The shape of terrestrial abundance distributions

Area of Science:

• Ecology
• Biodiversity Science
• Theoretical Ecology

Background:

• Ecologists commonly assume species abundance distributions are flat but dominated by a few species.
• This assumption is based on several theoretical and empirical distribution models.
• Previous research has been limited to a few specific distribution types.

Purpose of the Study:

• To test the accuracy of existing theoretical distributions in predicting species abundance patterns.
• To identify a more accurate model for species abundance distributions across diverse communities.
• To explore the ecological mechanisms underlying species coexistence and abundance.

Main Methods:

• Analyzed 1055 ecological samples from various taxa (trees, mammals, birds, insects, etc.).
• Evaluated five existing theoretical distributions using Kullback-Leibler divergence.
• Proposed and supported a novel "double geometric" distribution model.

Main Results:

• Five common theoretical distributions inaccurately predicted species frequencies and overall patterns.
• The proposed "double geometric" distribution demonstrated a superior fit to empirical data.
• This new model incorporates finite richness and unequal resource competition in a multidimensional niche landscape.

Conclusions:

• Existing theoretical distributions are inadequate for describing species abundance patterns.
• The "double geometric" distribution offers a more accurate framework for understanding community structure.
• Multidimensional niche space and unequal competition are key factors enabling high species coexistence.