Characteristics of temporal changes in communities where dynamics differ between species

Abstract

Communities with different phenotypic variation among species can have identical species abundance distributions, although their temporal dynamics may be very different. By using stochastic species abundance models, both the lognormal and beta prime abundance distributions can be obtained with either homogeneous or heterogeneous dynamics among species. Assuming that anthropogenic activity disturbs the communities such that species' carrying capacities are decreasing deterministically, the structure of the communities are studied using simulations. In order to construct homogeneous communities with reasonable variation in abundance, the parameter values describing the dynamics of the species can be unrealistic in terms of long return times to equilibrium. Species in heterogeneous communities can have stronger density regulation, while maintaining the same variation in abundance, by assuming heterogeneity in one of the dynamical parameters. The heterogeneity generates variation in carrying capacity among species, while reducing the temporal stochasticity. If carrying capacity decreases, changes in community structure occur at a much slower rate for the homogeneous compared to the heterogeneous communities. Even over short time periods, the difference in response to deterministic changes in carrying capacity between homogeneous and heterogeneous community models can be substantial, making the heterogeneous model a recommended starting point for community analysis.

Keywords: Beta prime species abundance distribution; Beverton–Holt density regulation; Community dynamics; Environmental stochasticity; Lognormal species abundance model; Time dependent parameters.