Stephen Stern

Assistant Professor


Department of Biological Sciences
1100 North Avenue
Colorado Mesa University
Grand Junction, CO 81501

phone: (970) 248-1674

sstern at coloradomesa dot edu


Stephen Stern


In the Bohs Lab I have been working on the taxonomy and phylogenetics of the genus Solanum through a variety of projects. These include creating phylogenies for the Geminata clade and the Old World spiny Solanum clade, revising section Gonatotrichum, and my PhD project, which focused on the section Micracantha.

I began my lab work on creating a molecular phylogeny of section Geminata with a collaborator from Colombia, Juan Carlos Granados Tochoy. This project is an effort to clarify the relationships within this very diverse group of Neotropical plants, and is meant to complement the excellent monograph produced by our collaborator Sandra Knapp at the British Museum. This monograph, combined with a molecular phylogeny, will make this group, which has been described as “remarkably uniform on the herbarium sheet”, more accessible to study. This study has confirmed the monophyly of section Geminata and has clarified the placement of certain troublesome taxa.


Solanum maturecalvans
Solanum maturecalvans- A Bolivian member of section Geminata.


I have also helped to construct a molecular phylogeny of the large Old World spiny Solanum clade. I have been obtaining molecular sequences to build on work done by Levin et al (2006). The major focal points of this study are to resolve the relationships between Old World taxa to see if clades correspond to geographic areas. The phylogeny is also being used to explore the evolution of breeding systems in the genus. Solanum is one of the few plant groups that contains hermaphroditic, andromonoecious, and dioecious species. Using our phylogeny we are investigating the evolution of these various floral systems.

I have also been working on a revision of section Gonatotrichum. This is a small section of herbaceous species in Central and South America that are unique in Solanum because the fruits have exploding dehiscence. There was thought to be only two species in the section, however it appears that there are new species. Additionally, the elbow-shaped hairs that were thought to be a synapomorphy for the group appear to be lacking in many of the species. There is also a change in names as the name S. adscendens has been misapplied to a widespread Bolivian species and should be applied to a geographically restricted Brazilian species.


Solanum turneroides

Solanum turneroides- A member of section Gonatotrichum with
exploding fruits and heteranthery or unequal stamen length.


Finally, for my dissertation I am focusing on Solanum section Micracantha, which is a group of vines that climb using recurved prickles. The group is found throughout the Neotropics from Southern Florida, through Central and South America to its southern limits in Bolivia. While the Central American species are better understood, there are many understudied species in South America, especially species endemic to Brazil. I am currently working on a phylogeny to resolve the relationships within the section and relationships between Micracantha and other spiny Solanum sections with which Micracantha species are often confused. To clarify these relationships my work will focus both on taxonomic and phylogenetic methods. 


Solanum arachnidanthum- A rarely collected species from
Northern Bolivia and adjacent areas of Brazil.



Stern, S.R. and L. Bohs. 2009. Two new species of Solanum from Ecuador and new combinations in Solanum section Pachyphylla (Solanaceae).Journal of the Botanical Research Institute of Taxas 3: 503-510. PDF

Stern, S.R., E.J. Tepe and L. Bohs. 2008. Checklist of Solanum of north-central Peru, a hot spot of biological diversity. Arnoldoa 15: 277-284. PDF

Bohs, L., T. Weese, N. Myers, V. Lefgren, N. Thomas, and S. Stern. 2007. Zygomorphy and heterandry in Solanum in a phylogenetic context. In L. Bohs, J. Giovanni, R. Olmstead, D. Shibata, and D. Spooner [eds.] Solanaceae VI: Genomics Meets Biodiversity, Madison, Wisconsin. PDF