Confronting assumptions about spontaneous autogamy in populations of Eulophia alta (Orchidaceae) in south Florida: assessing the effect of pollination treatments on seed formation, seed germination and seedling development

The breeding system of the terrestrial orchid Eulophia alta was investigated in south Florida where it has previously been reported as an auto-pollinated species. The effect of breeding system on seed viability and germinability and seedling development was also investigated. Incidences of spontaneous autogamy in E. alta were rare at the study site, resulting in only 7.1% of observed flowers forming capsules. In addition, hand pollination resulted in significantly greater capsule formation when flowers were subjected to induced autogamy (46.4%), artificial geitonogamy (64.3%) and xenogamy at both short (pollen source 10-100 m away; 42.9%) and long (pollen source > 10 km away; 67.9%) distances. Pollen source had little effect on seed viability and germinability or seedling growth rates. However, seed resulting from spontaneous autogamy developed more slowly than seed originating from the other treatments. These data indicate that spontaneous autogamy is rare in E. alta and that naturally forming capsules may be the result of unobserved pollination events. (C) 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 161, 78-88.