Demography and life history variation of Puya dasylirioides, a long-lived rosette in tropical subalpine bogs.

Puya dasylirioides (Bromeliaceae) was studied in bogs of Costa Rica. After c36 yr of vegetative growth, a rosette (ramet) reproduces once and dies. Amount of vegetative propagation, occurring many years prior to reproduction, varies greatly within and among sites. Thus ramets are monocarpic; a genet (genetic individual) may be polycarpic. Reproductive rosettes vary greatly in radius (20-72 cm); they are larger in the margins than the center of bogs. The number of mature fruits varies greatly among rosettes (50-1224) and rises exponentially with an increase in rosette radius. Recruitment of new rosettes from seed is uncommon and sporadic in space and time. Germination sites are restricted and Puya seedlings compete poorly where grasses and sedges are common. Survival probabilities rise as rosettes increase in size. After they attain 11 cm radius, requiring an estimated 12 yr, almost no rosettes die prior to reproduction. As these bogs undergo natural succession toward more mesic conditions, or undergo accelerated succession due to human disturbance of their drainage, populations of Puya decline rapidly.-from Author