Strawberry guava (Psidium cattleianum) is an aggressive invasive species that dominates many tropical forests worldwide. While guava trees have been shown to significantly impact animal populations, hydrology, and terrestrial plant populations, little is known about the effects of guava invasions on epiphyte communities. Epiphytes have been overlooked in most studies of biological invasions, despite their substantial contributions to water storage, nutrient cycling, and animal habitat. We investigated the impact of invasive guava trees on epiphyte communities in a montane rainforest in Madagascar where large, monotypic stands of invasive guava are increasingly encroaching on the diverse native forest community.
Results/Conclusions
We found that invasive guava trees held on average a three-fold lower abundance of epiphytes relative to native trees, a pattern driven primarily by lower coverage of bryophytes and lichens on guava. These patterns remained after controlling for variation in tree diameter. We also found that guava trees supported no vascular epiphyte species including the diverse fern and orchid taxa. The depauperate epiphyte coverage on guava may be due to its smooth, shedding bark, which may limit epiphyte establishment to early successional species and prevent the later-successional establishment of vascular epiphytes. While previous studies have shown that guava reduces native tree recruitment and diversity, our results suggest guava invasion can also negatively impact diverse and ecologically important epiphyte communities. These results have important implications for conservation and forest management because of the commonly overlooked but important role that epiphytes play in tropical forest communities. Epiphytes hold and cycle significant amounts of water and nutrients. They also reduce forest temperature, buffer species against climate change, and create microhabitats for many frogs, lizards, arthropods, and birds. These results have implications beyond Madagascar and place increasing urgency on finding solutions to control guava invasions across tropical forests worldwide.