For one tropical tree, effective seed dispersal relies especially on elephants
Friday, August 17, 2018
Posted by: Dana Walker
Known collectively as megafauna, large animals, and particularly herbivores, ARE critical for
dispersal of seeds of many terrestrial plants, especially those bearing large fruits ("megafaunal fruits"), which depend on megafauna for spreading their seeds. But as a group, megafauna encompass a diverse range of body sizes and physiology, and the relative contribution of each to seed dispersal for most megafaunal plant species is poorly characterized.
To address this question, the authors tracked fruit consumption, seed dispersal, and seed viability for the forest tree Platymitra macrocarpa, a member of the Annonaceae (custard apple) family, which bears 3"-5" long fruits that are eaten by elephants, sambar deer, bears, and gibbons, among other forest animals. By observing fruiting trees over the fruiting period, sampling dung piles and other sites of deposited seeds, and measuring the rate of germination and growth of deposited seeds, the authors calculated the seed dispersal effectiveness for each megafauna species feeding on the tree's fruit. While elephants consumed only 3% of the available fruit, they were responsible for 37% of the seeds that produced viable seedlings. In contrast, sambar deer consumed 23% of fruit, but accounted for only 17% of seedlings, due in part to much heavier beetle damage done to the seeds they excreted.