Loss of animal seed dispersal increases extinction risk in a tropical tree species due to pervasive negative density dependence across life stages

T. Trevor Caughlin, Jake M. Ferguson, Jeremy W. Lichstein, Pieter A. Zuidema, Sarayudh Bunyavejchewin, Douglas J. Levey

Research output: Contribution to journalArticlepeer-review

88 Scopus citations

Abstract

Overhunting in tropical forests reduces populations of vertebrate seed dispersers. If reduced seed dispersal has a negative impact on tree population viability, overhunting could lead to altered forest structure and dynamics, including decreased biodiversity. However, empirical data showing decreased animal-dispersed tree abundance in overhunted forests contradict demographic models which predict minimal sensitivity of tree population growth rate to early life stages. One resolution to this discrepancy is that seed dispersal determines spatial aggregation, which could have demographic consequences for all life stages. We tested the impact of dispersal loss on population viability of a tropical tree species, Miliusa horsfieldii, currently dispersed by an intact community of large mammals in a Thai forest. We evaluated the effect of spatial aggregation for all tree life stages, from seeds to adult trees, and constructed simulation models to compare population viability with and without animal-mediated seed dispersal. In simulated populations, disperser loss increased spatial aggregation by fourfold, leading to increased negative density dependence across the life cycle and a 10-fold increase in the probability of extinction. Given that the majority of tree species in tropical forests are animal-dispersed, overhunting will potentially result in forests that are fundamentally different from those existing now.

Original languageEnglish
Article number20142095
JournalProceedings of the Royal Society B: Biological Sciences
Volume282
Issue number1798
DOIs
StatePublished - Nov 12 2014

Bibliographical note

Publisher Copyright:
© 2014 The Author(s) Published by the Royal Society.

Keywords

  • Extinction
  • Overhunting
  • Seed dispersal
  • Spatial model
  • Tree population
  • Tropical forest dynamics

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology (all)
  • Immunology and Microbiology (all)
  • Environmental Science (all)
  • Agricultural and Biological Sciences (all)

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