Understanding diversity–stability relationships: towards a unified model of portfolio effects

Abstract

A major ecosystem effect of biodiversity is to stabilise assemblages that perform particular functions. However, diversity–stability relationships (DSRs) are analysed using a variety of different population and community properties, most of which are adopted from theory that makes several restrictive assumptions that are unlikely to be reflected in nature. Here, we construct a simple synthesis and generalisation of previous theory for the DSR. We show that community stability is a product of two quantities: the synchrony of population fluctuations, and an average species-level population stability that is weighted by relative abundance. Weighted average population stability can be decomposed to consider effects of the mean-variance scaling of abundance, changes in mean abundance with diversity and differences in species' mean abundance in monoculture. Our framework makes explicit how unevenness in the abundances of species in real communities influences the DSR, which occurs both through effects on community synchrony, and effects on weighted average population variability. This theory provides a more robust framework for analysing the results of empirical studies of the DSR, and facilitates the integration of findings from real and model communities.

Plankton Community Stability and Its Relationship with Phytoplankton Species Richness in Lake Nansihu, China

“…The temporal stability indices (TSI) of different phytoplankton and zooplankton taxa were measured as the coefficient of variation (the variance in a time series of biomass related to the mean value), which is widely used in ecology [12,14,15]. The index was calculated using the following equation [12,14,15].…”

“…These aspects of stability may respond differently to variations in diversity caused by extinction or invasion [9][10][11]. Among all of these measures of stability, temporal stability is an important one and has drawn much attention [12][13][14][15]. The potential underlying mechanisms of the diversity-stability relationship include overyielding, the portfolio effect and species asynchrony [12,[16][17][18][19][20][21].…”

Effects of Environmental Factors on the Temporal Stability of Phytoplankton Biomass in a Eutrophic Man-Made Lake

“…The temporal stability index (TSI) of phytoplankton biomass was measured as the coefficient of variation (the variance in a time series of biomass related to the mean value), which is widely used in ecology [29,31]. The index was calculated using the following equation [29,31]:…”

“…Among all of the measures of stability, temporal stability is an important one and has drawn much attention [29][30][31]. Ecologists have defined the temporal stability of a community as the coefficient of variation-i.e., the variance in a time series of biomass related to the mean value [29,31].…”

“…Ecologists have defined the temporal stability of a community as the coefficient of variation-i.e., the variance in a time series of biomass related to the mean value [29,31]. Therefore, there are two components in calculating the temporal stability of a community: the temporal mean and temporal variability of biomass.…”