An invasive species spread by threatened diurnal lemurs impacts rainforest structure in Madagascar

Abstract

Invasive species are a major threat to biodiversity and ecosystem function. Thus, understanding their spread and ecological impacts is critical for management and control. Strawberry guava (Psidium cattleianum Sabine) is an aggressive invader across the tropics and has been rapidly spreading throughout the eastern rainforests of Madagascar. However, both the mechanisms of its spread on the island and the consequences of its invasion on native floral and faunal communities remain largely unexplored. By surveying multiple sites across Madagascar’s eastern rainforests, we demonstrate that the introduction of P. cattleianum significantly correlates with changes in forest structure—namely tree/shrub size, taxonomic richness, and taxonomic diversity. Further, at a local scale, the presence of P. cattleianum was associated with an increase in frugivore species richness; its primary dispersers during our study period were lemurs. Moreover, we identified species-specific effects of lemur gut-passage on the germination of P. cattleianum seeds. Finally, microsatellite analysis of P. cattleianum from a variety of locations across Madagascar demonstrated three distinct, highly differentiated, genetic population clusters, each with high levels of intra-population diversity, suggesting multiple independent introductions of P. cattleianum into Madagascar followed by long-distance dispersal. Collectively, these findings illuminate the complex status of strawberry guava invasion in Madagascar, which poses a growing threat to the island’s unique flora and yet provides important forage for threatened and charismatic animal species.