Seasonal habitat selection and space use by a semi‐free range herbivore in a heterogeneous savanna landscape

Understanding factors that influence habitat selection in heterogeneous landscapes is fundamental for establishing realistic models on animal distribution to inform rangeland management. In this study, we tested whether seasonal variation in habitat selection within the home range of a large herbivore was influenced by constraints such as, distances from water and central place using semi‐free range cattle (Bos taurus) as a case study. We also tested whether shifts in space use over time were dependent on spatial scale and on the overall abundance of resources. We predicted that distance from water significantly influenced dry season habitat selection while the influence of the central place on habitat selection was season‐independent. We also predicted that shifts in space use over time were spatial scale‐dependent, and that large herbivores would include more diverse habitats in their home ranges during the dry season, when water and food resources are less abundant. Multinomial logit models were used to construct habitat selection models with distances from water and central place as habitat‐specific constraints. Results showed significant variations in habitat selection between the dry and wet season. As predicted, the effect of distance from central place was season‐independent, while the effect of water was not included in the top dry season models contrary to expectation. A diverse range of habitats were also selected during the dry season including agricultural fields. Results also indicated that shifts in space use were spatial scale dependent, with core areas being more sensitive to changes than the home range. In addition, shifts in space use responded to temporal changes in habitat composition. Overall, our results suggest that semi‐free range herbivores adopt different foraging strategies in response to spatial‐temporal changes in habitat availability.     

Adaptability of the semi‐invariant natural killer T‐cell receptor towards structurally diverse CD1d‐restricted ligands

The semi‐invariant natural killer (NK) T‐cell receptor (NKTcr) recognises structurally diverse glycolipid antigens presented by the monomorphic CD1d molecule. While the α‐chain of the NKTcr is invariant, the β‐chain is more diverse, but how this diversity enables the NKTcr to recognise diverse antigens, such as an α‐linked monosaccharide (α‐galactosylceramide and α‐galactosyldiacylglycerol) and the β‐linked trisaccharide (isoglobotriaosylceramide), is unclear. We demonstrate here that NKTcrs, which varied in their β‐chain usage, recognised diverse glycolipid antigens with a similar binding mode on CD1d. Nevertheless, the NKTcrs recognised distinct epitopic sites within these antigens, including α‐galactosylceramide, the structurally similar α‐galactosyldiacylglycerol and the very distinct isoglobotriaosylceramide. We also show that the relative roles of the CDR loops within the NKTcr β‐chain varied as a function of the antigen. Thus, while NKTcrs characteristically use a conserved docking mode, the NKTcr β‐chain allows these cells to recognise unique aspects of structurally diverse CD1d‐restricted ligands.     

Validation of communication between elderly denture wearers and dentists: a questionnaire on satisfaction with complete dentures using semi-structured interviews

Objectives: To validate a semi‐structured interview (SSI) for communication between complete denture wearers and dentists. Design: A SSI using a questionnaire with eight questions on satisfaction with complete dentures (CD): covering function, aesthetics and comfort. The first seven questions used a five‐point Likert scale and the last was dichotomous. Two dentists, carefully trained in the use of the structured questionnaire, administered the SSI. Setting: A Greek Department of Prosthetic Dentistry. Subjects: A consecutive sample of 78 CD wearers took part in the study. All subjects presented with complaints from their dentures. Intervention: All participants and their dentures underwent clinical examination. Results: The method showed good reliability, verified by the Cronbach alpha (0.86). Both dentists used the questionnaire produced very similar results. (Wilcoxon test 61–99%). Further, the association of the answers with respect to the five‐point Likert scale was very high; all gamma coefficients were statistically significant except for pain and discomfort from the upper CD (CDU). Conclusions: This method of communication between patients and dentists is reliable and can be used to give good repeatability for qualitatively assessing satisfaction with CD. It can be valuable for clinical use and for extending the study of denture quality to establish outcome measures based on the subjective criteria of satisfaction.     

Experimental changes in disturbance type do not induce short‐term shifts in plant community structure in three semi‐arid grasslands of the Victorian Riverine Plain managed for nature conservation

Summary Since the mid 1990s, there has been a significant increase in the area of semi‐arid grasslands included in the National Reserve Systems in the Victorian Riverine Plain. This expansion has not been matched by an improved understanding of the alternate disturbance regimes that might produce better outcomes for native ecosystem conservation. Over the past 150 years, stock grazing has completely replaced fire in these grasslands. As a result, the impact of fire on native (and exotic) plant biodiversity is little understood. This study compared the current grazing regime (i.e. ‘status quo’) with burning and the removal of grazing (‘deferred’ management) across three grasslands in the Victorian Riverine Plain to determine the effects of short‐term exposure to alternate disturbances on community structure. Our results showed little change in species density, composition or abundance under the three disturbance treatments. A long exposure to stock grazing may have reduced the abundance of species likely to respond positively to burning. The cover of the biological soil crust responded positively to fire; such changes are known to significantly influence establishment and the functional composition of communities. As such, further investigation of the functional attributes of these communities may broaden our understanding of short‐term responses to alternate disturbance events. To better understand the utility of fire as a management tool, a long‐term commitment to expanding the implementation of this regime from its current extent will greatly increase the understanding of alternate disturbances in this landscape.     

Discrimination between the endoplasmic reticulum and mitochondria by spontaneously inserting tail‐anchored proteins

Tail‐anchored (TA) proteins insert into their target organelles by incompletely elucidated posttranslational pathways. Some TA proteins spontaneously insert into protein‐free liposomes, yet target a specific organelle in vivo. Two spontaneously inserting cytochrome b5 forms, b5‐ER and b5‐RR, which differ only in the charge of the C‐terminal region, target the endoplasmic reticulum (ER) or the mitochondrial outer membrane (MOM), respectively. To bridge the gap between the cell‐free and in cellula results, we analyzed targeting in digitonin‐permeabilized adherent HeLa cells. In the absence of cytosol, the MOM was the destination of both b5 forms, whereas in cytosol the C‐terminal negative charge of b5‐ER determined targeting to the ER. Inhibition of the transmembrane recognition complex (TRC) pathway only partially reduced b5 targeting, while strongly affecting the classical TRC substrate synaptobrevin 2 (Syb2). To identify additional pathways, we tested a number of small inhibitors, and found that Eeyarestatin I (ES_I) reduced insertion of b5‐ER and of another spontaneously inserting TA protein, while not affecting Syb2. The effect was independent from the known targets of ES_I, Sec61 and p97/VCP. Our results demonstrate that the MOM is the preferred destination of spontaneously inserting TA proteins, regardless of their C‐terminal charge, and reveal a novel, substrate‐specific ER‐targeting pathway.      

Recent drought stress leads to growth reductions in Larix sibirica in the western Khentey,Mongolia

Trends in air temperature and precipitation in the forest‐steppe ecotone of the western Khentey, northern Mongolia were studied and related to stem increment and shoot water relations in Mongolia's most common tree species, Siberian larch (Larix sibirica). The area has been subject to a significant increase of summer temperature and a decrease of summer precipitation during the last 47 years. Tree‐ring width series from >400 larch trees show a strongly decreasing annual increment since the 1940s. The onset of this decrease is independent of the age of the trees and, therefore, can be attributed to the increasing aridity in the 20th century. Simultaneously to the declining annual increment, regeneration of Siberian larch decreased as well; today regeneration is virtually lacking in the larch forests on mountain slopes of the western Khentey. Measurements of shoot water potentials during the growing season exhibited daily minimum water potentials close to the point of zero turgor for extended periods. The drought stress indicated by these results is in line with the current low annual increment. Trees in the forest interior were more severely stressed and grow more slowly than trees at the forest line to steppe. This is attributable to the recent increase in aridity, as the stand density and probably also the trees themselves in the forest interior are adapted to moister conditions, whereas the trees at the forest edge have always been exposed to a more extreme microclimate. The progressing increase in aridity during the 21st century that is predicted for the western Khentey, suggests a future decline of larch forests. A widespread increase of aridity predicted for most parts of the Mongolian forest belt, suggests even a supra‐regional decline of larch.     

Species limits and phylogenetic relationships of red‐finned cryptic species of the seasonal killifish genus Hypsolebias from the Brazilian semi‐arid Caatinga (Teleostei: Cyprinodontiformes: Rivulidae)

Members of the Hypsolebias antenori species group comprise a diverse clade of morphologically similar seasonal killifishes occurring in a vast region of the semi‐arid savannah of northeastern Brazil. The present paper focuses on an assemblage of three allopatric cryptic species (H. antenori from isolated coastal river drainages, Hypsolebias igneus from the São Francisco River basin and Hypsolebias coamazonicus sp. nov. from the Parnaíba River basin) sharing almost identical colour patterns, including the presence of an orangish red anal fin in males, thus herein named as the red‐finned assemblage. A tree‐based approach using mt‐DNA (cytochrome b) supports delimitation of all three species, but indicates that the red‐finned assemblage is paraphyletic – H. igneus and H. coamazonicus are closely related to Hypsolebias nudiorbitatus, whereas H. antenori is the sister group to a clade comprising all 13 species of the H. antenori group included in the analysis. Morphological characters are useful to diagnose species, but are not informative for most clades highly supported by molecular data. H. coamazonicus is distinguished from all other congeners by the possession of a dark grey or black stripe on the dorsal fin in males. The basal position of H. antenori is related to uplift episodes involving the Araripe‐Borborema plateau during the Miocene, which isolated the coastal area inhabited by H. antenori from the remaining areas of the Caatinga. The sister group relationship between H. igneus and H. coamazonicus is attributed to a past connection between the São Francisco and Paranaíba River until the Tertiary.     

Strain stiffening in collagen I networks

Biopolymer gels exhibit strain stiffening that is generally not seen in synthetic gels. Here, we investigate the strain‐stiffening behavior in collagen I gels that demonstrate elasticity derived from a variety of sources including crosslinking through telopeptides, bundling through low‐temperature gelation, and exogenous crosslinking with genipin. In all cases, it is found that these gels exhibit strain stiffening; in general, onset of strain stiffening occurs earlier, yield strain is lower, and degree of strain stiffening is smaller in higher concentration gels and in those displaying thick fibril bundles. Recovery after exposure to high strains is substantial and similar in all gels, suggesting that much of the stiffening comes from reversible network deformations. A key finding of this study is that collagen I gels of identical storage and loss moduli may display different nonlinear responses and different capacities to recover from high strain. © 2012 Wiley Periodicals, Inc.     

半干旱黄土高原地区地膜覆盖和底墒对春小麦生长及产量的影响

在年均降水量为415mm的半干旱地区黄绵土旱地上,以春小麦为供试作物进行大田实验,研究不同底墒(包括低底墒、中底墒和高底墒)下．地膜覆盖(包括不覆膜、播种后覆膜30d、覆膜60d和覆膜120d即全程覆膜)进程对作物生产的影响。结果表明．增加底墒和合理的覆膜进程均会显著增加作物的生长和产量,但底墒不同,其最佳覆膜进程不同：在低底墒时,覆膜处理反而使产量低于不覆膜处理;在中底墒时．覆膜30d产量最高,随着覆膜时间延长．产量呈下降趋势,甚至全程覆膜产量低于不覆膜处理;高底墒以覆膜60d产量最高。综合作物生长和产量,全程覆膜并没有多少实际意义。在同种覆膜处理下,随着底墒的增加,根生物量、地上干物质、叶面积及产量也增加显著,高底墒覆膜60d处理的产量在所有处理中为最高。