EVANS, RODGER C.1* and TIMOTHY A. DICKINSON2. 1Biology Department, Acadia University, Wolfville, NS, Canada, B0P 1X0; 2Center for Biodiversity & Conservation Biology, Royal Ontario Museum, Toronto, ON, Canada M5S 2C6. - An untapped source of characters: insights into phylogeny from ontogenetic studies of pistils and ovules in Rosaceae.
Recent phylogenetic analyses of data from chloroplast and nuclear
genomes have not only provided significant insight into evolution
within the Rosaceae, but have also begun to help elucidate
relationships within and between taxa within this large and
extraordinary flowering plant family. While such studies provide a
much-needed basis for refining classification and hypothesizing
evolution, they also provide a context for comparative analyses of
ontogenetic patterns and mature morphology. In return, molecule-based
phylogenies may receive confirmation from these same independently
derived sources of data. Gynoecium and ovule morphology are diverse
but generally underutilized in evaluating relationships within the
Rosaceae. One large clade delimited by molecular studies includes
Rosoideae s.s. where gynoecia are either sessile or develop upon an
enlarged receptacle of varying size and shape, whose ovule number and
position within the ovary vary, and whose ovules lack an obturator.
Another large clade includes the Maloideae and a number of
traditionally classified Spiraeoideae (Gillenia,
Kageneckia, Lindleya, and Vauquelinia). These
taxa all share the initiation of a common primordium early in
gynoecium development, as well as similar development and mature
morphology of ovules and obturators. The remaining Rosaceae comprise a
number of smaller clades. Although relationships between these smaller
clades are less clear, gynoecium and ovule ontogeny and mature
morphology may provide insights into floral evolution in these clades.
Gynoecium morphology and connation varies from solitary to five and
from free to fused, respectively. Ovule number varies from one to
many, ovule insertion along the locule wall varies from basal to
terminal, and when present there is variation with respect to the
position of the obturator. Understanding the relationships of the
Rosaceae and their gynoecial characters not only provides greater
insight into floral evolution within the family, but also provides
context for studying their reproductive biology.
Key words: floral ontogeny, ovule, phylogeny, pistil, Rosaceae