Influence of Propagule Flotation Longevity and Light Availability on Establishment of Introduced Mangrove Species in Hawaiʻi

Abstract

Although no mangrove species are native to the Hawaiian Archipelago, both (Rhizophora mangle) and (Bruguiera sexangula) were introduced and have become naturalized. (Rhizophora mangle) has spread to almost every major Hawaiian island, but (B. sexangula) has established only on Oʻahu, where it was intentionally introduced. To examine the possibility that differences in propagule characteristics maintain these patterns of distribution, we first reviewed the literature on surface currents around the Hawaiian Islands, which suggest that propagules ought to disperse frequently from one island to another within 60days. We then tested the ability of propagules of the two species to float for periods of up to 63 days and to establish under two light intensities. On average, (R. mangle) propagules floated for longer periods than those of (B. sexangula), but at least some propagules of both species floated for a full 60 days and then rooted and grew for 4 months under relatively dense shade. A large percentage (~83%) of (R. mangle) would be expected to float beyond 60 days, and approximately 10% of (B. sexangula) also would have remained afloat. Therefore, it seems likely that factors other than flotation ability are responsible for the failure of (B. sexangula) to become established on other Hawaiian islands.

Citation

Allen, James A.; Krauss, Ken W. 2006. Influence of Propagule Flotation Longevity and Light Availability on Establishment of Introduced Mangrove Species in Hawai‘i. Pacific Science 60(3): 367-376.