Evolutionary Suicide and Evolution of Dispersal in Structured Metapopulations

In this article we study the evolution of dispersal in a structured metapopulation model. The metapopulation consists of a large (infinite)number of local populations living in patches of habitable environment. Dispersal between patches is modeled by a disperser pool and individuals in transit between patches are exposed to a risk of mortality. Occasionally, local catastrophes eradicate a local population: all individuals in the affected patch die, yet the patch remains habitable. The rate at which such disasters occur can depend on the local population size of a patch. We prove that, in the absence of catastrophes, the strategy not to migrate is evolutionarily stable. It is also convergence stable unless there is no mortality during dispersal. Under a given set of environmental conditions, a metapopulation may be viable and yet selection may favor dispersal rates that drive the metapopulation to extinction. This phenomenon is known as evolutionary suicide. We show that in our model evolutionary suicide can occur for certain types of size-dependent catastrophes. Evolutionary suicide can also happen for constant catastrophe rates, if local growth within patches shows an Allee effect. We study the evolutionary bifurcation towards evolutionary suicide and show that a discontinuous transition to extinction is a necessary condition for evolutionary suicide to occur. In other words, if population size smoothly approaches zero at a boundary of viability in parameter space, this boundary is evolutionarily repelling and no suicide can occur

Function-Valued Adaptive Dynamics and the Calculus of Variations

Adaptive dynamics has been widely used to study the evolution of scalar-valued, and occasionally vector-valued, strategies in ecologically realistic models. In many ecological situations, however, evolving strategies are best described as function-valued, and thus infinite-dimensional, traits. So far, such evolution has only been studied sporadically, mostly based on quantitative genetics models with limited ecological realism. In this article we show how to apply the calculus of variations to find evolutionarily singular strategies of function-valued adaptive dynamics: such a strategy has to satisfy Euler's equation with environmental feedback. We also demonstrate how second-order derivatives can be used to investigate whether or not a function-valued singular strategy is evolutionarily stable. We illustrate our approach by presenting several worked examples

The Adaptive Dynamics of Function-valued Traits

This study extends the framework of adaptive dynamics to function-valued traits. Such adaptive traits naturally arise in a great variety of settings: variable or heterogeneous environments, age-structured populations, phenotypic plasticity, patterns of growth and form, resource gradients, and in many other areas of evolutionary ecology. Adaptive dynamics theory allows analyzing the long-term evolution of such traits under the density-dependent and frequency-dependent selection pressures resulting from feedback between evolving populations and their ecological environment. Starting from individual-based considerations, we derive equations describing the expected dynamics of a function-valued trait in asexually reproducing populations under mutation-limited evolution, thus generalizing the canonical equation of adaptive dynamics to function-valued traits. We explain in detail how to account for various kinds of evolutionary constraints on the adaptive dynamics of function-valued traits. To illustrate the utility of our approach, we present applications to two specific examples that address, respectively, the evolution of metabolic investment strategies along resource gradients, and the evolution of seasonal flowering schedules in temporally varying environments

Evolution of Dispersal in Metapopulations with Local Density Dependence and Demographic Stochasticity

Selective pressures governing the evolution of dispersal rates are difficult to evaluate and currently poorly understood. In particular, predictions of evolutionarily stable dispersal strategies have only been derived under a number of limiting conditions regarding the ecology of of dispersing species. In this paper we predict the outcome of dispersal evolution in metapopulations based on a suit of assumptions that are more likely to be met in the field: (i) population dynamics within patches are density-regulated by realistic growth functions,(ii) demographic stochasticity resulting from finite population sizes within patches is accounted for and (iii) the transition of individuals between patches is explicitly modeled by a disperser pool. In addition we make few further changes which add to the models interest for comparison purposes; (iv) individuals can disperse between habitable patches throughout their lifetime, and (v) metapopulations are described in continuous time instead of relying on season-to-season descriptions. Extending available models in regard to these features, we demonstrate the existence of two general patterns of metapopulation adaptation. We show,first, that evolutionarily stable dispersal rates do not necessarily increase with rates for the local extinction of populations due to external disturbances in habitable patches. Instead, without demographic stochasticity, adapted dispersal rates exhibit a maximum for intermediate levels of disturbance and fall off for both higher and lower rates of local extinction. Second, we describe how the demographic stochasticity that inevitably occurs in finite populations affects the evolution of dispersal rates. Contrary to predictions from deterministic models, evolutionarily stable dispersal rates in metapopulations composed of small local populations can remain high even when rates of local extinction are low. The first pattern is shown to be robust, provided that demographic stochasticity is not too severe. under a range of local growth conditions, including logistic growth and its variants. We also demonstrate that high degrees of demographic stochasticity can enrich the behavior of adapted dispersal rates in response to varied levels of disturbance: monotonic increases or decreases can be observed as well as intermediate maxima or minima

Towards a governance perspective to mergers and acquisitions

The aim of the present study is to conceptually integrate insights from governance theories of the firm to the research area of mergers and acquisitions (M & A). The primary governance theories of the firm are understood to consist of the neoclassical view of the firm, the nexus of contracts perspective, agency theory, early incomplete contracting theory, transaction cost economics and property rights theory. This study uses a bipartite research agenda, consisting of conceptual and bibliometric methodologies to investigate two aspects of conceptual integration. Firstly, the role of the governance theories in the de facto structuring of the M & A discourse, with a focus on disciplinary research orientations, underlying theories and key antecedents to performing M & A research, is investigated. Secondly, the contribution of the governance theories to M & A in the form of interlinkages between the two discourses is analyzed. It is shown that the governance theories assume significant roles that vary vis-à-vis their importance and function within the M & A discourse. Based on various types of identified interlinkages between governance theoretical thinking and the M & A discourse, a novel, holistic governance perspective to M & A is presented. This perspective, consisting of an academically oriented exploratory mapping of the research field as well as a set of suggestions on how to apply governance theory into M & A decision-making, is intended to stimulate further integrative research in the area of M & A. Simultaneously, it demonstrates the usefulness of a general governance perspective to management research and highlights the need to consider governance not as an administrative exercise, but as an area of strategic decision-making.reviewe

Function-valued adaptive dynamics and optimal control theory

In this article we further develop the theory of adaptive dynamics of function-valued traits. Previous work has concentrated on models for which invasion fitness can be written as an integral in which the integrand for each argument value is a function of the strategy value at that argument value only. For this type of models of direct effect, singular strategies can be found using the calculus of variations, with singular strategies needing to satisfy Euler's equation with environmental feedback. In a broader, more mechanistically oriented class of models, the function-valued strategy affects a process described by differential equations, and fitness can be expressed as an integral in which the integrand for each argument value depends both on the strategy and on process variables at that argument value. In general, the calculus of variations cannot help analyzing this much broader class of models. Here we explain how to find singular strategies in this class of process-mediated models using optimal control theory. In particular, we show that singular strategies need to satisfy Pontryagin's maximum principle with environmental feedback. We demonstrate the utility of this approach by studying the evolution of strategies determining seasonal flowering schedules

Effective implementation of relationship orientation in new product launches

The critical role of relationships in business performance is widely recognized in the business marketing literature. However, to date, the prevailing new product launch research has concentrated on firms&#39; general customer and competitor focus on predicting launch performance, and mainly applied a product centered or marketing mix perspective on considering effective strategic and tactical launch activities. Consequently, there is only scant knowledge on the relevance of a relational perspective when launching new products. The study contributes to this gap by examining the impact of firms&#39; relationship orientation on launch performance and the key activities through which it is transformed into performance in the new product launch context. A set of hypotheses is developed and tested with data collected from 109 new product launches in pharmaceutical companies. The results show that sales force management and relationship leveraging mediate relationship orientation&#39;s impact on launch performance through complexly intertwined relationships. From a theoretical perspective, this study highlights the role of the relational perspective in new product launch and fosters our understanding on how relationship-focused culture is effectively implemented in practice. From a managerial perspective, the results offer insights on how firms can effectively enhance the successful commercialization of new products through relationship-oriented sales and marketing activities.</p

Extinction, Persistence, and Evolution

Extinction can occur for many reasons. We have a closer look at the most basic form, extinction of populations with stable but insufficient reproduction. Then we move on to competing populations and evolutionary suicide