POLLINATION ECOLOGY OF OXALIS-VIOLACEA (OXALIDACEAE) FOLLOWING A CONTROLLED GRASS FIRE

Vernal grass fires may encourage profuse flowering in clonal, colonies of Oxalis violacea. Long-styled colonies appear to be more floriferous than short-styled colonies and set a greater number of capsules. Individual flowers of both morphs live one or two days, change position on their respective pedicels and advertise nectar concealed at the base of the floral throat. Although Diptera, Hymenoptera, and Lepidoptera forage for nectar, bees (Andrenidae,Anthophoridae, Halictidae, and Megachilidae) probably make the only effective pollen transfers between the two morphs. Both male and female bees may transport pollen of both morphs and short-tongued bees (e.g., Augochlorella spp., Dialictus spp.) may be more common but as effective as pollinators as long-tongued bees (e.g., Calliopsis andreniformis and Hoplitis spp.). The conversion rate of flowers into capsules is only 13-17%. The spreading style in the short-styled morph is interpreted as an adaptation restricting insect-mediated, self-pollination but encouraging bee-stigma contact during nectar foraging. © 1990 Springer-Verlag.