Abstract:The systematic position, evolutionary trends, modem distribution pattern, center ofdistribution and differentiation of Styracaceae are discussed. Styracaceae, comprising 11 genera, is a natural group in the Ebenales. Embryological and morphological evidences indicatethat it was most fibly evolved from Theaceae. Morphologically, the superior ovary, imbricatecorolla-lobes, stamens twice as many as corolla-lobes and inflorescences paniculate areconsidered as primitive features, while the inferior ovary, valvate corolla-lobes, stamens asmany as corolla-lobes and inflorescences with fascicled or solitary nowers, advanced features. In Styracaceae, Styrax is the largest and most diverse genus with both primitive andadvanced features. The other genera are closely ailled and seem to have a common originfrom tile Styrax stock.Floristically, six distribution patterns of the eleven genera are recognized. 1. Pantropic:Styrax, 2. Tropical Asia f Rehderodendron,Huodendron, Alniphyllum, Parastyrax, Bruinsmia,3. E. Asia and N. America disjunct:Halesia. 4. E. Asia: Pterostyrax, 5. Endemic to China: Sinojackia,Melliodendron,6.Tropical America f Pamphilia. Among the seven genera distributed to tropical areas only three actually occur in tropical regions,the others are insubtropical regions or on the fringe of it. Therefore, Styracaceae may be considered asmainly but not typically a tropical family,and originated from tropical mountains in thepast.The floristic analysis shows that there are 10 genera and 57 species(8 endemic genera,34 endemic species)in East Asia,occupying 91% and 36% of the total genera and speciesin this family respecitively.Ther are 10 genera and 54 species in China,mostly in areasfrom Qinling Mountains and Changjiang river to Naming Mountains,and S.W.China,including most primitive group (Styrax series Imbricatae)and the group of variousevolutionary stages.In tropical America there are two genera,83 species(1 endemic genera,76 endemic species),occupying 18% and 52% of the total genera and species of this familyrespectively.Although, tropical America is most rich in species, but there are only two generaand lack of primitive group. For this reason,East Asia is considered as a primary centerof the distribution of Styracaceae species,and tropical America, secondary center.According to the fossil record and modern distribution pattern of Styracaceae, the ancestor of this family maybe originated in Cathaysia flora during the Cretaceous time.
