Paper 1

Macroecology: the division of food and space among species on continents. 1989. Science 243:1145-50.

Blurb Authors: James H. Brown and Brian A. Maurer

James H. Brown: 

• PhD from University of Michigan, 1967
• Emeritus Distinguished Professor of Biology, University of New Mexico
• Research Interests:  "Science is driven by curiosity about the diversity of life." Conducts research in biogeography, scaling and metabolic theory of ecology, macroecology, and biocomplexity.
• current whereabouts: retired to Monterey Bay, CA

Brian A. Maurer

• PhD from University of Arizona
• Professor in Department of Geography and Department of Fisheries and Wildlife at Michigan State University
• Research Interests: "My interest focuses on the largest spatial and longest temporal scales studied by ecologists.  To understand the importance of processes at geographical scales, it is important to understand how they connect to local scale processes.  Thus, I am interested in modeling population and community dynamics in a geographical context. "

Paper Authors: James H. Brown and Brian A. Maurer - (see above)

Summary/Main points

1. Main Question: 

• background: They were interested in trying answer questions about the abundance and distribution of birds in an area where field work wasn't really a good option. They realized that new datasets that were being published would allow them to ask questions about bird abundance and distributions in a different way that didn't rely on field work.

• They were also interested in understanding how to compare among small scale and experimental approaches to understand which were demonstrating general rules in ecology and which were simply unique to a particular study system.

• assumptions: data are ecologically relevant.
• body mass tells you something about the energetic requirements of an organism, 
• local population density is an accurate measure of the number of individuals that can be sustained in a given area, 
• size/shape of species range is an accurate representation of their distribution.

• main question: What are the processes that characterize the assembly of continental biotas of mammals and birds in North America? How are "the physical space and nutritional resources of large areas divided among diverse species?"

2. Methods:

• data: 
• study organisms: NA breeding land birds and nonvolant mammals
• traits: body size, local population density, area and shape of geographic range

• methods: 
• multivariate analyses
• compare among many species 
• define sets of species taxonomically - this helps control for phylogenetic effects, but ignores others such as ecological interactions - trophic interactions, competition, etc. 
• examined relationships among the traits for birds and mammals (e.g., body size distributions, relationship between population density and body mass, geographic range size and body mass, energy use and body mass, dispersal distance and body mass, and range shape).

3. Results: 

• body size patterns:
• birds and mammals have similar body size distributions: right-skewed, unimodal, with a mode between 50 and 100 g
• shape of body size distributions flattens with smaller spatial scales (shown with mammals only)
• geographic range area is related to body size, only small species have small ranges, large species have large ranges
• population density scales with body size in two ways: species <100g show a decrease in population density with size, species >100 g show a decrease in population density with size, peak occurs around 100 g.
• relative energy use increases with body size

• geographic range size/shape: 
• In North America, small ranges are elongated north-south
• In North America, large ranges are elongated east-west
• different pattern for Europe

4. Conclusions/Inference

• body size patterns:
• small bodied species should be more specialized than large bodied species
• this pattern is a result of energetic constraints
• interspecific competition drives changes in shapes of body size distributions at different spatial scales
• large bodied species are more vulnerable to extinction over long time scales

• geographic range size/shape: 
• species with small ranges are limited by habitat and topographic features
• species with large ranges are limited by climate and biomes.

5. Questions: 

1. How does this differ from traditional ecology?
2. What did you think about the way they built a case and made inferences rather than setting up experiments to test hypotheses?
3. How might you test the 3 hypotheses they outline for body size patterns?