Madagascar's fauna is thought to have coevolved to a certain extent with its flora: The famous plant–pollinator mutualism predicted by Charles Darwin, between the orchid Angraecum sesquipedale and the moth Xanthopan morganii, is found on the island. Highly unstable rainfall in Madagascar was suggested to have created unpredictable patterns of flowering and fruiting in plants; this in turn would have narrowed opportunities for flower- and fruit-feeding animals and could explain their relatively low numbers in Madagascar. Among these, lemurs are the most important, but the historic extinctions of giant lemurs probably deprived some large-seeded plants of their seed dispersers. The extinct Madagascan megafauna also included grazers such as two giant tortoises (Aldabrachelys) and the Malagasy hippopotamuses, but it is unclear to what extent their habitats resembled today's widespread grasslands.
