Dickinson Lab


My interest in Rosaceae phylogeny stems directly from analyses of floral development in Crataegus section Douglasii (Evans 1994). My Ph.D. dissertation entails the study of floral development and phylogeny within the Rosaceae. The primary goal of this research is to reconstruct phylogenetic relationships within the Rosaceae using both non-molecular and molecular sources of cladistic data. The results of the cladistic studies are used to hypothesize evolution within the family, particularly the origin of the Maloideae.

Maloideae are hypothesized to have originated through an ancient polyploidization event as there base chromosome number is x=17; all other Rosaceae are primarily x= 7, 8, or 9.

Two most popular hypotheses for the origin of the Maloideae are:

allotetraploidization following an ancient hybridization event between Amygdaloideae (x=8) and "Spiraeoideae" (x=9) ancestors

a polyploidization event (allo- or auto-) within the "Spiraeoideae"

SEM and light microscopy were used to examine floral development within the Amygdaloideae, Spiraeoideae, and Maloideae to look for ontogenetic evidence for one these hypotheses. Manuscripts from the Amygdaloideae and Spiraeoideae floral development studies have been published in the International Journal of Plant Sciences.

The study of floral development also led to the collection of a number of micromorphological characters that are used in a non-molecular cladistic analysis.

Molecular data was collected from from the chloroplast gene ndhF. The results from ndhF are similar to previous molecular phylogenies (Morgan et al. 1994; Campbell et al. 1995; Eriksson et al. 1998)

The non-molecular and molecular data sets were combined in order to obtain a phylogeny for the Rosaceae that is based upon as wide a range of data as is currently available. The results of this combined analysis are used to present hypotheses for the origin of the Maloideae.



Research Affiliations


All photographs on these pages copyright © Rodger Evans 1999.

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Department of Botany - University of Toronto

© 1999 Botany Department, University of Toronto.

Please send your comments to revans@maine.edu; last updated 1-November-99