bluuebunny/crossref_metadata_2025_split huggingface dataset:
Genetic diversity and differentiation at MHC genes in island populations of tuatara (Sphenodon spp.)
Authors: MILLER HILARY C. , ALLENDORF FRED , DAUGHERTY CHARLES H. 
Published: August 2010

AbstractNeutral genetic markers are commonly used to understand the effects of fragmentation and population bottlenecks on genetic variation in threatened species. Although neutral markers are useful for inferring population history, the analysis of functional genes is required to determine the significance of any observed geographical differences in variation. The genes of the major histocompatibility complex (MHC) are well‐known examples of genes of adaptive significance and are particularly relevant to conservation because of their role in pathogen resistance. In this study, we survey diversity at MHC class I loci across a range of tuatara populations. We compare the levels of MHC variation with that observed at neutral microsatellite markers to determine the relative roles of balancing selection, diversifying selection and genetic drift in shaping patterns of MHC variation in isolated populations. In general, levels of MHC variation within tuatara populations are concordant with microsatellite variation. Tuatara populations are highly differentiated at MHC genes, particularly between the northern and Cook Strait regions, and a trend towards diversifying selection across populations was observed. However, overall our results indicate that population bottlenecks and isolation have a larger influence on patterns of MHC variation in tuatara populations than selection.
Genes essential for morphological development and antibiotic production in Streptomyces coelicolor are targets of BldD during vegetative growth
Authors: Den Hengst Chris D. , Tran Ngat T. , Bibb Maureen J. , Chandra Govind , Leskiw Brenda K. , Buttner Mark J. 
Published: August 2010

SummaryBldD is a transcriptional regulator essential for morphological development and antibiotic production in Streptomyces coelicolor. Here we identify the BldD regulon by means of chromatin immunoprecipitation‐microarray analysis (ChIP‐chip). The BldD regulon encompasses ∼167 transcriptional units, of which more than 20 are known to play important roles in development (e.g. bldA, bldC, bldH/adpA, bldM, bldN, ssgA, ssgB, ftsZ, whiB, whiG, smeA‐ssfA) and/or secondary metabolism (e.g. nsdA, cvn9, bldA, bldC, leuA). Strikingly, 42 BldD target genes (∼25% of the regulon) encode regulatory proteins, stressing the central, pleiotropic role of BldD. Almost all BldD binding sites identified by ChIP‐chip are present in the promoters of the target genes. An exception is the tRNA gene bldA, where BldD binds within the region encoding the primary transcript, immediately downstream of the position corresponding to the processed, mature 3′ end of the tRNA. Through gene overexpression, we identified a novel BldD target gene (cdgA) that influences differentiation and antibiotic production. cdgA encodes a GGDEF domain protein, implicating c‐di‐GMP in the regulation of Streptomyces development. Sequence analysis of the upstream regions of the complete regulon identified a 15 bp inverted repeat that functions as a high‐affinity binding site for BldD, as was shown by electrophoretic mobility shift assays and DNase I footprinting analysis. High‐scoring copies of the BldD binding site were found at relevant positions in the genomes of other bacteria containing a BldD homologue, suggesting the role of BldD is conserved in sporulating actinomycetes.
A path from predation to mutualism
Authors: Danchin Antoine 
Published: August 2010

SummaryLuminescent bacteria and nematodes associate in a strategy where the bacteria act as virulent pathogens of insects, used as their food supply, while the nematodes graze on them. Upon reaching high density, the bacteria produce light and metabolites that turn the nematodes into hosts permitting them to be carried over to further nematode preys. In this issue of Molecular Microbiology, Lango and Clarke show that the corresponding shift in lifestyle is triggered by a metabolic switch closely linked to the tricarboxylic acid cycle, but apparently not by the well‐known acetate switch that monitors entry of bacteria into the stationary phase of growth.
A backtrack‐inducing sequence is an essential component of Escherichia coli	σ70‐dependent promoter‐proximal pausing
Authors: Perdue Sarah A. , Roberts Jeffrey W. 
Published: August 2010

SummaryRNA polymerase of both bacteria and eukaryotes can stall or pause within tens of base pairs of its initiation site at the promoter, a state that may reflect important regulatory events in early transcription. In the bacterial model system, the σ70 initiation factor stabilizes such pauses by binding a downstream repeat of a promoter segment, especially the ‘−10’ promoter element. We first show here that the ‘−35’ promoter element also can stabilize promoter‐proximal pausing, through interaction with σ70 region 4. We further show that an essential element of either type of pause is a sequence just upstream of the site of pausing that stabilizes RNA polymerase backtracking. Although the pause is not intrinsically backtracked, we suggest that the same sequence element is required both to stabilize the paused state and to potentiate backtracking.
A rainbow coalition of lipid transcriptional regulators
Authors: Zhang Yong‐Mei , Rock Charles O. 
Published: August 2010

SummaryLipids are essential structural constituents of bacterial cell membranes and walls, and their biosynthetic pathways are stringently regulated at both biochemical and genetic levels. The recent surge of new information about transcriptional regulation of bacterial lipid metabolism is highlighted by two studies in this issue of Molecular Microbiology by Hugo Gramajo's research group, who add two transcription factors to the diverse repertoire of lipid biosynthesis regulators. FasR is a Streptomyces coelicolor transcriptional activator of genes in fatty acid synthesis, which supplies substrates for membrane phospholipid and triglyceride storage droplets. MabR is a regulator in Mycobacterium tuberculosis that functions as a repressor of essential genes in the cell wall mycolic acid biosynthetic pathway. MabR also affects the expression of fas, which encodes the multifunctional fatty acid synthase that supports phospholipid and triglyceride synthesis. Despite belonging to the same protein family, the distinct ligand binding domains of FasR and MabR suggest different ligands may regulate their DNA binding. The characterization of FasR/MabR exemplifies the structural and functional diversity of the rainbow coalition of lipid transcriptional regulators that reflects the diverse life styles of bacteria.
The FACT subunit TbSpt16 is involved in cell cycle specific control of VSG expression sites in Trypanosoma brucei
Authors: Denninger Viola , Fullbrook Alexander , Bessat Mohamed , Ersfeld Klaus , Rudenko Gloria 
Published: August 2010

SummaryThe African trypanosome Trypanosoma brucei monoallelically expresses one of more than 1000 Variant Surface Glycoprotein (VSG) genes. The active VSG is transcribed from one of about 15 telomeric VSG expression sites (ESs). It is unclear how monoallelic expression of VSG is controlled, and how inactive VSG ESs are silenced. Here, we show that blocking synthesis of the T. brucei FACT subunit TbSpt16 triggers a G2/early M phase cell cycle arrest in both bloodstream and insect form T. brucei. Segregation of T. brucei minichromosomes in these stalled cells is impaired, implicating FACT in maintenance of centromeres. Strikingly, knock‐down of TbSpt16 results in 20‐ to 23‐fold derepression of silent VSG ES promoters in bloodstream form T. brucei, with derepression specific to the G2/M cell cycle stage. In insect form T. brucei TbSpt16 knock‐down results in 16‐ to 25‐fold VSG ES derepression. Using chromatin immunoprecipitation (ChIP), TbSpt16 was found to be particularly enriched at the promoter region of silent but not active VSG ESs in bloodstream form T. brucei. The chromatin remodeler FACT is therefore implicated in maintenance of repressed chromatin present at silent VSG ES promoters, but is also essential for chromosome segregation presumably through maintenance of functional centromeres.
Male territoriality and ‘sex confusion’ in recently adapted lizards at White Sands
Authors: ROBERTSON J. M. , ROSENBLUM E. B. 
Published: August 2010

AbstractThe evolution of intersexual interactions, like mate choice, during ecological speciation has received widespread attention. However, changes in intrasexual interactions, like male territoriality, during ecological divergence are largely unexamined. We conducted field experiments with adaptively diverged populations of the eastern fence lizard (Sceloporus undulatus) to determine whether territorial males behaved differently towards ecologically similar vs. dissimilar intruders. We performed trials with light‐coloured males from White Sands, New Mexico and dark‐coloured males from the surrounding desert. We found that intruders from White Sands elicited more aggression than intruders from dark‐soil habitat. We also documented a case of ‘sex confusion’ where white‐sand males courted dark‐soil intruders. We found population differences in signalling patch size that can explain both aggression bias and sex misidentification. We argue that direct selection (for population recognition or optimal signal transmission) and indirect selection (by‐products of ecological adaptation) should influence both intersexual and intrasexual interactions during ecological speciation.
Fire, storm, flood and drought: The vegetation ecology of Howards Peninsula, Northern Territory, Australia
Authors: WILSON B. A. , BOWMAN D. M. J. S. 
Published: August 2010

AbstractTwenty different communities, characteristic of the coastal vegetation of the northern portion of the Northern Territory, were recognized by photo‐interpretation and ground truthing a 20 × 20 km area near Darwin. Data collected from 161 quadrats placed throughout the study area showed a strong relationship between subjective and objective measures of vegetation structure. Photopattern is best explained by a combination of structural, lifeform and floristic data. The mangrove, grassland, forest and woodland communities form a complex spatial pattern. Variations in moisture regime, through the interaction of topography and soils with temporal fluctuations of salt and/or fresh water supply, appear to best explain vegetation distribution. Three anomalously open eucalypt communities are interpreted as being the consequence of a severe tropical cyclonic storm which destroyed much of Darwin in 1974. These communities are frequently burnt by the nearby urban population and possess layers of sapling size eucalypts, although the height and density of the regrowth appears to vary with site quality. It is argued that fire is a characteristic of the seasonal climate, and that the fire pattern largely reflects the vegetation pattern. Occasional severe tropical storms also affect vegetation types differently. The greatest amount of windthrow occurs in moist monsoon forests while the eucalypts on well drained soils are more windfirm, but remain obviously damaged for over 10 years.
Mulga bird communities. I. Species composition and predictability across Australia
Authors: CODY MARTIN L. 
Published: August 2010

Abstract
Data are presented from bird censuses at 20 mulga (Acacia aneura) sites across Australia. Null (binomial) models show that community composition is far more consistent among censuses than is expected by a random drawing from all candidate species. By denning and using the designations ‘core species’, ‘peripheral species’, and ‘casual species’, it was shown that 32% of the total 81 bird species censused constituted core species and core niches that account for nearly 75% of the bird density in mulga bird communities countrywide.A minor proportion of the variation in the mulga censuses was attributable to geographic variation in vegetation structure, related to the β‐component of diversity. Some mulga niches have regional replacements that contribute to a species turnover among sites and to the γ‐diversity of the species set; other species of sporadic occurrence are attributable to the geographic position of the mulga site in terms of adjacent habitats (mostly eucalypt woodland and mixed acacia scrub), a ‘spillover’ effect.Regional variations in the composition of some specific guilds, namely ‘crows’, ‘wrens’, ‘butcherbirds’, foliage insectivores, ground‐foraging insectivores, perch‐and‐pounce foragers and mid‐sized, ground‐foraging omnivores, are analysed in some detail to illustrate factors that contribute to a large species total in mulga, despite the predominance of core species.
Long‐term changes in the vegetation after the cessation of livestock grazing in Eucalyptus marginata (jarrah) woodland remnants
Authors: Pettit N. E. , Froend R. H. 
Published: August 2010

AbstractThis paper documents changes in the floristic composition of Eucalyptus marginata Donn (jarrah) woodlands over 7 years of recovery from continual, intensive livestock grazing. In remnants of native woodland left after agricultural clearing, which have been subjected to livestock grazing, comparisons were made between the floristics of fenced exclosure plots and open plots that continued to be grazed. The vegetation in nearby remnants, which had not been subjected to livestock grazing, was also surveyed. An initial increase in annual exotic pasture species after grazing relief was only temporary and highly influenced by fluctuations in annual climatic patterns, particularly rainfall distribution and abundance. Subsequent years saw a decrease in exotic annuals in exclosure plots and an increase in native perennials, in a trend towards becoming more floristically similar to the ungrazed sites. Germination of overstorey species was observed in the exclosure plots, however, development of seedlings and saplings was sparse. Results indicate that for jarrah woodland in southwestern Australia, natural regeneration is possible after the removal of livestock, with the return (within 6 years) of native species richness to levels similar to those found in ungrazed vegetation. Re‐establishment of cover, however, appears to take longer. The floristic dynamics are described in terms of a nonequilibrium model. Two vegetation states exist, degraded remnants with an understorey dominated by annual species, and ungrazed vegetation with an understorey dominated by perennial shrubs and herbs. The former state is maintained by continual heavy grazing by livestock. Upon relief from grazing, the vegetation undergoes a transition towards floristic similarity to ungrazed vegetation. After 6 years, vegetation change in the exclosure plots appears to be continuing and therefore it is still in transition.
Estimates of forest floor litter frog communities: A comparison of two methods
Authors: Rocha Carlos Frederico D. , Sluys Monique Van , Alves Maria Alice S. , Bergallo Helena G. , Vrcibradic Davor 
Published: August 2010

AbstractEstimates of forest leaf litter frog density, mass, richness and diversity given by the widely used 8 m × 8 m large plot method (LPM) were compared with estimates obtained by a newly proposed method (small 2 m × 1 m plots with leaf removal; SPLR). The study site was an undisturbed area of the Atlantic Rainforest of Ilha Grande, an island located in the south of Rio de Janeiro State, Brazil. Twenty‐four LPM (totalling 1536 m2 of forest floor) and 90 SPLR (totalling 180 m2 of forest floor) were performed. The estimates obtained by the two methods differed markedly, indicating that even using a much smaller sampling area (11.7% of that of LPM), SPLR gave frog density estimates six times higher, and frog mass estimates approximately 2.5 times higher than estimates provided by LPM. The species richness and diversity obtained by the two methods were similar, despite the fact that the total area sampled with SPLR was much smaller. These data suggest that LPM may underestimate the abundance and biomass of leaf litter frogs in a given area.
Interannual variability in fruit abundance and the reproductive seasonality in Sumatran Long‐tailed macaques (Macaca fascicularis)
Authors: Schaik Carel P. van , Noordwijk Maria A. van 
Published: August 2010

In an environment with a seasonal food supply, most primate species show birth peaks which precede the peak food period by some two to five months. Sumatran Long‐tailed macaques (Macaca fascicularis), however, showed birth peaks during or after the fruit peak. Years of high birth rates and early birth peaks alternated with years of low birth rates and late peaks. The timing of births was strongly influenced by a female's condition, which depends on food supply and her previous reproductive history. Pregnant females were more active than other females, whereas females with young infants were less active.The unusual timing of births is ascribed to the unpredictability of the height of the annual fruit peak. This hypothesis is supported by the reproductive patterns of other South‐east Asian primates and by a model comparing the two types of reproductive timing. Further differences between the two strategies of reproductive timing are predicted.
Condition and related mortality of nyala Tragelaphus angasi in Zululand, South Africa
Authors: Anderson J. L. 
Published: August 2010

The kidney fat index (KFI) was used to examine the condition of nyala over a 27‐m‐onth period. From a sample in which both marrow fat and KFI were examined, it was noted that, as has been found in other bovid, kidney fat was mobilized before marrow fat. Seasonal changes in condition were observed and correlated with the rainfall in the previous month. Following periods of less than 50 mm of rain, the larger adult males were in significantly poorer condition than other animals.The sexual difference in condition is attributed to the differences in body size, where males of asymptotic body mass required 62% more kcal/day than asymptotic mass females. When die‐offs occurred during periods of nutritional stress, significantly more old adults died than would be expected. Further, significantly more males died than females.
Horizontal variations in associations of zooplankton in Lake Kariba
Authors: GREEN J. 
Published: August 2010

The horizontal distribution of the zooplankton in Lake Kariba was sampled by means of vertical hauls using 55 and 250 μm meshed nets. Crustacea were sparse in the main lake, but increased dramatically in the very shallow water at the end of Crocodile Creek. The composition of the zooplankton is influenced by the presence in the main lake of the Tanganyika sardine, Limnothrissa miodon, and by the large size of the dominant diatom in the phytoplankton. In the creeks the distribution can be explained by the zooplankton occurring in open spaces into which planktivorous fish do not enter because of the possibility of predation by Tiger fish (Hydrucyori) and birds.The systematic composition of the zooplankton in L. Kariba is reviewed and compared with two natural lakes and another man‐made lake. It is concluded that the zooplankton and the fishes in L. Kariba have reached approximately the specific diversity that one would expect from a similar sized natural lake in the same geographical area.
Temporal patterns of circulating LH and steroid hormones in a brood parasite, the Brown‐headed cowbird, Molothrus afer.
Authors: Dufty A. M. , Wingfield J. C. 
Published: August 2010

The breeding behaviour of female Brown‐headed cowbirds, Molothrus ater, is remarkably distinct from that of females of most other passerine species. Cowbirds are brood parasites that do not build nests, incubate eggs or feed young. Instead, they have an extended egg‐laying stage, and deposit eggs in the nests of hosts within large breeding territories that are defended from other female cowbirds. In this communication, we report the changes in plasma levels of circulating hormones and in morphological characteristics that occur in free‐living female Brown‐headed cowbirds over a breeding season.Plasma LH in female cowbirds increases at the onset of breeding and remains elevated for approximately eight weeks, at which time levels decline to basal values. This pattern is similar to that of follicle development, and is consistent with the prolific reproductive output by individuals of this species. Circulating E, levels are quite variable and do not demonstrate any discernible pattern, while plasma B is elevated during the egg‐laying period and declines subsequently.Testosterone titre (T) is highest early in the breeding season, when territorial interactions are generally most frequent. T levels decline slowly thereafter, reaching their lowest values at the season's end. Plasma DHT levels are slightly higher than those for T; DHT exhibits little change until late in the breeding season, when it declines. Fat scores are highest prior to egg laying, and fat reserves diminish as the breeding season progresses. In contrast, body weight increases during the reproductive season, probably as a result of developing eggs in the ovary. These results are consistent with the hypothesis that temporal patterns of hormone secretion are correlated with the expression of social systems.
Socio‐ecology of Bat‐eared foxes (Otocyon megalotis)
Authors: Malcom J. R. 
Published: August 2010

Bat‐eared foxes were studied for eight months at four sites in Kenya and Tanzania with the main study in the Masai Mara Game Reserve. Eleven foxes were caught and four fitted with radio‐collars. Foxes in Masai Mara feed mainly on ants and termites. They showed a marked preference for short grass habitat, and their range expanded when wildebeest lowered grass height by grazing and trampling. Foxes lived in groups (x̄= 2.8) with overlapping home ranges, and relations between groups were usually amicable. Foxes gave birth from September‐December and all members of the group provided some care to the cubs.A review of Bat‐eared fox ecology from other studies reveals a consistent picture of this aberrant insectivorous canid. The species foraging strategy involves locating social insects by sound in short grass areas. The species is able to find suitable habitat and multiply rapidly. Although usually living in monogamous pairs, reports of polygyny, and non‐reproductive males in groups also exist. Living in groups may increase each fox's chance of feeding on insect swarms, and also provides protection from predators.
Main arteries to the female reproductive organs in the helmeted guineafowl (Numida meleagris)
Authors: Onyeanusi B. I. , Ema A. N. , Ojo S. A. 
Published: August 2010

The helmeted guineafowl, Numida meleagris, is a member of the Galliformes (King & McLelland, 1975). This order includes the domestic fowl, Callus domeslicus, which has undoubtedly dominated research studies in poultry production generally. Many of the anatomical studies in birds have been carried out using the domestic fowl, with comparatively little mention of other genera. Although the genera in the Galliformes have very many similarities, few anatomical differences have been shown to exist. For example, Crowe & Crowe (1979) have found some striking differences between the blood supply to the head and neck of the guineafowl and the domestic fowl.The guineafowl has become a popular poultry bird in Nigeria, and has been said to rank second to the domestic fowl, despite its seasonal breeding pattern. The further improvement of this genus in our poultry production has necessitated increased studies into its nutritional requirements, management procedures and disease prevalence. In line with this improvement is the need for anatomical data on the female reproductive organs as a basis for the breeding and selection programme. The aim of this study is to describe the macroscopic arterial blood supply to the reproductive organs of the guineafowl.