Mass flowering and parental death in the regeneration of Cerberiopsis candelabra (Apocynaceae), a long-lived monocarpic tree in New Caledonia

摘要

Monocarpy is rare among forest trees, and the selective conditions allowing this life history to evolve are poorly known. Here we examined the regeneration dynamics of a New Caledonian monocarpic tree species, Cerberiopsis candelabra, to better understand how postreproductive mortality and mass flowering might contribute to the success of this strategy. We investigated population size structures and seedling establishment patterns in 18 stands following the 2003 flowering event. We found little evidence of recent recruitment. Instead, population size structures suggested a history of one or more substantial recruitment events followed by recruitment failure, despite multiple flowering events in most populations. The canopy gap created by death of an individual parent appeared generally insufficient to allow seedling establishment, but mass flowering and consequent death of many adults appeared to enhance seedling recruitment by opening more of the canopy. Site means of seedling density below dead parents correlated strongly with light availability and with the proportional density of flowering trees. Therefore, we suggest that mass flowering and gregariousness may have been necessary preconditions for the evolution of monocarpy in this species. However, the degree to which regeneration relies on synchronous flowering and gregariousness vs. infrequent catastrophic disturbances remains uncertain.