Documenting Cmpleteness, Species‐Area Relations, and the Species‐Abundance Distribution of a Regional Flora

Abstract

Four data sets containing randomly distributed species observations were computer generated. Each data set was characterized by a different species—abundance distribution: (1) the distribution of rare vascular plants in the southern Appalachians, (2) a uniform distribution, (3) a Poisson distribution, and (4) a truncated lognormal distribution. A computerized sampling methodology (miller 1986) recorded the statistically significant and unique species—area relations distinguishing each data set. The most robust species–are relations (i.e., highest r2 adjusted values) typified the rare southern Applachian plant distribution and the truncated canonical lognormal distribution. A method is presented for obtaining a reliable estimate of the total number of species characterizing a taxonomic group within a region. This method is based on analyses of the accumulation of new species vs. The accumulation of observations recorded from a sampling of each of the data sets. A statistically robust negative exponential model was fitted to each of these accmulation distributions. From this model, 195 rare vascular plant species were predicted to inhabit the central southern Appalachians region. This estimate was in close agreement with the actual total of 188 species determined from 150 yr of field observations. Thus, this method of fitting the data from a set of species observations to the negative exponential model provided an estimate of the total number of species for a taxonomic category (rare vascular plants) and a region (southern Appalachians).