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1.
2.
In a study of the early meiotic prophase stages of mouse oogenesis from d12 of gestation to 10d post-partum the patterns of RNA synthesis during these stages of oogenesis using H3-uridine incorporation as visualized by light microscope autoradiography are reported. We find that chromosomal RNA synthesis occurs in all stages except early to mid-pachytene, the time of maximum chromosome condensation. Diplotene and dictyate nuclei are the most heavily labelled stages. Nucleolar labelling ceases before leptotene and reappears in late pachytene or early diplotene, even though nucleoli can be identified in all stages except early to mid-pachytene. 相似文献
3.
T. R. McClanahan N. A. J. Graham 《Proceedings. Biological sciences / The Royal Society》2015,282(1821)
Ecological baselines are disappearing and it is uncertain how marine reserves, here called fisheries closures, simulate pristine communities. We tested the influence of fisheries closure age, size and compliance on recovery of community biomass and life-history metrics towards a baseline. We used census data from 324 coral reefs, including 41 protected areas ranging between 1 and 45 years of age and 0.28 and 1430 km2, and 36 sites in a remote baseline, the Chagos Archipelago. Fish community-level life histories changed towards larger and later maturing fauna with increasing closure age, size and compliance. In high compliance closures, community biomass levelled at approximately 20 years and 10 km2 but was still only at approximately 30% of the baseline and community growth rates were projected to slowly decline for more than 100 years. In low compliance and young closures, biomass levelled at half the value and time as high compliance closures and life-history metrics were not predicted to reach the baseline. Biomass does not adequately reflect the long-time scales for full recovery of life-history characteristics, with implications for coral reef management. 相似文献
4.
Timothy R. McClanahan Nyawira A. Muthiga Caroline Abunge Albogast T. Kamukuru Eliezer Mwakalapa Hassan Kalombo 《PloS one》2015,10(10)
The coral reefs of Tanga, Tanzania were recognized as a national conservation priority in the early 1970s, but the lack of a management response led to damage by dynamite, beach seines, and high numbers of fishers until the mid 1990s. Subsequently, an Irish Aid funded IUCN Eastern Africa program operated from 1994 to mid 2007 to implement increased management aimed at reducing these impacts. The main effects of this management were to establish collaborative management areas, reduce dynamite and seine net fishing, and establish small community fisheries closures beginning in 1996. The ecology of the coral reefs was studied just prior to the initiation of this management in 1996, during, 2004, and a few years after the project ended in 2010. The perceptions of resource users towards management options were evaluated in 2010. The ecological studies indicated that the biomass of fish rose continuously during this period from 260 to 770 kg/ha but the small closures were no different from the non-closure areas. The benthic community studies indicate stability in the coral cover and community composition and an increase in coralline algae and topographic complexity over time. The lack of change in the coral community suggests resilience to various disturbances including fisheries management and the warm temperature anomaly of 1998. These results indicate that some aspects of the management program had been ecologically successful even after the donor program ended. Moreover, the increased compliance with seine net use and dynamite restrictions were the most likely factors causing this increase in fish biomass and not the closures. Resource users interviewed in 2010 were supportive of gear restrictions but there was considerable between-community disagreement over the value of specific restrictions. The social-ecological results suggest that increased compliance with gear restrictions is largely responsible for the improvements in reef ecology and is a high priority for future management programs. 相似文献
5.
6.
M. A. MacNeil N. A. J. Graham M. J. Conroy C. J. Fonnesbeck N. V. C. Polunin S. P. Rushton P. Chabanet T. R. McClanahan 《Journal of fish biology》2008,73(7):1748-1763
This study shows how capture–mark–recapture (CMR) models can provide robust estimates of detection heterogeneity (sources of bias) in underwater visual‐census data. Detection biases among observers and fish family groups were consistent between fished and unfished reef sites in Kenya, even when the overall level of detection declined between locations. Species characteristics were the greatest source of detection heterogeneity and large, highly mobile species were found to have lower probabilities of detection than smaller, site‐attached species. Fish family and functional‐group detectability were also found to be lower at fished locations, probably due to differences in local abundance. Because robust CMR models deal explicitly with sampling where not all species are detected, their use is encouraged for studies addressing reef‐fish community dynamics. 相似文献
7.
Valeriano Parravicini Sébastien Villéger Tim R. McClanahan Jesus Ernesto Arias‐González David R. Bellwood Jonathan Belmaker Pascale Chabanet Sergio R. Floeter Alan M. Friedlander François Guilhaumon Laurent Vigliola David Mouillot 《Ecology letters》2014,17(9):1101-1110
The impact of anthropogenic activity on ecosystems has highlighted the need to move beyond the biogeographical delineation of species richness patterns to understanding the vulnerability of species assemblages, including the functional components that are linked to the processes they support. We developed a decision theory framework to quantitatively assess the global taxonomic and functional vulnerability of fish assemblages on tropical reefs using a combination of sensitivity to species loss, exposure to threats and extent of protection. Fish assemblages with high taxonomic and functional sensitivity are often exposed to threats but are largely missed by the global network of marine protected areas. We found that areas of high species richness spatially mismatch areas of high taxonomic and functional vulnerability. Nevertheless, there is strong spatial match between taxonomic and functional vulnerabilities suggesting a potential win–win conservation‐ecosystem service strategy if more protection is set in these locations. 相似文献
8.
T. R. McClanahan V. Hendrick M. J. Rodrigues N. V. C. Polunin 《Coral reefs (Online)》1999,18(3):195-203
The consequences of macroalgal overgrowth on reef fishes and means to reverse this condition have been little explored. An
experimental reduction of macroalgae was conducted at a site in the Watamu Marine National Park in Kenya, where a documented
increase in macroalgal cover has occurred over the last nine years. In four experimental 10 m by 10 m plots, macroalgae were
greatly reduced (fleshy algal cover reduced by 84%) by scrubbing and shearing, while four similar plots acted as controls.
The numerical abundance in all fish groups except wrasses and macroalgal-feeding parrotfishes (species in the genera Calotomus and Leptoscarus) increased in experimental algal reduction plots. Algal (Sargassum) and seagrass (Thalassia) assays, susceptible to scraping and excavating parrotfishes, were bitten more frequently in the algal reduction plots one
month after the manipulation. Further, surgeonfish (Acanthurus leucosternon and A. nigrofuscus) foraging intensity increased in these algal reduction plots. The abundance of triggerfishes increased significantly in experimental
plots relative to control plots, but densities remained low, and an index of sea urchin predation using tethered juvenile
and adult Echinometra mathaei showed no differences between treatments following macroalgal reduction. Dominance of reefs by macrofleshy algae appears
to reduce the abundance of fishes, mostly herbivores and their rates of herbivory, but also other groups such as predators
of invertebrates (triggerfishes, butterflyfishes and angelfishes).
Accepted: 2 February 1999 相似文献
9.
Nuclear gene trees and the phylogenetic relationships of the mangabeys (Primates: Papionini) 总被引:3,自引:1,他引:2
Phylogenetic relationships of mangabeys within the Old World monkey tribe
Papionini are inferred from analyses of nuclear DNA sequences from five
unlinked loci. The following conclusions are strongly supported, based on
congruence among trees derived for the five separate gene regions: (1)
mangabeys are polyphyletic within the Papionini; (2) Cercocebus is the
sister taxon to the genus Mandrillus; and (3) Lophocebus belongs to a clade
with Papio and Theropithecus, with Papio as its most likely sister taxon.
Morphologically based phylogenies positing mangabey monophyly were
evaluated by mapping the sequences for each locus on these trees. The data
seem to fit these trees poorly in both maximum-parsimony and likelihood
analyses. Incongruence among nuclear gene trees occurred in the
interrelationships among Lophocebus, Papio, and Theropithecus. Several
factors that may account for this incongruence are discussed, including
sampling error, random lineage sorting, and introgression.
相似文献
10.
PPCMatrix: a PowerPC dotmatrix program to compare large genomic sequences against protein sequences 总被引:1,自引:0,他引:1
Summary : An interactive dotmatrix program for the MacOS was designed that
allows comparison of DNA to protein sequences using nested 3-frame
translations. Availability : Shareware, available at
http://copan.bioz.unibas.ch/software/ Contact : burglin@ubaclu. unibas.ch
相似文献