COPING WITH THE EPIPHYTIC EXISTENCE: POLLINATION STRATEGIES

Abstract

Populations of epiphytic flowering plants are often composed of scattered individuals or small, hyperdispersed clusters. These characteristics create conditions for pollination'somewhat different from that encountered by many terrestrial plants. For example, plant distribution and size constraints imposedby theepiphytic habitmay have limitedfloral apparency orcompetitivenessfor adequate pollinator service. To cope with these problems, epiphytes employ one ofseveral specialized pollinatipn strategies which involve deception, or exclusive or unique rewards. Each of the specialized strategies is probably most efficient for diffusely distributed species and may have either a terrestrial or an epiphytic origin. In one system, plants produce few flowers per day for long periods. The blossoms contain a high quality reward which is exclusively accessible to large traplining pollinators. In another, pollinator attraction is based on deceit which by-passes constraints directly imposed by pollinator foraging energetics. The deception may exploit sexual, feeding or egg-laying behaviors oftheir pollinators. A third strategy employed by many neotropical epiphytes is pollination by male euglossine bees. The flowers produce fragrances which serve as specific attmctants and perhaps precursors to sex pheromones ofthe bees. Pollination occurs when male bees arrive and collect the fragrance compounds. All three strategies are not unique to epiphytes.
Both terrestrials and epiphytes with shared size and dispersion constraints seem to have more specialized pollination biologies than their more densely populated and floriferous neighbors. The dispersion-specialization hypothesis genemtes testable predictions, some of which are presented.