Resource distribution and soil moisture content can regulate bait control in an ant assemblage in Central Amazonian forest

Resources influence population growth, interspecific interactions, territoriality and, in combination with moisture content, affect terrestrial arthropod distribution and abundance. Ants are usually described as interactive and compete in transitive hierarchies, where the dominants behaviourally exclude subordinate species from food resources. In this study, we evaluated the effects of (i) dominant ants, soil moisture and an artificial resource gradient on the number of ant species attracted to baits; and (ii) how soil moisture and an artificial resource gradient change the number of controlled baits in a Central Amazonian rain forest. We sampled 30 100‐m‐long transects, located at least 200 m apart. The transects were established with six different bait densities varying between six and 41 baits and the soil moisture content was measured at 10 points for each transect. Six ant species were considered dominant, and had negative correlations with the number of species at baits (r² = 0.186; F_1,28 = 6.419; P = 0.017). However, almost half of the transects showed low abundance of dominant species (<30%), and relatively high number of species (mean of 20.1 ± 8.75). Resource availability and soil moisture had negative and positive correlations, with number of controlled baits. These results suggest that, even though the dominance is relatively poorly developed on the floor of this tropical forest, both resource availability and soil moisture affect resource control, and thus, the number of species that use baits.     

El Niño,grazers and fisheries interact to greatly elevate extinction risk for Galapagos marine species

Comparisons between historical and recent ecological datasets indicate that shallow reef habitats across the central Galapagos Archipelago underwent major transformation at the time of the severe 1982/1983 El Niño warming event. Heavily grazed reefs with crustose coralline algae (‘urchin barrens’) replaced former macroalgal and coral habitats, resulting in large local and regional declines in biodiversity. Following recent threat assessment workshops, a total of five mammals, six birds, five reptiles, six fishes, one echinoderm, seven corals, six brown algae and nine red algae reported from coastal environments in Galapagos are now recognized as globally threatened. The 2008 International Union for the Conservation of Nature (IUCN) Red List includes 43 of these species, while two additional species (Galapagos damsel Azurina eupalama and 24‐rayed sunstar Heliaster solaris) not seen for > 25 years also fulfil IUCN threatened species criteria. Two endemic species (Galapagos stringweed Bifurcaria galapagensis and the damselfish A. eupalama) are now regarded as probably extinct, while an additional six macroalgal species (Dictyota galapagensis, Spatoglossum schmittii, Desmarestia tropica, Phycodrina elegans, Gracilaria skottsbergii and Galaxaura barbata) and the seastar H. solaris are possibly extinct. The removal of large lobster and fish predators by artisanal fishing probably magnified impacts of the 1982/1983 El Niño through a cascade of indirect effects involving population expansion of grazing sea urchins. Marine protected areas with adequate enforcement are predicted to ameliorate but not eliminate ecosystem impacts caused by increasing thermal anomalies associated with El Niño and global climate change.     

Studies on the Germination of Cereals: 4. The Oxygen Requirement for Germination of Wheat Grains during Maturation

The oxygen required by the wheat embryo, for germination atdifferent stages of maturation, has been determined by the numberof grains with the embryo exposed which germinated in differentoxygen concentrations. Some embryos required only 0.5 per cent.,and the majority required less than 5 per cent., but there wasalso a proportion which required a concentration approachingthe level in air. There were more embryos in the last categoryin the grains of a red variety than in those of a white varietybut this did not account for the varietal difference in germinationwhen the grains were intact. The effect of the covering layers was also determined in eachatmosphere by the difference in germination between intact grainsand grains with the embryo exposed. The covering layers weresufficiently impermeable to prevent germination in both varietieswhen the external oxygen concentration was very low; when theconcentration was increased from 5 to 60 per cent., however,the inhibiting effect of the covering layers was reduced inthe white variety but not in the red. The delayed germinationof the red grains was therefore attributed to some factorotherthan the impermeability of the covering layers to oxygen.     

Studies on the Germination of Cereals: 3. The Effect of the Covering Layers on the Uptake of Water by the Embryo of the Wheat Grain

The uptake of water by imbibition, vacuolation, and growth ofthe embryo, has been determined when wheat grains were placedunder germination conditions before maturation was completed;and the effect of the covering layers has been investigatedin a red and a white variety at three stages during ripening. The water lost during ripening was replace by imbibition withoutcausing the embryo to expand sufficiently to rupture the coveringlayers. The cells of the coleorhiza and epiblast absorbed waterby vacuolation as soon as they were imbibed; but afurther periodelapsed before the scutellum became imbibed and water uptakewas associated with an increase in embryo dry weight. In both varieties, uptake opf water by the imbibed embryo wasprevented by the inner layer of the pericarp and the tesa inunripe grains, and by the epidermal layer of the pericarp duringthe early staes of ripening. But after the final stage of rapiddesiccation the covering layers of the white grains were rupturedwhen the embryo absorbed water by vacuolation; whereas the coveringlayers of the red grains remained intact and the uptake of waterwas delayed until a sufficient period had elapsed for nutrientsfrom the endosperm to be available for growth ofr the embryo. The varietal difference in germinationj is therefore attributedto the greater strength of the covering layers of the red grains,which are not disrupted during ripening, and prevent expansionof the embryo until the water absorbing capacity has been increasedby the transfer of reserves from the endosperm.     

Epidendrum caparaoense (Orchidaceae), a new species from Minas Gerais, Brazil

A new species of Orchidaceae, Epidendrum caparaoense W.Forst. & V.C.Souza, is described and illustrated. This species is known only from the type locality, Caparaó National Park, in Minas Gerais State, where it grows on low tree trunks in gallery forests, at approximately 1300 m. The taxon is distinct from the other species of the genus by its laterally compressed stems, a long tubular spathaceous bract at the base of the inflorescence, a labellum with the free portion three-lobed and the clinandrium with an entire margin. It is considered similar to E. geniculatum and E. hololeucum .  © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society, 2007, 155 , 157–159.     

Evidence for transfer of antibiotic-resistance genes in soil populations of streptomycetes

Phylogenetic analysis was used to evaluate the hypothesis of gene transfer in streptomycetes, many of which are antibiotic producers. The diversity and possible origins of streptomycin-resistance genes was investigated for a population of Streptomyces strains isolated from a site in Brazil where antibiotic production had previously been implicated. The analysis provides compelling evidence for the transfer of these genes. Examination of other Streptomyces -type strains also reveals a scattered distribution of streptomycin producers with respect to the overall phylogeny. These results suggest that horizontal gene transfer may be an important factor in the evolution of antibiotic genes in streptomycetes.     

Studies on the Germination of Cereals: I. The Germination of Wheat Grains in the Ear during Development, Ripening, and After-ripening

The ability of individual grains to germinate in the ears ofa red and a white wheat variety has been determined at differentperiods after anthesis, and at different moisture contents,before the stage of full maturity. No grains germinated while active growth was taking place, butafter desiccation during ripening, 88·5 per cent. ofthe white grains and 7 per cent. of the red grains were ableto germinate in the ear; the percentage germination of the redgrains increased to 83 per cent., when further desiccation occurredduring the first 5 weeks of after-ripening, but some grainsin the basal spikelets of the ears of both varieties failedto germinate until they had been subjected to the same desiccationfrom 13 to 23 weeks after anthesis. The ability of the grains to germinate has been correlated withtheir desiccation at different stages during maturation, andthe effect of certain factors, which inhibit the germinationof immature grains, are discussed in relation to varietal differencesin the colour of the grains and their position in the ear.