BIOSYSTEMATIC STUDY OF LASTHENIA-CALIFORNICA (ASTERACEAE)

This study examined variation in morphology and isozymes for 36 popula tions of Lasthenia californica representing the entire range of the sp ecies. These and previous results suggest the formation of two geograp hical races based on pappus shape, isozymes, and flavonoid chemistry. The races appear to coexist in a population examined in more detail (J asper Ridge). Genetic parameters indicating differentiation within and among populations suggest reduction in pollen and seed movement withi n the Jasper Ridge population (G(st) = 0.417; Nm = 0.350) and among po pulations (G(st) = 0.36; Nm = 0.439) of L. californica. In spite of th e considerable differentiation among the populations for pappus shape, flavonoid chemistry, and isozymes, there is no indication that the po pulations could be recognized as taxonomic groups as suggested in earl ier taxonomic treatments. The patterns of variation observed in this s tudy are further complicated by the presence of three cytotypes, none of which could be distinguished by the data sets examined. The isozyme study suggests that tetraploid populations are of autopolyploid origi n. The only hexaploid population sampled was not analysed for isozyme variation. We believe that the patterns of variation observed in L. ca lifornica best fit the model of geographical speciation. The pattern o f variation observed at Jasper Ridge suggests that this population mig ht have been established by two colonists-one a northern type and the other a southern type-representing the two geographical races.