33 research outputs found
Nested species interactions promote feasibility over stability during the assembly of a pollinator community
The foundational concepts behind the persistence of ecological communities have been based on two ecological properties: dynamical stability and feasibility. The former is typically regarded as the capacity of a community to return to an original equilibrium state after a perturbation in species abundances and is usually linked to the strength of interspecific interactions. The latter is the capacity to sustain positive abundances on all its constituent species and is linked to both interspecific interactions and species demographic characteristics. Over the last 40 years, theoretical research in ecology has emphasized the search for conditions leading to the dynamical stability of ecological communities, while the conditions leading to feasibility have been overlooked. However, thus far, we have no evidence of whether species interactions are more conditioned by the community's need to be stable or feasible. Here, we introduce novel quantitative methods and use empirical data to investigate the consequences of species interactions on the dynamical stability and feasibility of mutualistic communities. First, we demonstrate that the more nested the species interactions in a community are, the lower the mutualistic strength that the community can tolerate without losing dynamical stability. Second, we show that high feasibility in a community can be reached either with high mutualistic strength or with highly nested species interactions. Third, we find that during the assembly process of a seasonal pollinator community located at The Zackenberg Research Station (northeastern Greenland), a high feasibility is reached through the nested species interactions established between newcomer and resident species. Our findings imply that nested mutualistic communities promote feasibility over stability, which may suggest that the former can be key for community persistence
A structural approach for understanding multispecies coexistence
Although observations of species-rich communities have long served as a primary motivation for research on the coexistence of competitors, the majority of our empirical and theoretical understanding comes from two-species systems. How much of the coexistence observed in species rich communities results from indirect effects among competitors that only emerge in diverse systems remains poorly understood. Resolving this issue requires simple, scalable, and intuitive metrics for quantifying the conditions for coexistence in multispecies systems, and how these conditions differ from those expected based solely on pairwise interactions. To achieve these aims, we develop a structural approach for studying the set of parameter values compatible with n-species coexistence given the geometric constraints imposed by the the matrix of competition coefficients. We derive novel mathematical metrics analogous to stabilizing niche differences and fitness differences that measure the range of conditions compatible with multispecies coexistence, incorporating the effects of indirect interactions emerging in diverse systems. We show how our measures can be used to quantify the extent to which the conditions for coexistence in multispecies systems differ from those that allow pairwise coexistence, and apply the method to a field system of annual plants. We conclude by presenting new challenges and empirical opportunities emerging from our structural metrics of multispecies coexistence
Stochastic Dynamical Structure (SDS) of Nonequilibrium Processes in the Absence of Detailed Balance. IV: Emerging of Stochastic Dynamical Equalities and Steady State Thermodynamics from Darwinian Dynamics
This is the fourth paper, the last one, on solution to the problem of absence
of detailed balance in nonequilibrium processes. It is an approach based on
another known universal dynamics: The evolutionary dynamics first conceived by
Darwin and Wallace, referring to as Darwinian dynamics in the present paper,
has been found to be universally valid in biology; The statistical mechanics
and thermodynamics, while enormously successful in physics, have been in an
awkward situation of wanting a consistent dynamical understanding; Here we
present from a formal point of view an exploration of the connection between
thermodynamics and Darwinian dynamics and a few related topics. We first show
that the stochasticity in Darwinian dynamics implies the existence temperature,
hence the canonical distribution of Boltzmann-Gibbs type. In term of relative
entropy the Second Law of thermodynamics is dynamically demonstrated without
detailed balance condition, and is valid regardless of size of the system. In
particular, the dynamical component responsible for breaking detailed balance
condition does not contribute to the change of the relative entropy. Two types
of stochastic dynamical equalities of current interest are explicitly discussed
in the present approach: One is based on Feynman-Kac formula and another is a
generalization of Einstein relation. Both are directly accessible to
experimental tests. Our demonstration indicates that Darwinian dynamics
represents logically a simple and straightforward starting point for
statistical mechanics and thermodynamics and is complementary to and consistent
with conservative dynamics that dominates the physical sciences. Present
exploration suggests the existence of a unified stochastic dynamical framework
both near and far from equilibrium.Comment: latex, 49 page
Integrated systems analysis at PIK: A brief epistemology
SIGLEAvailable from FIZ Karlsruhe / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman
Qualitative analysis of a diffusive prey-predator model with trophic interactions of three levels
10.3934/dcdsb.2012.17.127Discrete and Continuous Dynamical Systems - Series B171127-15