Image of the Library Building

Dennis Wm. Stevenson

Senior Curator Emeritus
Editor, Botanical Review

Ph.D., University of California
Davis, 1975


Cycadales (Cycads)


Cycads, Monocots, Genomics

Research locations

neotropics, worldwide


My major research interests in the past few years have focused upon the evolution and classification of the Cycadales (cycads) and their placement in seed plant phylogeny. To this end I am conducting research on various facets of the biology of the Cycadales and Gnetales. These facets include reproductive biology, anatomy, cytology, molecular systematics, as well as taxonomic monographs and treatments of these groups for various floras being prepared for the neotropics. These research interests are being pursued by an active field program, particularly in the neotropics, to survey population sizes and demographics, to understand phenology, to study the recently discovered insect pollination biology of cycads and Gnetum. As part of this field program, live plants are also collected for laboratory research and for breeding purposes in order to try to save the cycads from extinction. I have recently expanded the scope of this program to include the paleotropic species of the cycads to produce a monograph of all Cycadales in collaboration with Ken Hill of the Royal Botanic Gardens Sydney. In addition, I have a collaborative research program with Gloria Coruzzi of New York University on the biology,syntheisis, and genetic control of the nonprotein amino acid, BMAA, which is implicated in Guam Dementia. I am part of the Plant Genomics Consortium and am conducting research, with the other consortium members, on the origin, development, and modification of the seed with a focus on the integuments and arils as well as heterospory. My other major research interest is the systematics of the monocots, particularly, the Commelinidae. The topics under investigation include developmental floral morphology, embryology, and inflorescence structure because this basic information is incomplete or unknown for many of these families. These data are being combined with gene sequence data to generate phylogenetic hypothesis on the origin and classification of the monocots.

More information

The Cycad Pages

The Plant Genomics Consortium

Plant Systematics

Botanical Classics – Cycadeae quaedam Americanae. F.A.W. Miquel describes several American Zamia and Dioon.

Botanical Classics – Prodromus Systematis Cycadearum. F.A. Miquel. 1861.

Botanical Classics – Monographia Cycadearum. F. A. G. Miquel. 1842.

Botanical Classics – Analecta Botanica Indica Volume 1. F. A. G. Miquel. 1850.

Botanical Classics – Cycads from Analecta Botanica Indica Volume 2. F. A. G. Miquel. 1851.

Biography and Bibliography of F.A. Miquel. Wentia XVI.

Botanical Classics – Pugillus Sextus. Joannes Georgius Lehmann. 1834

Morphology Classics: Marie Stopes – Adventitious budding and branching in Cycas.

Morphology Classics – Eduard Strasburger on Taxus embryology

Morphology Classics – Carl Wilson: The Telome Theory

Morphology Classics – Hofmeister on the Higher Cryptogamia

Morphology Classics – J.D. Hooker on Welwitschia

Morphology Classics – Miyake on Cycad Spermatozoids

Morphology Classics – Robert Brown on the embryo development of Coniferae

Morphology Classics – Robert Brown on the female flower in Cycadeae and Coniferae

Morphology Classics – A. W. Eichler on Dioon spinulosum

Morphology Classics – Marie Stopes on the double nature of the Cycadean integument

Morphology Classics – Hugo Mohl on the structure of Cycad trunks and a comparison to those of conifers and tree-ferns

Scientific Classics – Robert Brown on microscopical observations of active molecules (Brownian motion)

Selected Publications

Stevenson, D.W. 1988. “Strobilar ontogeny in the Cycadales.” In: Leins, P., P. Endress, and S. Tucker, eds. Aspects of Floral Evolution. J. Cramer, Stuttgart. 205-224pp.

Loconte, H. and D. Stevenson. 1990. “Cladistics of the Spermatophyta.” Brittonia 42:197-211.

Stevenson, D.W. 1990. “Morphology and Systematics of the Cycadales.” Mem. N. Y. Bot. Gard. 57:8-55.

Stevenson, D.W. and H. Loconte. 1995. “Cladistic analysis of monocot families.” In: P.J. Budall, P.J. Cribb, D.F. Cutler & C.J. Humphries, editors. Monocotyledons: Systematics and Evolution, pp. 543-578, Royal Botanic Gardens, Kew.

Stevenson, D.W. and H. Loconte. 1997. “Ordinal and familial relationships of pteridophyte genera.” In: J. Camus, M. Gibby & R. Johns, editors. Pteridology in Perspective, pp. 435-467. Royal Botanic Gardens, Kew.

Stevenson, D.W., K. Norstog, & P. Fawcett. 1999. “Pollination biology of cycads.” In: S. Owens & P. Rudall, editors. Reproductive Biology: In Systematics, Conservation, and Economic Botany, pp. 277-294. Royal Botanic Gardens, Kew.

Stevenson, D.W., J. Davis, J. Freudenstein, C. Hardy, M. Simmons and C. Specht. 2000. “A phylogenetic analysis of the monocotyledons based on morphological and molecular character sets, with comments on the placement of Acorus and Hydatellaceae.” In: K. Wilson & D. Morrison, editors. Monocots: Systematics and Evolution. pp. 17-24. CSIRO, Melbourne.

Daly, D., K. Cameron, & D. Stevenson. 2001. Plant systematics in the age of genomics. Pl. Physiol. 127: 1328-1333.

Stevenson, D. 2001. Cycadales. Flora de Colombia 21: 1-92.

Brenner, E., D. Stevenson, & R. Twigg. 2003. Cycads: Evolutionary innovations and the role of plant-derived neurotoxins. Trends in Plant Science 8: 446-452.

Davis, J., D. Stevenson, G. Petersen, O. Seberg, L. Campbell, J. Freudenstein, D. Goldman, C. Hardy, F. Michelangeli, M. Simmons, C. Specht, F. Vergara Silva, & M. Gandolfo. 2004. A Phylogeny of the monocots, as Inferred from rbcL and atpA sequence variation, and a comparison of methods for calculating jackknife and bootstrap values. Syst. Bot. 29: 467-510.

Artabe, A., A. Zamuner, & D. Stevenson. 2004. Two new petrified cycad stems, Brunoa gen. nov. And Worsdellia gen. nov., from the Cretaceous of Patagonia (Bajo De Santa Rosa, Province of Rio Negro), Argentina. Bot. Rev. 70: 121-133.

Smith, N., S. Mori, A Henderson, D. Stevenson, & S. Heald (eds.). 2004. Flowering Plants of the Neotropics. 594 pp. Princeton University, Press, Princeton.

Nixon, K., W. Crepet, D. Stevenson, & E-M. Friis. 1994. A reevaluation of seed plant phylogeny. Ann. Missouri Bot. Gard. 81: 484-533.

Norstog, K., E. M. Gifford, & D. Stevenson. 2004. Comparative development of the spermatazoids of cycads and Ginkgo biloba. Bot. Rev. 70: 5-15.

Hardy, C., D. Stevenson, & J. Davis. 2004. Floral organogenesis in Plowmanianthus (Commelinaceae). Int. J. Pl. Sci. 165: 511-519.

Hermsen, E., E. Taylor, T. Taylor, & D. Stevenson. 2006. Cataphylls of the middle Triassic cycad Antarcticycas schopfii and new insights into cycad evolution. Amer. J. Bot. 93: 724–738. 2006.

Specht, C. & D. Stevenson. 2006. A new phylogeny-based generic classification of Costaceae (Zingiberales). Taxon 55: 153-163.

Davis, J. I., G. Petersen, O. Seberg, D. Stevenson, C. Hardy, M. Simmons, F. Michelangeli, D. Goldman, L. Campbell, C. Specht, & J. Cohen. 2006. Are mitochondrial genes useful for the analysis of monocot relationships? Taxon 55: 857-870.

Petersen, G., O. Seberg, J. Davis, & D. Stevenson, 2006. RNA editing and phylogenetic reconstruction in two monocot mitochondrial genes. Taxon 55: 871-886.

Douglas, A., D. Stevenson, & D. Little. 2007. Ovule development in Ginkgo biloba L., with emphasis on the collar and nucellus. Int. J. Plant Sci. 168(9):1207–1236.

Little, D. P. & D. W. Stevenson. 2007. A comparison of algorithms for the identification of specimens using DNA barcodes: examples from gymnosperms. Cladistics 22: 1-21.

Rudall, P. J., V. Remizowam, A. S. Beer, E. Bradshaw, D. W. Stevenson, T. D. MacFarlane, R. E. Tuckett, S. R. Yadav & D. D. Sokoloff. 2008. Comparative ovule and megagametophyte development in Hydatellaceae and water lilies reveal a mosaic of features among the earliest angiosperms. Ann. Bot. 101: 941-956.

de la Torre-Bárcena, E. S. Kolokotronis, E. K. Lee, D. W. Stevenson, E. D. Brenner, M. S. Katari, G. M. Coruzzi, & R. DeSalle. 2009. The Impact of Outgroup Choice and Missing Data on Major Seed Plant Phylogenetics Using Genome-Wide EST Data. PLoS ONE 4(6): e5764.

Nicolade-Morejón, F, A. P. Vovides, & D. W. Stevenson. 2009. Taxonomic revision of Zamia in Mega-Mexico. Brittonia 61: 1-38.

Crane, P., S. Hopper, P. Raven, & D, Stevenson. 2009. Plant science research in botanic gardens. Trends in Pl. Science 14: 575-577.

Hernández-Hernández, V., T. Terrazas, D. Stevenson 2009. Ontogeny of Ctenitis melanosticta (Kunze) Copel. and Diplazium expansum Willd. (Dryopteridaceae) fronds with emphasis on the circumendodermal sheath. Feddes Repertorium 120: 7–8, 426–442.

Crepet, W. & D. Stevenson. 2010. The Bennettitales (Cycadeoidales): a preliminary perspective on this arguably enigmatic group. Pp. 215- 246 in C. Gee (ed), Plants in Mesozoic Time. Indiana University Press, Bloomington.

Schulz, C. J., D. P. Little, D. W. Stevenson, D. Bauer, C. Moloney & T. Stutzel An overview of the morphology, anatomy, and life cycle of a new model species: the lycophyte Selaginella apoda (L.) Spring. Int. J. Plant Sci. 171(7): 693–712. 2010.

Cibrian-Jaramillo, A., J. E. De la Torre-Bárcena, E. K. Lee, M. S. Katari, D. P. Little, D. W. Stevenson, R. Martienssen, G. M. Coruzzi, & R. DeSalle. 2010. Using Phylogenomic Patterns and Gene Ontology to Identify Proteins of Importance in Plant Evolution. Genome Biol. Evol. 2:225-239.

Cuenca, A., G. Petersen, O. Seberg, J. Davis, & D. Stevenson. 2010. Are substitution rates and RNA editing correlated? BMC Evolutionary Biology 10: 349-64.