Eriocnema fulva Naudin is an endangered perennial herbaceous plant, endemic to Minas Gerais state, Brazil. This study was conducted in the Jambreiro Forest (19° 58' -59'S and 43° 52' -55' W, 800-1100 m altitude). In an attempt to describe the population size structure and its association with individual fertility, fifteen 1 x 1 m contiguous plots were set. We tagged, counted, and measured a total of 260 individuals in 1997, 1998 and 1999. Young individuals with leaf lamina lengths < 3.4 cm comprised 33% of the total sampled, indicating that the population was reproducing locally. The number of leaves varied significantly, growth differences being detected only after two years of measurements. Stem length was the variable that best showed population size variation. The length of the largest leaf lamina was the best indication of its development phase. Assessing the number of leaves helped to evaluate the alteration in plant size during the study. The probability that individuals with laminas > 10 cm in length did not reproduce was 2.69%. The highest survival probability of the large-sized individuals confirmed the strong correlation between size and survival. The data indicated that size is important for the fertility of E. fulva, and it may be one of the relevant aspects to be considered for analyses of survival probability. The intraspecific competition, which was indicated by negative correlation between fruit production per size unit and density, can affect fertility, as larger plants had higher fruit production.
size; fertility; plant population; intraspecific competition
