The role of extinct giant tortoises in the germination of extant baobab Adansonia rubrostipa seeds in Madagascar

摘要

This study was conducted to explore the role of extinct giant tortoises (Aldabrachelys gigantea) in the germination of extant baobab Adansonia rubrostipa seeds in Madagascar. Results showed that all of five adult tortoises readily ate most (approximately 3/4) of baobab fruits offered to them. Seed retention times ranged from 15 to 23 days. After acid scarification, the germination percentage of defecated seeds (44.25+or- 3.78%) did not differ from those of manually depulped seeds (52+or- 6.06%) (Mann-Whitney-Wilcoxon: W = 4, P = 0.34). It is established that considering the long retention time, Madagascan giant tortoises could have played a predominant role in the dispersal of baobab seeds to enable them to potentially colonize new areas. Morphologically, they are similar to Galapagos giant tortoises (Chelonoidis nigra), which can disperse seeds more than 4 km from the parent plant. Thus, the extinction of Madagascan giant tortoises and Madagascar's other megaherbivore, which were once abundant under the stands of baobab, can result in poor recruitment in baobab populations. Ultimately, this has important implications for the long-term viability of baobab species in Madagascar.