Size‐Related Differential Seed Predation in a Heavily Defaunated Neotropical Rain Forest

Size‐Related Differential Seed Predation in a Heavily Defaunated Neotropical Rain Forest ABSTRACT Hunting and habitat loss represent an increasingly common anthropogenic impact. Available evidence suggests that defaunation is typically differential: medium/large mammals are most affected while small rodents are less affected, or even favored. In heavily impacted areas, such as Los Tuxtlas, the residual mammalian fauna is dominated by small rodents. We tested the expectation that if small rodents will preferentially attack small‐seeded species, large‐seeded species may escape predation in the absence of medium/large seed predators and that this may affect germination and, possibly, recruitment. Experiments with caged rodents (Heteromys desmarestianus) under laboratory conditions showed a preference for smaller seeds. A field experiment involving seeds of contrasting size showed that small, unprotected seeds experienced a predation risk 30‐times larger than protected seeds, while the effect of protection was not significant for large seeds. These patterns of predation led to significant differences in germination: protected small‐seeded species had a fourfold greater germination than unprotected small‐seeded species, while germination was not significantly different between exposed and protected large seeds. The observed contrasts in germination suggest that under heavy defaunation, small‐seeded species are likely to be penalized by the overabundance of small rodents, while large‐seeded species escape predation. Our results are consistent with the observation of dense seedling carpets dominated by large‐seeded species in the understory of Los Tuxtlas. We speculate that the patterns we uncovered may explain, at least partly, the impoverished diversity of the understory vegetation that characterizes heavily defaunated understories and that this has the potential to affect forest regeneration. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Biotropica Wiley

Size‐Related Differential Seed Predation in a Heavily Defaunated Neotropical Rain Forest

Biotropica, Volume 39 (3) – May 1, 2007

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Publisher
Wiley
Copyright
© 2007 The Author(s) Journal compilation © 2007 by The Association for Tropical Biology and Conservation
ISSN
0006-3606
eISSN
1744-7429
D.O.I.
10.1111/j.1744-7429.2007.00274.x
Publisher site
See Article on Publisher Site

Abstract

ABSTRACT Hunting and habitat loss represent an increasingly common anthropogenic impact. Available evidence suggests that defaunation is typically differential: medium/large mammals are most affected while small rodents are less affected, or even favored. In heavily impacted areas, such as Los Tuxtlas, the residual mammalian fauna is dominated by small rodents. We tested the expectation that if small rodents will preferentially attack small‐seeded species, large‐seeded species may escape predation in the absence of medium/large seed predators and that this may affect germination and, possibly, recruitment. Experiments with caged rodents (Heteromys desmarestianus) under laboratory conditions showed a preference for smaller seeds. A field experiment involving seeds of contrasting size showed that small, unprotected seeds experienced a predation risk 30‐times larger than protected seeds, while the effect of protection was not significant for large seeds. These patterns of predation led to significant differences in germination: protected small‐seeded species had a fourfold greater germination than unprotected small‐seeded species, while germination was not significantly different between exposed and protected large seeds. The observed contrasts in germination suggest that under heavy defaunation, small‐seeded species are likely to be penalized by the overabundance of small rodents, while large‐seeded species escape predation. Our results are consistent with the observation of dense seedling carpets dominated by large‐seeded species in the understory of Los Tuxtlas. We speculate that the patterns we uncovered may explain, at least partly, the impoverished diversity of the understory vegetation that characterizes heavily defaunated understories and that this has the potential to affect forest regeneration.

Journal

BiotropicaWiley

Published: May 1, 2007

References

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