UCB Moorea Class: Biology and Geomorphology of Tropical Islands

The growing concern for threatened or endangered species has made conservationists recognize the need to accurately assess the status of small populations. In order to do this, the survivorship and fecundity of each life stage must be established to determine the population’s overall growth rate. A small population of the evergreen tree Calophyllum inophyllum can be found on the island of Moorea in French Polynesia. This tree is an excellent study organism because it has been internationally recognized as an endangered species and its large spherical seeds allow it to be traced easily. It grows along the coast, and the seeds float in water and continue to be viable for over three months. Determining the fate of the seed is one important step in developing useful models for conservation managers. The factors tested are survivorship, loss, and fecundity in the seed to seedling life stage. A seed-sowing experiment yielded 36.24% germination, which is much lower than past germination rates of this tree. The terrestrial crab, C. carnifex, was found to be the primary predator of the C. inophyllum seed, causing a 59% loss of seeds. This high predation loss could be impacting the population growth rate. The long-distance dispersal study provided evidence that the seeds were capable of moving past the reef. This has important implications in the studies of island colonization.