COLONIZATION OF ECOLOGICAL ISLANDS - GALLING APHID POPULATIONS (STERNORRHYNCHA, APHIDOIDEA, PEMPHIGIDAE) ON RECOVERING PISTACIA TREES AFTERDESTRUCTION BY FIRE

Pistacia palaestina (Anacardiaceae) is a common tree in the natural fo rest of Mt. Carmel, Israel, and the primary host of five common specie s of gall-forming aphids (Sternorrhyncha: Aphidoidea: Pemphigidae: For dinae). After a forest fire, resprouting P. palaestina trees, which ar e colonized by migrants from outside the burned area, become ''ecologi cal islands'' for host-specific herbivores. A portion of the Carmel Na tional Park was destroyed by fire in September of 1989. The same winte r, thirty-nine resprouting trees that formed green islands in the othe rwise barren environment were identified and marked. Tree growth was e xtraordinarily Vigorous during the first year after the fire, but shoo t elongation declined markedly in subsequent years. Recolonization of the 39 ''islands'' by the Fordinae was studied for six consecutive yea rs. Although the life cycle of the aphids and the deciduous phenology of the tree dictate that the ''islands'' must be newly recolonized eve ry year, the results of this study show that trees are persistently oc cupied once colonized. This is probably due to establishment of aphid colonies on the roots of secondary hosts near each tree following the first successful production of a gall. Differences in colonization suc cess of different species could be related to both the abundance of di fferent aphid species in the unburned forest and the biological charac teristics of each aphid species.