SEXUAL POLYMORPHISMS IN NARCISSUS-TRIANDRUS (AMARYLLIDACEAE) - IS THIS SPECIES TRISTYLOUS

The sexual polymorphism tristyly is well documented in three flowering plant families (Lythraceae, Oxalidaceae and Pontederiaceae). Controve rsy has arisen as to whether the polymorphism exists in Narcissus tria ndrus L. of the Amaryllidaceae. Surveys of floral variation in 80 popu lations in Spain and Portugal were undertaken to determine the nature of sexual polymorphisms in the species. Most populations (85 per cent) contained three discrete floral morphs that differ from one another i n the sequence in which the stigma and the two anther levels within a flower are presented. Hence, the species is genuinely tristylous. Flor al morph frequencies deviated strongly from the isoplethic expectation s (1:1:1) typical of tristylous species. Average frequencies for the m orphs were L morph = 0.59, M morph = 0.19 and S morph = 0.22. In 15 pe r cent of the populations sampled, the mid-styled morph was absent. Co ntrolled crosses indicated that individuals are moderately self-steril e but cross-compatible with other individuals, regardless of morph. Th erefore, the species does not possess a conventional heteromorphic inc ompatibility system. Self-sterility operates in the ovary, and prior s elf-pollination of flowers renders ovules nonfunctional as judged by r educed seed-set in subsequent cross-pollinations. Multilocus outcrossi ng estimates in four tristylous populations averaged t = 0.77, range 0 .68-0.87, with significant variation evident among morphs but not popu lations. All population estimates were less than 1, indicating signifi cant amounts of selfing. Although N. triandrus is clearly tristylous, the expression of the polymorphism is unique among tristylous families .