The role of rodents in tropical forest regeneration : seed predation and seed dispersal
File(s)
Date
2014-05Author
Dittel, Jacob W.
Advisor(s)
Adler, Gregory
Metadata
Show full item recordAbstract
Small rodents have long been considered to be seed predators rather than effective
seed dispersers. Particularly in the Neotropics, this predatory role has been thought to be
especially true for large-seeded plant species that likely had mutualistic relationships with
megafauna that went extinct after the last ice age. Small rodents are not thought to be dispersers
because they presumably eat a large proportion of the seeds or cannot move the large seeds
sufficiently far to be effective dispersers. In this study, I tracked the removal of seeds from
three different heights of three species of large-seeded trees in central Panama, Attalea
butyracea, Astrocaryum standleyanum, and Dipteryx oleifera, and followed the removed seeds to
deposition sites in central Panama. Removals were most likely perpetrated by two small rodents, the
strictly terrestrial Proechimys semispinosus (Central American spiny rat) and the arboreal Sciurus
granatensis (red- tailed squirrel) because they were the most abundant small rodents in the study
sites. At each deposition site, I measured 9 microhabitat variables to determine if these two
rodents were preferentially depositing seeds at sites with certain characteristics or were randomly
depositing seeds. During my study, rodents handled 98 seeds; 12 seeds were taken into subterranean
burrows or into the canopy and therefore unlikely to successfully recruit, while only one seed was
preyed upon. On average, A. butyracea was moved 6.5 m before being deposited. Astrocaryum
standleyanum had an average distance moved of
1.4 m. In all cases, seeds were most likely to be deposited with the fruit eaten, but the seed
remained intact. Additionally, rodents deposited seeds in locations with large logs (> 10cm
diameter), high herbaceous cover, and an intact canopy. The number of large logs was significantly
different from random locations. Despite not being able to determine long-term fate (greater than
ca. 1 year), I show that these small rodents are not primarily seed predators and may in fact be
important mutualists by dispersing seeds relatively long
distances to favorable germination sites.
Subject
Forest regeneration - Tropics
Seeds - dispersal
Seed dispersal by animals
Granivores