Randy Smallís Research Interests

Randy Small’s Research Interests

Plant Molecular Systematics


The field of molecular systematics uses data from DNA sequences to analyze relationships among species. An understanding of relationships among species allows systematists to produce useful taxonomic classification systems, as well as to study biologically important phenomena such as the evolution of morphological characters, biogeography, and speciation mechanisms.

Plant cells have three different genomes that contain information that could be exploited to analyze species relationships: the chloroplast, mitochondrial, and nuclear genomes. These three different genomes differ greatly in size, structure, and evolutionary rate. Thus, different genomes may be useful for different kinds of systematic studies. Plant molecular systematic studies have relied primarily on data from the chloroplast genome, as well as from ribosomal DNA sequences of the nuclear genome. The remainder of the nuclear genome, however, has been left relatively unexplored by molecular systematists, primarily because of the more complex genetic architecture of the nuclear genome.

Part of my research interests are in exploring the utility of nuclear genes for systematic studies. In particular, I am focusing on two gene families: the alcohol dehydrogenase (Adh) gene family; and the granule-bound starch synthase (GBSSI) gene family. The plant family I work in is Malvaceae, and in particular I am interested the cotton genus (Gossypium), and in the large and heterogeneous genus Hibiscus.

In Gossypium, Adh sequences have proven to be extremely useful in some cases, providing significantly more information than either chloroplast or ribosomal DNA sequences. In other cases, Adh sequences provide relatively similar levels of resolution when compared to other sequences. With funding from the National Science Foundation I am beginning to explore the phylogenetic utility of the Adh gene family in Hibiscus section Furcaria (a circumtropical section with 200+ species) as well.

Studies of the GBSSI gene family in Malvaceae are in the preliminary stages, but initial data from Gossypium and Hibiscus section Muenchhusia (the North American Rose Mallows) suggest that GBSSI is likely to be a good tool for unravelling species-level phylogenetic questions. I am in the process of characterizing the GBSSI gene family from a collection of species that represent all of the tribes of the Malvaceae to determine the generality and limits of its usefulness.

Systematics Papers