Phylogeny, Classification and Evolutionary Phytogeography of Flowering Plants
Research interests include the comparative morphology and systematics of primitive dicotyledons and monocotyledons, comparative studies of pollen grains of living and fossil primitive angiosperms, evolutionary phytogeography of the flowering plants, and general classification and phylogeny of angiosperm families. After initial study of the large tropical family Annonaceae, my research interests broadened to include comparative studies, especially of the pollen, of the approximately two dozen families in the magnolialean complex, which constitutes the group of living flowering plants generally considered to be the most primitive of extant angiosperms. Following this, my interest turned to investigation using scanning and transmission electron microscopy of the earliest known fossil angiosperm pollen grains from rocks of the Lower Cretaceous. More recently, I have been interested in studies of the pollen of primitive lilialean monocotyledons, and the classification, phylogeny and evolutionary phytogeography of monocotyledons in general.
Walker, J.W. and A.G. Walker. 1986. Ultrastructure of Early Cretaceous angiosperm pollen and its evolutionary implications. In Pollen and Spores: Form and Function, S Blackmore and IK Ferguson, eds., Academic Press.
Walker, J.W. and A.G. Walker. 1984. Ultrastructure of Lower Cretaceous angiosperm pollen and the origin and early evolution of flowering plants. Ann. Missouri Bot. Gard. 71: 464-521.
Walker, J.W., G.J. Brenner and A.G. Walker. 1983. Winteraceous pollen in the Lower Cretaceous of Israel: early evidence of a magnolialean angiosperm family. Science 220: 1273-1275.
Walker, J.W. and J.A. Doyle. 1976. The bases of angiosperm phylogeny: palynology. Ann. Missouri Bot. Gard. 62: 664-723.
Walker, J.W. 1976. Evolutionary significance of the exine in the pollen of primitive angiosperms. In The Evolutionary Significance of the Exine, IK Ferguson and J Muller eds., Academic Press, London, pp. 251-308.
Walker, J.W. 1976. Comparative pollen morphology and phylogeny of the ranalean complex. In Origin and Early Evolution of Angiosperms, CB Beck, ed., Columbia University Press, New York, pp. 241-299.
Walker, J.W. (ed.) 1976. The Bases of Angiosperm Phylogeny. Ann. Missouri Bot. Gard. Vol. 62, pp. 515-834.
Walker, J.W. and J.J. Skvarla. 1975. Primitively columellaless pollen: a new concept in the evolutionary morphology of angiosperms. Science 187: 445-447.