Reproduction in the Cycad Zamia pumila in a Fire-Climax Habitat: An Eight-Year Study

TANG, W. (Fairchild Tropical Garden, 10901 Old Cutler Road, Miami, FL 33156). Reproduction in the cycad Zamia pumila in a fire-climax habitat: an eight-year study. Bull. Torrey Bot. Club 117: 368-374, 1990.-Zamia pumila L. (Cycadales) is a long-lived dioecious plant with a herb-like habit common in the fire-climax pine forests of southeast Florida. To evaluate sex-related differences in its reproductive strategy, frequency and size of reproductive effort were monitored for males and females in a population over an 8-year period after fire. Eightyseven percent of the non-seedling plants in the population coned during the study period, revealing a sex ratio of 1.8 male/female. Coning sex ratios for each season varied from 2.7-12 male/female. On average males coned once every 1.6 years and produced a mean of 1.45 cones/ yr while females coned once every 3.7 yr with a mean of 0.35 cones/yr. Energy investment in reproduction over the entire study period, however, was on average 3.4 times greater for females. Leaf and cone production declined by the 8th and 9th year after fire, as shrubs recovering from fire damage shaded the habitat. Reproduction in Z. pumila is compared with that in other iteroparous dioecious plants and animals in which there is divergent selection between the sexes for reproductive success.