Taxonomy and Natural History of Bacopa (Scrophulariaceae) in California

Abstract

Three of California's four species of Bacopa are aliens. Bacopa rotundi- folia, a tetraploid, native to central United States, was first recorded for California in 1923 and has since become one of the commonest weeds in rice fields of the state. Californian populations of this species were named B. nobsiana in 1952. Bacopa repens, a neotropical diploid, has been known from a single California station since 1949; its range within the state has not increased in some 30 years. The third alien, the pantropical B. monnieri, has been found in California only recently. The native, B. eisenii, is tetraploid and has apparently invaded rice fields to a significant degree only recently. Taxonomic interpretation of these species has depended on a synthesis of field, experimental, and herbarium studies. The phytogeography and migratory histories of alien or immigrant