion severity increased, showing that some species are more susceptible to invasion than others. These findings suggest that declines in species richness associated with L. japonica invasion resulted from effects on local colonization rates only and not through the competitive displacement of established species. [source] Climate change affects colonization dynamics in a metacommunity of three Daphnia speciesGLOBAL CHANGE BIOLOGY, Issue 6 2008FLORIAN ALTERMATT Abstract Climate change is expected to alter the range and abundance of many species by influencing habitat qualities. For species living in fragmented populations, not only the quality of the present patches but also access to new habitat patches may be affected. Here, we show that colonization in a metacommunity can be directly influenced by weather changes, and that these observed weather changes are consistent with global climate change models. Using a long-term dataset from a rock pool metacommunity of the three species Daphnia magna, Daphnia longispina and Daphnia pulex with 507 monitored habitat patches, we correlated a four-fold increase in colonization rate with warmer, drier weather for the period from 1982 to 2006. The higher colonization rate after warm and dry summers led to an increase in metacommunity dynamics over time. A mechanistic explanation for the increased colonization rate is that the resting stages have a higher exposure to animal and wind dispersal in desiccated rock pools. Although colonization rates reacted in the same direction in all three species, there were significant species-specific effects that resulted in an overall change in the metacommunity composition. Increased local instability and colonization dynamics may even lead to higher global stability of the metacommunity. Thus, whereas climate change has been reported to cause a unidirectional change in species range for many other species, it changes the dynamics and composition of an entire community in this metacommunity, with winners and losers difficult to predict. [source] Feedbacks between community assembly and habitat selection shape variation in local colonizationJOURNAL OF ANIMAL ECOLOGY, Issue 4 2010Johanna M. Kraus Summary 1.,Non-consumptive effects of predators are increasingly recognized as important drivers of community assembly and structure. Specifically, habitat selection responses to top predators during colonization and oviposition can lead to large differences in aquatic community structure, composition and diversity. 2.,These differences among communities due to predators may develop as communities assemble, potentially altering the relative quality of predator vs. predator-free habitats through time. If so, community assembly would be expected to modify the subsequent behavioural responses of colonists to habitats containing top predators. Here, we test this hypothesis by manipulating community assembly and the presence of fish in experimental ponds and measuring their independent and combined effects on patterns of colonization by insects and amphibians. 3.,Assembly modified habitat selection of dytscid beetles and hylid frogs by decreasing or even reversing avoidance of pools containing blue-spotted sunfish (Enneacanthus gloriosus). However, not all habitat selection responses to fish depended on assembly history. Hydrophilid beetles and mosquitoes avoided fish while chironomids were attracted to fish pools, regardless of assembly history. 4.,Our results show that community assembly causes taxa-dependent feedbacks that can modify avoidance of habitats containing a top predator. Thus, non-consumptive effects of a top predator on community structure change as communities assemble and effects of competitors and other predators combine with the direct effects of top predators to shape colonization. 5.,This work reinforces the importance of habitat selection for community assembly in aquatic systems, while illustrating the range of factors that may influence colonization rates and resulting community structure. Directly manipulating communities both during colonization and post-colonization is critical for elucidating how sequential processes interact to shape communities. [source] Can invasion patches of Acacia mearnsii serve as colonizing sites for native plant species on Réunion (Mascarene archipelago)?AFRICAN JOURNAL OF ECOLOGY, Issue 3 2009J. Tassin Abstract There is need for documenting the long-term effects of plant invasions at the landscape scale. We investigated the possible catalytic effect of invasive Acacia mearnsii De Wild. on the colonization of rural landscapes by native plant species on Réunion Island (Mascarene Archipelago, Indian Ocean). Data were recorded from 182 circular plots of 50 m2 within a set of 48 large invasion patches, aged from 1 to 48+ years. Only eighteen native plant species were present in the invaded patches and these in only 21 of the 48 patches. The Acacia invasion patches colonized by native flora were older and closer to the closest forest remnant. Most invasion patches colonized by native species were located <200 m from forest remnants. Results are consistent with studies on colonization rates of nonindigenous forest plantations, which increase with age and decrease with distance to seeds sources. Yet, the rate of Acacia invasion patches colonized by native flora remained very low compared to studies on the colonization of exotic plantations in other tropical countries. We conclude that invasion patches of Acacia mearnsii are poor colonizing sites for native plant species. Allelopathy is suspected as one of the strongest factors, which prevent this colonization. Résumé Il est nécessaire de documenter les effets à long terme des invasions de plantes à l'échelle du paysage. Nous avons étudié l'effet potentiellement catalyseur de la plante invasive Acacia mearnsii De Wild. sur la colonisation de paysages ruraux par des espèces végétales natives sur l'île de la Réunion (archipel des Mascareignes, océan Indien). On a récolté des données sur 182 parcelles circulaires de 50 m2 dans un ensemble de 48 grandes zones envahies âgées de un à plus de 48 ans. Il n'y avait que 18 espèces végétales natives dans les endroits envahis, et celles-là ne se trouvaient que dans 21 des 48 zones. Les zones envahies par les Acacia qui étaient colonisées par des espèces natives étaient plus âgées et se situaient plus près des reliquats forestiers les plus fermés. La plupart des zones envahies colonisées par des espèces natives étaient situées à moins de 200 m de forêts relictuelles. Les résultats sont cohérents avec des études sur les taux de colonisation de plantations forestières non indigènes, qui augmentent avec l'âge et diminuent avec la distance de la source des semences. Ceci dit, le taux de zones envahies par les acacias qui sont colonisées par la flore indigène reste très faible en comparaison avec les études sur la colonisation de plantations exotiques dans d'autres pays tropicaux. Nous concluons que les zones d'invasion d'Acacia mearnsii sont des sites de colonisation médiocre pour les espèces végétales indigènes. On suspecte que l'allélopathie est un des facteurs les plus actifs dans la prévention de cette colonisation. [source] Temporal and spatial genetic variation in a metapopulation of the annual Erysimum cheiranthoides on stony river banksJOURNAL OF ECOLOGY, Issue 1 2009Olivier Honnay Summary 1Metapopulation dynamics , the recurrent extinction and colonization in spatially discrete habitats , is expected to strongly affect within and between population genetic diversity. So far, however, accounts of true plant metapopulations are extremely scarce. 2We monitored the colonization and extinction dynamics of an assemblage of populations of the annual Erysimum cheiranthoides on stony river banks during three consecutive years. Each year, winter flooding drives some populations to extinction, while vacant banks may become colonized. We describe the dynamics of these ephemeral populations using amplified fragment length polymorphism (AFLP) markers to quantify changes in the metapopulation genetic structure over time, and assessing the direction and relative amount of migration and colonization events. 3Average extinction and colonization rates were high (0.39 and 0.34, respectively). While population genetic differentiation (FST) tripled from 0.06 in 2005 to 0.17 in 2007, total metapopulation genetic diversity remained fairly constant through the years. Genetic assignment analyses allowed assigning more than 50% of the genotyped individuals to populations extant the year before. Colonizing individuals originated from different source populations (, << 1) and there was considerable evidence of upstream seed dispersal. 4The degree and pattern of spatial genetic structure varied between years and was related to variation in the flooding intensity of the Meuse River through the years. Possibly, activation of the soil seed bank also played a role in structuring the genetic make-up of the populations. 5Because migration and colonization events were qualitatively equal, and colonizing individuals originated from different sources, the increase in FST was in agreement with previous theoretical work. Very high migration and colonization rates, and the short monitoring period, may explain why there was no loss of genetic diversity from the metapopulation through recurrent extinction and colonization events. 6Synthesis. This study gives one of the first accounts of the dynamics of a true plant metapopulation. Temporal monitoring of genetic variation gave evidence of extensive and bidirectional seed dispersal, highly variable and increasing genetic differentiation, and rather constant within population genetic diversity. An important suggestion from this research is to include a dormant seed stage in further theoretical work on (meta) population genetics. [source] Invasion impacts diversity through altered community dynamicsJOURNAL OF ECOLOGY, Issue 6 2005KATHRYN A. YURKONIS Summary 1Invading plant species often alter community structure, composition and, in some instances, reduce local diversity. However, the community dynamics underlying these impacts are relatively unknown. 2Declines in species richness with invasion may occur via displacement of resident species and/or reduction of seedling establishment by the invader. These two mechanisms differ in the demographic stage of the interaction. 3We document turnover dynamics using long-term permanent plot data to assess the mechanism(s) of invasion impacts of four exotic species on a mixed community of native and exotic species. These mechanisms were evaluated at both the neighbourhood (1-m2 plot) and population (individual species) scales. 4During invasion, species richness declined with increasing invader cover for three of the four invaders. All invaders reduced colonization rates, but had no effect on extinction rates at the neighbourhood scale. Populations differed in their susceptibility to invasion impacts, with significant reductions in colonization for 10 of 25 (40%) species and increases in extinction for only 4 of 29 (14%) species. 5At neighbourhood and population scales, influences of invasion on community dynamics were essentially the same for all invaders regardless of life-form. While individual resident species had some increase in extinction probability, community richness impacts were largely driven by colonization limitation. 6The consistency of invasion impacts across life-forms suggests establishment limitation as a general mechanism of invasion impact. This common causal mechanism should be explored in other systems to determine the extent of its generality. [source] Temporal changes in the island flora at different scales in the archipelago of SW FinlandAPPLIED VEGETATION SCIENCE, Issue 4 2010Jens-Johan Hannus Abstract Question: How have species richness and vegetation patterns changed in a group of islands in the northern Baltic Sea over a 58-yr period of changing land use and increasing eutrophication? Location: A group of 116 islands, the Brunskär sub-archipelago, in SW Finland. Methods: A complete survey of vascular plant species performed in 1947,1949 by Skult was repeated by our group using the same methodology in 2005,2007 (historical versus contemporary, respectively). DCAs were performed and total number of species, extinction,colonization rates, species frequency changes and mean Ellenberg indicator values for light, moisture and nitrogen and Eklund indicator values for dependence of human cultural influence were obtained for each island and relevé. Results: Species richness has declined on large islands and increased on small islands. The increase in number of species on small islands is driven by a strong increase in frequency of shore species, which in turn is induced by more productive shores. The decrease in species richness on large islands is related to overgrowth of open semi-natural habitats after cessation of grazing and other agricultural practices. Conclusions: After the late 1940s, open habitats, which were created and maintained by cattle grazing and other traditional agricultural activities, have declined in favour of woody shrub and forest land. Shores have been stabilized and influenced by the eutrophication of the Baltic Sea, and the vegetation has become more homogeneous. This development, resulting in lower species diversity, poses a challenge for the preservation of biodiversity both on a local and on a landscape level. [source] Rate of succession in restored wetlands and the role of site contextAPPLIED VEGETATION SCIENCE, Issue 3 2010Jeffrey W. Matthews Abstract Question: Are changes in plant species composition, functional group composition and rates of species turnover consistent among early successional wetlands, and what is the role of landscape context in determining the rate of succession? Location: Twenty-four restored wetlands in Illinois, USA. Methods: We use 4 years of vegetation sampling data from each site to describe successional trends and rates of species turnover in wetlands. We quantify: (1) the rate at which composition changes from early-successional to late-successional species and functional groups, as indicated by site movement in ordination space over time, and (2) the rate of change in the colonization and local extinction of individual species. We correlate the pace of succession to site area, isolation and surrounding land cover. Results: Some commonalities in successional trends were evident among sites. Annual species were replaced by clonal perennials, and colonization rates declined over time. However, differences among sites outweighed site age in determining species composition, and the pace of succession was influenced by a site's landscape setting. Rates of species turnover were higher in smaller wetlands. In addition, wetlands in agricultural landscapes underwent succession more rapidly, as indicated by a rapid increase in dominance by late-successional plants. Conclusions: Although the outcome of plant community succession in restored wetlands was somewhat predictable, species composition and the pace of succession varied among sites. The ability of restoration practitioners to accelerate succession through active manipulation may be contingent upon landscape context. [source] Plant colonization windows in a mesic old field successionAPPLIED VEGETATION SCIENCE, Issue 2 2003Sándor Bartha Abstract. Closed canopy vegetation often prevents the colonization of plant species. Therefore the majority of plant species are expected to appear at the initial phase of post-agricultural succession in mesic forest environment with moderate levels of resources. This hypothesis was tested with data from the Buell-Small Successional Study, NJ, USA, one of the longest continuous fine-scale studies of old-field succession. The study started in 1958, including old fields with different agricultural histories, landscape contexts, and times of abandonment. In each year of the study, the cover values of plant species were recorded in 48 permanent plots of 1 m2 in each field. We analysed the temporal patterns of colonization at plot scale and related these to precipitation data and other community characteristics. The number of colonizing species decreased significantly after ca. 5 yr, coinciding with the development of a continuous canopy of perennial species. However, species turnover remained high throughout the whole successional sequence. The most remarkable phenomenon is the high inter-annual variation of all studied characteristics. We found considerable temporal collapses of vegetation cover that were synchronized among fields despite their different developmental stages and distinctive species compositions. Declines of total cover were correlated with drought events. These events were associated with peaks of local species extinctions and were followed by increased colonization rates. The transitions of major successional stages were often connected to these events. We suggest that plant colonization windows opened by extreme weather events during succession offer optimum periods for intervention in restoration practice. [source] Does Bathing Newborns Remove Potentially Harmful Pathogens from the Skin?BIRTH, Issue 3 2001Jennifer M. Medves RN Background: Newborn infants are routinely bathed after birth partly to reduce the possibility of transmitting potential pathogens to others. The extent to which a mild soap reduces the quantity and type of microbes found on the skin through normal colonization has not been reported. The objective of the study was to compare colonization rates between infants bathed in soap and water and infants bathed in plain water. Method: One hundred and forty infants were randomly assigned to one group bathed in a mild pH neutral soap and water or to another group bathed in water alone. Microbiology swabs were taken on three occasions (before the first bath, 1 hour after the bath, and 24 hours after birth) from two sites (anterior fontanelle and umbilical area). Results: No difference occurred between groups on type or quantity of organisms found at each time period. Skin colonization is a function of time, and the quantity of organisms identified increased over time (Friedman A 2= 111.379, df = 5, p < 0.001). Conclusions: Bathing with mild soap as opposed to bathing in water alone has minimal effect on skin bacterial colonization. Skin colonization increased over time. The findings did not support the efficacy of bathing with soap and water to reduce skin colonization of bacterial pathogens. Although the incidence of potential pathogens colonizing the skin during the first day of life is low and unlikely to pose a risk to healthy newborns, health care professionals may wish to wear gloves until the infant has been bathed. [source] | |||||||||||||