The cost of selfing in Encyclia cochleata (Orchidaceae)

To determine whether inbreeding depression accounts for the maintenance of outcrossing in populations of the self-compatible orchid Encyclia cochleata , the estimated selective advantage of selfing was compared to a measure of inbreeding depression. Individuals from three populations of E. cochleata and some of their progeny were phenotyped using isozyme analysis. The elect rophoretic data were used to estimate the outcrossing rate and the theoreti cal cost of outcrossing. Inbreeding depression was estimated by comparing t he fitness of the progeny resulting from both types of pollinations. The se eds from outcrossed and selfed hand-pollinations and naturally pollinated s eeds from a population of the triandrous form of E, cochleata were grown as eptically on culture media, and their development over the next three years recorded. Inbreeding was common, particularly in one population (outcrossi ng rate 40%). However, the level of inbreeding depression was only 1-2%, co nsiderably less inbreeding depression than expected.