scholarly journals Asymmetric habitat isolation and sexual isolation predicted by the cost of migration and hybridization generate novel signatures of reinforcing selection

2022 ◽  
Author(s):  
Linyi Zhang ◽  
Glen Ray Hood ◽  
Jim R Ott ◽  
Scott P Egan
Keyword(s):  
Empirical Studies ◽  
Evolutionary Process ◽  
Sexual Isolation ◽  
Sympatric Species ◽  
Habitat Isolation ◽  
Quercus Virginiana ◽  
Alternative Habitat ◽  
Allopatric Species ◽  
Gall Wasps ◽  
The Cost

Reinforcement is an evolutionary process whereby increased prezygotic reproductive isolation evolves in response to the cost of hybridization. Despite theory predicting that multiple prezygotic barriers can evolve via reinforcement, most empirical studies examine a single barrier. We test novel predictions for the reinforcement of both habitat isolation and sexual isolation between ecologically divergent lineages under asymmetric migration: the lineage that emigrates more should evolve stronger habitat isolation due to the lower fitness of immigrants in the alternative habitat, while the lineage that receives more immigrants should exhibit stronger sexual isolation due to the lower fitness of hybrids. We found both signatures of reinforcement in two sympatric sister species of gall wasps that are host specific to the southern live oaks, Quercus virginiana and Q. geminata, respectively. Specifically, we observed stronger habitat isolation in the species with higher emigration rates, Belonocnema treatae, and stronger sexual isolation in the species facing more immigrants, B. fossoria. In contrast, comparisons of both species to a third, allopatric, species showed that B. kinseyi exhibited both lower habitat isolation and sexual isolation than the sympatric species, consistent with the classic predictions of reinforcement. Our study provides a rare examination of the interplay of ecology and geography in the evolution of multiple reproductive barriers to gene flow. Given that asymmetric migration between ecologically divergent lineages increasingly appears to be the rule rather than the exception, concomitant asymmetries in the strength of habitat and sexual isolation could be more widespread than currently understood.

Factors explaining a cost-based pricing essence

2019 ◽  
Vol 34 (8) ◽  
pp. 1850-1865
Author(s):  
Juliana Ventura Amaral ◽  
Reinaldo Guerreiro
Keyword(s):  
Design Methodology ◽  
Empirical Studies ◽  
Pricing Strategy ◽  
Company Size ◽  
Price Setting ◽  
Marketing Theory ◽  
Content Type ◽  
Industrial Companies ◽  
Five Factors ◽  
The Cost

Purpose Empirical studies have found that cost-based pricing remains dominant in pricing practice and suggest that practice conflicts with marketing theory, which recommends value-based prices. However, empirical studies have yet to examine whether cost-plus formulas represent the pricing approach or essence. Design/methodology/approach This study aims to address the factors that explain price setting whereby the cost-plus formula is not just the pricing approach but also the pricing essence. This examination is grounded in a survey conducted on 380 Brazilian industrial companies. Findings The results show that, for price-makers, the cost-based pricing essence is positively associated with four factors (two obstacles to deploying value-based pricing, company size and differentiation), but it is negatively related to one factor (premium pricing strategy). For price-takers, the cost-based pricing essence is positively associated with four factors (two obstacles to deploying value-based pricing, coercive isomorphism and use of full costs), but it is negatively related to five factors (one obstacle to deploying value-based pricing, company size, competitors’ ability to copy, normative isomorphism and experience). Originality/value The key contribution of this paper is demonstrating that cost-plus formulas do not go against the incorporation of competitors and value information. This study reveals that it is possible to set prices based on either value or competitors’ prices while simultaneously preserving the simplicity of the cost-plus formulas. Via the margin, firms may connect costs to information about competition and value. The authors also demonstrate the drawbacks of not segregating companies into price-makers and price-takers and an excessive focus on the pricing approach at the expense of pricing essence.

High cryptic diversity in the kleptoparasitic genus Hyalorisia Dall, 1889 (Littorinimorpha: Capulidae) with the description of nine new species from the Indo-West Pacific

2020 ◽  
Vol 86 (4) ◽  
pp. 401-421 ◽  
Author(s):  
Giulia Fassio ◽  
Valeria Russini ◽  
Barbara Buge ◽  
Stefano Schiaparelli ◽  
Maria Vittoria Modica ◽  
...  
Keyword(s):  
Trophic Ecology ◽  
Molecular Data ◽  
Sympatric Species ◽  
Water Current ◽  
Phylogenetic Position ◽  
Nominal Species ◽  
West Pacific ◽  
Allopatric Species ◽  
Wide Range ◽  
The Family

ABSTRACT Species in the family Capulidae (Littorinimorpha: Capuloidea) display a wide range of shell morphologies. Several species are known to live in association with other benthic invertebrates—mostly bivalves and sabellid worms, but also other gastropods—and are believed to be kleptoparasitic filter feeders that take advantage of the water current produced by the host. This peculiar trophic ecology, implying a sedentary lifestyle, has resulted in highly convergent shell forms. This is particularly true for the genus Hyalorisia Dall, 1889, which occurs in deep water in the Caribbean and Indo-West Pacific provinces, with two nominal species recognized so far. Combining morphological, ecological and molecular data, we assessed the diversity of the genus, its phylogenetic position inside the family and its association with its bivalve host, the genus Propeamussium de Gregorio, 1884 (Pectinoidea), resulting in the description of nine new cryptic species. When sympatric, species of Hyalorisia are associated with different host species, but the same species of Propeamussium may be the host of several allopatric species of Hyalorisia.

Business uncertainty and financial leverage: should the firm double up on risk?

2019 ◽  
Vol 45 (4) ◽  
pp. 536-544
Author(s):  
Khaled Elkhal
Keyword(s):  
Financial Distress ◽  
Empirical Studies ◽  
Past Research ◽  
Optimum Level ◽  
Business Risk ◽  
Financial Leverage ◽  
Research Papers ◽  
Content Type ◽  
The Cost ◽  
The Relationship

Purpose The purpose of this paper is to examine the nature of the relationship between business risk and financial leverage. While past theoretical and empirical studies on this topic use similar variables, overall, their findings are inconclusive. In this paper, the author contends this is partially due to inappropriate proxies for business risk that are commonly used in these research papers. To correct for this misspecification, this paper proposes an alternative proxy for business risk that is isolated from the effects of financial leverage. Design/methodology/approach Past research on the relationship between business risk and financial leverage uses some variations in a firm’s operating cash flow as a proxy for business risk. This proxy cannot solely reflect business risk and may very well be affected by the level of financial leverage, especially for financially distressed firms. This paper proposes an alternative proxy for business risk that is isolated from the effects of financial leverage. This proxy is the cost of capital of an all-equity firm. The theoretical model developed in this paper is based on deriving the optimum level of debt as a function of business risk in the context of the Modigliani and Miller Proposition II model. Findings The findings show a positive linkage between business risk and financial leverage. This relationship is robust to the various forms the cost of financial distress function may take. Originality/value The mixed findings in past research papers regarding the relationship between business risk and financial leverage are mainly due to “inappropriate” measures of business risk that do not only reflect one firm attribute and are contaminated with other factors mainly financial leverage. As such, since the variable of interest is misspecified, the outcome of these studies cannot be credible. This paper attempts to correct for such misspecification by proposing a proxy that only reflects business risk. In addition, the proposed model is based on the widely acceptable Modigliani and Miller static theory of capital structure.

Males, but not females, contribute to sexual isolation between two sympatric species of Gambusia

2009 ◽  
Vol 24 (4) ◽  
pp. 865-878 ◽  
Author(s):  
Celeste M. Espinedo ◽  
Caitlin R. Gabor ◽  
Andrea S. Aspbury
Keyword(s):  
Sexual Isolation ◽  
Sympatric Species

scholarly journals Genes, Environments, and Developmental Research: Methods for a Multi-Site Study of Early Substance Abuse

2013 ◽  
Vol 16 (2) ◽  
pp. 505-515 ◽  
Author(s):  
E. Jane Costello ◽  
Lindon Eaves ◽  
Patrick Sullivan ◽  
Martin Kennedy ◽  
Kevin Conway ◽  
...  
Keyword(s):  
Repeated Measures ◽  
Stressful Life Events ◽  
Developmental Stages ◽  
Empirical Studies ◽  
Data Sets ◽  
Gene Environment ◽  
Human Pathology ◽  
Significant Gene ◽  
Environmental Measures ◽  
The Cost

The importance of including developmental and environmental measures in genetic studies of human pathology is widely acknowledged, but few empirical studies have been published. Barriers include the need for longitudinal studies that cover relevant developmental stages and for samples large enough to deal with the challenge of testing gene–environment–development interaction. A solution to some of these problems is to bring together existing data sets that have the necessary characteristics. As part of the National Institute on Drug Abuse-funded Gene-Environment-Development Initiative, our goal is to identify exactly which genes, which environments, and which developmental transitions together predict the development of drug use and misuse. Four data sets were used of which common characteristics include (1) general population samples, including males and females; (2) repeated measures across adolescence and young adulthood; (3) assessment of nicotine, alcohol, and cannabis use and addiction; (4) measures of family and environmental risk; and (5) consent for genotyping DNA from blood or saliva. After quality controls, 2,962 individuals provided over 15,000 total observations. In the first gene–environment analyses, of alcohol misuse and stressful life events, some significant gene–environment and gene–development effects were identified. We conclude that in some circumstances, already collected data sets can be combined for gene–environment and gene–development analyses. This greatly reduces the cost and time needed for this type of research. However, care must be taken to ensure careful matching across studies and variables.

scholarly journals Structure of sexual networks determines the operation of sexual selection

2017 ◽  
Vol 115 (1) ◽  
pp. E53-E61 ◽  
Author(s):  
Grant C. McDonald ◽  
Tommaso Pizzari
Keyword(s):  
Sexual Selection ◽  
Mating Success ◽  
Empirical Studies ◽  
Evolutionary Process ◽  
Population Level ◽  
Network Size ◽  
Male Mating ◽  
Male Mating Success ◽  
Sexual Network ◽  
Bateman Gradient

Sexual selection is a fundamental evolutionary process but remains debated, particularly in the complexity of polyandrous populations where females mate with multiple males. This lack of resolution is partly because studies have largely ignored the structure of the sexual network, that is, the pattern of mate sharing. Here, we quantify what we call mating assortment with network analysis to specify explicitly the indirect as well as direct relationships between partners. We first review empirical studies, showing that mating assortment varies considerably in nature, due largely to basic properties of the sexual network (size and density) and partly to nonrandom patterns of mate sharing. We then use simulations to show how variation in mating assortment interacts with population-level polyandry to determine the strength of sexual selection on males. Controlling for average polyandry, positive mating assortment, arising when more polygynous males tend to mate with more polyandrous females, drastically decreases the intensity of precopulatory sexual selection on male mating success (Bateman gradient) and the covariance between male mating success and postcopulatory paternity share. Average polyandry independently weakened some measures of sexual selection and crucially also impacted sexual selection indirectly by constraining mating assortment through the saturation of the mating network. Mating assortment therefore represents a key—albeit overlooked—modulator of the strength of sexual selection. Our results show that jointly considering sexual network structure and average polyandry more precisely describes the strength of sexual selection.

scholarly journals Testing the Role of Habitat Isolation among Ecologically Divergent Gall Wasp Populations

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Scott P. Egan ◽  
Glen R. Hood ◽  
James R. Ott
Keyword(s):  
Reproductive Isolation ◽  
Assortative Mating ◽  
Host Plants ◽  
Habitat Preferences ◽  
Habitat Isolation ◽  
Native Plant ◽  
Gall Wasp ◽  
Quercus Virginiana ◽  
Respective Host

Habitat isolation occurs when habitat preferences lower the probability of mating between individuals associated with differing habitats. While a potential barrier to gene flow during ecological speciation, the effect of habitat isolation on reproductive isolation has rarely been directly tested. Herein, we first estimated habitat preference for each of six populations of the gall waspBelonocnema treataeinhabiting eitherQuercus virginianaorQ. geminata. We then estimated the importance of habitat isolation in generating reproductive isolation betweenB. treataepopulations that were host specific to eitherQ. virginianaorQ. geminataby measuring mate preference in the presence and absence of the respective host plants. All populations exhibited host preference for their native plant, and assortative mating increased significantly in the presence of the respective host plants. This host-plant-mediated assortative mating demonstrates that habitat isolation likely plays an important role in promoting reproductive isolation among populations of this host-specific gall former.

scholarly journals Option replication and the performance of a market timer

2016 ◽  
Vol 33 (1) ◽  
pp. 2-25 ◽  
Author(s):  
Georges Hübner
Keyword(s):  
Empirical Studies ◽  
Market Timing ◽  
Factor Models ◽  
Similar Reasoning ◽  
Content Type ◽  
Practical Applications ◽  
Timing Model ◽  
Portfolio Managers ◽  
Initial Idea ◽  
The Cost

Purpose – The Treynor and Mazuy framework is a widely used return-based model of market timing. However, existing corrections to the regression intercept can be manipulated through derivatives trading. Because they are conceptually flawed, these corrections produce biased performance measures. This paper aims to get back to Henriksson and Merton’s initial idea of option replication to overcome this issue and adapt the market timing model to various kinds of trading strategies and return-generating processes. Design/methodology/approach – This paper proposes a theoretical adjustment based on Merton’s option replication approach adapted to the Treynor and Mazuy specification. The linear and quadratic coefficients of the regression are exploited to assess the cost of the replicating option that yields similar convexity for a passive portfolio. A similar reasoning applies for various timing patterns and in multi-factor models. Findings – The proposed framework induces a potential rebalancing risk and involves the delicate issue of choosing the cheapest option. This paper shows that these issues can be overcome for reasonable tolerance levels. The option replication approach is a workable approach for practical applications. Originality/value – The adaptation of Merton’s reasoning to the Treynor and Mazuy model has surprisingly never been proposed so far. This paper has the potential to correct for a pervasive bias in the estimation of the performance of a market timer in the context of this very popular quadratic regression setup. Because of the power of the option replication approach, the reasoning is shown to be applicable to multi-factor models, negative timing and market neutral strategies. This paper could fuel empirical studies that would shed new light on the genuine market timing skills of active portfolio managers.

scholarly journals Evolution of male and female choice in polyandrous systems

2017 ◽  
Vol 284 (1851) ◽  
pp. 20162174 ◽  
Author(s):  
Mikael Puurtinen ◽  
Lutz Fromhage
Keyword(s):  
Mate Choice ◽  
Empirical Studies ◽  
Mating Strategies ◽  
Sperm Production ◽  
Female Fecundity ◽  
Male And Female ◽  
Sperm Limitation ◽  
Multiple Partners ◽  
Mating Costs ◽  
The Cost

We study the evolution of male and female mating strategies and mate choice for female fecundity and male fertilization ability in a system where both sexes can mate with multiple partners, and where there is variation in individual quality (i.e. in the availability of resources individuals can allocate to matings, mate choice and production of gametes). We find that when the cost of mating differs between sexes, the sex with higher cost of mating is reluctant to accept matings and is often also choosy, while the other sex accepts all matings. With equal mating costs, the evolution of mating strategies depends on the strength of female sperm limitation, so that when sperm limitation is strong, males are often reluctant and choosy, whereas females tend to accept available matings. Male reluctance evolves because a male's benefit per mating diminishes rapidly as he mates too often, hence losing out in the process of sperm competition as he spends much of his resources on mating costs rather than ejaculate production. When sperm limitation is weaker, females become more reluctant and males are more eager to mate. The model thus suggests that reversed sex roles are plausible outcomes of polyandry and limited sperm production. Implications for empirical studies of mate choice are discussed.

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