Systematics within Gyps vultures: a clade at risk

Background  

Populations of the Oriental White-backed Vulture (Gyps bengalensis) have declined by over 95% within the past decade. This decline is largely due to incidental consumption of the non-steroidal anti-inflammatory veterinary pharmaceutical diclofenac, commonly used to treat domestic livestock. The conservation status of other Gyps vultures in southern Asia is also of immediate concern, given the lack of knowledge regarding status of their populations and the continuing existence of taxonomic uncertainties. In this study, we assess phylogenetic relationships for all recognized species and the majority of subspecies within the genus Gyps. The continuing veterinary use of diclofenac is an unknown but potential risk to related species with similar feeding habits to Gyps bengalensis. Therefore, an accurate assessment of the phylogenetic relationships among Gyps vultures should aid in their conservation by clarifying taxonomic uncertainties, and enabling inference of their respective relatedness to susceptible G. bengalensis.     

Territory defense by the ant Azteca trigona: maintenance of an arboreal ant mosaic

Mosaics of exclusive foraging territories, produced by intra-and interspecific competition, are commonly reported from arboreal ant communities throughout the tropics and appear to represent a recurring feature of community organization. This paper documents an ant mosaic within mangrove forests of Panama and examines the behavioral mechanisms by which one of the common species, Azteca trigona, maintains its territories. Most of the mangrove canopy is occupied by mutually exclusive territories of the ants A. trigona, A. velox, A. instabilis, and Crematogaster brevispinosa. When foraging workers of A. trigona detect workers of these territorial species, they organize an alarm recruitment response using pheromonal and tactile displays. Nestmates are attracted over short distances by an alarm pheromone originating in the pygidial gland and over longer distances by a trail pheromone produced by the Pavan's gland. Recruits are simultaneously alerted by a tactile display. No evidence was found for chemical marking of the territory. Major workers are proportionally more abundant at territory borders than on foraging trails in the interior of the colony. The mechanisms of territory defense in A. trigona are remarkably similar to those of ecologically analogous ants in the Old World tropics.     

The fertile island effect varies with aridity and plant patch type across an extensive continental gradient

Plant and Soil - Perennial plants play important roles in maintaining ecosystem functions by forming fertile islands beneath their canopies. Little is known about how the fertile island effect...     

Antagonism by theophylline of respiratory inhibition induced by adenosine

The effects on respiration of an analogue of adenosine, L-2-N6-(phenylisopropyl)adenosine (PIA), and of the methylxanthine, theophylline, were determined in 19 vagotomized glomectomized cats whose end-tidal PCO2 was kept constant by means of a servo-controlled ventilator. Integrated phrenic nerve activity was used to represent respiratory output. Our results show that PIA, whether given systemically or into the third cerebral ventricle, depressed respiration. Systemically administered theophylline stimulated respiration. Theophylline given intravenously, or into the third ventricle not only reversed the depressive effects of previously administered PIA but caused further increases of respiration above the control level. Prior systemic administration of theophylline blocked both respiratory and hypotensive effects of subsequently administered PIA. Effects of either agent on medullary extracellular fluid pH did not explain the results. We conclude that the adenosine analogue PIA, acts to inhibit neurons in the brain that are involved in the control of respiration and that its effects are blocked by theophylline. We suggest that adenosine acts as a tonic modulator of respiration and that theophylline stimulates breathing by competitive antagonism of adenosine at neuronal receptor sites.     

Synergism of interleukin 7 with the thymocyte growth factors interleukin 2, interleukin 6, and tumor necrosis factor alpha in the induction of thymocyte proliferation

The role of previously defined thymocyte (Thm) growth factors in interleukin (IL)-7-induced Thm growth has not been fully elucidated. Therefore, experiments were designed to examine the capacity of IL-7 to: (i) directly induce Thm proliferation in the absence of experimental and known physiologic costimulators of Thm mitogenesis, and (ii) synergize with other Thm growth factors in supporting Thm proliferation. The data indicate that IL-7 is directly mitogenic for Thm; that is, IL-7 induces Thm proliferation in the absence of experimental comitogens such as concanavalin A, phytohemagglutinin, and phorbol myristate acetate and in the presence of neutralizing antibodies to murine IL-1 alpha, IL-1 beta, IL-2, IL-2 receptor (IL-2R)(p55), IL-2R(p70), IL-4, IL-6, and tumor necrosis factor (TNF). We also tested previously described Thm growth factors, i.e., IL-2, IL-4, IL-6, and TNF-alpha, for the capacity to synergize with IL-7 in Thm growth. Our results indicate that IL-2, IL-6, and TNF-alpha, but not IL-4, synergize with IL-7 in supporting Thm proliferation. These data suggest that IL-7 functions alone and in a synergistic fashion with other cytokines to regulate Thm growth.     

Characterization of the antigens involved in serotyping strains ofCampylobacter jejuni by passive hemagglutination

Components of outer membrane preparations, heated saline extracts, and phenolwater lipopolysaccharide extracts obtained from strains ofCampylobacter jejuni representing seven passive hemagglutination serotypes (Penner serotypes 1–4, 13, 16, and 50) were electrophoresed in sodium dodecyl sulfate-polyacrylamide gels. Tests of gel eluates demonstrated that lipopolysaccharide antigens are involved in serotypingC. jejuni by passive hemagglutination and that other cell surface components have no activity. This finding was confirmed by hemagglutination inhibition. In the typing ofC. jejuni by passive hemagglutination, each serotype is probably defined by the presence of one or more specific lipopolysaccharides. These findings may lead to a clarification of the serotyping nomenclature for those systems that depend on passive hemagglutination. It is recommended that a single internationally agreed numbering system be adopted for lipopolysaccharides derived fromC. jejuni.     

Is the removal of aboveground shrub biomass an effective technique to restore a shrub‐encroached grassland?

Encroachment of woody plants into grasslands is a global phenomenon that has substantial impacts on pastoral productivity and ecosystem services. Over the past half century, pastoralists and land management agencies have explored various options to control woody plants in order to improve ecosystem services in shrub‐encroached grasslands. We examined the effectiveness of controlling the encroachment of the shrub Caragana microphylla into grassland in Inner Mongolia, China. We cut and removed all of the aboveground biomass from 450 shrubs, predicting that the effectiveness of this technique to control shrubs would depend on shrub morphology. Specifically, we expected that larger shrubs with more biomass would be more difficult to kill by cutting than smaller shrubs. A year after treatment, we found that cutting killed only 11% of the 450 treated shrubs, and of these, three‐quarters of the locations that they occupied reverted to grasses and one‐quarter to bare soil. Shrubs that survived the cutting treatment produced more stems and leaf biomass, and therefore had a greater leaf to stem ratio. Shrubs that died after cutting had a lower crown area and basal area, and less stem biomass than shrubs that resprouted within 12 months of cutting. There were no effects of shrub height on the fate of treated shrubs. Cutting had no effect on understory plant cover or richness, but reproductive plants were taller under shrubs that were not cut. Overall, our study showed that removing aboveground shrub biomass by cutting is an ineffective technique for “restoring” the original grassland community unless shrubs are very small. Strategic targeting of small shrubs would be a more effective technique for controlling the spread of C. microphylla in the long term.     

Soil-foraging animals alter the composition and co-occurrence of microbial communities in a desert shrubland

Animals that modify their physical environment by foraging in the soil can have dramatic effects on ecosystem functions and processes. We compared bacterial and fungal communities in the foraging pits created by bilbies and burrowing bettongs with undisturbed surface soils dominated by biocrusts. Bacterial communities were characterized by Actinobacteria and Alphaproteobacteria, and fungal communities by Lecanoromycetes and Archaeosporomycetes. The composition of bacterial or fungal communities was not observed to vary between loamy or sandy soils. There were no differences in richness of either bacterial or fungal operational taxonomic units (OTUs) in the soil of young or old foraging pits, or undisturbed soils. Although the bacterial assemblage did not vary among the three microsites, the composition of fungi in undisturbed soils was significantly different from that in old or young foraging pits. Network analysis indicated that a greater number of correlations between bacterial OTUs occurred in undisturbed soils and old pits, whereas a greater number of correlations between fungal OTUs occurred in undisturbed soils. Our study suggests that digging by soil-disturbing animals is likely to create successional shifts in soil microbial and fungal communities, leading to functional shifts associated with the decomposition of organic matter and the fixation of nitrogen. Given the primacy of organic matter decomposition in arid and semi-arid environments, the loss of native soil-foraging animals is likely to impair the ability of these systems to maintain key ecosystem processes such as the mineralization of nitrogen and the breakdown of organic matter, and to recover from disturbance.