, Volume 137, Issue 3, pp 436–445 | Cite as

Regeneration of Rhizophora mangle in a Caribbean mangrove forest: interacting effects of canopy disturbance and a stem-boring beetle

  • Wayne P. Sousa
  • Swee P. Quek
  • Betsy J. Mitchell
Community Ecology


Current theory predicts that in low-density, seed-limited plant populations, seed predation will be more important than competition in determining the number of individuals that reach maturity. However, when plant density is high, competition for microsites suitable for establishment and growth is expected to have a relatively greater effect. This dichotomous perspective does not account for situations in which the risk of seed predation differs inside versus outside recruitment microsites. We report the results of a field experiment and sampling studies that demonstrate such an interaction between microsite quality and the risk of propagule predation in mangrove forests on the Caribbean coast of Panama, where it appears to play a key role in shaping the demography and dynamics of the mangrove, Rhizophora mangle. Rhizophora's water-borne propagules establish wherever they strand, but long-term sampling revealed that only those that do so in or near lightning-created canopy gaps survive and grow to maturity. These microsites afford better growth conditions than the surrounding understory and, as importantly, provide a refuge from predation by the scolytid beetle, Coccotrypes rhizophorae. This refuge effect was confirmed with a field experiment in which Rhizophora seedlings were planted at different positions relative to gap edges, from 5 m inside to 20 m outside the gap. Mortality due to beetle attack increased linearly from an average of 10% inside a gap to 72% at 20 m into the forest. The interaction between canopy disturbance and propagule predation may be having a large impact on the composition of our study forests. Being shade-tolerant, Rhizophora seedlings that escape or survive beetle attack can persist in the understory for years. However, the high rate of beetle-induced mortality effectively eliminates the contribution of advance regeneration by Rhizophora saplings to gap succession. This may explain why the shade-intolerant mangrove, Laguncularia racemosa, is able to co-dominate the canopy in low intertidal forests at our study sites.


Advance regeneration Coccotrypes rhizophorae Light gap Panama Propagule predation 



We are very grateful for the field and laboratory assistance provided by J. Abraham, E. Adams, A. Beaulaurier, W. Bragg, L. Chan, C. Coldewey, A. Cundiff, J. Dunn, J. Gunn-Glanville, N. Hausmann, I. Herriott, D. Hitchcock, P. Huang, J. Kemp, P. Kennedy, S. Lehigh, J. Levine, G. Lopez, H. Malhi, A. McCray, J. McGraw, K. Marsee, D. Matias, G. Mendoza, M. Metz, A. Minn, C. Nerney, J. Parrent, G. Peracca, S. Poetker, R. Raban, J. Roelands, C. Sagers, J. Shors, A. Smyth, G. Sousa, J. Steele, B. Tonkonogy, M. Venkatesan, J. Walker, J. Williams, and H. Wright, and for the logistical assistance provided by S. Lemos, F. Sanchez, R.Thompson, and the Visitors Services Office of the Smithsonian Tropical Research Institute (S.T.R.I.). J. Abraham, A. Beaulaurier, A. Ellison, N. Hausmann, P. Kennedy, J. McGraw, M. Metz, and J. Skene provided helpful comments on the manuscript, J. Battles and E. Simms suggested key references, L. Bjostad and K. Downum enlightened us on the possible role of phototoxins in defending Rhizophora against beetle attacks, and N. Hausmann and G. Roderick expertly helped produce Fig. 1. Special thanks to M. Geber for supplying her light gap sampling data from 1985: the seed from which our study has grown. We thank S.T.R.I. for allowing us to use the Galeta Marine Laboratory. This study was supported by National Science Foundation grants DEB-9221074, DEB-9615887, and DEB-0108146 to W.P.S., by the Committee for Research, University of California at Berkeley, and by the Miller Institute for Basic Research in Science. It was conducted under research permits from the Panamanian National Institute for Renewable Natural Resources. We especially thank the Republic of Panama for preserving their forests and making them available for study.


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Copyright information

© Springer-Verlag 2003

Authors and Affiliations

  • Wayne P. Sousa
    • 1
  • Swee P. Quek
    • 2
  • Betsy J. Mitchell
    • 1
  1. 1.Department of Integrative BiologyUniversity of CaliforniaBerkeleyUSA
  2. 2.Museum of Comparative ZoologyHarvard UniversityCambridgeUSA

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