Vigilance and grouping in the southern African ground squirrel (Xerus inauris)

Animals may form groups in response to the foraging–vigilance trade‐off, through enhanced predator detection (collective detection hypothesis) or reduced predation risk to the individual (dilution hypothesis), allowing individuals to decrease vigilance levels. Both hypotheses predict decreasing individual vigilance levels with increasing group size; however, the collective detection hypothesis also predicts increasing overall group vigilance with increasing group size. However, in species in which vigilance and foraging are not mutually exclusive, where vigilance may not be as costly, neither of these hypotheses may apply. Here, we examine the relationship between group size and vigilance in the social Cape ground squirrel (Xerus inauris), a species that can combine foraging and vigilance behaviours. Ten groups were observed using scan sampling, measuring both group and individual vigilance and group size. A negative relationship existed between individual vigilance and group size and a positive relationship between group vigilance and group size. Therefore, in Cape ground squirrels, vigilance seems to be costly even though it can be combined with foraging behaviours. Furthermore, group vigilance behaviour gives support to the collective detection hypothesis, whilst individual vigilance gives support to both hypotheses.     

罗霄山脉东坡—江西省种子植物新记录

报道江西省种子植物1个新记录属萼脊兰属Sedirea Garay et Sweet,及4个新记录种短茎萼脊兰Sedirea subparishii (Z. H. Tsi) Christenson、白花过路黄Lysimachia huitsunae Chien、黄脉莓Rubus xanthoneurus Focke ex Diels、桂东锦香草Phyllagathis guidongensis K. M. Liu & J. Tian,均发现于罗霄山脉东坡。文中简述各新记录种区系地理学意义。     

Calculation of impingement-free combined cup and stem alignments based on the patient-specific pelvic tilt

Proper cup alignment is crucial in total hip arthroplasty for reducing impingement risks, dislocations and wear. The Lewinnek “safe zone” is often used in clinical routine. This safe zone does not consider functional aspects and dislocation can occur even when the cup is oriented within the safe zone. Functional safe zones based on the hip range of motion (ROM) were introduced but are not commonly used in clinical routine. The reason might be that these methods are time-consuming due to complex simulations. A relatively fast method based on analytical mathematical formulas was proposed, but it is difficult to consider arbitrary motion. This work introduces an efficient algorithm for calculating a patient-specific target zone based on the target ROM which can consider any set of motions. The method is based on matrix transformations and trigonometric formulas. The resulting target zone which contains all impingement-free cup orientations is dependent on the patient-specific pelvic tilt, the 3D angular neck and stem orientation within the femur, and the technical prosthesis ROM. This method could be integrated into computer-assisted preoperative planning and intra-operative navigation tools. As pelvic tilt and stem orientation influence the optimal cup orientation they need to be acquired from the patient to derive a patient-specific ROM-based target zone.     

The role of temperature in determining distributions and coexistence of three species of Plestiodon

The Common Five-Lined Skink (Plestiodon fasciatus), Southeastern Five-Lined Skink (P. inexpectatus), and Broadheaded Skink (P. laticeps) are all found in forested ecosystems of the southeastern United States and occur in apparent sympatry. No aspect of their ecology has been quantitatively shown to be different. Differences in their natural history, such as northern extent of geographic range, observations of differences in habitat preference, and differing physiological responses to temperature, implicate the thermal environment as a potential niche dimension by which these organisms partition resources. Here we show that the northernmost extent of each species' range can be adequately discriminated by temperature extremes and that their preferred habitats differ in canopy cover, mean temperature, and daily maximum temperatures. These differences are supported by observations in the field. Based upon these findings and observations, we conclude that these species may be able to exist in such close proximity due to differences in their thermal niche, particularly the two like-sized species, P. fasciatus and P. inexpectatus. P. laticeps is a much larger lizard as an adult and functionally coexists with its congeners, potentially by partitioning resources along a different axis.     

Isolation, Pathogenicity and Safety of Curvularia eragrostidis Isolate QZ-2000 as a Bioherbicide Agent for Large Crabgrass (Digitaria sanguinalis)

A pathogen isolated from lesions on blighted leaves of crabgrass in three different locations of China was identified as Curvularia eragrostidis. Isolate QZ-2000 was the most virulent of six isolates tested. Experiments on morphology, pathogenicity, effect of environmental factors, and host-range of isolate QZ-2000 were conducted in the laboratory, greenhouse and field to assess the potential of this isolate as a biocontrol agent for grassy weeds. Pathogenicity was quantitatively determined based on mortality and dry-weight reduction of infected large crabgrass. Inoculum concentration, rapeseed oil concentration in formulaton, post-inoculation dew temperature and duration, and plant growth age all significantly influenced the efficacy of the isolate. A total of 85-100% control of large crabgrass was obtained when inoculum concentrations were ≥1×10⁶ conidia mL^-1, oil concentrations ≥0.9% (v/v), dew period ≥24 h and air temperatures 20-30°C in the greenhouse. A total of 51 plant species in 20 families were screened against isolate QZ-2000 in host-range studies. Six other species of grassy weeds were susceptible to isolate QZ-2000, but no mortality or significant dry-weight reduction was observed for maize (Zea mays), rice (Oryza sativa), soya bean (Glycine max), cotton (Gossypium hirsutum), or any other economically important crops and plants. In field trials, with 5×10⁶ conidia mL^-1 inoculum density, 60-7% reduction in dry weight was achieved for large crabgrass seedlings under natural dew-free conditions. These results indicate that isolate QZ-2000 is a potential microbial bioherbicide for control of large crabgrass in crops such as corn, soybean, cotton, water-melon, and peanut.     

Bioenergy harvest,climate change,and forest carbon in the Oregon Coast Range

Forests provide important ecological, economic, and social services, and recent interest has emerged in the potential for using residue from timber harvest as a source of renewable woody bioenergy. The long‐term consequences of such intensive harvest are unclear, particularly as forests face novel climatic conditions over the next century. We used a simulation model to project the long‐term effects of management and climate change on above‐ and belowground forest carbon storage in a watershed in northwestern Oregon. The multi‐ownership watershed has a diverse range of current management practices, including little‐to‐no harvesting on federal lands, short‐rotation clear‐cutting on industrial land, and a mix of practices on private nonindustrial land. We simulated multiple management scenarios, varying the rate and intensity of harvest, combined with projections of climate change. Our simulations project a wide range of total ecosystem carbon storage with varying harvest rate, ranging from a 45% increase to a 16% decrease in carbon compared to current levels. Increasing the intensity of harvest for bioenergy caused a 2–3% decrease in ecosystem carbon relative to conventional harvest practices. Soil carbon was relatively insensitive to harvest rotation and intensity, and accumulated slowly regardless of harvest regime. Climate change reduced carbon accumulation in soil and detrital pools due to increasing heterotrophic respiration, and had small but variable effects on aboveground live carbon and total ecosystem carbon. Overall, we conclude that current levels of ecosystem carbon storage are maintained in part due to substantial portions of the landscape (federal and some private lands) remaining unharvested or lightly managed. Increasing the intensity of harvest for bioenergy on currently harvested land, however, led to a relatively small reduction in the ability of forests to store carbon. Climate change is unlikely to substantially alter carbon storage in these forests, absent shifts in disturbance regimes.     

Natural disturbance and treefalls in a pine-oak forest on the Peninsula of Baja California,Mexico

The magnitude of natural disturbances by treefalls and their spatial occurrence were studied in a pine-oak forest of Sierra de La Laguna, located at the southern part of the Peninsula of Baja California in Mexico.Twenty transects covering 4 ha, perpendicular to north- and south-facing slopes were sampled. The percentages of rocky outcrops, slope, orientation, and gap size created by treefalls were recorded. The mode of tree death, treefall direction, trunk length, and basal diameter were also measured. Data were analyzed using principal component analysis, one-way ANOVA, multiple comparison tests by contrasts, and chi-square independence tests.Results suggest that exogenous disturbances have an important effect in this community. A mean number of 80 gaps per ha was recorded comprising 18.1% of the observed area. Gap sizes were fitted to a lognormal distribution as 2.3±1.4 and patches were found to be created by single treefalls. Analysis of dead material shows that there are significant differences between numbers of fallen trees on N vs S facing slopes, and that forms of dead trees are significantly associated with species. Snapped trees represent 39.5% of treefalls, dead standing trees 26.4%, uprooted trees 20.5% and cut-down trees 0.9%. The frequency of occurrence of various forms of the dead trees suggests that the cause of mortality is primarily due to the high incidence of tropical hurricanes, and secondly to the combined effect of wind and natural fire which occurs during the rainy summer season.     

Lower lethal temperatures for fourteen non-native fishes in Florida

Synopsis The most important factor affecting the potential range of 14 non-native fishes in Florida appears to be their lack of tolerance to low temperatures. In this study, temperatures associated with reduction in feeding, cessation of feeding, loss of equilibrium and death were identified by decreasing water temperature 1°C day^–1. Fishes tested and their mean lower lethal temperatures were: Astronotus ocellatus (12.9°C), Belonesox belizanus (9.7°C), Cichlasoma bimaculatum (8.9°C), C. cyanoguttatum (5.0°C), C. meeki (10.3°C), C. octofasciatum (8.0°C), C. trimaculatum (10.9°C), Clarias batrachus (9.8°C), Hemichromis bimaculatus (9.5°C), Hypostomus sp. (11.2°C), Tilapia aurea (6.2°C), T. mariae (11.2°C), T. melanotheron (10.3°C) and T. mossambica (9.5°C). These data indicate that temperature is less limiting for these fishes in Florida than was previously recognized.Contribution Number 18, Non-Native Fish Research Laboratory, Florida Game and Fresh Water Fish Commmission, 801 N. W. 40th Street, Boca Raton, FL 33431, U.S.A.     

Impacts of dust on plant health,survivorship and plant communities in semi‐arid environments

There is a general perception that dust accumulation on plant surfaces causes negative impacts to plants. Consequently, it is common for environmental regulatory agencies to apply vegetation monitoring requirements to oil, gas and mining developments. We use two independent, medium‐term monitoring studies in semi‐arid Australia to examine this relationship at two scales: plant health and survivorship of a threatened subspecies (Tetratheca paynterae paynterae: Elaeocarpaceae) at Windarling Range between 2003 and 2014; and changes in plant health and floristic composition on Barrow Island between 2009 and 2014. Accumulation of dust decreased rapidly with distance from source. At Windarling Range, even at the site with the highest dust load, there was no significant impact on Tetratheca paynterae paynterae compared with the less dusty sites for 10 years. Similarly, there was no significant effect between distance from the source of dust and floristic composition on Barrow Island for 5 years. The probability of plants transitioning to a lower health condition between one year and the next did not appear to be related to dust load. This is further supported by comparing the same site before and after paving the road (removal of dust source), which showed no clear trends. Trends in plant health are likely to be driven more by the variability of cumulative rainfall in the preceding 5 months than dust load. The observed temporal variation in the mean dust load may also be related to variation in rainfall. In conclusion, in these case studies from semi‐arid Australia, we find no evidence to support the perception that, under the observed climatic condition and dust deposition rates up to 20 or 77 g m^?2 per month at Windarling Range and Barrow Island, respectively, dust accumulation on plants causes negative impacts.     

Intraspecific trait variation influences physiological performance and fitness in the South Africa shrub genus Protea (Proteaceae)

Background and AimsGlobal plant trait datasets commonly identify trait relationships that are interpreted to reflect fundamental trade-offs associated with plant strategies, but often these trait relationships are not identified when evaluating them at smaller taxonomic and spatial scales. In this study we evaluate trait relationships measured on individual plants for five widespread Protea species in South Africa to determine whether broad-scale patterns of structural trait (e.g. leaf area) and physiological trait (e.g. photosynthetic rates) relationships can be detected within natural populations, and if these traits are themselves related to plant fitness.MethodsWe evaluated the variance structure (i.e. the proportional intraspecific trait variation relative to among-species variation) for nine structural traits and six physiological traits measured in wild populations. We used a multivariate path model to evaluate the relationships between structural traits and physiological traits, and the relationship between these traits and plant size and reproductive effort.Key ResultsWhile intraspecific trait variation is relatively low for structural traits, it accounts for between 50 and 100 % of the variation in physiological traits. Furthermore, we identified few trait associations between any one structural trait and physiological trait, but multivariate regressions revealed clear associations between combinations of structural traits and physiological performance (R² = 0.37–0.64), and almost all traits had detectable associations with plant fitness.ConclusionsIntraspecific variation in structural traits leads to predictable differences in individual-level physiological performance in a multivariate framework, even though the relationship of any particular structural trait to physiological performance may be weak or undetectable. Furthermore, intraspecific variation in both structural and physiological traits leads to differences in plant size and fitness. These results demonstrate the importance of considering measurements of multivariate phenotypes on individual plants when evaluating trait relationships and how trait variation influences predictions of ecological and evolutionary outcomes.