In comparing the population structure of epiphytic and saxicolous Tillandsia species I found no significant differences between polycarpic species. Epiphytic T. ionochroma populations had a higher seedling:adult ratio than saxicolous T. ionochroma populations, but the difference was not statistically significant. Tillandsia ultriculala, a monocarpic epiphyte, had a significantly higher seedling:adult ratio than the polycarpic species. T. utriculata's higher ratio may result from its greater seed production and lack of vegetative propagation. Unlike the polycarpic species, all adult-size rosettes grow from seeds in T. utriculata. Tillandsia sphaerocephala, an obligate saxicole, occurred in larger clusters (i.e. more rosettes per genet) than T. ionochroma. The increased tendency for vegetative reproduction in T. sphaerocephala suggests that spatial patchiness is less of a constraint than with epiphytes.
