scholarly journals Benefits and Costs of Mixed-Species Aggregations in Harvestmen (Arachnida: Opiliones)

2022 ◽  
Vol 9 ◽  
Author(s):  
Ignacio Escalante ◽  
Marisol Domínguez ◽  
Daisy A. Gómez-Ruiz ◽  
Glauco Machado

Many animals form aggregations with individuals of the same species (single-species aggregations, SSA). Less frequently, individuals may also aggregate with individuals of other species (mixed-species aggregations, MSA). Although the benefits and costs of SSA have been intensively studied, the same is not true for MSA. Here, we first review the cases of MSA in harvestmen, an arachnid order in which the records of MSA are more frequent than other arthropod orders. We then propose several benefits and costs of MSA in harvestmen, and contrast them with those of SSA. Second, using field-gathered data we describe gregariousness in seven species of Prionostemma harvestmen from Costa Rica. These species form MSA, but individuals are also found solitarily or in SSA. We tested one possible benefit and one possible cost of gregariousness in Prionostemma harvestmen. Regarding the benefit, we hypothesized that individuals missing legs would be more exposed to predation than eight-legged individuals and thus they should be found preferentially in aggregations, where they would be more protected from predators. Our data, however, do not support this hypothesis. Regarding the cost, we hypothesized that gregariousness increases the chances of parasitism. We found no support for this hypothesis either because both mite prevalence and infestation intensity did not differ between solitary or aggregated individuals. Additionally, the type of aggregation (SSA or MSA) was not associated with the benefit or the cost we explored. This lack of effect may be explained by the fluid membership of the aggregations, as we found high turnover over time in the number of individuals and species composition of the aggregations. In conclusion, we hope our review and empirical data stimulate further studies on MSA, which remains one of the most elusive forms of group living in animals.

2003 ◽  
Author(s):  
M. Spano ◽  
P. Toro ◽  
M. Goldstein
Keyword(s):  
The Cost ◽  

Author(s):  
Matthew Hindman

The Internet was supposed to fragment audiences and make media monopolies impossible. Instead, behemoths like Google and Facebook now dominate the time we spend online—and grab all the profits from the attention economy. This book explains how this happened. It sheds light on the stunning rise of the digital giants and the online struggles of nearly everyone else—and reveals what small players can do to survive in a game that is rigged against them. The book shows how seemingly tiny advantages in attracting users can snowball over time. The Internet has not reduced the cost of reaching audiences—it has merely shifted who pays and how. Challenging some of the most enduring myths of digital life, the book explains why the Internet is not the postindustrial technology that has been sold to the public, how it has become mathematically impossible for grad students in a garage to beat Google, and why net neutrality alone is no guarantee of an open Internet. It also explains why the challenges for local digital news outlets and other small players are worse than they appear and demonstrates what it really takes to grow a digital audience and stay alive in today's online economy. The book shows why, even on the Internet, there is still no such thing as a free audience.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Leanne Proops ◽  
Camille A. Troisi ◽  
Tanja K. Kleinhappel ◽  
Teresa Romero

AbstractEcological factors, such as predation, have traditionally been used to explain sociability. However, it is increasingly recognised that individuals within a group do not associate randomly, and that these non-random associations can generate fitness advantages. The majority of the empirical evidence on differentiated associations in group-living mammals, however, comes from a limited number of taxa and we still know very little about their occurrence and characteristics in some highly social species, such as rats (Rattus spp.). Here, using network analysis, we quantified association patterns in four groups of male fancy rats. We found that the associations between rats were not randomly distributed and that most individuals had significantly more preferred/avoided associates than expected by random. We also found that these preferences can be stable over time, and that they were not influenced by individuals’ rank position in the dominance hierarchy. Our findings are consistent with work in other mammals, but contrast with the limited evidence available for other rat strains. While further studies in groups with different demographic composition are warranted to confirm our findings, the occurrence of differentiated associations in all male groups of rats have important implications for the management and welfare of captive rat populations.


2016 ◽  
Vol 7 (3) ◽  
pp. 126-129 ◽  
Author(s):  
Sreenivas Koka ◽  
Galya Raz

What does ‘value’ mean? In the context of dental care, it can be defined as the quality of care received by a patient divided by the cost to the patient of receiving that care. In other words: V =Q/C, where Q equals the quality improvement over time, which most patients view in the context of the outcome, the service provided and safety/risk management, and C equals the financial, biological and time cost to the patient. Here, the need for, and implications of, value-based density for clinicians and patients alike are explored.


2000 ◽  
Vol 12 (S1) ◽  
pp. 67-72 ◽  
Author(s):  
William H. Coleman

There is a direct relationship between years lived beyond age 65 and the number of individuals diagnosed with dementia, primarily Alzheimer's disease (AD). The occurrence of AD has no socioeconomic, geographical, or ethnic limitations. The problem is worldwide. Its magnitude is demonstrated by the following facts: (a) approximately 6% to 8% of persons 65 years or older have AD, and the prevalence of the disease doubles each 5 years after 60 years of age; (b) 30% of 85-year-old individuals can be expected to have the disease; (c) AD affects an estimated 4 million people in the United States, and is expected to affect approximately 14 million Americans within the next few decades; (d) AD patients average 6 to 10 years of comprehensive treatment from symptom onset to death; (e) AD is the fourth leading cause of mortality among elderly Americans, more than 100,000 each year; (f) caregiver attempts at management of the behavioral and psychological symptoms of AD result in up to 50% developing significant psychological distress themselves; and (g) the cost for the management of AD patients is estimated to be between US $80 billion and US $120 billion annually. Primary care is essential for the appropriate diagnosis and treatment of the complex set of behavioral and psychological symptoms of dementia (BPSD) associated with AD.


Author(s):  
Peter Chinloy ◽  
Matthew Imes

A procedure confirms whether a return-factor correlation is anomalous or results from endogenous simultaneous-equations bias. The identification strategy sorts the cost of capital components for instruments. In the first stage, the initially found factors are regressed on cost instruments. In the second stage, a confirmed anomaly has predicted value significant in returns and exogenous. Taxes, depreciation and capital structure are strong instruments, affecting 1980–2017 quarterly U.S. stock returns. Size, value and profitability decisions are significant in instruments. Returns increase in fitted profits, but not small size. Actual and predicted values have weaker correlation with returns over time.


2021 ◽  
pp. 1-45
Author(s):  
Ray Miller ◽  
Neha Bairoliya

Abstract We estimate the distribution of well-being among the older U.S. population using an expected utility framework that incorporates differences in consumption, leisure, health, and mortality. We find large disparities in welfare that have increased over time. Incorporating the cost of living with poor health into elderly welfare substantially increases the overall inequality. Disparity measures based on cross-sectional income or consumption underestimate the growth in aggregate welfare inequality. Moreover, health is a better indicator of an individual's relative welfare position than income or consumption.


1987 ◽  
Vol 38 (5) ◽  
pp. 607
Author(s):  
AR Jones

Temporal patterns in number of species, number of individual animals and community composition of the soft-sediment zoobenthos of the Hawkesbury estuary are described and related to physicochemical factors. Replicate grabs were taken at 3-month intervals over 3 years (1977-1979) from sites located in three zones: the lower, middle and upper reaches. The number of species and number of individuals showed significant seasonal and annual differences in all zones. However, the pattern of these differences varied among sites and seasonal differences were not repeatable over years. Similarly, differences in community composition as revealed by classification were not seasonal. In the middle and lower reaches, these differences were apparently caused by the over- riding influence of non-seasonal climatic events, i.e. a major flood in 1978 and a drought throughout 1979. In the first two sampling following the flood, sample values for the numbers of both species and individuals were usually lowest and community composition was distinct from pre-flood and drought times. During the drought, the number of species was usually high and community composition relatively distinct. Whereas the number of species and community composition groupings were both significantly related to river discharge, the number of individuals was significantly correlated with temperature. All community variables were sometimes significantly related to salinity. The identity of numerically dominant species, as determined by Fager rankings, varied among times in both the lower and middle reaches. However, the polychaete Nephtys australiensis and the bivalve mollusc Notospisula trigonella were highest ranked overall in both zones. Community patterns in the low-salinity upper reaches differed from those further downstream by showing little change in numbers of species and community composition following the flood. Only the number of species was significantly correlated with any of the measured physicochemical variables, this being partly due to an influx of species during the drought. Furthermore, the upstream community was always dominated by the polychaete Ceratonereis limnetica and was thus the only community that could be characterised by a single species.


2004 ◽  
Vol 61 (8) ◽  
pp. 1398-1409 ◽  
Author(s):  
Morten Vinther ◽  
Stuart A. Reeves ◽  
Kenneth R. Patterson

Abstract Fishery management advice has traditionally been given on a stock-by-stock basis. Recent problems in implementing this advice, particularly for the demersal fisheries of the North Sea, have highlighted the limitations of the approach. In the long term, it would be desirable to give advice that accounts for mixed-fishery effects, but in the short term there is a need for approaches to resolve the conflicting management advice for different species within the same fishery, and to generate catch or effort advice that accounts for the mixed-species nature of the fishery. This paper documents a recent approach used to address these problems. The approach takes the single-species advice for each species in the fishery as a starting point, then attempts to resolve it into consistent catch or effort advice using fleet-disaggregated catch forecasts in combination with explicitly stated management priorities for each stock. Results are presented for the groundfish fisheries of the North Sea, and these show that the development of such approaches will also require development of the ways in which catch data are collected and compiled.


2018 ◽  
Vol 49 ◽  
pp. 159-169
Author(s):  
Muna H. Haroun Abdelhamed

AbstractLegumes seem to have been cultivated and to have formed an essential part of the human diet during the Greek and Roman periods. This paper examines the cultivation of pulses in Cyrenaica during the Hellenistic era. It considers the regional production capacity for legumes to meet local needs and argues the involvement of different kinds of pulses in interregional commerce alongside cereals and other dry grains. This study has been implemented via investigating Hellenistic epigraphic evidence from Cyrene. It has traced the cost of pulses mentioned in inscriptions of the fourth and third/second centuries BC and compared them with that of wheat and barley. Pulses and cereal costs indicated by Diocletian's ‘Edict on Maximum Prices of AD 301’ have also been investigated to assess the general trend of their prices over time. The examination demonstrates that varieties of pulses were produced in Cyrenaica during the Hellenistic era and were likely as significant as wheat and barley. It also indicates that they were probably traded from the region alongside other dry commodities.


Sign in / Sign up

Export Citation Format

Share Document