scholarly journals An experimental test of the area–heterogeneity tradeoff

2020 ◽  
Vol 117 (9) ◽  
pp. 4815-4822 ◽  
Author(s):  
Eyal Ben-Hur ◽  
Ronen Kadmon
Keyword(s):  
Habitat Heterogeneity ◽  
Competitive Exclusion ◽  
Fundamental Property ◽  
Theoretical Models ◽  
Effective Area ◽  
Individual Species ◽  
Relative Importance ◽  
Average Area ◽  
Fixed Area ◽  
Positive Effect

A fundamental property of ecosystems is a tradeoff between the number and size of habitats: as the number of habitats within a fixed area increases, the average area per habitat must decrease. This tradeoff is termed the “area–heterogeneity tradeoff.” Theoretical models suggest that the reduction in habitat sizes under high levels of heterogeneity may cause a decline in species richness because it reduces the amount of effective area available for individual species under high levels of heterogeneity, thereby increasing the likelihood of stochastic extinctions. Here, we test this prediction using an experiment that allows us to separate the effect of the area–heterogeneity tradeoff from the total effect of habitat heterogeneity. Surprisingly, despite considerable extinctions, reduction in the amount of effective area available per species facilitated rather than reduced richness in the study communities. Our data suggest that the mechanism behind this positive effect was a decrease in the probability of deterministic competitive exclusion. We conclude that the area–heterogeneity tradeoff may have both negative and positive implications for biodiversity and that its net effect depends on the relative importance of stochastic vs. deterministic drivers of extinction in the relevant system. Our finding that the area–heterogeneity tradeoff may contribute to biodiversity adds a dimension to existing ecological theory and is highly relevant for understanding and predicting biodiversity responses to natural and anthropogenic variations in the environment.

scholarly journals The relative importance of wetland area versus habitat heterogeneity for promoting species richness and abundance of wetland birds in the Prairie Pothole Region, USA

The Condor ◽  
2019 ◽  
Vol 122 (1) ◽  
Author(s):  
Lisa H Elliott ◽  
Lawrence D Igl ◽  
Douglas H Johnson
Keyword(s):  
Species Richness ◽  
Habitat Heterogeneity ◽  
Prairie Pothole Region ◽  
Individual Species ◽  
Relative Importance ◽  
Prairie Pothole ◽  
Wetland Area ◽  
Habitat Area ◽  
Landscape Scales ◽  
Species Richness And Abundance

Abstract Recent work has suggested that a tradeoff exists between habitat area and habitat heterogeneity, with a moderate amount of heterogeneity supporting greatest species richness. Support for this unimodal relationship has been mixed and has differed among habitats and taxa. We examined the relationship between habitat heterogeneity and species richness after accounting for habitat area in glacially formed wetlands in the Prairie Pothole Region in the United States at both local and landscape scales. We tested for area–habitat heterogeneity tradeoffs in wetland bird species richness, the richness of groups of similar species, and in species’ abundances. We then identified the habitat relationships for individual species and the relative importance of wetland area vs. habitat heterogeneity and other wetland characteristics. We found that habitat area was the primary driver of species richness and abundance. Additional variation in richness and abundance could be explained by habitat heterogeneity or other wetland and landscape characteristics. Overall avian species richness responded unimodally to habitat heterogeneity, suggesting an area–heterogeneity tradeoff. Group richness and abundance metrics showed either unimodal or linear relationships with habitat heterogeneity. Habitat heterogeneity indices at local and landscape scales were important for some, but not all, species and avian groups. Both abundance of individual species and species richness of most avian groups were higher on publicly owned wetlands than on privately owned wetlands, on restored wetlands than natural wetlands, and on permanent wetlands than on wetlands of other classes. However, we found that all wetlands examined, regardless of ownership, restoration status, and wetland class, supported wetland-obligate birds. Thus, protection of all wetland types contributes to species conservation. Our results support conventional wisdom that protection of large wetlands is a priority but also indicate that maintaining habitat heterogeneity will enhance biodiversity and support higher populations of individual species.

scholarly journals You are what you eat: relative importance of diet, gut microbiota and nestmates for honey bee, Apis mellifera, worker health

Apidologie ◽  
2021 ◽  
Author(s):  
Gina Retschnig ◽  
Johannes Rich ◽  
Karl Crailsheim ◽  
Judith Pfister ◽  
Vincent Perreten ◽  
...  
Keyword(s):  
Body Weight ◽  
Apis Mellifera ◽  
Gut Microbiota ◽  
Honey Bee ◽  
Exposure Period ◽  
Short Exposure ◽  
Relative Importance ◽  
Worker Health ◽  
Negative Effect ◽  
Positive Effect

AbstractIn eusocial honey bees, Apis mellifera, diet, gut microbiota and nestmates can all contribute to the health of freshly emerged individual workers, but their relative importance for longevity and body weight is currently unknown. Here, we show that diet is most relevant, followed by gut microbiota and the presence of nestmates. Freshly emerged workers were randomly assigned to eight treatments (with or without honey/pollen, protein-substitute lactalbumin, antibiotic tetracycline and nestmates for 24 h) and maintained under standardised laboratory conditions. Longevity and food consumption were measured daily and fresh body weight was assessed at day 7. The data show a significantly better survival and a higher body weight in workers supplied with honey/pollen. Survival was higher in the lactalbumin treatments compared to the ones restricted to sucrose only, but lower compared to those with honey/pollen, highlighting the importance of micronutrients. In contrast, antibiotic treatment had a significant negative effect on longevity and body weight, which may be explained by inactivated gut microbiota and/or toxicity of the antibiotics. There was no positive effect of nestmates, probably due to the short exposure period. In contrast, nestmates showed a negative effect on survival in antibiotic-treated workers, possibly by transmitting pathogens and antibiotic-induced gut dysbiosis. In conclusion, a macro- and micronutrient-rich diet appears to be the key to individual honey bee worker health. Providing an optimal diet and possibly gut microbiota appears to be a promising way to promote managed A. mellifera health.

The Effect of Effort on Sales Performance and Job Satisfaction

1994 ◽  
Vol 58 (2) ◽  
pp. 70-80 ◽  
Author(s):  
Steven P. Brown ◽  
Robert A. Peterson
Keyword(s):  
Job Satisfaction ◽  
Conceptual Models ◽  
Theoretical Models ◽  
Sales Performance ◽  
Sales Force ◽  
Work Behavior ◽  
Direct Selling ◽  
Work Related ◽  
Managerial Implications ◽  
Positive Effect

The authors address a fundamental gap in understanding how sales performance and job satisfaction are determined in an investigation of the sales force of a direct-selling organization. Results indicate a direct positive effect of work-related effort on job satisfaction that is not mediated by sales performance. This is inconsistent with commonly accepted theoretical models and suggests that the perspective of work as a “terminal value” (i.e., an end in itself, rather than strictly a means to an end) has been underemphasized in models of work behavior. As such, either (1) measures of sales performance should be broadened to encompass the terminal value perspective on the psychological value of work or (2) conceptual models should be revised to reflect that narrowly defined measures of sales performance do not completely mediate the effect of effort on job satisfaction. The authors conclude with a discussion of managerial implications of these findings.

Disturbance impacts on large rain-forest vertebrates differ with edge type and regional context in Sulawesi, Indonesia

2015 ◽  
Vol 31 (6) ◽  
pp. 509-517 ◽  
Author(s):  
Graden Z.L. Froese ◽  
Adrienne L. Contasti ◽  
Abdul Haris Mustari ◽  
Jedediah F. Brodie
Keyword(s):  
Camera Trap ◽  
Individual Species ◽  
Relative Importance ◽  
Vertebrate Species ◽  
Edge Type ◽  
Regional Context ◽  
Red Jungle Fowl ◽  
Local Abundance ◽  
Viverra Tangalunga ◽  
Landscape Level

Abstract:Anthropogenic edge effects, whereby disturbance strength increases in proximity to ecotone boundaries, are known to strongly affect individual species but we lack a general understanding of how they vary by species, disturbance type and regional context. We deployed 46 camera-trap stations for a total of 3545 trap-days at two sites in Sulawesi, Indonesia, obtaining 937 detections of five vertebrate species. Anoa (Bubalus spp.) were more abundant near edges, booted macaque (Macaca ochreata) and red jungle fowl (Gallus gallus) were less abundant near edges, and edges did not impact Sulawesi warty pig (Sus celebensis) or Malay civet (Viverra tangalunga). But the relative importance of habitat disturbance from agriculture, roads and villages differed for each species, and edge-induced disturbances varied not only in magnitude but also in direction between the study areas. In the strongest instance, macaque local abundance was 3.5 times higher near villages than it was 3 km into the forest in one reserve, but 2.8 times higher 3 km into the forest than near villages in the other reserve. Our results suggest that responses to habitat edges among species and edge types are idiosyncratic, and that landscape-level context can strongly alter the influence of local disturbance on biodiversity.

scholarly journals Pleiotropic effects of sex-determining genes in the evolution of dioecy in two plant species

2019 ◽  
Vol 286 (1913) ◽  
pp. 20191805 ◽  
Author(s):  
Takashi Akagi ◽  
Deborah Charlesworth
Keyword(s):  
Theoretical Models ◽  
Ancestral State ◽  
Relative Importance ◽  
Sexual Antagonism ◽  
Dioecious Plant ◽  
Dioecious Species ◽  
Dioecious Plants ◽  
Sexual Dimorphisms ◽  
Evolution Of Dioecy ◽  
Plant Sex

One reason for studying sex chromosomes of flowering plants is that they have often evolved separate sexes recently, and the genomes of dioecious species may not yet have evolved adaptations to their changes from the ancestral state. An unstudied question concerns the relative importance of such adaptation, versus the effects of the mutations that led to separate sexes in the first place. Theoretical models for such an evolutionary change make the prediction that the mutations that created males must have sexually antagonistic effects, not only abolishing female functions, but also increasing male functions relative to the ancestral functional hermaphrodites. It is important to test this critical assumption. Moreover, the involvement of sexual antagonism also implies that plant sex-determining genes may directly cause some of the sexual dimorphisms observed in dioecious plants. Sex-determining genes are starting to be uncovered in plants, including species in the genera Diospyros and Actinidia (families Ebenaceae and Actinidiaceae, respectively). Here, we describe transgenic experiments in which the effects of the very different male-determining genes of these two dioecious species were studied in a non-dioecious plant, Nicotiana tabacum . The results indeed support the critical assumption outlined above.

Modeling and Simulation of Implant-Supported Fixed Partial Dentures Prosthodontic

2009 ◽  
Vol 16-19 ◽  
pp. 1112-1116
Author(s):  
Dong Lei Liu ◽  
Hua Yan ◽  
Zong Bao Shen ◽  
Xin Hua Song ◽  
Xiao Wang
Keyword(s):  
Finite Element ◽  
Modeling And Simulation ◽  
Optimum Design ◽  
Theoretical Models ◽  
Finite Element Models ◽  
Sectional Area ◽  
Positive Effect ◽  
Maximum Stresses

The theoretical models and finite element models of implant-supported fixed partial dentures and surrounding osseous tissues were founded. It was studied of the influence of connector sectional area on implant-supported fixed partial dentures and surrounding osseous tissues. The results indicate that increasing the connector sectional areas to some extent has positive effect on fixed bridge itself. But the maximum stresses in some regions of surrounding osseous tissues increase as the connector sectional areas increase, the change extent is smaller comparatively. The study provides biomechanics evidence for the optimum design of implant-supported fixed partial dentures.

The Role of External Interaction for Innovation in Irish High-Technology Businesses

2011 ◽  
Vol 12 (4) ◽  
pp. 248-256 ◽  
Author(s):  
Declan Jordan ◽  
Eoin O'Leary
Keyword(s):  
High Technology ◽  
Process Innovation ◽  
Relative Importance ◽  
Business Innovation ◽  
Negative Effect ◽  
Product And Process Innovation ◽  
Innovation Output ◽  
Product And Process ◽  
Positive Effect

There is growing empirical evidence that external interaction is an important source of knowledge for business innovation. This paper contributes to the innovation literature by using new measures of interaction to explore the relative importance of external interaction for innovation in Irish high-technology businesses. Based on survey data, the paper finds that external interaction increases the probability of product and process innovation, but the effect is inconsistent across all external interaction agents. Interaction along the supply chain has a positive effect on innovation, and interaction with competitors has an insignificant effect on innovation output. Notably, the paper finds that interaction with higher education institutions has a negative effect on the probability of product and process innovation.

Intensity Profile of Electron Beam

1970 ◽  
Vol 28 ◽  
pp. 52-53
Author(s):  
S. M. Ohr ◽  
T. S. Noggle
Keyword(s):  
Electron Beam ◽  
Theoretical Models ◽  
Effective Area ◽  
Oak Ridge ◽  
Black And White ◽  
Viewing Screen ◽  
Shadow It ◽  
Electron Dosimetry ◽  
Made In

In situ studies of electron displacement damage in graphite are being made in Oak Ridge using a 200 kV Hitachi HU 200-E electron microscope. Examples of the damage structure that develops in the area upon which the illuminating beam is incident are shown in Fig. 1. The spot structures (both black and white) are identified as clusters of interstitial atoms. It is of particular interest in this study to have accurate electron dosimetry in order to relate the damage structures to theoretical models. In this paper we wish to report on the technique and some preliminary results obtained in measuring the intensity profiles of the electron beam.Measurements of the beam profiles have been made by replacing one of the side windows of the viewing chamber with a 1” brass plate in which is mounted a retractable arm which can insert a Faraday cup into a position on the axis and at a level approximately one-third the distance from the projector lens to the viewing screen. This arrangement allows one to take pictures with the cup in position, and from the shadow it casts determine its effective area in the magnified image of the beam.

STUDY OF THE RADAR CROSS SECTION OF SIMPLE BODIES

2020 ◽  
pp. 81-85
Author(s):  
С.А. Антипов ◽  
А.В. Володько ◽  
Е.А. Ищенко ◽  
В.Н. Кострова ◽  
К.А. Разинкин ◽  
...  
Keyword(s):  
Side Surface ◽  
Dielectric Materials ◽  
Effective Area ◽  
Metal Plate ◽  
The Body ◽  
Simple Metal ◽  
Cylindrical Object ◽  
Effective Scattering Area ◽  
Upper Face ◽  
Positive Effect

Рассмотрены картины моностатической эффективной площади рассеяния для простых геометрических тел. Для простой металлической пластины был произведен теоретический расчет значения эффективной площади рассеяния (ЭПР), а также произведено моделирование с использованием метода Вейланда, по результатам которого были доказаны точность и эффективность моделирования в специализированном программном обеспечении (ПО). Для определения эффективной площади рассеяния шара рассматривались три случая: когда размеры шара превосходят длину волны; размеры малы, а в качестве материала изготовления выбран проводник; при сохранении размеров материал изготовления заменяется на диэлектрик - стекло. По полученным результатам сделаны выводы о важности сопоставления длины волны с геометрическими размерами тела, а также о положительном влиянии диэлектрических материалов на значение ЭПР. При исследовании цилиндра рассматривались два случая, которые могут возникнуть при исследовании ЭПР цилиндрического объекта, а именно, когда волна падает на боковую поверхность тела и на верхнюю грань. Было показано, что наихудшие значения эффективной площади рассеяния наблюдаются при падении плоской волны на верхние - идеально плоские грани цилиндра. Приведены результаты в виде картин моностатической ЭПР, максимальных значений эффективной площади рассеяния The article considers the figures of the monostatic effective scattering area for simple geometric bodies. For a simple metal plate, a theoretical calculation of the RCS value was carried out, as well as modeling using the Vayland method, the results of which proved the accuracy and efficiency of modeling in specialized software. To determine the effective area of dispersion of the ball, three cases were considered when the dimensions of the ball exceed the wavelength; the dimensions are small, and a conductor is selected as the material of manufacture; while maintaining the dimensions, the material of manufacture is replaced by glass. Based on the results obtained, conclusions are drawn about the importance of comparing the wavelength with the geometric dimensions of the body, as well as the positive effect of dielectric materials on the value of the RCS. In the study of the cylinder, two cases were considered that can arise when studying the RCS of a cylindrical object, namely, when the wave falls on the side surface of the body and on the upper face. It was shown that the worst values of the effective scattering area are observed when a plane wave is incident on the upper, ideally flat, faces of the cylinder. The results are presented in the form of monostatic RCS patterns, maximum values of the effective scattering area

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