Collembolan associations in natural versus improved pastures of the New England Tableland,NSW: Distribution of native and introduced species

Native Australian species of Collembola dominated natural pasture in numbers of species present and in abundance, while introduced Collembola dominated fertilized pasture sown to exotic species. Those collembolan species which were restricted to one pasture type only were mainly epigeal and hemiedaphic species of the herbage and litter. Increased grazing by sheep decreased species richness and increased uniformity of Collembola in both pasture types. The abundance of introduced Collembola was positively associated with phosphorus content of litter.     

Carbohydrate-Free Media for Crithidia

SYNOPSIS. The insect trypanosomatid Crithidia fasciculata grew well at pH 3.8–6.3 in defined carbohydrate-free media containing arginine (an essential amino acid) + proline + glutamic acid as substrates; glycerol was effective by itself. Precipitation of hemin in the acid media did not hinder growth. Further addition of succinic acid permitted growth matching that with carbohydrate. At pH 6.9–7.5 growth in this medium without carbohydrate with the aforementioned non-fermentable substrates was slight; added carbohydrate (as sucrose or sorbitol) permitted good growth. Utilization of non-carbohydrate substrates may contribute to Crithidia 's ability (and presumably to that of pathogenic trypanosomatids as well) to multiply in the insect gut and to the ability of some Trypanosoma species to multiply in the insect hemocoel and salivary gland.     

A POLARLY FLAGELLATED MEMBER OF THE ENTEROBACTERIACEAE

SUMMARY: An organism which has been frequently isolated from the rhizosphere of plants of Lolium perenne (Perennial Rye-grass) is described; it has the typical morphology and flagellation of Pseudomonas but the biochemical reactions of Klebsiella.     

Genetic relatedness and disrupted social structure in a poached population of African elephants

We use genetic measures of relatedness and observations of female bonding to examine the demographic signature of historically heavy poaching of a population of free-ranging African elephants. We collected dung samples to obtain DNA and observed behaviour from 102 elephant families over a 25-month period in 2003–2005 in Mikumi National Park, Tanzania. Poaching reduced the population by 75% in the decade prior to the 1989 ivory trade ban; park records indicate that poaching dropped significantly in Mikumi following the ban. Using 10 microsatellite loci, DNA was genotyped in 203 elephants and pair-wise relatedness was calculated among adult females within and between groups. The Mikumi population is characterized by small group size, considerable variation in group relatedness, females with no first-order adult relatives and females that form only weak social bonds. We used gene-drop analysis and a model of a genetically intact pedigree to compare our observed Mikumi group relatedness to a simulated genetically intact unpoached expectation. The majority of groups in Mikumi contain 2 to 3 adults; of these, 45% were classified as genetically disrupted. Bonding, quantified with a pair-wise association index, was significantly correlated with relatedness; however only half of the females formed strong bonds with other females, and relatedness was substantially lower for a given bond strength as compared to an unpoached population. Female African elephants without kin demonstrated considerable behavioural plasticity in this disturbed environment, grouping with other females lacking kin, with established groups, or remaining alone, unable to form any stable adult female-bonds. We interpret these findings as the remaining effect of poaching disturbance in Mikumi, despite a drop in the level of poaching since the commercial trade in ivory was banned 15 years ago.     

Selection for individual recognition and the evolution of polymorphic identity signals in Polistes paper wasps

Individual recognition (IR) requires individuals to uniquely identify their social partners based on phenotypic variation. Because IR is so specific, distinctive phenotypes that stand out from the crowd facilitate efficient recognition. Over time, the benefits of unique appearances are predicted to produce a correlation between IR and phenotypic variation. Here, we test whether there is an association between elevated phenotypic polymorphism and IR in paper wasps. Previous work has shown that Polistes fuscatus use variable colour patterns for IR. We test whether two less variable wasp species, Polistes dominulus and Polistes metricus, are capable of IR. As predicted, neither species is capable of IR, suggesting that highly variable colour patterns are confined to Polistes species with IR. This association suggests that elevated phenotypic variation in taxa with IR may be the result of selection for identity signals rather than neutral processes. Given that IR is widespread among social taxa, selection for identity signalling may be an underappreciated mechanism for the origin and maintenance of polymorphism.     

Effects of experimental drought on soil respiration and radiocarbon efflux from a temperate forest soil

Soil moisture affects microbial decay of SOM and rhizosphere respiration (RR) in temperate forest soils, but isolating the response of soil respiration (SR) to summer drought and subsequent wetting is difficult because moisture changes are often confounded with temperature variation. We distinguished between temperature and moisture effects by simulation of prolonged soil droughts in a mixed deciduous forest at the Harvard Forest, Massachusetts. Roofs constructed over triplicate 5 × 5 m² plots excluded throughfall water during the summers of 2001 (168 mm) and 2002 (344 mm), while adjacent control plots received ambient throughfall and the same natural temperature regime. In 2003, throughfall was not excluded to assess the response of SR under natural weather conditions after two prolonged summer droughts. Throughfall exclusion significantly decreased mean SR rate by 53 mg C m^?2 h^?1 over 84 days in 2001, and by 68 mg C m^?2 h^?1 over 126 days in 2002, representing 10–30% of annual SR in this forest and 35–75% of annual net ecosystem exchange (NEE) of C. The differences in SR were best explained by differences in gravimetric water content in the Oi horizon (r²=0.69) and the Oe/Oa horizon (r²=0.60). Volumetric water content of the A horizon was not significantly affected by throughfall exclusion. The radiocarbon signature of soil CO₂ efflux and of CO₂ respired during incubations of O horizon, A horizon and living roots allowed partitioning of SR into contributions from young C substrate (including RR) and from decomposition of older SOM. RR (root respiration and microbial respiration of young substrates in the rhizosphere) made up 43–71% of the total C respired in the control plots and 41–80% in the exclusion plots, and tended to increase with drought. An exception to this trend was an interesting increase in CO₂ efflux of radiocarbon‐rich substrates during a period of abundant growth of mushrooms. Our results suggest that prolonged summer droughts decrease primarily heterotrophic respiration in the O horizon, which could cause increases in the storage of soil organic carbon in this forest. However, the C stored during two summers of simulated drought was only partly released as increased respiration during the following summer of natural throughfall. We do not know if this soil C sink during drought is transient or long lasting. In any case, differential decomposition of the O horizon caused by interannual variation of precipitation probably contributes significantly to observed interannual variation of NEE in temperate forests.     

Flow cytometric analysis for ploidy level differentiation of 45 hairy vetch accessions

Determining the ploidy of plant germplasm is a necessary step in breeding or genetic studies in species. The purpose of this research was to determine the presence of ploidy level differentiation of hairy vetch (Vicia villosd) germplasm. Flow cytometry and root tip chromosome squashing methods were employed to assess 45 accessions labeled V. villosa available through the USDA germplasm collection. Flow cytometry determined that 43 of the accessions were 2C, one accession was 4C, and one accession was 6C. Analysis of accessions by root tip chromosome counts indicated that all accessions were diploid. The 2C accession contains 14 chromosomes and their chromosomes were approximately one-half and one-third in size as compared to the chromosomes of the 4C and 6C accessions, respectively. The 4C accession was observed to have 16 chromosomes and the 6C accession was observed to have 14 chromosomes. The large-scale differences in DNA amounts were due to chromosomal size variability as opposed to ploidy differences. This revealed the incidence of species misidentification of these two V. villosa accessions to be Vicia pannonica. All the V. villosa accessions were observed to be diploid and have similar DNA amounts. Flow cytometry proved to be useful in the efficient assessment of these accessions.     

COMPARISONS OF VOLATILE COMPOUNDS RELEASED DURING CONSUMPTION OF A COMPLEX FOOD BY DIFFERENT ASSESSORS WITH EXPRESSIONS OF PERCEIVED FLAVOR DETERMINED BY FREE CHOICE PROFILING

Comparisons of volatile compounds released during consumption by different assessors with individual differences in the assessors'chewing patterns, saliva production rates and ultimately their expressions of perceived flavor have received little research attention to date, although such comparisons are fundamental to the understanding of flavor. To address this, eight untrained assessors were chosen and each consumed six Cheddar cheeses during Buccal Headspace Analysis of the volatile compounds released, while in parallel measures of each assessor's mastication behavior using Electromyography, their stimulated saliva production during consumption and their sensory perceptions of the cheeses flavor during Free Choice Profiling were determined. Relationships between the volatile compounds released and the sensory and physiological measures were investigated using Principal Components Analysis, Generalised Procrustes Analysis and Partial Least Squares regression. It was found that although there were differences between assessors'mastication behavior and saliva production rates, the assessors'individual volatile profiles obtained by Buccal Headspace Analysis were similar for each cheese examined. Also, Partial Least Squares was successful in predicting the most important flavor differences between cheeses from the volatile compounds released during their consumption by different assessors.