Opposing forces of seed dispersal and seed predation by mammals for an invasive cactus in East Africa
thesisposted on 01.04.2016, 00:00 by Megan Dudenhoeffer
Animal-mediated dispersal can increase germination and subsequent survival of plants. The invasive prickly-pear cactus Opuntia stricta has reduced rangeland quality and altered understory-plant communities throughout much of the globe. In central Kenya's Laikipia County, olive baboons (Papio anubis) frequently consume O. stricta fruits and subsequently disperse the seeds via defecation. The facilitation of O. stricta's spread by native animals is of concern to both ranchers and conservationists, due to O. stricta's history as an aggressively invasive in systems across the globe. However, consumption of seeds (seed predation) by rodents may offset the potential benefits of seed dispersal for cactus establishment. We investigated foraging preferences of a common and widely-distributed small mammal--the fringe-tailed gerbil (Gerbilliscus robustus) for O. stricta seeds deposited in baboon feces versus bare O. stricta seeds. Our data shows that seed predation was higher for seeds within feces than for control seeds, suggesting that high abundances of rodents may disrupt the process of seed dispersal and reduce rates of cactus reproduction.