Breeding systems inClivia(Amaryllidaceae): late-acting self-incompatibility and its functional consequences

Abstract

Late-acting (ovarian) self-incompatibility, characterized by minimal or zero seed production following self-pollen tube growth to the ovules, is expected to show phylogenetic clustering, but can otherwise be difficult to distinguish from early-acting inbreeding depression. In Amaryllidaceae, late-acting self-incompatibility has been proposed for Narcissus (Narcisseae) and Cyrtanthus (Cyrtantheae). Here, we investigate whether it occurs in the horticulturally important genus Clivia (Haemantheae) and test whether species in this genus experience ovule discounting in wild populations. Seed-set results following controlled hand pollinations revealed that Clivia miniata and C. gardenii are largely self-sterile. Self- and cross-pollinated flowers of both species had similar proportions of pollen tubes entering the ovary, and those of C. gardenii also did not differ in the proportions of pollen tubes that penetrated ovules, thus ruling out classical gametophytic self-incompatibility acting in the style, but not early inbreeding depression. Flowers that received equal mixtures of self- and cross-pollen set fewer seeds than those that received cross-pollen only, but it was unclear whether this effect was a result of ovule discounting or interactions on the stigma. The prevention of self-pollination by the emasculation of either single flowers or whole inflorescences in wild populations did not affect seed set, suggesting that ovule discounting is not a major natural limitation on seed production. Flowers typically produce one to three large fleshy seeds from approximately 16 available ovules, even when supplementally hand pollinated, suggesting that fecundity is mostly resource limited. The results of this study suggest that Clivia spp. are largely self-sterile as a result of either a late-acting self-incompatibility system or severe early inbreeding depression, but ovule discounting caused by self-pollination is not a major constraint on fecundity. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 175, 155–168.