Seed protection through dispersal by African savannah elephants (loxodonta africana) in Northern Tanzania

African elephant - Behavior;African elephant;Elephants

Spanbauer, Bradley RAdler, Gregory ;

University of Wisconsin

关键词: African elephant - Behavior;    African elephant;    Elephants;   

Others  :  https://minds.wisconsin.edu/bitstream/handle/1793/69526/Spanbauer%2c%20Bradley.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: University of Wisconsin

【 摘 要 】

Seed dispersal by animals is important for maintaining healthy populationsof many tree species. The Janzen-Connell hypothesis, states that trees are underselective pressures to the have their seeds dispersed away from the parent plantand into an environment more suitable for growth. Seeds typically do not surviveunderneath the parent plant for a myriad of reasons, including light and nutrientlimitations, and excessive predation. Large-seeded tree species are especiallyaffected by these factors because their seeds cannot be dispersed by abiotic factors,such as wind. Trees with large seeds that can only be effectively dispersed by largebodiedanimals are referred to as megafaunal syndrome species. African forestelephant disperser effectiveness has been well studied. African savannah elephantsmay fill a similar niche, although experimental data are few. African savannahelephants have been suggested as critical seed dispersers, and may be the onlyremaining organisms capable of effectively dispersing seeds of megafaunalsyndrome species.I examined the effectiveness of savannah elephant dung as a protectivebarrier for three tree species: Acacia tortilis, Tamarindus indica, and Balanitesaegyptiaca. Experimental treatments were established to measure the effect of dungin protecting passed seeds. I also addressed the Janzen-Connell model. I predictedthat seeds in dung and seeds away from the parent tree would experience lessinfestation than fresh seeds. Simple linear regression was used to determine dailyremoval and infestation rates. Two-way analysis of variance was used to comparetime in days and treatment and their interaction. Multiple comparisons using aTukey;;s test of honest significant differences were made to check for truedifferences between paired treatments from the ANOVA. Finally, loglinear analysiswas used to test for differences among infestation of seeds at different distancesfrom adult conspecific trees.In January 2013, ants or termites in Experiment 1 likely removed passedseeds in dung. Fresh seeds experienced similar levels of removal. Chi-squareanalysis of data supported my hypothesis and revealed differences in beetleemergence between passed and fresh seeds. In support of my prediction, in October2013, seeds in dung experienced less beetle infestation than fresh seeds inExperiment 2. Seeds at distances greater than five meters experienced less beetleinfestation than seeds underneath conspecific trees in Experiment 3. This study wasthe first to experimentally address post-dispersal seed fate for megafaunalsyndrome species by savannah elephants. It creates a link between dispersereffectiveness of forest and savannah elephants, and provides foundation for furtherexamining savannah elephants as seed dispersers of megafaunal syndrome species.