Tropical Biology Section
Read, Jennifer , Sanson, Gordon , Burd, Martin , Evans, Robert , Jaffre, Tanguy .
Possible pre-conditions to the evolution of monocarpy in a long-lived tropical rainforest tree, Cerberiopsis candelabra (Apocynaceae).
Monocarpy is an intriguing life history strategy for a long-lived forest tree because of the inherent risk – the tree’s lifetime fitness depends on a single reproductive event during conditions of uncertain suitability for reproduction and seedling establishment. Cerberiopsis candelabra, native to the rainforests of New Caledonia (southwest Pacific), is a potentially long-lived tree, with ages of up to c. 140 years estimated from tree rings. In this species, monocarpy is combined with mass-flowering, so that a substantial (but variable) proportion of the trees in a stand may flower together at multi-year intervals. We ask what pre-conditions may have facilitated the evolution of this rare life-history strategy in C. candelabra, focusing on the roles of mass flowering, post-reproductive mortality, gregariousness and rapid growth. Population size structures and age structures commonly suggest a history of one or more recruitment episodes followed by a period of recruitment failure, the latter despite recent flowering events in most populations. Canopy gaps created by death of individual parents appear to be too small to allow seedling establishment, but mass flowering in high-density stands, with the consequent death of many adults, appears to enhance seedling recruitment by increasing light availability. This suggests that synchronous flowering and gregariousness have facilitated the evolution of monocarpy in this species. However, the paucity of recent recruitment in many stands suggests that infrequent catastrophic disturbance is a necessary adjunct for regeneration. We show that C. candelabra has low wood density, allowing relatively rapid growth after a disturbance, but high wood strength per unit density. The latter, together with the unusual tree architecture, potentially allows it to survive cyclones and tune its reproduction to coincide with infrequent severe catastrophes that open the forest canopy. Hence, the coincidence of multiple key traits may have facilitated the evolution of monocarpy in this species.
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1 - Monash University, School of Biological Sciences, Victoria, 3800, Australia
2 - Commonwealth Scientific and Industrial Research Organisation, Materials Science and Engineering, Clayton, Victoria, 3168, Australia
3 - Institut de recherche pour le developpement, Centre de Noumea, Laboratoire de Botanique et d'Ecologie Appliquees, Noumea, 98848, New Caledonia
Presentation Type: Oral Paper:Papers for Sections
Location: 552A/Convention Center
Date: Monday, August 2nd, 2010
Time: 10:15 AM