Fluctuating Growth Rates Link Turnover and Unevenness in Species-Rich Communities

Area of Science:

• Ecology
• Theoretical Ecology
• Community Ecology

Background:

• Species-rich communities exhibit constant diversity maintenance, rarity, and compositional turnover.
• Understanding the drivers of these community features is crucial for ecological theory.

Purpose of the Study:

• To investigate how environmental stochasticity, competition, and dispersal interact to maintain diversity in species-rich communities.
• To explore the relationship between community statistics, species abundance distributions, and turnover dynamics.

Main Methods:

• Development and analysis of a minimal ecological model.
• Examination of the interplay between environmental stochasticity, intra- and interspecific competition, and dispersal.
• Analysis of species abundance distributions and their variation across a parameter plane.

Main Results:

• Environmental fluctuations can drive communities towards unevenness and extinction, but self-limitation and dispersal sustain species-rich states.
• Species abundance distributions show systematic variations related to the strength of ecological processes, exhibiting power-law and unimodal shapes.
• A focal species dynamics model links static abundance distributions with turnover dynamics, even with differing mean fitness.

Conclusions:

• Self-limitation and dispersal are key mechanisms for sustaining biodiversity against environmental stochasticity.
• Community statistics and species time series data can elucidate the relative importance of ecological processes structuring biodiversity.