Flowering of Thalassia testudinum banks ex König in the Mexican Caribbean: age-dependence and interannual variability

The flowering intensity of Thalassia testudinum Banks ex König, along the Mexican Caribbean coast, was studied. Only 17% of the shoots examined had flowered during their lives, and the mean flowering frequency for the population was estimated to be 5.6 × 10^-3 flowers per plastochrone interval (PI^-1), which corresponds, on average, to a flowering event every 13 years. Thus, most short shoots will not flower during their lives, although some old shoots had flowered twice and even three times. None of the shoots examined flowered before reaching an age of 15 PI (about 1 year), and flowering intensity increased with age up to PI (about 2 years), thereby indicating the need for sexual maturation. Reconstruction of the flowering intensity in previous years showed a four-fold increase since the passage of Hurricane Gilbert (in September 1988), which caused substantial perturbation to the seagrass meadows, thereby indicating the importance of perturbation on interannual variability in flowering intensity. Comparison of the flowering intensity observed with published reports for other seagrass species suggests that differences in flowering intensity among species, which averaged about 10% of the shoots flowering each year, are narrow and probably not greater than variability among years or populations of a single species.