Notes on the Breeding Systems of Sacoila Lanceolata (Aublet) Garay (Orchidaceae)

Abstract

To document breeding systems in the widespread neotropical terrestrial orchid, Sacoila lanceolata pollination and seed development were studied in the field and in cultivated plants. In the southern Florida [USA] study area, plants of var. lanceolata were not pollinated and hummingbird pollinators were apparently absent. When plants from southern Florida were moved to a situation where hummingbirds were abundant in southern Ontario [Canada], hummingbird-pollination was observed on numerous occasions and the incidence of pollination was approximately 90%. Pollination experiments demonstrated a reliance on pollen vectors in plants of var. lanceolata from central Guyana, where a variety of hummingbird pollinators are available, but the plants of the same variety from southern Florida were found to be agamospermic. Examination of serial sections of ovaries in successive developmental stages indicated that agamospermy is by adventitious embryony, the embryos (one or more) being formed by proliferation of the inner integument. Adventitious embryony can be detected through association with polyembryonic seed, is characteristic of Florida populations of var. lanceolata, and occurs also in portions of the tropical range. Plants of S. lanceolata var. paludicola from southern Florida were found to self-pollinate. The pollinator-independent breeding systems in southern Flroida popluations of S. lanceolata var. lanceolata and var. paludicola and the apparent absence of races totally reliant upon pollen vectors are associated with pollinator-paucity.