CHEMOSYSTEMATIC STUDY OF HYBRIDIZATION IN CALIFORNIAN LIVE OAK - ACORN STEROIDS

Acorns from 85 individuals of Quercus agrifolia and a wislizenii from seven native populations in California were sampled and analysed for s teroid composition. The most abundant steroid was beta-sitosterol (83- 87%), with campestrol, stigmasterol and DELTA5-avenastenol in small am ounts (2-7%) and DELTA7-stigmastenol and DELTA7-avenastenol at very lo w levels (<1%). Small, but significant differences between the two spe cies were found in campesterol, stigmasterol, DELTA5-avenastenol and b eta-sitosterol. Percentage composition of the first three of these ste roids was intermediate in three putative hybrid populations. Putative hybrid populations differed from the combined parents in frequency dis tributions of percentage composition of these steroids providing suppo rt for true intermediacy in these populations. Principal components an alysis in conjunction with morphological data was used to identify pro bable hybrid and backcross individuals. Estimates of hybrid frequency indicated highest levels (ca 60%) in the northern range of Q. agrifoli a.