Research Scientist, Rancho Santa Ana Botanic Garden
Professor of Botany, Claremont Graduate University
Systematics of grasses (Gramineae)
My research involves the evolutionary biology and taxonomy of grasses (Gramineae), especially Chloridoideae, a subfamily of some 1400 warm-season, mostly subtropical and tropical species. My goals are to discover the phylogenetic relationships among the taxa, improve the classification, and learn about the evolution of traits, especially inflorescence architecture, breeding system, leaf anatomy, and photosynthetic pathway.
Employing DNA sequences from the nuclear and chloroplast genomes, my collaborators and I are estimating phylogenetic relationships both across Chloridoideae, by sampling many genera, and within genera, by sampling all species and intraspecific taxa. In the latter case, we have sampled all species of Bouteloua (grama grasses), a New World (predominantly North American) genus of 57 species, and are pursuing Muhlenbergia (muhly grasses), which comprises 147 species and has a similar geographic distribution. The grama grass research began with a study of Bouteloua sensu stricto and nine satellite genera (comprising a subtribe, Boutelouinae, in part). Concordance between the nuclear and plastid phylogenies led to taxonomic expansion of Bouteloua to include the satellites and render the genus monophyletic. Interestingly, these data point to a multiple origin of sexually dimorphic spikelets within the genus, and a trend towards fewer-flowered, deciduous inflorescence branches.
My approach to systematics is grounded in molecular phylogenetics and generous taxon sampling. Good sampling of taxa and analyses of DNA sequences from multiple genomes lead to robust estimates of organismal phylogeny. From these phylogenies, improvements to the classification can be made and a better understanding of trait evolution gained. I am a strong believer in field studies, not only to collect material (pressed specimens, seeds, and pickled material for anatomical study) for laboratory and greenhouse studies, but to gain knowledge of populations and their habitats.
I enjoy collaborating with hard-working, motivated students, no matter what group of plants interests them, who desire broad-based education and research experiences that include field studies, morphology, anatomy, chromosome biology, phylogenetics, taxonomy, and geography.
Ph. D., University of California, Berkeley, Department of Integrative Biology, 1996
M. S., New Mexico State University, Department of Animal and Range Sciences, 1988
B. S., New Mexico State University, Department of Animal and Range Sciences, 1986
Recent courses taught:
Agrostology (study of grasses)
Principles of Plant Systematics
Columbus, J. T., and N. F. Refulio-Rodriguez. 2004. The chromosome number of Schaffnerella gracilis (Gramineae, Chloridoideae). Aliso 21: 31–32.
Kinney, M. S., J. T. Columbus, and E. A. Friar. 2003. Molecular evolution of the maize sex-determining gene TASSELSEED2 in Bouteloua (Poaceae). Molecular Phylogenetics and Evolution 29: 519–528.
Columbus, J. T., H. L. Bell, R. Cerros-Tlatilpa, M. P. Griffith, and J. M. Porter. 2002. Schaffnerella rediscovered! (Gramineae, Chloridoideae). Aliso 20: 45–50.
Roalson, E. H., J. T. Columbus, and E. A. Friar. 2001. Phylogenetic relationships in Cariceae (Cyperaceae) based on ITS (nrDNA) and trnT-L-F (cpDNA) region sequences: Assessment of subgeneric and sectional relationships in Carex with emphasis on section Acrocystis. Syst. Bot. 26: 318–341.
Columbus, J. T., M. S. Kinney, M. E. Siqueiros D., and J. M. Porter. 2000. Phylogenetics of Bouteloua and relatives (Gramineae: Chloridoideae): Cladistic parsimony analysis of internal transcribed spacer (nrDNA) and trnL F (cpDNA) sequences, pp. 189–194. In S. W. L. Jacobs and J. Everett [eds.], Grasses: Systematics and Evolution. CSIRO Publishing, Melbourne, Australia.
Columbus, J. T. 1999. Morphology and leaf blade anatomy suggest a close relationship between Bouteloua aristidoides and B. (Chondrosium) eriopoda (Gramineae: Chloridoideae). Syst. Bot. 23: 467–478.
Columbus, J. T. 1999. An expanded circumscription of Bouteloua (Gramineae: Chloridoideae): New combinations and names. Aliso 18: 61–65.
Roalson, E. H., and J. T. Columbus. 1999. Glume absence in the Orcuttieae (Gramineae: Chloridoideae) and a hypothesis of intratribal relationships. Aliso 18: 67–70.
Columbus, J. T., M. S. Kinney, R. Pant, and M. E. Siqueiros D. 1998. Cladistic parsimony analysis of internal transcribed spacer region (nrDNA) sequences of Bouteloua and relatives (Gramineae: Chloridoideae). Aliso 17: 99–130.
Peterson, P. M., and J. T. Columbus. 1997. Allelic variation in the amphitropical disjunct Scleropogon brevifolius (Poaceae: Eragrostideae). BioLlania, Edicíon Especial 6: 473–490.
Columbus, J. T. 1996. Bouteloua chihuahuana (Gramineae), a new nomenclatural combination. Aliso 14: 227.
Present and former graduate students:
Vanessa E. T. M. Ashworth (Ph. D., 1999)
Hester L. Bell (Ph. D. Candidate)
Rosa Cerros Tlatilpa (Ph. D., 2004)
Naomi S. Fraga (M. S., 2005)
Elizabeth A. Kempton (Ph. D. student)
Gilberto A. Ocampo-Acosta (Ph. D. student)
Nancy F. Refulio Rodriguez (Ph. D. Candidate)
Eric H. Roalson (Ph. D., 2000)
Maria Elena Siqueiros Delgado (Ph. D., 2001)