Biosystematic studies in the North American species of Linum, section Adenolinum (Linaceae)

Abstract

Variation patterns and interpopulational relationships were examined in Linum lewisii Pursh and L. pratense (Norton) Small, the two native North American blue-flowered flax species. The two principal evolutionary trends in the North American populations have been toward self-pollination and an annual life habit. A third trend, toward greater outcrossing, is considered probable. Hybridizations between and within species indicate that evolution has occurred mainly by the accumulation of small genic changes in geographically isolated populations. The buildup of sterility barriers between populations regardless of species has not been extensive and in no case do hybrids have less than 30% good pollen. In general, morphological evolution has occurred independently of the buildup of sterility barriers. A new taxonomic combination, L. lewisii ssp. lepagei (Boivin) Mosquin, is adopted.