scholarly journals Trait dimensionality explains widespread variation in local adaptation

2015 ◽  
Vol 282 (1802) ◽  
pp. 20141570 ◽  
Author(s):  
Ailene MacPherson ◽  
Paul A. Hohenlohe ◽  
Scott L. Nuismer
Keyword(s):  
Gene Flow ◽  
Local Adaptation ◽  
Growth Rates ◽  
Environmental Conditions ◽  
Strong Correlation ◽  
Empirical Support ◽  
Reciprocal Transplant ◽  
Population Growth Rates ◽  
Using Data ◽  
The Relationship

All species are locked in a continual struggle to adapt to local ecological conditions. In cases where species fail to locally adapt, they face reduced population growth rates, or even local extinction. Traditional explanations for limited local adaptation focus on maladaptive gene flow or homogeneous environmental conditions. These classical explanations have, however, failed to explain variation in the magnitude of local adaptation observed across taxa. Here we show that variable levels of local adaptation are better explained by trait dimensionality. First, we develop and analyse mathematical models that predict levels of local adaptation will increase with the number of traits experiencing spatially variable selection. Next, we test this prediction by estimating the relationship between dimensionality and local adaptation using data from 35 published reciprocal transplant studies. This analysis reveals a strong correlation between dimensionality and degree of local adaptation, and thus provides empirical support for the predictions of our model.

Life history and environmental influences on population dynamics in sockeye salmon

2014 ◽  
Vol 71 (8) ◽  
pp. 1198-1208 ◽  
Author(s):  
Douglas C. Braun ◽  
John D. Reynolds
Keyword(s):  
Population Dynamics ◽  
Life History ◽  
Population Growth ◽  
Growth Rates ◽  
Environmental Conditions ◽  
Sockeye Salmon ◽  
Life History Traits ◽  
Relative Importance ◽  
Population Growth Rates ◽  
Habitat Variables

Understanding linkages among life history traits, the environment, and population dynamics is a central goal in ecology. We compared 15 populations of sockeye salmon (Oncorhynchus nerka) to test general hypotheses for the relative importance of life history traits and environmental conditions in explaining variation in population dynamics. We used life history traits and habitat variables as covariates in mixed-effect Ricker models to evaluate the support for correlates of maximum population growth rates, density dependence, and variability in dynamics among populations. We found dramatic differences in the dynamics of populations that spawn in a small geographical area. These differences among populations were related to variation in habitats but not life history traits. Populations that spawned in deep water had higher and less variable population growth rates, and populations inhabiting streams with larger gravels experienced stronger negative density dependence. These results demonstrate, in these populations, the relative importance of environmental conditions and life histories in explaining population dynamics, which is rarely possible for multiple populations of the same species. Furthermore, they suggest that local habitat variables are important for the assessment of population status, especially when multiple populations with different dynamics are managed as aggregates.

Virtual vs physical platform: organizational capacity and slack, strategic decision and firm performance

2020 ◽  
Vol 35 (12) ◽  
pp. 1983-1995 ◽  
Author(s):  
Hang Lee ◽  
Yung-Chang Hsiao ◽  
Chung-Jen Chen ◽  
Ruey-Shan Guo
Keyword(s):  
Firm Performance ◽  
Empirical Support ◽  
Organizational Capacity ◽  
Strategic Choice ◽  
Retail Industry ◽  
Content Type ◽  
Using Data ◽  
Virtual Platform ◽  
The Relationship ◽  
Better Than

Purpose This study aims to examine the relationship between organizational capacity, slack resource, platform strategic choice and firm performance. It also tackles the endogenous issues regarding the strategic choice of platform types. Design/methodology/approach This study uses Heckman’s two-stage procedures to examine the relationship between the variables. The sample in this study comes from Compustat annual company and segment files. The sample used in the main analysis consists of 252 individual corporations globally and 3,528 firm-year observations from 2004–2017. Findings The empirical results suggest that: (1) firms are more likely to develop physical platforms than virtual platforms when they possess higher levels of available slack, potential slack, research and development (R&D) capacity and marketing capacity; (2) in general, firms developing physical platforms perform better than firms developing virtual platforms after the endogeneity bias are controlled; and (3) firms that choose to develop physical platforms perform better than if they had chosen to develop virtual platforms. Research limitations/implications This study contributes to the platform research literature by proposing the endogenous role of platform type choice in firm performance in the context of the retail industry. Prior conceptual and theoretical platform studies have seldom focused on the retail industry through a strategic choice perspective. Furthermore, one of the contributions of this study is the derivation of empirical support for the research’s prediction using data from actual firms carried out by global physical and virtual platform companies. This study also presents many opportunities for further explorations on the relationship between firm strategic choice and firm performance in the context of platform retail industry. Practical implications The findings of this study suggest that firms must realize that their performance is not necessarily affected by these platform type choice determinants in terms of potential slack, available slack, R&D capacity and marketing capacity. By contrast, they should pay more attention to developing physical platforms if it is possible. The study findings indicate that although virtual platforms have grown rapidly because of the development of technology, firm performance is at all times superior when firms choose to develop physical platforms. Originality/value Prior platform studies have focused on the topic of network structure, platform architecture, pricing strategy, platform leadership and platform design and governance within the context of video game industry, software industry, hardware industry and telecommunications industry. Seldom of them focus on other industries through a strategic choice perspective. Furthermore, one of the contributions of this study is the derivation of empirical support for the research’s prediction using data from actual firms carried out by global physical and virtual platform companies.

scholarly journals Founder effects drive the genetic structure of passively dispersed aquatic invertebrates

2018 ◽  
Author(s):  
Javier Montero-Pau ◽  
Africa Gomez ◽  
Manuel Serra
Keyword(s):  
Life Cycle ◽  
Genetic Structure ◽  
Population Growth ◽  
Local Adaptation ◽  
Growth Rates ◽  
High Population ◽  
Founder Effects ◽  
Population Growth Rates ◽  
High Population Growth ◽  
The Impact

Populations of passively dispersed organisms in continental aquatic habitats typically show high levels of neutral genetic differentiation, despite their high dispersal capabilities. Several evolutionary factors, including founder events and local adaptation, and life cycle features such as high population growth rates and the presence of propagule banks, have been proposed to be responsible for this paradox. Here, we have modeled the colonization process in these organisms to assess the impact of migration rate, growth rate, population size, local adaptation and life-cycle features on their population genetic structure. Our simulation results show that the strongest effect on population structure is caused by persistent founder effects, resulting from the interaction of a few population founders, high population growth rates, large population sizes and the presence of diapausing egg banks. In contrast, the role of local adaptation, genetic hitchhiking and migration is limited to small populations in these organisms. Our results indicate that local adaptation could have different impact on genetic structure in different groups of zooplankters.

scholarly journals Scaling in the growth of geographically subdivided populations: invariant patterns from a continent-wide biological survey

2002 ◽  
Vol 357 (1421) ◽  
pp. 627-633 ◽  
Author(s):  
Timothy H. Keitt ◽  
Luis A. N. Amaral ◽  
Sergey V. Buldyrev ◽  
H. Eugene Stanley
Keyword(s):  
Growth Rates ◽  
Scaling Laws ◽  
Total Population ◽  
Breeding Birds ◽  
Population Growth Rates ◽  
Biological Survey ◽  
Subdivided Population ◽  
Subdivided Populations ◽  
Power Law Function ◽  
The Relationship

We consider statistical patterns of variation in growth rates for over 400 species of breeding birds across North America surveyed from 1966 to 1998. We report two results. First, the standard deviation of population growth rates decays as a power–law function of total population size with an exponent β = 0.36 ± 0.02. Second, the number of subpopulations, measured as the number of survey locations with non–zero counts, scales to the 3/4 power of total number of birds counted in a given species. We show how these patterns may be related, and discuss a simple stochastic growth model for a geographically subdivided population that formalizes the relationship. We also examine reasons that may explain why some species deviate from these scaling laws.

Provision of Optional versus Standard Product Features in Competition

2017 ◽  
Vol 81 (3) ◽  
pp. 80-95 ◽  
Author(s):  
Subramanian Balachander ◽  
Esther Gal-Or ◽  
Tansev Geylani ◽  
Alex Jiyoung Kim
Keyword(s):  
Empirical Support ◽  
Product Line ◽  
Product Lines ◽  
Product Features ◽  
Car Market ◽  
Standard Product ◽  
Quality Image ◽  
Using Data ◽  
The Cost ◽  
The Relationship

Competing brands differ in the extent to which they offer a given feature as standard or optional in their product lines. In this article, the authors study the competitive basis for this difference in brands’ product line strategies. Specifically, they analyze the relationship between a brand's quality image and its propensity to offer a wider product line, from a relatively stripped-down base model to a more feature-rich model. They develop a conceptual framework and hypotheses by considering an analytical model with two vertically differentiated firms: They show that a low-quality firm would offer a feature as optional—that is, it would offer both a feature-added product and a stripped-down base product—if it chose to add the feature to its product. In contrast, a high-quality firm would offer the feature as a standard component unless the cost of the feature was high. This asymmetry in the propensity of high- and low-quality firms to offer optional and standard features with their products is tested using data from the U.S. passenger car market; the authors find empirical support for their model.

scholarly journals Founder effects drive the genetic structure of passively dispersed aquatic invertebrates

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e6094 ◽  
Author(s):  
Javier Montero-Pau ◽  
Africa Gómez ◽  
Manuel Serra
Keyword(s):  
Life Cycle ◽  
Genetic Structure ◽  
Population Growth ◽  
Local Adaptation ◽  
Growth Rates ◽  
High Population ◽  
Founder Effects ◽  
Population Growth Rates ◽  
High Population Growth ◽  
The Impact

Populations of passively dispersed organisms in continental aquatic habitats typically show high levels of neutral genetic differentiation despite their high dispersal capabilities. Several evolutionary factors, including founder events, local adaptation, and life cycle features such as high population growth rates and the presence of propagule banks, have been proposed to be responsible for this paradox. Here, we have modeled the colonization process to assess the impact of migration rate, population growth rate, population size, local adaptation and life-cycle features on the population genetic structure in these organisms. Our simulations show that the strongest effect on population structure are persistent founder effects, resulting from the interaction of a few population founders, high population growth rates, large population sizes and the presence of diapausing egg banks. In contrast, the role of local adaptation, genetic hitchhiking and migration is limited to small populations in these organisms. Our results indicate that local adaptation could have different impact on genetic structure in different groups of zooplankters.

Relationship between body size and population growth rate in two opportunistic polychaetes

2002 ◽  
Vol 82 (3) ◽  
pp. 403-408 ◽  
Author(s):  
D. Prevedelli ◽  
R. Simonini
Keyword(s):  
Growth Rate ◽  
Body Size ◽  
Sex Ratio ◽  
Population Growth ◽  
Growth Rates ◽  
Life Histories ◽  
Population Growth Rate ◽  
Population Growth Rates ◽  
The Relationship ◽  
Dinophilus Gyrociliatus

The relationship between body size and population growth rate λ has been studied in two species of opportunistic polychaetes, Dinophilus gyrociliatus and Ophryotrocha labronica, which colonize harbour environments. These species exhibit a semi-continuous iteroparous reproductive strategy, are phylogenetically closely-related but differ in body size and in some aspects of their sexuality. Ophryotrocha labronica is about 4 mm in body length, displays only slight sexual dimorphism and its sex ratio is biased towards the female sex in the ratio 2:1. Dinophilus gyrociliatus is about 1 mm in length, the males are extremely small and the sex ratio is strongly biased (3:1) in favour of the females. In spite of the considerable differences in all traits of their life histories and in many demographic parameters, the growth rates of the two populations are very similar. The analyses carried out have shown that the rapid attainment of sexual maturity of D. gyrociliatus gives it an advantage that offsets the greater fecundity of O. labronica. It is very likely that the reproductive peculiarities of D. gyrociliatus help to raise the population growth rates. The ‘saving’ on the male sex achieved both by the shift of the sex ratio in favour of the females and by the reduction in the males' body size would appear to enable D. gyrociliatus to grow at the same rate as O. labronica, a larger and more fecund species.

scholarly journals Using niche models of indicator species to predict the distribution of xerophytic shrub dune communities

Web Ecology ◽  
2016 ◽  
Vol 16 (1) ◽  
pp. 47-49 ◽  
Author(s):  
R. M. Chefaoui ◽  
S. Chozas ◽  
O. Correia ◽  
A. M. C. Santos ◽  
J. Hortal
Keyword(s):  
Environmental Conditions ◽  
Species Interactions ◽  
Sand Dune ◽  
Climatic Conditions ◽  
Different Types ◽  
Characteristic Species ◽  
Using Data ◽  
Dune Plant ◽  
Threatened Habitat ◽  
The Relationship

Abstract. Dune plant assemblages are affected by severe conditions, which makes them excellent models for studying the effects of species interactions and environmental conditions on community structure. We evaluate the relationship between the structure of dune communities, local environmental conditions and the suitability of climatic conditions for their characteristic species. Using data from an extensive survey of xerophytic inland sand dune scrub communities from Portugal – one of the most threatened habitat types of Europe – we identify the main gradients of vegetation composition, the different types of communities and their indicator shrub species. Then, we model the geographical responses of these species to the environment. Soil organic matter, isothermality and the habitat suitability for Stauracanthus genistoides defined the distribution of three shrub communities in the study area.

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