Paper 18 - K. Sullivan

Brown J.H. and P.F. Nicoletto. 1991. Scaling of species composition – body masses of North American land mammals. American Naturalist 138:1478-1512.

Blog by Kaitlyn Sullivan                                 

Paper Authors: James H. Brown & Paul F. Nicoletto

(Commentary by Felisa A. Smith)

James H. Brown                

·       Professor of Biology at the University of New Mexico

·       Bachelor of Arts, Zoology, 1963, Cornell University

·       Ph.D., Zoology, 1967, University of Michigan

Research Interests:

“Community ecology and biogeography, with special projects on granivory in desert ecosystems; biogeography of insular habitats; and structure of dynamics of geographic-scale assemblages of many species.”

Department of Biology at UNM, http://biology.unm.edu/core-faculty/brown.shtml

Paul F. Nicoletto

·       Professor and Chair of the Department of Biology at Lamar University

Research Interests:

”Dr. Nicoletto is a behavioral ecologist interested in animal communication and mating systems. His primary interests are in the physiological costs of ornamentation and courtship behavior and their relationship to male physical condition. A current project in development is assessing sound production in pupfish and its use in mating displays. He is also working on survey of reptiles and amphibians in Village Creek State Park.”

Paul F. Nicoletto. (n.d.). Retrieved February 28, 2017, from https://artssciences.lamar.edu/biology/faculty-staff/paul-f-nicoletto.html

Felisa A. Smith

·       Professor of Ecology and Evolutionary Biology at the University of New Mexico

Research Interests:

“Paleoecological and evolutionary research; effects of current global and past climatic change on mammals”.

F.A. Smith. (n.d.). Retrieved March 01, 2017, from https://biology.unm.edu/core-faculty/smith.shtml

Summary

In this paper, Brown and Nicoletto used the body mass of organisms to examine patterns “of mammalian communities across varying spatial scale”.  Through their research, they found that “at a local level, the body size structure of communities appeared to be uniform on a logarithmic scale”.  Significant differences in mean, median, and skew suggested that the species coexisting within a local site, are a nonrandom subset from the regional species pool.  This also implies that there is a limited number of species from each body size that can coexist in the same location at the same time.

                  In their abstract, they propose a mechanistic hypothesis, stating “we hypothesize that three mechanisms are necessary and possibly sufficient to produce this result:

1.     Competitive exclusion of species of similar size within local habitats

2.     Differential extinction if species of large size with small geographic ranges

3.     Greater specialization of modal-sized species owing to energetic and dietary constraints”.

 This hypothesis is based off the observed pattern of assembly among North American terrestrial mammals which “indicates that species of modal size (20-250 g) tend not to coexist in local habitat patches and they replace each other more frequently from habitat to habitat across the landscape than species of relatively large or small size”.

                  To test the variations in the distributions of body sizes among species in regards to spatial scale, the frequency distributions for three scales, the entire continent of North America, regional biomes, and local habitat patches. 

                  They concluded “that the processes for operating over a wide range of spatial scales ---- from interspecific interactions that affect coexistence within local habitats to colonization, speciation, and extinction events that affect the distribution of species over the continent --- interact to determine the composition of the biota at all scales from local to continental”.

Questions

How has this model influenced current conservation strategies?