ANT-POLLINATION OF THE GRANITE OUTCROP ENDEMIC DIAMORPHA SMALLII (CRASSULACEAE)

Formica schaufussi, a medium-sized ant common throughout the Piedmont and Coastal Plain of the southeastern United States, has been observed in association with Diamorpha smallii, a self-incompatible annual endemic to granite outcrops in the Southeast, over a 6-yr period. Observations of ants collected on the flowers show large numbers of the sticky pollen grains adhering to hairs and indentations primarily on the thoraces of the ants. Though small native bees and flies are frequent and sometimes effective pollinators, it is highly unlikely that the monotypic genus Diamorpha coevolved with the introduced honeybee, as has been suggested. Characteristics indicative of an “ant-pollination syndrome” include occurrence in hot, dry habitats, a high density of very small plants bearing overlapping inflorescences at a uniform height, and low seed number, pollen volume, and nectar quantity.