Changes in interspecific association with age were used to determine trends of species replacement on tree islands in Chase Prairie, Okefenokee Swamp. Convergence was the most commonly observed phenomenon as species diversity in- creased with island age and time since the last disturbance. Disturbed islands were characterized by a species assemblage different from that of undisturbed islands. Fire history, seed dispersal and island age appear to be the major factors determining the ern Florida, includes various habitats. Different patches represent both alternative and sequential successional stages, the composition of which is in part determined by the timing and severity of past disturbances such as logging and fire (Hamilton, 1982). Marshes, called prairies, of either aquatic or emergent macrophytes are the earliest seral stage, and occur in areas of severe or frequent burns. There are two requirements for marsh formation. First, existing woody vegetation must be killed, either by a fire that burns deeply enough into the peat to kill the roots, or by more superficial fires that recur often enough to exhaust the regenerative potential of surviving roots. Second, enough of the peat surface must be burned away to permit an increase in water depth, thus preventing the germination of woody species (Cypert, 1973). Because it can take as long as 1000 years for 0.3 m of peat to accrue and severe peat-burning fires occur every few hundred years, the succession of marshes to forested swampland via peat accumulation occurs quite slowly (Cypert, 1961). However, the process is greatly accelerated by the formation of both floating and attached peat islands that provide substrate for invasion by trees and shrubs. Cypert (1972) described several mechanisms of island formation and recorded the development of vegetation on two such islands. By analyzing growth rings of the largest individuals of each species, Duever and Riopelle (1983) estimated the minimum ages of islands at various stages of succession and provided a colonization order for woody species. The purpose of this study was to determine successional relationships of island spe- cies by comparing their age structures. SITE DESCRIPTION Field sampling was done in Chase Prairie, an aquatic macrophyte marsh near the center of the swamp. With an area of approximately 2670 ha, it is the largest Okefeno- kee marsh. Its predominant vegetation is the white water lily (Nymphea odorata), neverwet (Orontium aquaticum) and several species of bladderwort (Utricularia). There are more than 4000 peat islands within Chase Prairie, ranging in size from a few meters in diameter to areas as large as 10 ha. All successional stages are represented, from re- cently exposed bare peat islands to ones supporting cypress trees 600 years old. Newly formed islands are colonized initially by grasses and sedges. Species of beak- rush (Rhynchospora) are followed by redroot (Lachnanthes caroliniana), hard head (Xyris smalliana) and maiden cane (Panicum hemitomon). After an island has been in existence for several years, sedges (Carex spp.) begin to dominate. The establishment of woody vegetation is a relatively slow process, requiring more than 2 decades to cover islands