The Spatial Pattern and Reproductive Consequences of Outbreak Defoliation in Quararibea Asterolepis, A Tropical Tree

Abstract

Quararibea asterolepis (Bombacaceae), a common canopy tree in the old forest on Barro Colorado Island, Panama, was the only species defoliated during an outbreak of Eulepidotis (Noctuidae) larvae in May and June 1985. The level of defoliation among 460 potentially reproductive trees (.gtoreq. 16 cm dbh) over a 50-ha plot was related to local conspecific density and to the severity of defoliation of the three nearest neighbors. Young leaves suffered greater damage than mature leaves in the same Quararibea crown. Trees with mostly young leaves before the outbreak suffered heavier defoliation than those with mostly mature leaves. Trees that escaped defoliation had either all or mostly mature leaves. When sapling pairs were matched with respect to leaf age, saplings near an infested adult suffered heavier defoliation than distant saplings. The distance effect was reversed, however, when near saplings had mature leaves and far saplings had young leaves. Heavily defoliated crowns of large (.gtoreq. 64 cm dbh) Quararibea trees produced significantly fewer flowers and fruits than lightly defoliated crowns. Flowering also occurred later and was less synchronized for heavily defoliated trees. This difference in reproductive output did not persist beyond the outbreak year.