RESUMO
Biological diversity can be divided into: alpha (α, local), beta (ß, difference in assemblage composition among locals), and gamma (γ, total diversity). We assessed the partitioning of taxonomic diversity of Ephemeroptera, Plecoptera and Trichoptera (EPT) and of functional feeding groups (FFG) in neotropical savanna (southeastern Brazilian cerrado) streams. To do so, we considered three diversity components: stream site (α), among stream sites (ß1), and among hydrologic units (ß2). We also evaluated the association of EPT genera composition with heterogeneity in land use, instream physical habitat structure, and instream water quality variables. The percentage of EPT taxonomic α diversity (20.7%) was smaller than the ß1 and ß2 diversity percentages (53.1% and 26.2%, respectively). The percentage of EPT FFG collector-gatherer α diversity (26.5%) was smaller than that of ß1 diversity (55.8%) and higher than the ß2 (17.7%) diversity. The collector-gatherer FFG was predominant and had the greatest ß diversity percentage among stream sites (ß1, 55.8%). Our findings support the need for implementing regional scale conservation strategies in the cerrado biome, which has been degraded by anthropogenic activities.
RESUMO
Sea ice and dust flux increased greatly in the Southern Ocean during the last glacial period. Palaeorecords provide contradictory evidence about marine productivity in this region, but beyond one glacial cycle, data were sparse. Here we present continuous chemical proxy data spanning the last eight glacial cycles (740,000 years) from the Dome C Antarctic ice core. These data constrain winter sea-ice extent in the Indian Ocean, Southern Ocean biogenic productivity and Patagonian climatic conditions. We found that maximum sea-ice extent is closely tied to Antarctic temperature on multi-millennial timescales, but less so on shorter timescales. Biological dimethylsulphide emissions south of the polar front seem to have changed little with climate, suggesting that sulphur compounds were not active in climate regulation. We observe large glacial-interglacial contrasts in iron deposition, which we infer reflects strongly changing Patagonian conditions. During glacial terminations, changes in Patagonia apparently preceded sea-ice reduction, indicating that multiple mechanisms may be responsible for different phases of CO2 increase during glacial terminations. We observe no changes in internal climatic feedbacks that could have caused the change in amplitude of Antarctic temperature variations observed 440,000 years ago.
Assuntos
Meio Ambiente , Gelo , Ferro , Cálcio/análise , Clima , Ferro/análise , Biologia Marinha , Mesilatos/análise , Oceanos e Mares , Periodicidade , Sódio/análise , América do SulRESUMO
Nearly 51,000 Cubans were afflicted during an outbreak of an optic neuropathy (ON) and peripheral neuropathy (PN) between 1991 and 1993. We re-examined 14 of 20 affected individuals 16 months after an initial evaluation. The optic features were painless symmetric vision loss with poor visual acuity, color vision loss, central or cecocentral scotoma, optic disc pallor, and nerve fiber layer drop-out. The neurologic symptoms included stocking-glove sensory changes, hearing loss, leg cramps, sensory ataxia, hyperactive or absent reflexes, and complaints of memory loss. Two of 11 ON probands tested harbored Leber's hereditary optic neuropathy (LHON)-associated mitochondrial DNA mutations. All patients had received multivitamin therapy. We performed comparisons using the paired two-tailed t test. On re-examination, 12 of 14 patients demonstrated improvement. One patient remained unchanged. One woman with the nt-3460 mtDNA mutation showed a decline in vision. In patients not harboring mtDNA mutations, overall visual acuity, color vision, and peripheral neuropathy manifestations improved significantly (p < 0.001 for each manifestation). Most of the patients with Cuban ON and PN improved on multivitamin therapy. The significance of the mtDNA mutations is unclear. In the 2 LHON patients, manifestation of the disease may have been precipitated by nutritional deficiency. Patients with poor recovery or further deterioration should be evaluated for other factors, including poor vitamin therapy compliance and alternative diagnoses.