Endemics and Cosmopolitans: Application of Statistical Mechanics to the Dry Forests of Mexico.

Michael G Bowler,Colleen K Kelly

doi:10.3390/e21060616

Abstract

Data on the seasonally dry tropical forests of Mexico have been examined in the light of statistical mechanics. The results suggest a division into two classes of species. There are drifting populations of a cosmopolitan class capable of existing in most dry forest sites; these have a statistical distribution previously only observed (globally) for populations of alien species. We infer that a high proportion of species found only at a single site are specialists, endemics, and that these prefer sites comparatively low in species richness.

Highlights

The techniques of statistical physics have been applied to problems of community structure with some success, primarily in achieving an understanding of the principles underlying the rather universal form of the species abundance distribution
In [5] it is speculated that similar principles may apply more generally to community assembly, for there are examples of the number of species with the number of sites occupied being distributed exponentially in populations of heteroflagellates and of tree species in the seasonally dry tropical forests of Mexico
In [9] a species abundance distribution for estuarine fish was decomposed into a sum of two popular forms; here we have examined, not a species abundance distribution, but several distributions characterizing the abundance of species

Summary

Introduction

The techniques of statistical physics have been applied to problems of community structure with some success, primarily in achieving an understanding of the principles underlying the rather universal form of the species abundance distribution This is traced to the rate of change of a population being proportional to the number of individuals each species contains [1,2,3,4]. Having clarified in [6] the roles of the alien species’ exponentials, we have returned to the dry forests of Mexico, where the data [7] contain the exponential distribution of the number of species with the number of sites (which first drew our attention), and list the number of species at each site, and beyond that the number of species common to each pair of sites These three aspects of the data set are explained by a category of cosmopolitan species, distributed in accord with the model for alien species, and in addition, a category of specialists, endemic species found preferentially at high rank sites, i.e., those that are relatively species poor

The Underlying Model

Relevant

Disentangling the Conundrum

Discussion and Conclusions