Two projects with Dr. McCauley

My research focuses on Plant Systematics, encompassing a broad range of techniques involving field, herbarium, and molecular laboratory work. Most of my work focuses on the generation of phylogenetic, phylogeographic, and population genetic data to understand the origin and diversification of unique plant species or groups. Recently, much of this has focused on rare and endangered plants and generates key insights to help with conservation measures. For a summary of much of my recent work see my personal research webpage.

In this section of Senior Seminar, I want to focus on two different projects. One related to my long-time study of the systematics of the plant family Amaranthaceae, and the second on generating data needed by the New Mexico Endangered Plant Program to facilitate conservation of an endangered species in the north-central region of the state.

Unraveling the origin of the North American caespitose Gomphrena (Amaranthaceae)

The genus Gomphrena is a group of plants principally native to the tropics and subtropics of the western hemisphere. Most of the diversity of the genus, close to 100 species, is found in central South America. Between 8-15 species occur in North America with the distribution across Mexico and the American Southwest. Within the North American group, the most distinctive species is G. caespitosa (and the sometimes recognized G. viridis) restricted to southwestern New Mexico, southeastern Arizona, northeastern Sonora, and northwestern Chihuahua. These plants exhibit a caespitose form of growth – they grow hugging the desert soil in which they grow. My preliminary phylogenetic data indicate that these plants may not be as closely associated with the genus as we have suspected. This finding warrants expanded sampling and analysis. I will be making field collections of Gomphrena and other related Amaranthaceae this summer from southern Arizona and New Mexico and these samples can be combined with my earlier samples collected across Mexico to create a detailed phylogenetic analysis to investigate the evolutionary origin of these unique plants.

Opportunities associated with this project would involve DNA extraction from collected leaf samples, PCR amplification of multiple gene regions, DNA sequence analysis, and phylogenetic analysis. Morphological work using herbarium material from the University of Arizona and/or the University of New Mexico could be performed to understand the variation presented among different populations. This could also be expanded to analyze plant/environment interactions which may be related to phenotypic plasticity.

Verifying the species status of Santa Fe Cholla (Cylindropuntia viridiflora)

Cylindropuntia viridiflora is a New Mexico state endangered species with a range restricted around the cities of Santa Fe and Española. The species is extremely rare and seriously impacted by development. Due to this rarity the Santa Fe Botanical Garden maintains some individuals in ex situ conservation and the species is occasionally cultivated. Its species status however has been questioned. Some scientists feel it may simply be a hybrid between other more common members of the genus, C. imbricata and C. whipplei and the Flora of North America does not even recognize it as a species. The populations in the Santa Fe/Española area however, breed true and can easily be grown from seed, something not generally seen in hybrid-derived individuals. Another aspect of its biology is that C. viridifolia may be a human construct as it is often associated with ancient inhabitations.

For this project we will need to sample all the known sites of C. viridiflora in the Santa Fe/Española area and multiple populations of C. imbricata and C. whipplei from north-central New Mexico. Following sampling we will extract and purify DNA, perform PCR and generate DNA sequence data from a variety of chloroplast and nuclear genes. We will likely analyze this in a phylogeographc context. There may also be the potential to apply population genetic markers, specifically microsatellites, depending upon available funding. Students interested in working on this project would most likely have the opportunity to perform fieldwork for tissue collection. This work would be completed in August or September 2019 and be coordinated with personnel of the New Mexico Endangered Plant Program in Santa Fe.

Senior Sem Form