SELF-INCOMPATIBILITY, SEED ABORTION AND CLONALITY IN THE BREEDING SYSTEMS OF SEVERAL WESTERN-AUSTRALIAN DROSERA SPECIES (DROSERACEAE)

Western Australian Drosera L. species include one annual and many tube rous and pygmy perennials. In 20 species or subspecies, 17 taxa were s elf-incompatible (SI) and three were self-compatible (SC), as assessed by patterns of seed set and pollen tube growth. All SI species were c lonal (tubers or gemmae), but two SC species were clonal (gemmae) and one was annual. Self-pollen tube inhibition confirmed that SI species were pre-zygotically self-sterile. The sites of SI pollen tube inhibit ion varied from early (stigmatic) to fate (stylar, placental, ovular), which suggests continuing evolution in the expression of the SI respo nse. Self-compatible species showed little inbreeding depression, but SI species showed considerable inbreeding depression as measured by se ed abortion. In the three species tested, open-pollinated capsules wer e typically more fecund than hand-pollinated capsules. In D. glandulig era Lehm., this might represent position effects in an inflorescence t hat were reflected in the sampling method. In other species, however, this might also reflect biparental inbreeding depression in the glassh ouse plants. Interspecific crosses between D. tubaestylis N.Marchant & A.Lowrie (n = 14) and D. rosulata Lehm. (n = 13) were slightly succes sful, with no pollen-pistil incompatibility interaction, but with exte nsive seed abortion. This is the first report of SI in Droseraceae.