THE INFLUENCE OF TAXONOMIC LEVEL ON BIOGEOGRAPHIC PATTERNS

Identifying organisms to the species level is a common practice in ecology when conducting community analyses. However, because species-level identification is not always feasible, higher level taxonomic identifications are often used as surrogates. Numerous modern studies have demonstrated that supraspecific identifications capture the same community structure that is seen using species-level identification, but the majority of these studies have been performed using benthic macroinvertebrates. Studies examining community analyses based on validity of higher level taxonomic identification of vertebrates are rare. This study tests the validity of supraspecific identification in the analysis of the biogeography of modern terrestrial vertebrates from 16 national parks in the Northern Colorado Plateau using Nonmetric Multidimensional Scaling.

Results show that taxonomic level (species, genus, and family) does not substantially influence the major biogeographic patterns in this case. The robustness of the ordination patterns is even more evident with the removal of avian taxa (56-69%) or rare taxa (20 to 70%). However, similarities in the ordination patterns at different taxonomic levels could occur because all higher taxa are ubiquitous and variation is between congeneric species or cofamilial genera. To assess this, taxon richness at each taxonomic level were cross-plotted. Results show that the correlation slope between diversity at two taxonomic levels were statistically significant and positive, thus indicating that higher taxa are not ubiquitous.

The results of this study demonstrate that taxonomic level need not influence the pattern of regional biogeographic relationships among sites. While the results of this study have direct applications to regional biogeographic studies of modern vertebrates, especially with respect to the management and preservation of vertebrate communities, the implications of these results are especially exciting for the fossil record, since many fossil taxa can only be identified to the family-level due to poor preservation or poor understanding of a group’s systematics. The results of this study suggest that even such limited data can provide useful information on biogeography in Earth's past and how it has changed through time.