scholarly journals Short‐term insurance versus long‐term bet‐hedging strategies as adaptations to variable environments

Evolution ◽  
2018 ◽  
Vol 73 (2) ◽  
pp. 145-157 ◽  
Author(s):  
Thomas Ray Haaland ◽  
Jonathan Wright ◽  
Jarle Tufto ◽  
Irja Ida Ratikainen
Keyword(s):  
Bet Hedging ◽  
Short Term ◽  
Hedging Strategies ◽  
Variable Environments ◽  
Term Insurance

scholarly journals Time-dependent fitness effects can drive bet-hedging populations extinct

2016 ◽  
Author(s):  
Eric Libby ◽  
William Ratcliff
Keyword(s):  
Resource Competition ◽  
Bet Hedging ◽  
Short Term ◽  
Time Intervals ◽  
Hedging Strategies ◽  
Diversification Strategies ◽  
Environmental Fluctuations ◽  
Long Time ◽  
Temporally Correlated

AbstractTo survive unpredictable environmental change, many organisms adopt bet-hedging strategies that trade short-term population growth for long-term fitness benefits. Because the benefits of bet-hedging may manifest over long time intervals, bet-hedging strategies may be out-competed by strategies maximizing short-term fitness. Here, we investigate the interplay between two drivers of selection, environmental fluctuations and competition for limited resources, on different bet-hedging strategies. We consider an environment with frequent disasters that switch between which phenotypes they affect in a temporally-correlated fashion. We determine how organisms that stochastically switch between phenotypes at different rates fare in both competition and survival. When disasters are correlated in time, the best strategy for competition is among the worst for survival. Since the time scales over which the two agents of selection act are significantly different, environmental fluctuations and resource competition act in opposition and lead populations to evolve diversification strategies that ultimately drive them extinct.

scholarly journals Modes of response to environmental change and the elusive empirical evidence for bet hedging

2011 ◽  
Vol 278 (1712) ◽  
pp. 1601-1609 ◽  
Author(s):  
Andrew M. Simons
Keyword(s):  
Environmental Change ◽  
Empirical Evidence ◽  
Natural Environments ◽  
Bet Hedging ◽  
Fluctuating Selection ◽  
Hedging Strategies ◽  
Evolutionary Response ◽  
Human Decision ◽  
Response To Environmental Change

Uncertainty is a problem not only in human decision-making, but is a prevalent quality of natural environments and thus requires evolutionary response. Unpredictable natural selection is expected to result in the evolution of bet-hedging strategies, which are adaptations to long-term fluctuating selection. Despite a recent surge of interest in bet hedging, its study remains mired in conceptual and practical difficulties, compounded by confusion over what constitutes evidence for its existence. Here, I attempt to resolve misunderstandings about bet hedging and its relationship with other modes of response to environmental change, identify the challenges inherent to its study and assess the state of existing empirical evidence. The variety and distribution of plausible bet-hedging traits found across 16 phyla in over 100 studies suggest their ubiquity. Thus, bet hedging should be considered a specific mode of response to environmental change. However, the distribution of bet-hedging studies across evidence categories—defined according to potential strength—is heavily skewed towards weaker categories, underscoring the need for direct appraisals of the adaptive significance of putative bet-hedging traits in nature.

scholarly journals Temporal variability and cooperative breeding: testing the bet-hedging hypothesis in the acorn woodpecker

2015 ◽  
Vol 282 (1816) ◽  
pp. 20151742 ◽  
Author(s):  
Walter D. Koenig ◽  
Eric L. Walters
Keyword(s):  
Reproductive Success ◽  
Cooperative Breeding ◽  
Group Living ◽  
Bet Hedging ◽  
Hedging Strategy ◽  
Ecological Conditions ◽  
Variable Environments ◽  
Melanerpes Formicivorus ◽  
Mean Fitness

Cooperative breeding is generally considered an adaptation to ecological constraints on dispersal and independent breeding, usually due to limited breeding opportunities. Although benefits of cooperative breeding are typically thought of in terms of increased mean reproductive success, it has recently been proposed that this phenomenon may be a bet-hedging strategy that reduces variance in reproductive success (fecundity variance) in populations living in highly variable environments. We tested this hypothesis using long-term data on the polygynandrous acorn woodpecker ( Melanerpes formicivorus ). In general, fecundity variance decreased with increasing sociality, at least when controlling for annual variation in ecological conditions. Nonetheless, decreased fecundity variance was insufficient to compensate for reduced per capita reproductive success of larger, more social groups, which typically suffered lower estimated mean fitness. We did, however, find evidence that sociality in the form of larger group size resulted in increased fitness in years following a small acorn crop due to reduced fecundity variance. Bet-hedging, although not the factor driving sociality in general, may play a role in driving acorn woodpecker group living when acorns are scarce and ecological conditions are poor.

scholarly journals The influence of length of relationship, gender and age on the relationship intention of short-term insurance clients: an exploratory study

2011 ◽  
Vol 11 (2) ◽  
pp. 139-156 ◽  
Author(s):  
Derik Steyn ◽  
Pierre Mostert ◽  
Jan-Willem De Jager
Keyword(s):  
Relationship Marketing ◽  
Strong Relationship ◽  
Short Term ◽  
Gender And Age ◽  
Term Insurance ◽  
Length Of Relationship ◽  
Gender Display ◽  
The Relationship ◽  
Different Levels

Building long-term relationships with clients is extremely beneficial for organisations. This does not necessarily imply, however, that the clients themselves need or want a long-term relationship with an organisation. Relationship marketing could profitably be looked at from the client’s perspective, at the same time identifying those clients who have a strong relationship intention and would, in fact, like to engage in a long-term relationship with organisations.The objective of this research was to explore whether three aspects relating to clients, that is, the varying lengths of their relationship with organisations, their age and their gender display significantly different levels of relationship intention. Relationship intention is measured in terms of constructs like involvement, expectations, forgiveness, feedback and fear of relationship loss.Non-probability sampling was used in this study, and 114 respondents from the short-terminsurance industry completed self-administered questionnaires. Findings indicate that, for a group of high relationship-intention clients of a short-term insurance organisation, no practically significant discrimination exists on any of the relationship-intention constructs for clients’ length of relationship, gender or age.

scholarly journals A Short Note on Overall Risk Management in an Insurance Concern

1971 ◽  
Vol 6 (2) ◽  
pp. 153-156 ◽  
Author(s):  
Karl Borch
Keyword(s):  
Short Note ◽  
Insurance Contract ◽  
Short Term ◽  
Term Contract ◽  
Term Insurance ◽  
Short Term Contract ◽  
Proper Perspective ◽  
Image Position ◽  
Sound Foundation

1. At an earlier ASTIN Colloquium participants were invited to present notes on problems which they considered as important but unsolved. There was little response to this invitation, presumably because a problem, once it is well formulated, is almost solved.In this Note I do not present any new problems. In stead I try to outline a framework which may be useful for analysing different risk problems and seeing them in their proper perspective. In my view, a framework of this kind is urgently needed to place today's actuarial work on a sound foundation.2. In general an insurance contract will define two stochastic processes. We lose little by assuming that the processes are discrete, and describing them in the following manner:(i) The payment process: x0, x1 … xt …, where xt is the amount which the company pays to settle claims in period t, or at time t.(ii) The premium process: p0, p1 … pt …, where pt is the premium which the company receives in period t, or at time t.If the contract is concluded at time t = o, the Principle of Equivalence requires thatFor the typical short-term contract with premium payable in advance (i) will reduce to3. For a long-term insurance contract one usually requires that the inequalityshall hold for all τ. This means that the company must never be a net creditor of its customer.

scholarly journals Coral assemblages at higher latitudes favour short-term potential over long-term performance

2021 ◽  
Author(s):  
James Cant ◽  
James D Reimer ◽  
Brigitte Sommer ◽  
Katie Cook ◽  
Sun W Kim ◽  
...  
Keyword(s):  
Environmental Variability ◽  
Climatic Variability ◽  
Short Term ◽  
Variable Environments ◽  
Coral Communities ◽  
Long Term Performance ◽  
Term Performance ◽  
Thermal Variability ◽  
Current Exposure

The current exposure of species assemblages to high environmental variability may grant them resilience to future increases in climatic variability. In globally threatened coral reef ecosystems, management seeks to protect resilient reefs within variable environments. Yet, our lack of understanding for the determinants of coral population performance within variable environments hinders forecasting the future reassembly of coral communities. Here, using Integral Projection Models, we compare the short- (i.e., transient) and long-term (i.e., asymptotic) demographic characteristics of tropical and subtropical coral assemblages to evaluate how thermal variability influences the structural composition of coral communities over time. Exploring spatial variation across the dynamics of functionally different competitive, stress-tolerant, and weedy coral assemblages in Australia and Japan, we show that coral assemblages trade-off long-term performance for transient potential in response to thermal variability. We illustrate how coral assemblages can reduce their susceptibility towards environmental variation by exploiting volatile short-term demographic strategies, thus enhancing their persistence within variable environments. However, we also reveal considerable variation across the vulnerability of competitive, stress-tolerant, and weedy coral assemblages towards future increases in thermal variability. In particular, stress-tolerant and weedy corals possess an enhanced capacity for elevating their transient potential in response to environmental variability. Accordingly, despite their current exposure to high thermal variability, future climatic shifts threaten the structural complexity of coral assemblages, derived mostly from competitive coral taxa within highly variable subtropical environments, emulating the degradation expected across global coral communities.

scholarly journals The Impact of Exchange Rates and Interest Rates on Bank Stock Returns: Evidence from U.S. Banks

2016 ◽  
Vol 11 (1) ◽  
pp. 124-139 ◽  
Author(s):  
Verma Priti
Keyword(s):  
Exchange Rates ◽  
Interest Rates ◽  
Stock Returns ◽  
Short Term ◽  
Volatility Spillovers ◽  
Hedging Strategies ◽  
Bank Stock ◽  
The Impact ◽  
Bank Portfolios

AbstractThis paper examines the mean, volatility spillovers and response asymmetries between short-term and long-term interest rates, exchange rates and portfolios of money center, large and medium-sized banks in the U.S. I use the multivariate version of Nelson’s (1991) Exponential Generalized Autoregressive Conditionally Heteroscedastic (EGARCH) model. Results indicate mean and volatility spillovers from short-term interest rates and exchange rates and long-term interest rates and exchange rates to three bank portfolios. Results also show response asymmetries from short-term interest rates and exchange rates and long-term interest rates and exchange rates to all the three bank portfolios. These findings have important implications for bankers in terms of devising different hedging strategies against interest rates and exchange rate risks.

scholarly journals CURE OR CURSE? REGULATIONS ON THE DEMARCATION BETWEEN HEALTH-INSURANCE POLICIES AND MEDICAL SCHEMES

Obiter ◽  
2021 ◽  
Vol 33 (2) ◽  
Author(s):  
Daleen Millard
Keyword(s):  
Insurance Industry ◽  
Private Insurance ◽  
Health It ◽  
Short Term ◽  
Insurance Policies ◽  
Term Insurance ◽  
Insurance Business ◽  
The Difference ◽  
The Impact

In South Africa, private insurance policies are regulated by the Long-term Insurance Act and the Short-term Insurance Act. Medical schemes fall under the Medical Schemes Act (131 of 1998) and yet, despite the fact that there are three dedicated statutes that deal with the risks relating to ill health, it seems that the distinction between insurance products and medical-scheme benefits isnot so clear. On 2 March 2012 National Treasury published the proposed amendment of regulations made under section 72 of the LTIA and under section 70 of the STIA. These are jointly referred to as the “Demarcation Regulations”. This note provides an overview of these proposals against the background of the difference between insurance business and medical-schemes business. In addition, itinvestigates the policy principles that informed the Demarcation Regulations and comments on the impact of those on the insurance industry and on medical schemes.

Conceptual short-term memory (CSTM) supports core claims of Christiansen and Chater

2016 ◽  
Vol 39 ◽  
Author(s):  
Mary C. Potter
Keyword(s):  
Working Memory ◽  
Rapid Serial Visual Presentation ◽  
Language Comprehension ◽  
Short Term Memory ◽  
Visual Presentation ◽  
Long Term Memory ◽  
Short Term ◽  
Term Memory ◽  
Use Of Knowledge

AbstractRapid serial visual presentation (RSVP) of words or pictured scenes provides evidence for a large-capacity conceptual short-term memory (CSTM) that momentarily provides rich associated material from long-term memory, permitting rapid chunking (Potter 1993; 2009; 2012). In perception of scenes as well as language comprehension, we make use of knowledge that briefly exceeds the supposed limits of working memory.

Ultrastructural investigations of MDL 19,660-induced effects on the canine platelet and megakaryocyte

1990 ◽  
Vol 48 (3) ◽  
pp. 374-375
Author(s):  
D.E. Loudy ◽  
J. Sprinkle-Cavallo ◽  
J.T. Yarrington ◽  
F.Y. Thompson ◽  
J.P. Gibson
Keyword(s):  
Antidepressant Drug ◽  
Beagle Dogs ◽  
Long Term Effects ◽  
Short Term ◽  
Platelet Counts ◽  
Toxicological Studies ◽  
Induced Aggregation ◽  
Internal Architecture

Previous short term toxicological studies of one to two weeks duration have demonstrated that MDL 19,660 (5-(4-chlorophenyl)-2,4-dihydro-2,4-dimethyl-3Hl, 2,4-triazole-3-thione), an antidepressant drug, causes a dose-related thrombocytopenia in dogs. Platelet counts started to decline after two days of dosing with 30 mg/kg/day and continued to decrease to their lowest levels by 5-7 days. The loss in platelets was primarily of the small discoid subpopulation. In vitro studies have also indicated that MDL 19,660: does not spontaneously aggregate canine platelets and has moderate antiaggregating properties by inhibiting ADP-induced aggregation. The objectives of the present investigation of MDL 19,660 were to evaluate ultrastructurally long term effects on platelet internal architecture and changes in subpopulations of platelets and megakaryocytes.Nine male and nine female beagle dogs were divided equally into three groups and were administered orally 0, 15, or 30 mg/kg/day of MDL 19,660 for three months. Compared to a control platelet range of 353,000- 452,000/μl, a doserelated thrombocytopenia reached a maximum severity of an average of 135,000/μl for the 15 mg/kg/day dogs after two weeks and 81,000/μl for the 30 mg/kg/day dogs after one week.

Sign in / Sign up

Export Citation Format

Share Document