To determine if a nonlinear, threshold relationship exists between flying fox (Pteropus tonganus) abundance and their effectiveness as dispersers of large seeds.
Type of Study:
The relationship between ecological function (seed dispersal) and flying fox abundance was nonlinear - for most trees in sites below a threshold abundance of flying foxes, flying foxes dispersed <1% of the seeds they handled. Above the threshold, dispersal away from trees increased to 58% as animal abundance approximately doubled. Hence, flying foxes may cease to be effective seed dispersers long before becoming rare.
Our results indicate that flying-foxes' potential to disperse seeds is highly dependent on population density. Currently, 25 of the world’s 50 island-dwelling species of flying fox are threatened (seven critically endangered, four extinct; IUCN 2002). These dwindling flying fox populations inhabit some of the world’s most threatened biodiversity hotspots.
ANOVA and Regression
Tonga, Pacific Ocean
Response variable :
Flying fox abundance index, seed rain
85 plants, 4 transects at each
McConkey, K. R., Drake, D. R. (2006) Flying foxes cease to function as seed dispersers long before they become rare. Ecology. 87, 271–276.