PARENT SESSION
Oral Session #74: Spatial Ecology: Models and Methods. Presiding: C. Loehle.
Friday, August 10, 2001. 8:00 AM to 11:30 AM. Hall of Ideas E.

The random placement model as a null model of four well-known biogeographic patterns.

Veech, Joseph¹, ¹

ABSTRACT- The random placement model specifies the probability that a given species occurs on a given island (or habitat patch) based on the relative area of the island and the abundance of that species on all islands. In effect, the model describes the random distribution of individuals. Since its introduction more than 20 years ago, the random placement model has mostly been used in the analysis of species-area relationships. However, it can also be used to derive the species presence/absence matrix, the fundamental unit in the analysis of ecological patterns such as the nestedness of species subsets and species co-occurrence. In addition, the random placement model can aid in analyses of the distribution-abundance relationship and the relationship between local and regional species richness. I discuss the ways in which the model can be used in analyses of all four patterns. The random placement model provides the null or expected pattern against which to compare the observed pattern. In cases where the observed pattern is not significantly different from the null pattern, one can conclude that the random distribution of individuals (and species) explains the observed pattern. Obtaining such a result will lead ecologists and biogeographers into a greater appreciation for the role of randomness in producing apparently structured ecological patterns.

KEY WORDS: random placement model, null model, nestedness, species distribution