Vascular Plant and Vertebrate Species Richness in National Parks of the Eastern United States

Abstract

Given the estimates that species diversity is diminishing at 50-100 times the normal rate, it is critical that we be able to evaluate changes in species richness in order to make informed decisions for conserving species diversity. To contribute to the ongoing analysis of species richness relationships, I examined the potential of vascular plant species richness to be used as a surrogate for vertebrate species richness in the classes of amphibians, reptiles, birds, and mammals. Vascular plants, as primary producers, represent the biotic starting point for ecological community structure and are a logical starting point for understanding vertebrate species associations. I used data collected by the United States National Park Service (NPS) on species presence within parks in the eastern United States to estimate simple linear regressions between plant species richness and vertebrate richness. Because environmental factors in addition to plant species richness influence species diversity, I included simple linear regressions of total park area, park latitude, mean annual precipitation, mean annual temperature, and human population density surrounding the parks for estimating species richness relationships. I then combined plant species richness and the environmental variables in multiple regressions to determine the variables that remain as significant predictors of vertebrate species richness. To test whether there are differences in species richness patterns among Inventory and Monitoring networks of NPS, I used an analysis of covariance (ANCOVA) which included park area and plant species richness as covariates. I detected significant relationships between plant species richness and amphibian, bird, and mammal species richness. In multiple regressions, plant species richness was predicted by park area alone. Species richness of mammals was related to plant species richness and weakly to park area. Reptile species richness was related to park area and latitude, and amphibian species richness was related to plant species richness, park area, and latitude. Differences among networks were only statistically detected in the bird species richness ANCOVA, and interaction of park area and the networks was detected for all taxa species richness except for mammals. Plant species richness predicts spiecies richness of different vertebrate groups to varying degrees, and should not be exclusively used as a surrogate for vertebrate species richness. Plant species richness should be included with other variables such as sample area and climate when considering strategies to manage and conserve species richness in National Parks in the eastern United States. Based on the ANCOVA results it is recommended that park management of biodiversity be approached from the local and site specific criteria rather than applying management directives derived from different regions of the United States.