OLIGOTROPHIC TILLANDSIA CIRCINNATA SCHLECHT (BROMELIACEAE): AN ASSESSMENT OF ITS PATTERNS OF MINERAL ALLOCATION AND REPRODUCTION

Analyses of Tillandsia circinnata Schlecht specimens from nutrient‐stressed and more fertile habitats in southern Florida confirmed earlier findings that its vegetative and reproductive vigor are enhanced as shoot tissue concentrations of P, K and Mg increase. Demands by this perennial herb for N, P and K are more pronounced than for B, Ca, Cu, Fe, Mg, Mn, Mo and Zn, primarily because N, P and K must be maintained at relatively high concentrations in vegetative tissues and are heavily expended during seed production. When most or all of this epiphyte's self‐fertile flowers set fruit— a fairly common occurrence in most of the populations examined—asexual propagation by offshoot is subordinated to the sexual effort, especially if the specimen is growing in an unusually sterile habitat and has very limited mineral resources. Predictions implicit in r‐K selection and related life history theory are consistent with the notion presented here that T. circinnata is following a pattern of nutrient use for reproductive purposes that represents a highly adaptive way to expend slowly accumulated mineral resources in stressful habitats represented by small, scattered, short‐lived microsites. Specifically, it expends scarce mineral resources during the reproductive effort in a way that greatly enhances fecundity and vagility while minimizing the rate at which new microsites and reproducing individuals must be recruited. Reproduction and mineral use by T. circinnata is compared with that of T. utriculata , a semelparous epiphyte that shares many of the same forest habitats in southern Florida.