The unusual life history of Alseis blackiana: A shade-persistent pioneer tree?

Classifications of tree species into regeneration guilds or functional grou ps are often based on a limited number of life history characteristics indi cative of requirements for early establishment, with the assumption that th ese traits are correlated with growth requirements of larger individuals. W e tested the validity of this assumption for Alseis blackiana, a common can opy tree in central Panama, by examining its seed germination, seedling gro wth, and sapling distribution, growth, and mortality. We found that the ear ly life history of Alseis is characteristic of pioneer species: the seed ge rmination rate was much higher in forest gaps than in the forest understory , small seedlings were absent from the understory, and seedlings showed str ong plastic responses to variation in light. Seedling relative growth rate, leaf area production rate, and maximum carbon assimilation rates of Alseis are much more similar to those of the pioneer tree Miconia argentea than t o those of the non-pioneer tree Tetragastris panamensis. However, in contra st to Miconia, established seedlings of Alseis are capable of remarkable pe rsistence in the understory; in a 1-ha plot on Barro Colorado Island, the m ortality rate for 722 saplings <1 cm dbh was <4% per year between 1986 and 1998. We suspect that shade tolerance in Alseis is achieved by both physiol ogical and morphological adaptations, e.g., efficient light interception by thin, nonoverlapping leaves, tolerance to litterfall damage, and a high re sprouting capacity. These results show that existing functional group class ifications do not account for the full range of seedling trait combinations found in tropical trees and indicate that a gap requirement for seedling e stablishment need not limit the abundance of adult individuals in a stand.