Aberrant Plant Diversity in the Purgatory Watershed of Southeastern Colorado and Northeastern New Mexico

Abstract

Despite a dearth of biological study in the area, the Purgatory Watershed concentrated in southeastern Colorado and northeastern New Mexico is home to a number of unique land formations and endemic organisms. At onetime nonarable land where Dust Bowl storms of the 1930s originated, the Purgatory Watershed is presently home to the Comanche National Grasslands, the Picketwire Canyonlands, and the expansive Pinon Canyon Maneuver Site. The Purgatory Watershed is composed of deep canyons, eroded mesas, and extensive intact shortgrass plains, and is located at a crossroads of the biodiversity of the Southern Rocky Mountains, Great Plains, and Chihuahuan Desert. Here we describe 2 anomalous populations of 2 plant species, prompted by observation of these and several additional, unrelated plants marked by morphologically aberrant forms in this watershed. Specifically, we described morphology of and generated sequence data for Amorpha nana (Fabaceae) and Tetraneuris acaulis (Asteraceae) to assess potential differences between Purgatory populations of these plants and populations from elsewhere across their ranges. Morphometric data from Purgatory and non-Purgatory populations of these 2 unrelated species were collected from specimens housed at herbaria. Similarly, molecular data from Purgatory and non-Purgatory populations of these 2 species, plus near outgroups, were generated from herbarium collections to reconstruct phylogenetic relationships within each species complex. Maximum likelihood bootstrap analysis recovered moderate support for a clade of aberrant A. nana, indicating the presence of a distinct Purgatory lineage of A. nana, which was also supported by our morphological data. In contrast, insufficient phylogenetic signal and morphological results in our Tetraneuris data set yielded unresolved relationships between aberrant and nonaberrant forms. The Purgatory Watershed is a biologically unique region hosting marked biodiversity in numerous groups, despite having been the focus of little prior research.