The floral biology of Casearia grandiflora (Flacourtiaceae) was studied in a remnant of mesophyllous forest in the Parque do Sabiá, Uberlândia-MG. The species is an important understorey element in forests of this region, flowering during most of the year but more abundantly in March, April and May. Flowers are pale-green, 7 mm across, in sessile axillary heads. They are odourless, one-day flowers, with 10 free stamens adenate to the corolla base. Between the stamens there are receptacular appendages called inter-staminal disk lobes. The stamens and these structures form a cone around the pistil which retains the nectar. Anthesis occurs irregularly but mainly early in the morning. Nectar is relatively abundant (4 muL) and with 38% of sucrose equivalents. Pollen is released during the warmest hours of the day, with high viability levels (96.6%). Stigma is receptive at the same time. The most frequent visitor was the fly Ornidia obesa (Syrphidae), which was present on flowers most of the day, although other sporadic visitors such as Meliponinae bees, butterflies and other unidentified flies were also observed. Controlled hand pollinations showed the species is self-sterile and non-apomictic. However, pollen tubes were observed growing down to the ovary and penetrating the ovules in self-pollinated pistils, which suggest late-acting self sterility phenomena (post-fertilization) or inbreeding depression. Self-sterility in C. grandiflora contrasts with autogamous breeding systems observed in most studied myophillous forest species with similar generalist flower morphology occurring in central Brazil, but is similar to other neotropical woody species in the Flacourtiaceae.
Flacourtiaceae; myophily; fly pollination; Syrphidae; breeding system
