4,512 research outputs found
Temporal consistency of a facilitation cascade on shallow rocky reefs
No full textFacilitation cascades are increasingly recognized as key drivers of biodiversity in a variety of habitats, yet their temporal variability remains poorly investigated. On shallow subtidal rocky reefs, positive interactions between the canopy-forming species, Halopithys incurva, and its epiphyte, Jania rubens, enhance the abundance and di-versity of the associated mobile invertebrate assemblage. By means of a field experiment manipulating the presence of J. rubens on H. incurva plants, we investigated whether the effects of this facilitation cascade varied over time scales of months. Despite seasonal fluctuations in its biomass, J. rubens enhanced total invertebrate abundance and species richness by 64% and 45%, respectively, throughout the experiment. Our results suggest that the presence of J. rubens, likely by providing novel microhabitats and increasing resource availability, sustains invertebrate biodiversity of shallow macroalgal forests consistently between warm and cold periods. Understanding the temporal dynamics of facilitation cascades and their mechanisms can help inform manage-ment strategies targeting biodiversity conservation and restoration under current and future climates
Linking habitat interactions and biodiversity within seascapes - Dataset
No full textThis dataset supports the article:
Bugnot AB, Dafforn KA, Coleman RA, Ramsdale M, Gibbeson JT, Erickson K, Vila-Concejo A, Figueira WF, Gribben PE. Linking habitat interactions and biodiversity within seascapes. Ecospher
Comparative analysis of Mycobacterium tuberculosis pe and ppe genes reveals high sequence variation and an apparent absence of selective constraints.
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110619.pdf (Publisher’s version ) (Open Access)Mycobacterium tuberculosis complex (MTBC) genomes contain 2 large gene families termed pe and ppe. The function of pe/ppe proteins remains enigmatic but studies suggest that they are secreted or cell surface associated and are involved in bacterial virulence. Previous studies have also shown that some pe/ppe genes are polymorphic, a finding that suggests involvement in antigenic variation. Using comparative sequence analysis of 18 publicly available MTBC whole genome sequences, we have performed alignments of 33 pe (excluding pe_pgrs) and 66 ppe genes in order to detect the frequency and nature of genetic variation. This work has been supplemented by whole gene sequencing of 14 pe/ppe (including 5 pe_pgrs) genes in a cohort of 40 diverse and well defined clinical isolates covering all the main lineages of the M. tuberculosis phylogenetic tree. We show that nsSNP's in pe (excluding pgrs) and ppe genes are 3.0 and 3.3 times higher than in non-pe/ppe genes respectively and that numerous other mutation types are also present at a high frequency. It has previously been shown that non-pe/ppe M. tuberculosis genes display a remarkably low level of purifying selection. Here, we also show that compared to these genes those of the pe/ppe families show a further reduction of selection pressure that suggests neutral evolution. This is inconsistent with the positive selection pressure of "classical" antigenic variation. Finally, by analyzing such a large number of genes we were able to detect large differences in mutation type and frequency between both individual genes and gene sub-families. The high variation rates and absence of selective constraints provides valuable insights into potential pe/ppe function. Since pe/ppe proteins are highly antigenic and have been studied as potential vaccine components these results should also prove informative for aspects of M. tuberculosis vaccine design
Propagules are not all equal: traits of vegetative fragments and disturbance regulate invasion success
Get PDFInvasion success is regulated by multiple factors. While the roles of disturbance and propagule pressure in regulating the establishment of non-native species are widely acknowledged, that of propagule morphology (a proxy for quality) is poorly known. By means of a multi-factorial field experiment, we tested how the number (5 versus 10) and quality (intact, without fronds or without rhizoids) of fragments of the clonal invasive seaweed, Caulerpa cylindracea, influenced its ability to establish in patches of the native seagrass, Posidonia oceanica, exposed to different intensities of disturbance (0, 50 or 100% reduction in canopy cover). We hypothesized that the ability of fragments to establish would be greater for intact fragments (high quality) and reduced more by frond removal (low quality) than rhizoid removal (intermediate quality). At low propagule pressure or quality, fragment establishment was predicted to increase with increasing disturbance, whereas, at high propagule pressure or quality, it was predicted to be high regardless of disturbance intensity. Disturbance intensity, fragment number and quality had independent effects on C. cylindracea establishment success. Disturbance always facilitated fragment establishment. However, fragments retaining fronds, either intact or deprived of rhizoids, had higher establishment success than fragments deprived of fronds. Increasing propagule number had weak effects on the cover of C. cylindracea. Our results demonstrate that propagule traits enabling the acquisition of resources made available by disturbance can be more important than propagule number in determining the establishment and spread of clonal non-native plants. More generally, our study suggests that propagule quality is a key, yet underexplored, determinant of invasion success
On minimal non-PE-groups
No full textAbstractIf H is a subgroup of a finite group G, by HG denote the normal closure of H in G. G is called a PE-group if every minimal subgroup X of G satisfies NG(X) ∩ XG = X. The author proves that all PE-groups are solvable with the Fitting height at most 3 and classifies the minimal non-PE-groups
Gametogenic development and spawning of the razor clam, Zenatia acinaces in northeastern New Zealand
Get PDFThe potential exists for New Zealand to exploit already established markets for razor clams through development of fisheries or aquaculture industries for the nNew Zealand razor clam, Zenatia acinaces. However, fishery or aquaculture development for Z. acinaces requires an understanding of the reproductive cycle including the timing of gametogenic development and spawning. The reproductive cycle of Z. acinaces was studied over an 11-month period from May 2000 to March 2001 at Kennedy Bay, Coromandel Peninsula using qualitative syanrad histological analysis and quantitative measures of oocytes. Histological abalysis indictaed that Z. acinaces is dioecious between the sexes. Gametogenesis began in June with gametes maturing quickly and by August/September (late winter/early spring) most razor clams were ripe. Spawining began as early as September (spring) although spawning mainly occurred during October. By December (summer) nearly all clams were completely spent. From January 2001 most clams could not be sexed as all residual gametes qwew reabsorbed. Rqazor clams remained in this stage during March 2001. Spawning began when the water temperature was around its lowest c. 15degrees celcius. Monthly mean number of eggs/follicle was sensitive to changes in reproductive development, closely following patterns observed in the qualitative stagings. Patterns of monthly mean oocyte diameters did not adequately describe the spawning events observed in qualitative analyses. Sex ratios were equal over the size range (69-99 mm shell length) of clams that could be sexed. The data presented in this study provides valuable information on the timing of spawning events for Z. acinaces, necessary for developing sustainable management strategies and selecting broodstock for aqauculture
[[alternative]]The Study of Acknowledgement of Risk Management on Perception of PE Teachers in Taoyuan Junior High Schools
No full text[[abstract]]The purpose of this study was to (1) explore the acknowledgement about physical activity risk management of junior high school PE teachers in Taoyuan, (2) compare PE teachers’ perception difference about risk management with different background (3) realize the strategy of risk management plan of PE teachers in junior high school. (4) finally build effective risk management plan for all PE teachers in junior high school.
One hundred and ninety two Taoyuan PE teachers served as the subjects of this study with the questionnaire of ” PE Teacher’s Perception of The Risk Management”. This study used descriptive statistics, t-test, and one-way ANOVA to analyze data. Besides, the research also chose seven PE teachers to do semi-structured interview, trying to understand risk management strategy of PE teachers. The results were listed as below:
1.The perception of risk management of physical teachers in junior high school, based on the importance, was: theory layer, practical layer, law layer, entity and application layer.
2.Significant difference was found in gender, practical layer, law layer and entity; while other factors showed no significant difference.
3.All the interviewees didn’t take action about risk management , but all of them agreed that risk management plan of physical activity is necessary. They suggested higher authorities ask junior high school to set risk management plan for physical activity, and become an evaluated item.
In conclusion of the research, the PE teachers in junior high school think it is important to execute a better physical activity risk management. Author suggested junior high school should set risk management plan for physical activity to get “zero risk” in school.
Below-ground processes control the success of an invasive seaweed
Get PDFWhilst the successful establishment and spread of invasive species can be determined by above-ground processes, results are often equivocal. Emergent research, mostly from terrestrial ecosystems, demonstrates that below-ground processes (nutrient cycling, chemical properties) under microbial control can mediate interactions between native and invasive plants. Because microbes can control similar sediment properties in marine ecosystem that influence plant fitness, we argue that below-ground properties should also exert strong control interactions between native and invasive marine macrophytes. We coupled surveys of microbial communities and chemistry of sediments collected from an invasive alga (Caulerpa cylindracea), a native competitor (the seagrass Posidonia oceanica) and unvegetated sediments with a large field experiment, in which we manipulated the presence/absence of the canopies of both species to determine the effects of above- and below-ground processes on the success of C. cylindracea. Posidonia oceanica and C. cylindracea sediments have microbial communities and predicted metabolic process that reflect aerobic and anaerobic conditions, respectively. Moreover, the nutritional quantity of organic matter was higher, but quality lower in C. cylindracea sediments compared to the two native habitats. The growth of C. cylindracea fragments was equally low in the presence or absence of a P. oceanica canopy, whereas the growth of C. cylindracea was higher in the canopy removed vs. present treatment, possibly because, in the absence of a C. cylindracea canopy, fragments are released from intraspecific competition for resources. Synthesis. Sediment/soil processes are increasingly recognized as important drivers of the success and hence impacts of invasive plants. We extended this theory to marine ecosystems and suggest biotic resistance to invasion may not always be attributable to intact canopies, but may also result from indirect effects of native macrophytes on sediment quality and microbial processes. This information may, in part, resolve why above-ground interactions do not always explain invasive plant success and thus can be used to develop better informed management strategies
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