THE DEVELOPMENTAL BASIS OF MORPHOLOGICAL DIVERSIFICATION AND SYNORGANIZATION IN FLOWERS OF CONOSPERMEAE (STIRLINGIA AND CONOSPERMINAE, PROTEACEAE)

This comparative study of the monophyletic Stirlingia, Synaphea, and C onospermum (Proteaceae) aims to understand the morphology and function of the flowers as well as to determine the developmental processes re sponsible for extensive synorganization and floral architechiral diver gence. The diverse floral architectures among these taxa result from i ndependent developmental processes, both morphogenetic and histogenic, as well as regional modularization of floral organs. Most of the stru ctures and the underlying developmental processes associated with syno rganization are present in all of the taxa, including fused tepal claw s, coherent anthers, stamen adnation to the tepals, and style-filament and filament-filament support. In Synaphea and most Conospermum spp., the tepal limbs are fused, and there is support between the stamens a nd style involved with pollination syndromes. These are the products o f changes in the timing of developmental events and/or relative shifts in the location of these events. Among Conospermum flowers, a novel s upport/enclosure feature between the adaxial and abaxial stamen and mi ddle region of the style results from greater cellular differentiation . In Synaphea, the novel synorganization of staminode and stigma appea rs to be the product of differences in the timing (both accelerated an d delayed) of expression of four different developmental processes. Di vergence among the three genera appears related to a shift in symmetry from actinomorphy (Stirlingia) to zygomorphy (Conospermum and Synaphe a). Synaphea and most species of Conospermum have a bilabiate perianth and a partially sterile androecium although the sterility is found in different halves of the flower (abaxial half of androecium is sterile in Conospermum, and the adaxial half is sterile in Synaphea). The hyp othesis that zygomorphy and the bilabiate condition arose separately i n each lineage is tentatively supported by developmental differences. Stigma diversity among the three genera results from different express ions of marginal meristematic growth (a novelty in the clade). Most de velopmental processes are shared among taxa and vary only in their tim ing and duration of expression. The variation results in both elaborat ions and altered spatial relationships among the structures.